Update - Tune Parts are In - - Now What???

[Zilverado]

Sorry for the lengthy post here, but I need your help. In an attempt to fix a rough running/stalling condition, the following parts have gone in:

- Plugs
- Wires
- Dist. cap
- Rotor
- Air filter
- Air breather
- PCV
- Fuel filter
- and of course - - oil and filter change.

So I start it up to fill the oil filter. Runs great, oil light goes off, and I shut it down to top up the oil. Start it up again, runs great for about 15 secs, then starts to slow, eventually loping badly (rich exhaust). Rev it up and things clear slightly, but very quickly she slows and eventually lopes to a stall. Starting again is difficult and even reving up is rough.

Before anyone suggests it, I'm pretty confident I got the plug wires in the right order - and this condition existed before the work was done.

So does this sound like a carburation issue? I was thinking of maybe removing the top of the carb and cleaning things up a bit (as opposed to a full rebuid - due mainly to time). How can I tell which carb I have - I have attached some photos? Where are the fuel mix adjustments?

Again sorry for all the questions, but just want to get this fixed. Thanks.

[msgross]

did you also change the carb fuel filter (located where the fuel line enters the carb)? you will find numbers for your carb on the side near the throttle lever I think... you can get a rebuild kit with those but then someone has to do the job. Could be float issue as well... Q-jets are worth rebuilding so it might not hurt to look into that.

[Zilverado]

The carb filter is the only one I changed - - is there another one? It was pretty dirty.

As for the carb, if I did the rebuild, I would likely do it myself. I've got a good garage of tools and 20+ years of "weekend wrenching" at my disposal. Although it's been about 23 yrs since I did a carb rebuild on my first car - - '77 Plymouth.

Someone on this board suggested I could maybe do a float/bowl cleaning by simply removing the top of the carb, so that's what I was thinking of - - if that would work.

Another thing I forgot to mention before...

This problem came up suddenly. Drove the truck one weekend and all was well, a few days later, she'll barely go.

[msgross]

I would imagine that you have another frame mounted fuel filter. Follow the line baack to you tank and you're sure to find it. I don't that it's your culprit but if you have changed everything else then it can't hurt.

[Rc 415]

Is the choke pull off good?

[Zilverado]

Originally Posted by Rc 415

Is the choke pull off good?

Ok, while I have done alot and continue to do most of my own maintenance work, you'll have to take it a little slow when it comes to carb jargin.

If you are asking if the choke is functioning, my guess is "yes". The reason I say this is because even with the engine hot (after driving quite a while), and the choke completely open, the problem is the same.

Although, when the engine was running poorly today - first start, cold condition - the choke light stayed dimly on. I've never really notice this before.

[Rc 415]

Ok, the part outlined in red is your choke, you have an electric choke, and your carb appears to be a Rochester E4ME http://www.tocmp.com/manuals/Carbs/R...age064_jpg.htm
http://www.partschoice.com/carbs/tec...jet-index.html
The part outlined in blue is your choke pulloff, this holds the choke upen while the engine is cold. To see if it is working properly, push the lever coming out of the end of it in, and hold it in, then take a pair of needle nose pliers and pinch the vacuum tube that is attached to the choke pulloff, it is outlined in yellow. Then, let go of the lever and see if it stays in the pushed in, if it does not the choke pull offs seal is bad, and the whole part will need to be replaced.

[Zilverado]

Thanks for you patience Man - I appreciate it.

I went to check, and no the rod in the pull off does not stay in. It slowly slides back out (in about 5 sec). Even after removing the hose, and putting my finger over the end of the steel tube from the pick up, it still works the same.

So, please clarify for me... which butterflies are the choke - the BIG ones in hte back? I thought it was the smaller one in front. What position should the butterflies be in when the engine is first started - cause they are all closed. After warming up, the only one that is open is the front one.

[Rc 415]

To tell you the truth, I'm not sure what it does, all I know is my truck ran just like you are saying, I replaced the choke pull off, and it started running great again.

[84slopwaggin]

Well if its not holding vacuum it's definitely bad, so it's not a bad idea to change it. I also heard that the float can sometimes get holes in them and this leads to the carb running rich. I'm not sure if this only applies to Holleys or not. After you replace the choke pull off valve you can take a vacuum guage and readjust your carb. There should be a couple of tiny screws on front of the carb near the base on each side. A special tool or super tiny screw driver is needed to make the adjustment.

[poff]

The choke is the top butterfly plate in the front. The choke pull off uses ported vacuum, like the vacuum advance, to open the choke when the engine is off-idle. If you do not have a vacuum gauge, find a manifold vacuum port and hook it to the pull-off, it should open the choke. You may need to open the throttle plate a RCH just so the pull-off doesn't bind up (it's made to pull off when you hit the throttle). Your PCV and brake booster are manifold vacuum. You may need a DD socket to adjust the mixture screws, depends on the years. Most of the pro tool companies have a carb adjusting tool. http://buy1.snapon.com/catalog/item....re&dir=catalog Well worth the money in my opinion, keeps your fingers out of belts, fans and pulleys. As stated earlier, check the electric choke as well. Basically if it runs bad at idle it is probably not the pull-off, if it runs bad off-idle check the pull-off. That carb looks like it is in decent shape. What ever you do not trade it in for a rebuilt carb. If you buy a rebuilt carb keep that one, do not take it in as a core. The Q-Jets that you get from autopart stores are usually beat and have been rebuilt too many times.

[Zilverado]

Originally Posted by poff

...That carb looks like it is in decent shape. What ever you do not trade it in for a rebuilt carb. If you buy a rebuilt carb keep that one, do not take it in as a core. The Q-Jets that you get from autopart stores are usually beat and have been rebuilt too many times.

Yeah, the carb does look pretty good all things considered. I assume it is original to the engine, which only has around 100,000 miles on it.

Like I said earlier, this engine has run great up until just a week ago, when suddenly she won't idle - - hot or cold. I do not think this is choke related, because even with the engine at operating temp, and the choke butterfly all the way open, it runs poorly.

I spoke to a local carb rebuild place this morning. They agreed that I would be better off to have this original rebuilt (since it was originally working so well with the engine). They suggested around $250 for a rebuild (plus another $45 for the choke pull-off if required). These are Canadian prices.

It was also suggested to me that I should try and shoot some air through the carb to see if possibly the jets or ports have clogged up. I'll probably give it some shots of carb cleaner as well and then turn the compressor on it.

Any other thoughts?

[Malo83]

Originally Posted by Zilverado

Sorry for the lengthy post here, but I need your help. In an attempt to fix a rough running/stalling condition, the following parts have gone in:

- Plugs
- Wires
- Dist. cap
- Rotor
- Air filter
- Air breather
- PCV
- Fuel filter
- and of course - - oil and filter change.

So I start it up to fill the oil filter. Runs great, oil light goes off, and I shut it down to top up the oil. Start it up again, runs great for about 15 secs, then starts to slow, eventually loping badly (rich exhaust). Rev it up and things clear slightly, but very quickly she slows and eventually lopes to a stall. Starting again is difficult and even reving up is rough.

Before anyone suggests it, I'm pretty confident I got the plug wires in the right order - and this condition existed before the work was done.

So does this sound like a carburation issue? I was thinking of maybe removing the top of the carb and cleaning things up a bit (as opposed to a full rebuid - due mainly to time). How can I tell which carb I have - I have attached some photos? Where are the fuel mix adjustments?

Again sorry for all the questions, but just want to get this fixed. Thanks.

Zilverado your carb is a M4ME Qjet, first thing is get a big can of carb cleaner and spray the outside of the carb and get all that gum and varnish buildup off as well as spraying really well down the PRIMARY THROTTLE BORES working the butterflys, looking at the Chevy Factory manual under Carb troubleshooting it states these as possible culprits
Loose,broken or incorrect vacuum hose routing.
Choke valve not operating properly
Choke heater system malfunctioning
Fast idle speed low when cold
Choke valve sticking or binding
Fuel pump
Malfunction in accelarator pump system
Choke valve not closing
Insufficient fuel in bowl
Clogged or malfunctioning PCV system
Air leaks into carburetor bores beneath throttle valves, manifold leaks and or vacuum leaks.

Good way to find those vacuum leaks is to start the truck and spray Carb cleaner around the base of the carb and around the various vacuum lines and see if the RPM changes, if it does you have found your leak.
The idle mixture screws are located on the bottom front of the carb beneath the fuel filter, you might have plugs over them, easy to pop off then you can make your adjustments, if you adjust, turn them all the way in C/W then back out 3 complete turns for the initial adjustment then adjust each one to obtain your best idle. If all else fails it 's probably time for a carb rebuild, and it's best to keep the old carb. Hope this helps.
John

[Zilverado]

Thanks for the info John. I'll definitely be looking for my Factory Service Manuals tonight - - we recently painted a couple of rooms in the house, and the books got moved to ????

I'll do a little cleaning of the carb to start, and see if that maybe helps. It might be tricky trying to test systems with the truck running, since it does not want to stay running.

I've got a vaccuum tester, so I'll have to test some lines and see what happens.

Also, could you please clarify what the butterflies I see from the top are (in case I can't find my manuals tonight)? This is what I am thinking...

- Front (long narrow) - choke
- Rear top (large "roundish") - secondary throttle (open when mashing the skinny pedal)
- and primary throttle - is located beneath the secondaries?

Thanks again for the help. I'll be in touch.

[Malo83]

Originally Posted by Zilverado

Thanks for the info John. I'll definitely be looking for my Factory Service Manuals tonight - - we recently painted a couple of rooms in the house, and the books got moved to ????

I'll do a little cleaning of the carb to start, and see if that maybe helps. It might be tricky trying to test systems with the truck running, since it does not want to stay running.

I've got a vaccuum tester, so I'll have to test some lines and see what happens.

Also, could you please clarify what the butterflies I see from the top are (in case I can't find my manuals tonight)? This is what I am thinking...

- Front (long narrow) - choke
- Rear top (large "roundish") - secondary throttle (open when mashing the skinny pedal)
- and primary throttle - is located beneath the secondaries?

Thanks again for the help. I'll be in touch.

The Primary throttle valves (small) are located under the choke butterfly, looking straight down the carb as you work the throttle linkage you'll see them open, and the larger rear valves are the secondary throttle valves.
John

[WorkinLonghorn]

You posted in another thread that you were getting black smoke and that the choke valve was open all the way. That leaves float-bowl level too high as the next logical area to check. If it's been 100,000 miles It's due for a "rebuild" anyway so just do it and you will be happy you did,believe me. Do it yourself,it's easy,interesting,and you will be satisfied in your own ability to fix your truck yourself,and you'll be reminded every time you stab the peddle and feel all that re-newed power.

[Eyegore]

This is a great thread first of all. Malo83 I have a question for you.. if the engine runs cooler (I live in phoenix so we have them set to run cooler because of the heat) can this effect the choke? I can't my 86 to pass emissions and I believe that this may be the culprit. How do you fix the choke heater malfunctioning?

Tom

[Zilverado]

Originally Posted by WorkinLonghorn

You posted in another thread that you were getting black smoke and that the choke valve was open all the way. That leaves float-bowl level too high as the next logical area to check. If it's been 100,000 miles It's due for a "rebuild" anyway so just do it and you will be happy you did,believe me. Do it yourself,it's easy,interesting,and you will be satisfied in your own ability to fix your truck yourself,and you'll be reminded every time you stab the peddle and feel all that re-newed power.

The choke was open all the way when the engine was at operating temp, not when cold. The rough running symptoms are the same whether the engine is hot or cold. Also, manually manipulating the choke (i.e. forcing it open of closed by hand) does not seem to effect the running condition.

My gut is just telling me this thing is not getting the fuel it needs. And the sudden on-set of this condition (i.e. overnight), tells me there is a "catastrophic" failure somewhere. I'm thinking I may replace the fuel pump and see what happens. It's less than $30 and easy to get at, so that's maybe the next step.

I would also like to take the time to rebuild the carb, but if that ends up not being the current issue, then that may wait till later....

[piecesparts]

[QUOTE=Rc 415;2087165]Is the choke pull off good?[/QUOTE



I agree, check the choke.

[xtreme80]

This sounds more like a "too much" fuel issue rather than not enough. Before you spend 30 bucks on a fuel pump, try spending around that on a carb rebuild kit. It's a simple thing to do, and more than likely, you have fuel seeping through the gaskets. You probably have a mechanical fuel pump right? I don't even think it would be worth it to spend money on a new one.

When my carb decided to start leaking, it did it all at once. It was running fine, I shut it off, and literally the next time I fired it (an hour later or so) it started leaking. We rebuilt it, and everything that was causing the flooding that I rebuilt worked great and still did even when I replaced it with an Edelbrock.

I can't stress enough about how good it would be to just rebuild your carb. If anything, just replace the gaskets, float, and accelerater pump spring and sleeve. You also said you had a rich condition, so that would generally mean too much fuel.

[Zilverado]

Originally Posted by piecesparts

I agree, check the choke.

So, again, I certainly am not a carburation expert (as evidenced by all the questions), but my understanding is that choke operation becomes a mute point once the engine is hot (operating temp) and the choke butterfly is open. Right???

'cause my symptoms are the same whether the engine is cold (choking) or hot (choke open).

From testing the pull-off yesterday I'd say "yes, it's not working 100%" but once the engine warms up (driving 1/2 hour) and the choke is open it shouldn't matter should it?

[Zilverado]

Originally Posted by xtreme80

This sounds more like a "too much" fuel issue rather than not enough. Before you spend 30 bucks on a fuel pump, try spending around that on a carb rebuild kit. It's a simple thing to do, and more than likely, you have fuel seeping through the gaskets. You probably have a mechanical fuel pump right? I don't even think it would be worth it to spend money on a new one.

Yes, it's a mechanical pump.

Originally Posted by xtreme80

When my carb decided to start leaking, it did it all at once. It was running fine, I shut it off, and literally the next time I fired it (an hour later or so) it started leaking...

Leaking from where? Was fuel leaking to the exterior of the carb? Mine seems dry.

Originally Posted by xtreme80

I can't stress enough about how good it would be to just rebuild your carb. If anything, just replace the gaskets, float, and accelerater pump spring and sleeve...

Yes, I agree - it does feel good to fix things yourself. But in addition to the satisfaction, I've saved thousands of dollars over the years doing things myself. It's paid for all the fancy tools and my nice garage (or a part of it).

Originally Posted by xtreme80

You also said you had a rich condition, so that would generally mean too much fuel.

I'm not sure it is "rich" - - that's just what I'm calling it. It's just the exhaust smell you get when an engine is mis-firing, and loping to try and stay running...

[piecesparts]

Originally Posted by Zilverado

So, again, I certainly am not a carburation expert (as evidenced by all the questions), but my understanding is that choke operation becomes a mute point once the engine is hot (operating temp) and the choke butterfly is open. Right???

'cause my symptoms are the same whether the engine is cold (choking) or hot (choke open).

From testing the pull-off yesterday I'd say "yes, it's not working 100%" but once the engine warms up (driving 1/2 hour) and the choke is open it shouldn't matter should it?

Are you sure that the choke is opening all the way. If the butterfly is not all the way off of the closed position, then you could be overfueling your engine and the choke pull-off is the part that does that. That situation would happen, even if your engine is hot. At least start there and make sure the choke is not the problem.

[Zilverado]

Originally Posted by piecesparts

Are you sure that the choke is opening all the way. If the butterfly is not all the way off of the closed position, then you could be overfueling your engine and the choke pull-off is the part that does that. That situation would happen, even if your engine is hot. At least start there and make sure the choke is not the problem.

Understood - - but yes, when hot, the butterfly was 100% vertical and open fully. When cold, she closes of as expected.

[xtreme80]

Leaking from where? Was fuel leaking to the exterior of the carb? Mine seems dry.

Occasionally it will leak to the exterior, but mine was leaking down into the carb, thus dumping more fuel in it than it should be.

I'm not sure it is "rich" - - that's just what I'm calling it. It's just the exhaust smell you get when an engine is mis-firing, and loping to try and stay running...

The best way I can describe a rich smell, is that it smells a little more like gasoline than regular exhaust fumes would. It's not going to smell like gas it being poured out, but it will have a hint of that smell... if that makes sense, lol.