Occasional fuel loss?

[Charlie]

Been having, what seems to be, occasional loss of fuel. Sometimes when stopping at convenience store or sitting at a long traffic light, when accelerating bogs down. Try pumping pedal, tries to pick up then bogs again, pump pedal again then picks up and runs fine. Have also noticed been taking more time to start up when cold. Have recently inspected filter and no debris of any kind found.

New fuel tank, sending unit, hoses, in-carb filter December 2017
Carb professionally rebuilt July 2017. 4bbl. Carter, (Rochester) Quadrajet. Well plugs sealed. I think with JB Weld
New fuel pump October 2016.

Any ideas?

 

[1987 GMC Jimmy]

What kind of transmission do you have?

Never mind. I was going to suggest an issue with the torque converter clutch, but yours is too old.

How many miles are on the motor?

 

[Charlie]

What kind of transmission do you have?

TH350. Listed in my info.

 

[hatzie]

Could still be the fuel pump depending on the quality level of the new unit you put in two years ago... and the number of miles you cranked to it in the last two years.

 

[1987 GMC Jimmy]

Yeah, sorry about that. I was gonna suggest an issue with the torque converter clutch, but it’s too old to have lockup. Mine does some of what yours is doing, but I’ve done some testing, and I found that it was the TCC. At least it went away when it was unplugged. I’m going to test it again tomorrow to make sure that’s it because if it’s not, we have the identical problem. And mine only does it in summer. The rest of the year, it’s fine.

 

[Frankenchevy]

I’d install a pressure gauge between the pump and carb. If the pressure checks out, pull the coil wire and fuel line off the carb. Have a buddy crank the engine while you check the volume. If they both check out, it’d likely not be the pump, sender, lines, etc.

 

[Old77]

I've moved this to a more appropriate sub forum rather than it being stuck in "Site News"

 

[Charlie]

UPDATE...

Have not narrowed down the bogging down issue, but have discovered well plugs are leaking. Week before last, did not drive truck for 5 days. Did not plan it, just happened that way. Last week intentionally did not drive for 6 days, looked in carb and manually operated accelerator about 4 or 5 times and only saw 2 spits of gas. Also took longer to start. Now to decide to go back to last shop that rebuilt it 13 months ago or go another route. I am sure he will not warranty that due to time. I mentioned in OP that it was rebuilt professionally, well, carbs and throttle bodies are all they repair.

Is there any permanent fix for the leaking. Seems to be a common issue with quadrajets. I do not know the reason for them to be manufactured that way, but there could be a logical reason.

Any suggestions?

 

[chengny]

UPDATE...

Have not narrowed down the bogging down issue, but have discovered well plugs are leaking. Week before last, did not drive truck for 5 days. Did not plan it, just happened that way. Last week intentionally did not drive for 6 days, looked in carb and manually operated accelerator about 4 or 5 times and only saw 2 spits of gas. Also took longer to start. Now to decide to go back to last shop that rebuilt it 13 months ago or go another route. I am sure he will not warranty that due to time. I mentioned in OP that it was rebuilt professionally, well, carbs and throttle bodies are all they repair.

Is there any permanent fix for the leaking. Seems to be a common issue with quadrajets. I do not know the reason for them to be manufactured that way, but there could be a logical reason.

Any suggestions?

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[Quadrajet Power]

JB weld won’t hold in the carburetors. We see it often, because it is easy to find and buy, but will peel off easily.
We use a 2 part marine epoxy that has to be filed or ground after it hardens.
For stubborn leakers, we thread the well and screw in plugs that are epoxied.

That being said, most well plugs don’t leak, but some do of course.
Today’s fuels evaporate quicker, and the Quadrajet has a fairly small bowl for storage. It is not uncommon for fuel to evaporate enough in a few days of sitting for it to require extra cranking to fill the bowl. A few remedies can be to raise your float level, and remove the clip from the needle, so it will seal when there is no fuel pressure. This prevents backflow out of carb towards pump.

 

[75gmck25]

Most articles on Quadrajet well plug leaks are for Quadrajet carburetors from the sixties and early 70's, and the leak problem was supposed to be mostly fixed by the time square body trucks were produced. It doesn't mean its not a possibility, but its not a real common problem on the later Quadrajets.

If your '74 has a stock carb, you will find that online info for Quadrajet carb versions is confusing. Cars went to a newer version of Quadrajet in about 1975, so an article may refer to one model being used. However, they delayed the change for trucks and continued to use the older model for several years. Always use the number on the carburetor for reference, not the year of the vehicle.

Bruce

 

[1987 GMC Jimmy]

I was wondering if you were still having that carb issue with the hesitation on your Quadrajet. I’m still having mine, where it’s got a really sloppy response on that first takeoff when it’s warm outside but then it’s fine after, and I think it’s a heat soak issue because it doesn’t do it when it’s cool outside, and it’ll bog down in Park that first tap of the gas. I think I’m going to order a phenolic spacer and try that to see if I can insulate it from some of that direct heat conduction from the manifold. If you want, I’ll let you know what happens when I get around to it. I just thought of this, and it seems simple enough to try. Also, if anyone has any thoughts on this, that’d be great.

 

[75gmck25]

Do you already have one of the thick OEM carburetor gaskets? The stock gasket is flexible, and it should be close to about 3/8"-1/2" thick. It should provide quite a bit of insulation just by itself.

I've tried using a phenolic spacer (Mr. Gasket?) with my Quadrajet, but had problems getting it aligned so that the throttle plate did not bind on anything. There is a little play in the bolt holes, and with a spacer you have to get two gaskets, a spacer and the carburetor all properly aligned. I finally decided that I didn't really need the spacer.

Bruce

 

[Charlie]

I had forgotten about this post. Was using fuel pump from Oreilly. Got an AC Delco and original bogging down issue has stopped. May not be just from Oreilly, may have just gone bad.I was able to get warranty for it.

Did resolve to having fuel evaporation when sitting for several days and probably not leaking well plugs. Have not had any other fuel issues for a while, well, except fuel mileage....LOL.

 

[pitterpat]

I have this in my 84 Custom 20, in the past I wouldn't drive or start it for months because I had another truck. Now this is my only truck, as soon as I get new tires I'll be driving it more often.