No Electrical power battteries 100%???

[Tarm]

First post been a reader for yrs since I bought this square body.

Truck was garage kept owned by a senior until he pasted away and I bought it.
Truck is in very good shape other than paint.

The truck is for my daughter she loves older square bodies and similar.


Sorry for this being rather lengthy I wanted to insure all details and info was given. I apologize if its overkill

She calls me the other day says everything was fine she parked came out 4 hrs laters and no power. I figured dead bat. Got there a couple hours later and sure enough no electric power to anything. Hook up jumper and nothing. Hmmmm???

I go home and come back next day with tools. Open the door and interior light is on shining bright. Power 100% to everything. Starts right up and works 100%


Get it home and park it. As she stays local I told her to drive it to see if the symptom comes back so I could better diagnose. She comes in and says truck is dead again.

No power to any accessories : lights, radio, climate, starter. Battieries fully charged.

I go out next morning to start working on it. Light is on and everything working.

I check normal things like obviously battery term and cable etc.

Go back in and do some searches on here as I am new to older Chevys had mainly Ford diesels. Find a few threads on here and others.

They seem to indicate the firewall mounted octagonal shaped junction box with two lugs inside of the brake master cyl. From what I read for at least the yr trucks it was stated all power to the cab runs thru that block. Also fusible links and grounds were mentioned.

The junction box looked fine but to be sure I pulled all the connect off it and was going to pull it from the firewall. But I look in the cab where I left the light on to notice if a loose connection triggers it going out. The light is shinning??? I guess I just learned that on 1983s at least with 6.2 diesels all the power does not run thru this junction box or the light would be out. I deducted this would rule this as the site of the issue and all the terminals looked good anyways.

I looked at the grounds I could find. Off the passenger side battery ( diesel dual bats) I have a ground going to frame and another ground wire on the same stud on the frame going up to the radiator support frame I guess you could call it. I also found the typical non shielded/insulated factory flat braided wire going from the block to the firewall. All of these looked fine. No: fraying or burnt sections, corrosion, connections seem tight.

I thought about the fusible links but in my experience which is limited they are a case of working or burnt thru so either continuity or open not intermittent. Correct or incorrect I do not know???

With the interior light on and wiggles and tugged on various wires and connections but nothing triggered the no power condition.

The one spot I have left to inspect is the starter terminal connections and wires. My question is how could those connections effect all power in the cab as well.

When the power is dead no accessories work period.

I also have a bit of a issue with the neutral safety switch as the spring in the shifter broke and so you have to sometimes hold the shifter a bit to the left in park to get it to disengage and allow the starting. But it has never had any effect on anything but neutral disengagement and no effect on the current condition when it was happening.


I am at the point where I feel I have gone thru the search functions a good bit and tried the comments and suggestions found there.

I would be very appreciative for any help or suggestions anyone could offer.

I have never had a condition like this that did not have a obvious ground fuse or wire connection that was found quickly.

I have noticed that the in cab fuse box is mounted to the rear at the firewall. Could a moisture or ground there be the issue. I thought I recalled someone mentioning issues with water getting in and effecting the fuse box given its mount location. The thing that has me stumped is that it comes and go but is functional when it comes back its not effected when a load is put on it. Normally if this happened and the power came back I would expect when I tried to start it power to go back out and not allow it to start. That would also possibly indicate a weak feed side (positive) issue if grounds were good. But with it going back and forth between no power and everything is good not sure where to proceed to.

As here in this area we have dealt with lots of on and off rain this summer and into fall and was the case on these days it happened I was thinking of pulling out the garden hose and hitting all around the firewall etc and seeing if I could trigger the condition.


Again any help greatly appreciated. My trucks spec are below in my sig.

Thanks again for any help anyone can provide.

[cadillac_al]

Those dual positive cables have caused me troubles in the past on my Buick. Next time the truck is dead I would start by removing them and re-installing them to see what happens. My cables had to be oriented just right to tighten up right. If that has no effect then I would start tracing the power and check for power at the starter and then to the firewall junction box. Good luck.

[CSHADES]

pull the double positive cable and clean or replace all the parts ---bolt -spacer -terminals

[hatzie]

The year and engine type would be helpful...
Assuming it's an 80's Diesel with dual batteries and not a TP2 GM camper battery setup.
It's likely a corroded connection. Fixing it is tedious fussy work.

You can usually shotgun this one and fix the problem. It'll make the batteries, starter, and alternator happier too.

Looking at your pictures I can see a problem already...

The long battery bolt in your picture is a regular hardware store bolt... side post bolts are special parts. Especially the long bolt GM used to hook up the parallel battery to battery cable. Regular bolts will not work well and likely the special spacer GM used between the cable lugs is missing as well.
On a Dual Battery Diesel you need three regular length side post battery bolts and one long bolt with a special spacer to make contact between the positive cable connections.
Dorman 60310 is a "Long" "Diesel" Dual Battery Positive battery bolt and spacer. It's listed as a HELP! part...
You need three GM 8917444 or Dorman 60307, Short Regular side terminal battery bolts. Your RH battery negative has the correct bolt... I added this part number note because there isn't a picture of the LH battery so I can't tell what the previous owner did on that side.

You should clean up the battery lugs while they are off.
The puffy and crunchy crud on the cables is tin, arsenic, lead, and copper oxides and sulfate salts of some or all of the prior. Tin and sometimes arsenic were in the solder alloys used to tin the copper battery lugs. Your skin is not a serious barrier to Arsenic sulfate, lead sulfate, and copper sulfates and other similar metal salts. Swhy your hands turn a pretty blue and stay that way when you work with copper pipe on a hot day. Copper, lead, and arsenic are pretty nasty so it goes without saying you shouldn't breathe it or get it directly on your hands, near your eyes, or in your mouth etc. etc... Nuff said. We're all adults here.

GM battery cables are not overmolded so, after you remove the bolt, the cover can be removed from the battery lug and the connector can be cleaned with a brass brush. I usually clean off the connectors and re-install them with Vaseline or Battery cable protectant ( I use CRC 05046 because it's on the shelf locally but there are lots of them out there ) to keep out the weather and outgassing of Sulfuric acid from the battery vents.


Clean up the battery ground lugs at the alternator bracket and the LH side of the engine too. Spray them with battery protectant.

If that doesn't fix it move on to the starter BAT connections and the connections at the firewall J-studs. Remove, clean, and spray with battery protectant.

I would make a clean sweep of it with the braided ground straps... Rinse and repeat... remove, clean, re-install, and spray with battery protectant.

Last pull the 10ga BAT cable off the alternator (with the battery grounds disconnected), clean, re-install, and spray with battery protectant.

[Bandit130]

Welcome

[75C10]

I have had the same issue with my truck. Works one minute then it doesn't. 5 min later it works fine. Tightened the two nuts (1/4 turn) on the positive wires in your figure 1 and never again did this problem occur.

[v30crewcab]

I've had the factory fusable links by the starter cause the same problems.

[Wgesnerjr]

I have had this problem with an 89 R20. There was a short behind the fuse block. If I put my foot on it and turned the key, it would crank. Wouldn't do it all the time, just every 6 months or so. Cleaned the two big red wire connections and the purple wire connection at the bulkhead connector. Seemed great after that.

Also happened on my 94 Caprice Station Wagon. Had 2 different Optima batteries develop internal shorts that would kill the entire electrical system. This happened 4 years apart. Once it was towed home as I followed it, the lights came on and off. Once unloaded, it was fine to start for a couple of days.

Ironically, the second time it happened, was while I was selling it. It cut out on the test drive. (of all times, right) gave the buyer an automatic $150 off the price for a new battery.

Just thoughts on things to check.

[Tarm]

WOW!!! This forum......you guys are AWESOME!!!

Maybe this is the norm for this forum but its certainly not for 99% of the tech forums, regardless of subject, out there. I am a very informed person and would consider myself a very good researcher when it comes to finding obscure info on the net and wading thru forums using search functions. Thus, usually if I have to ask a question, rather than helping point someone else to the correct answer, I am stuck with vague or SOP/common sense type replies. Rarely ever helpful.

You guys not only gave me good info but also examples, detailed descriptions, and parts etc. This is only found from first experience and real understanding of the topic.

Hatzie,

Thank you for taking the time to type out such a through and detailed reply. It is extremely helpful and I will be going thru the parts to change them out. I am sorry that my trucks detailed info was not in my post. It should have been. Before I made the thread I went into my profile and filled out my signature. In it I included year model engine trans axles etc.. Not sure why it did not show up. When I first saw your comment I was thinking why did he not see the info in my sig. Scrolled up and I found the answer.......cause it was not there. duh!?! I'll add it to the end of this post.

As I have never had one of these trucks and I am the second owner I had no reference for what is an OEM part or not on something that can be as generic as a threaded bolt. Would have never had a clue if not for your info. My experience is mostly on the Fords the 7.3 PS the most we have little to any issues with the battery or starter harnesses. Now engine and under valve cover harnesses is another story. You giving me the parts number and where they go is fantastic and quite unexpected. ( its the kind of thing I would post if asked as I would take the time to look it up.) I have just never been on the receiving end of such info. LOL This is nice.

75C10,

That is exactly how mine acts. I was actually an electrician by trade for a number of years commercial mechanical did alot of fire protection systems. But it was rare and the hardest things to diagnose when issue like this came up. Nothing obviously loose or corroded nor effected by light wiggling and movement of the wires. Worse is having no schematic or knowing what is doing what beyond the obvious by the parts they are connected to.

v30crewcab,

So the fusible link or wire at the starter can cause complete in cab power loss?? See this is something without specific knowledge that common sense would not come up with. To me I would expect there to not be any thru circuits running across the starter lugs.

It seems rather poor choice given the heat and failure rate starters can have. Why run power that goes thru to all accessories thru the starter given the length of time high amperage load can be flowing thru and into those lugs during extended cranking which is very common with diesels. i.e. after fuel filter change (if not properly primed) running out of fuel which can happen accidentally with dual tanks not paying attention.

You mentioning this has caused me to recall that after doing fuel system work I had some extended start cranking that caused the starter to overheat a couple times to the point of smoking which was likely wire insulation at the terminals. If power thru the starter does go thru to the cab in my model year it sounds like one more thing I should check and address of there is any damage. What I wonder about the fusible link is are they not an either melted threw or still working just like a fuse so rarely intermittent. This is not to say the wires themselves still not the issue given that power could be running thru those lugs to cab.

Wgesnerjr,

Before I got the info on my battery terminal bolts and starter lug connections that is where I was going thru process of elimination. Thought the fuse block was the next logical step. May still check it as I seem to be going thru the electrical system anyways. Not sure on the diff between my model yr and yours but were those connections you cleaned very noticeable and were they at the top of the fuse block (is that were the bulkhead connector is? Sorry when I tried to look up the dash was away from home and I had no extra light so it was hard to see as its way back against the firewall.

Bandit,

Thanks for the welcome. Very glad I decided to join and ask.


So it looks like I need to do the following:

* Replace all the non factory bolts on the battery lug connectors and thoroughly inspect the cables or do I need to replace them as well??

* I need to carefully inspect the starter connections especially that now upon reflection I had those starter overheating issues.

* Inspect the main power and I assume ground connections at the fuse block in the cab

FYI: under a cursory inspection it seems the only non-OEM thing done to the electrical system (or frankly anything anywhere on the entire truck) other than the battery lug bolts was the addition of one of those musical programmable horns. Its controller is mounted under the dash and the wires go thru the rubber firewall grommet. I plan to remove it all as it does not work, is shoddy wiring work. (hand twisted wire ends with some electrical tape. No soldered connections or wire loom etc. Loose wires hanging. YUCK!!! Truck should be 100% factory then other than the bed liner insert.

Truck Info:

1983 Chevy K10 Silverado
Two Tone: Red/Gray
6.2L Diesel N/A
TH700R4
Corp 10 B Frnt/R(OEM locker)
Dual Tanks
OEM Frnt Quad Shock
OEM Block Warmer
200K Miles


Will report back after I go thru these things tomorrow.


Cheers,

Tim

[TKCR]

Welcome!! Yes this site and all the members are pretty helpful. Hatzie is actually one of the electrical gurus. I don't believe he mentioned it, but he has scanned all the electrical schematics and manuals for all our trucks. The links are in his signature.

[D13]

Mine would have key buzzer but when you went to crank everything would die. Found out I had a poor connectin on the RH battery that wHen the motor was cold it sometimes would make enough contact to go, and sometimes not. Appearently it was a a little lose and eventually it arced enough to melt the face of the battery terminal and caused the cables to be too loose to wrok some times. Ended up having to replace that battery.

I pulled the cables off the battery and cleaned the ends withn a small brass brush, dipped the positives in baking soda solution for an hour to clean out the acid,rinsed well then polished them up until shiny and let them dry overnight. Polished the battery terminal faces until they were shiny too. Replaced the positive battery bolts with gold plated studs, the ones the car stereo boys like. The RH one, where the LH cable feeds in, I replaced with a gold plated dual cable stud with a stud and nut on the end, this makes it a lot easier to jump the truck. It required a little trimmng of the plastic ends to get them in.

Put the studs into the battery (tight but no so tight as to strip the battery), installed the positive cables again being careful not to strip the battery out. It really doesn't take a ton of torque, they should be just tight enough that you can't rotate them by twisting the cable by hand. Then coated the outside and edges with a battery terminal protectant to prevent corrosion (or silicone grease - but it tends to get all over and is not paintable).

Be sure to check the connection at the starter (with BOTH ground cables disconnected). That nut can loosen or the positive cable starts breaking strands (pretty common), or the whole thing gets loose and oil soaked and oil is a bad conductor. Also the exposed end of the ground wires at the brackets can get corroded.
'If' I ever reo this truck ist getting new 2 gauge cables to a junction stud followed by 00 to the starter and 10 gauge to the junction block. That'll fix her.

[Wgesnerjr]

It was a long time ago and those sectors in my brain may have been over-written with new data.

From the remaining files, I removed the bolt in the bulkhead connector under the hood (on the firewall) and cleaned the contacts. I noticed that he purple wire was loose in the plastic bulkhead connector. Seems like the PO had the key in the "start" position for a long time and the brass terminal got hot enough to melt some of the plastic. Removed the terminal from the large Bulkhead plug for cleaning.

My friend had a portable sand blast set up so he hit the terminal real good and we put it back together with some Di-electric grease. I made sure to "push" the purple wire in after reassembly. Should have also looked at the other side terminal but never got back around to it.

Don't remember having a problem after then and before selling it.

[Tarm]

Ok am getting ready to go get some of the parts from the store. But I did a bit more testing. Went out and interior light was on. But when I went to key on and start everything went dead. This IMO points to a bad connection/high resistance. As I was in the cab I dropped down and looked at the fuse panel. I saw a large red wire near the top and pushed on it and lights came on and I could get the starter to turn over. So there is clearly a connection issue there. I also noticed its super close to the parking brake rod/release. My daughter uses this with every stop and I think that might have been the what caused this symptom to surface.

I am still going to replace the battery lug and inspect the starter connections.

But have been tugging and wiggling wires all thru the engine bay. The connection to the glow plug relay (I think that is what it has to be) looks weak. Its the smaller gauge wires that go thru the firewall to the cab. When I went to start it the WTS light did not come on and there was no click of the relay triggering the GPs. Its quite cool and would not start but I did not crank for long as I did not see the point.

So I have to work out the bad/weak connection at the fuse panel and the glow plug. As i have no idea currently they maybe the same connection issue in the panel or the GP may have come from me messing with the shoddy connection at the relay.


To be safe I am picking up the long bolt for the battery. The other bat not in the pics looks to have those OEM short bolts like the one Hatzie said OEM. Thus I think only the long bolt is a hardware store special.

So one long bolt and a relay About the relay: Is there a specific brand or amp above what the typical parts store system will tell me to use that I should get for best durability/reliability?

i am going to redo the control connection/connector for the relay as its covered in tape and feels quick flimsy.

What is the best way to get to the fuse panel and what connections should I be looking for that control main power to the whole panel?

[Tarm]

Ok ordered the doorman bolt for bat.

GM Alternator 2 wire plug end for the GP relay control wire connection.

Set of ACDelco 60g GPs

GP Controller.

This way I have a known starting place for these going into winter.

I just need to get up into the fuse box to figure out what wires have the poor connections. I assume the lower portion of the dash can be unbolted to get access to the box as its up in there and a tight space??

[cadillac_al]

While you are in the parts stores you should buy a side post battery wrench to carry in the truck. It makes working on the batteries a lot easier.

[andyh1956]

Tarm what yr truck are you working with?
Is your glow plug controller (GPC) a round one that is mounted on coolant passage plate at driver's rear cyl head w/ a separate relay?
If it is you need to upgrade to the later solid state relay assy.
Also know that those glow plug harnesses are made from fusible links.
When you get to glow plug testing I can help you with a diagram & diagnostics.

[hatzie]

You just need an 8mm or 5/16" Box-End wrench for the stock side terminal bolts. This is the one size that's so close that either wrench will work.
Ratcheting Box End wrenches are nice to have but not completely necessary. I actually prefer 6 point wrenches in this area.

The wiring to the fuse panel terminates in Pak Con connectors. You can purchase individuals of these terminals from Mouser and Del City but you'll need decent crimping tools. They are not cheap. The below tools used to be in the $89 range but they are up around $135 now.
They are very versatile tools... You can do most if not all of the terminals on these trucks and many other vehicles with those two tools. The exception would be the oddball double wire Packard & Pak-Con connectors. I would hazard a guess that you could re-sell them on evilbay for $120 and they would go fairly quickly.
12085271 is the Delphi Ratcheting tool for 14-20AWG Packard/Unsealed-Metripak/Pak-Con
12085270 is the Delphi Ratcheting tool for 10-12AWG Packard/Pak-Con/Sealed Metripak & Weatherpak connectors.



Older glow plugs...
If you have the round glow timer/thermal-switch on the front of the intake manifold they tended to get dodgy. The connector is GM 12004933. It's obsolete and a quick web search returns no information on it.

The round timer/switch and contactor can be updated to the more reliable controller and contactor one-piece control unit that GM used on the 6.2 & 6.5 diesels from 1985 through my 2000 GMC2500 that was built near the end of production of the 6.5L in the T400 chassis. The glow controller wiring page in the 1989 RV series wiring manual is easier to follow than the 1985-1988 wiring books. They are all wired the same.
The five terminal Metripak plug is labeled A-E.
-A is empty
-B is wired to the CRANK wire on the starter. I usually just fish a purple wire through the steel sleeve on the bellhousing and put a #8 ring terminal on the end so I can stack it under the stock CRANK wire on the #8 starter S terminal. If it's a #8 ring terminal then it can't fit on any other studs on the starter solenoid.
-C is from the temperature Inhibit switch
-D is tied to the same ignition switched circuit as the injection pump fuel cutoff. I used a piggyback terminal on the injection pump cutoff solenoid.
-E is Ground.


Piggyback terminal... McMaster Carr has these but they're all over the place...



Glow inhibit NOTE:
You can leave the inhibit switch out but it will glow when the engine temp is high enough to not need them. The wiring is self explanatory. Usually the inhibit switch is installed in the cylinder head... IIRC I just replaced the temperature gauge bung in the RH cylinder head with the inhibit switch. It's a normally closed thermal switch that opens when the engine temp reaches 125°F.
You may be able to just add a piggyback terminal to the HPCA (Housing Pressure Cold Advance) on the injection pump and run a single wire from there to terminal C. From the looks of things that'll accomplish the same thing as adding yet another thermal sensor. The difference is the HPCA thermal switch opens at 95-100°F. I didn't have the wiring diagrams when I updated my 1980 350 Diesel glow plugs or I would've used the HPCA power to the inhibit terminal.

[Tarm]

Thanks Hatzie
more awesome info. Unfortunately it means more things to order. I love excuses to get new tools though. Its how I have gotten most all the specialized tools I already own. I come into a job I need to do and buy it so I can do it myself. They add up over the years.

I forgot about the newer GP controller for the 6.2/5. Crap!! I ordered another old version from Rockauto. Should have gotten the newer square one. I may just return the older one then. But looking at my current one I have to say it looks to be the actual original one; 200K and 35yrs and still working. Not to shabby. I guess this engine got a good one LOL as I have read how inconsistent many are.

At this point I am not sure if the issue with the GP is at the fuse panel or the relay. It was all 100% till this complete elec power loss issue. It may just be the relay connection. Its not the controller I do not think as I do not hear the relay contacts close. I looked at a new relay and saw that it looks like a normal 2 wire GM alt connector will fit it perfect for the control wire contacts. I am not looking at any schematic and can not recall what I saw right now but I think one control wire goes to trigger in the cab and the other which follow it just goes to a ground? Is that correct??

I seem to recall seeing one of these 6.2 relays wired somewhere and they just had the one lead to a self tap screw in the inner fender next to it and the controller and waiting to start light worked. IIRC the one I saw also piggybacked a second control power lead to allow a manual override momentary switch. That will be a project for later as a back up.


Its rather interesting how my 7.3PS will start without GP to much cooler temp and the DT360 will start into the teens and has no GPs at all. But these 6.2 will just spin and spin even in the 50s if the GPs do not preheat things or you plug in the block heater for a couple hours.

Anyways looks like a few more hundred$$ in tools to order and waiting on the parts from Rock and Amazon. Want this GP system and this bad power connection to be all 100% before winter cold weather gets here. Need to also upgrade the headlights and put in some relays to the switch instead if full power running thru it. Bad design. Considering the DOT approved LED square lights. It looks like they can be wired to use all the led in two lights on low beam and 1/2 the leds in the second pair thats usually all high beam and then the other half for high. Not sure how they get aimed that way but I have seen a number of posts in places about it. I live in the sticks with almost all driving mountain back roads and highway the rest. Need the as much light as possible and still being legal. Up to 4 main lights are legal on low. So figured I would take advantage of it if I can.

Just not sure I like the look of those leds in these older body trucks but they sure are bright. The ones I am looking at everyone that has them says they are brighter than the halogen upgrades.

[D13]

I went to Delco 60G glows to eliminat ethe tip swelling. THey take a few more seconds of on time so I added a FERD starter relay and a momentary switch to fire it (mounted the relay to the intake studs wwith jusxt a touch of fiel work on the bracket), 4ga cable from input of factory relay to new one, and from new one's output to factory output. Ran trigger wire thru existing cab grommet to switch under dash. Great anti theft, thing won't staqrt cold without a few extra seconds glow.

Also vacilating LED's to halogen, prefer LED light but halogen look. Decisions.

[hatzie]

I re-read some threads on the Dieselpage about the HPCA system...

Since it's getting balky about starting at higher ambient temps I would replace the HPCA thermal switch when you do the glow plugs. It's a dealer only part or it was the last time I bought one. Tell the counter goon you have an 1988 Chevy Suburban 3/4 ton 4x4 with the 6.2 and you need the cold advance switch.

Robyn says to just leave the inhibit function of the glow controller unhooked and I respect her opinions. My 6.5L engines work just fine with it hooked up but they are also fairly youthful engines both being under 110,000 miles.

It's worth noting that you can usually retrieve a broken glow plug tip through the injector hole. Stuff a paper towel down under the tip to catch the pieces and vacuum out the pre-chamber before you re-assemble things with a new injector heat shield. Not a pleasant job but better than pulling the cylinder head.

[Tarm]

Yes I am hoping I have none that are broken and they all come out easy. Its not having trouble starting except when the GP are not used and its below say 60 degrees. With the GP it starts right up and also once warm without any issues. Still I may get that part just to have down the road. The parts I ordered came in this evening so I should be able to address some of it tomorrow.

[Tarm]

I replaced the battery post and pulled the GP relay. Why would there be a diode between the two control wires that goes to the relay? I looked on the 83 schematic on dieselplace and maybe I missed it but I do not see it. Just want to confirm its not needed as I have seen a number of people pic of replacing and I never saw a diode.

[Dead Parrot]

You want a diode. Most automotive relays include either a diode or resistor between the two posts of the relay coil. It is an electronics thing and will rarely show up on a wiring diagram as the diagram makers assume all relays have such protection internal.

Crude explanation: An energized coil, like the relay when on, stores power. When you turn the switch off, that power goes somewhere. The diode gives it a safe place to go. Otherwise you can get really high spike voltages backfeeding into your system. Think of the relay coil as one half of an ignition coil.

[hatzie]

They're called snubber or flyback diodes. They're usually connected in parallel with a relay coil. Glow plug contactors are very large relays and the backfeed voltage spike could be very large.

The stock 1983 CK pickup with a diesel doesn't have any sensitive electronics so if it's bone stock you don't need a snubber.

Sounds like a previous owner had some expensive radio equipment they didn't want damaged... Probably a HAM operator. Car stereo and CB folks generally wouldn't know to add snubbers to an older vehicle.

Uncle Sam thought it was important... The GM CUCV pickup and blazer has built-in snubbers in several places. Probably to protect the military radios.

This guy shows what happens on a multi-channel oscilloscope.

http://www.youtube.com/watch?v=c6I7Ycbv8B8

[Tarm]

Thanks guys for the explaination. I figured it had something to do with a discharge backfeed but thought it was odd given its pre electronic. I guess that also explains the non oem tape around the oem plug. It must have been done to ensure the diode stayed secure. My guess is its held in the crimp not soldered in. I was going to swap the plugs as I thought the oem one looked rough but it was actually just a bunch of deteriorated cloth and vinyl tape he had used.

I may solder in the diode unless you guys suggest otherwise? Should I solder the diode into the connector?

I'm still replacing the relay with the new one as part of prewinter tune up of the GP system. Will add some dielectric grease to the connector and put a heat shrink sleeve on it if I fully redo it. That way the entire back of the connector plug is sealed and gives it more support.

I noticed these relays are not default grounded through the bracket as it used rubber vibration isolation grommets. These grommets slide into the c channels and thus the bolt/screw going thru then into the fender do not create a ground. Would it be prudent to add a isolated ground from the bracket to the steel body? Why would this relay not have a ground connector? These look identical to a ford starter relay and you always ground them to the frame. Am I missing something? I looked at the wiring schematic on dieselplace for the 83 system thinking maybe one of the control wires grounded but tracing has LtBlue to the GP controller pin 3. The Pink/Blk seems to go thru the key switch to the HPCA system Hatzie referenced which is part of the whole fast idle system of the Inj Pump. I guess this is changed to the combo of thermo sensor and inhibit switch in later years?

If Hatzie or someone else has the time and does not mind double checking the schematic for me. Its over on dieselplace in the manuals section HERE Its the first one in that post and titled "1983 GM Wiring Manual CK ST P & G-VAN" the schematic is page 11 of the pdf.

I know when you install a manual switch instead of the controller system you must ground one of the control lug terms with the other going to the switch thru + connection. So which lead ends up being the ground in the OEM GP system off the relay? Lt BLue or Pink/Blk? This is sep from grounding the relay body itself.

I am only making such a deal about this because I have learned hard lessons of the type of gremlin problems a faulty or improper or not enough ground tabs can cause. More so with the new ECU sensor engine systems. But I've had problems I was tracing out for months end up being a oxidized ground tab or completely cured by adding a extra ground in a few places. From this I am a bit paranoid about insufficient grounding of engine systems. In fact, I tend to give any elec device not only the system ground of the wiring harness but also a dedicated ground to the frame. Always did it with electric fuel pumps, wiper motor. Actually found out a wiper motor was the root cause of a engine stalled because it was on the same single ground as the cam position sensor. Turned wipers on and the EMI from the aging dirty elec motor was freaking out the CPS which is nothing but a Hall-effect sensor or one the oldest and simplest types. Yet it still freaked out this rather basic sensor. Gave the wiper its own isolated ground and all things were good again. Eventually replaced the wiper motor just to be safe but the ground did cure the issue.


Well it looks like Hatzie you are a one stop shop of info for these systems etc. Just saw the notation in the manuals section over on DP. Thanking you for most of all the uploads of the various manuals for these Chevy's. That had to take some time getting all those scanned. Well you have my thanks thats for sure!!!

Cheers


EDT: Hatzie thanks for the video. That makes it very clear the effect. Surprised it was not part of even these earlier systems by OEM given you still have radios etc and would expect additional elec add ons that could be effected.