1987 Silverado Fuel Issue

[scorpion1110]

Read more than post but this one has be a bit stumped.

Thanks in advance for your help.

I have a 1987 Silverado with TBI

Issue: Wont start.

Ran fine until we had a serious cold snap of 5 degrees.

New parts:

new Fuel pumps and senders both tanks- Bosch
Rebuilt TBI with new injectors

Truck ran fine after new parts install, though only ran on left tank. NEVER tried right.

Current:

Truck wont start.

I tested for spark with an in-line tester and have spark
I tested injectors with a NOID tester and have pulse at injectors.
I ran the fuel pump relay red lead to battery and Fuel pumps ARE NOT clicking on. They also arent coming on at key.


Ideas? Might it be the divertor? I have heard sometimes it sticks so that both tanks are shutdown, but when it was full on left I couldnt get fuel, then I switched to right tank and still none.

I havent checked power at tanks yet, though everything was fine until the cold snap last week. Would the power at the fuel pumps become a sudden issue- from 100% to zero?

What would you recommend as next steps?

Thank you in advance!

[Big Port Jimmy 6]

Check the wiring at the tank selector switch. One set of wires(gray?) is gauge the other (tan) go to the pumps. The colors may be off I have not looked at mine in a while. Jay

[scorpion1110]

Will check wires next.

New fuel pump relay - installed - Issue still exists.

Red jump wire from harness does not activate pumps.

Checked fuses and they look ok.

Not getting juice to fuel pumps. Still looking.

Starting to get annoyed

[motornut]

check wires to pump front to back,mine cracked and i replaced the pump/tank/sender on my 87 ,then found a cut/nick over rear wheel,hard baked and green

[scorpion1110]

I have decided I must be losing my mind. I have never dealt with a car issue that has ticked me off this much:

Here is where we are:

Fuel pumps will not come on.

I have:

• Confirmed spark - have spark
• Verified a pulse to injectors - will start with gas in TBI
• Confirmed that check engine light works - it does
• checked all fuses - none fried
• Checked wiring and see no issues - no breaks and grounds look good
• Checked codes with paper clip- I get 12 just cycling - no other codes
• Tried to run a lead from positive BAT to red pigtail on Fuel pump relay- nothing happens
• Replaced fuel pump relay - nothing happens, no change

The pumps are new and I have never run the passenger pump. All was fine until we got to five degrees outside temperature.

At this point I THINK there might be two issues- I think diverter may be bad as is ECM. Though I read that a bad ICM at distributor can not feed power back to the pumps. Thoughts?

Couple questions:

• Make sense that an ECM just dies?
• When fully disconnect fuel pumps harnesses, gas gauge pegs to right. Reconnect and insert key and they go to half which is where left side is. Right should be at quarter. Suggests some power back there.
• Cant get right tank at all. Never tried til now so diverter could have been bad for a while. Truck sat for years so gas was varnish.

I am seriously fried on this truck and am reading far too many posts of guys getting stuck cause of fuel starvation- great design

Any help would be appreciated

[Big Port Jimmy 6]

You need to pull the glove box and check at the ecm. A1 is the Fuel pump pin on a 1227747 ecm (http://www.chevythunder.com/1227747_ecm_198892.htm)
This Diagram will be helpful also.

Jay

[gchemist]

Welcome to the site. Does it run for a few seconds with fuel poured down the TBI? If so, it's a fuel delivery problem. Send me a PM with your email address. I'll send you a PDF file with TBI troubleshooting info.

[scorpion1110]

I am bringing this to the top because the darn thing is still not running.

The weather has been crap so I have been doing what I can.

Here is where it is:

• ICM replaced
  New cap and rotor
• Fuel pump relay replaced
• tank selector switch replaced
• ECM B fuse hot slot hot at both sides

Also:

Rebuilt TBI with new injectors
New fuel pump senders and Bosch pumps

I cannot run 12 volts off the pigtail at the fuel pump relay and get anything at the pumps. I checked continuity at the FP relay pigtail and the ECM smaller connector pin shows continuity at tan white. I can also see continuity from the tank selector switch to the left pump which is my test side. But I cannot get it through the entire circuit. The fuel pump senders however have continuity if I run from the relay to the non tan terminal.

Have spark and a NOID tester shows a pulse at injectors.

I checked grounds at tanks and made sure they were good. I made sure that the fuel pump relay was tight at fire wall.

I also ran a direct hot bypassing the system to the pumps and heard them gurgle which makes sense since they are both new.

Key to run shows the check engine light on and a paperclip jump in the OBD1 tester gives me a 12 which should suggest that the ECM is functioning. I cant get a code because the battery took a powder when Maryland decided to become Siberia for 3 months and killed it.

Been through the troubleshooting guide and it says fuel pump relay. I tested new and old and they both click when I put current at opposite pins.

I have been playing with old cars since I was 15 and this is the first time this has happened- not being able to figure out the problem.

I am trying to avoid rollbacking this to a shop and then incurring that cost and the cost of a from scratch troubleshoot.

As soon as it starts it goes on Craigslist.

Any help would be appreciated.

I just ordered a new ECM but I dont think thats the problem.

[rfmaster]

ECM is not an issue

What you need to is to trace where FP circuit loses power. Since you have tried applying +12volts at the FP relay pig tail the problem is between FP relay socket and fuel pumps.

It is common for the fuel selector (diverter switch ) to fail. Big port Jimmy 6 was kind to post a schematic which is should be your guide.

To start I would remove FP relay from its socket and examine condition of the socket. You should see two smaller contacts which are used by ECM to power up relay coil and 3x larger (1/4") contacts. The three wires are:
Orange, NO: +B (12 volts from battery, always on!)
RED, NC: - this circuit is used to prime or bypass relay when ignition is on
Gray, Common: - this is the down stream circuit toward FP. You can apply +12 and one of the two FP' should turn on immediately.

In the photo below FP and FP socket (damaged) from car line, truck is very similar and has a red pig tail pin.



Relay and socket came out of Camaro which suffered from intermittent shut downs. Problem was narrowed down to a faulty FP socket - relay!

//RF

[scorpion1110]

Thanks for the info. This weekend the prop valve started leaking again- its the second new one. Still has fuel issue.

Thats it for me on this truck.

Friend offered me cash and a 1969 SBC counter replacement block (block/crank/rods/pistons/windage tray/oil pan) for it. So I cut my losses and got the planter out of the driveway.

Thanks for the help.

No trucks for me after 72 ever again.

S

[cadillac_al]

Those old TBI systems are usually very reliable. I would have bet on the ECM. I think the fuel pump relay gets it's signal from the ECM. Oh well I'm sure you don't want to think about it ever again. What is a 69 sbc counter replacement block? 350?

[scorpion1110]

I was thinking that way too. But when the prop valve started leaking again, I just decided to dump it. My friend will use it as a plow truck once he sorts it out.

The 69 block/engine was sold by the dealer as a replacement or was a warranty install. They have some value because they can technically make a non-matching numbers car/truck matching numbers. Its a 350. I am picking it up this weekend. Havent decided what to do with it- but it will probably be for sale unless I find a new project for it.

[scorpion1110]

Just talked to my friend who bought this.

He popped in a new ECM, the Truck ran for about 45 seconds and then shut down. He said it fried the ECM- could smell it.

So the diagnostic told me it wasnt bad, though I had a hunch - turns out it was.

So ideas what would fry it?

Even though its not my headache any more- I do want him to get it running.

Thanks as always.

S