Carb Help Needed!

[87FrYJ]

Hey everyone! Have been driving my '87 YJ for about a year now(4.3L Chevy swap),
and it has been behaving itself for the most part until recently. It is running a Carter/Quadrajet carb -electric choke
with an external fuel pump that is wired to the key switch.(ignition on fuel pump on).

The issue I have been having is after it is started and warmed up, it wants to die at idle,
has backfired through the carb once or twice while driving and behaves like it's loading up the Carb with gas.
Seems to works while i'm moving, but has died at a few stops now and won't re-start for an hour or so.
I have recently tried to adjust the choke mechanism and understand the basics of how the choke valve
is supposed to operate but I'm not sure it's exactly working like it's supposed to.
I am getting frustrated and don't want to just run out and buy another Carb.

I was hoping someone with some experience with these things might be able to help me out before I have it towed
or limp it to a Carb shop.(Might make it?) I don't know. It starts, and runs right now, but I'm afraid to take it out of the garage at this point
in fear that it will stall out in another busy intersection.

I can float some cash for sure and buy the beers.
Thanks in advance!

 

[DJRENO]

The Quadrajet was/is a Rochester product, not Carter. Q'jets are notoriously tough to get tuned correctly what with their metering rods and all. I'd save myseld some grief and go with a Holley

 

[87FrYJ]

The Quadrajet was/is a Rochester product, not Carter. Q'jets are notoriously tough to get tuned correctly what with their metering rods and all. I'd save myseld some grief and go with a Holley

Carter made Q-Jets under license for GM back in the 70's after there was a fire at the Rochester plant. They were made with Rochester tooling and are identical to the Rochesters except they say Carter on them. You're probably right about switching to something new tho.

 

[DJRENO]

I did not know that. I don't think that changes the fact that they are a pain to deal with. I always had good luck with Hollies and Webers. Never could get Qjets to run right - they always seems to run rich. Likely lack of knowledge on my part.

 

[87FrYJ]

I did not know that. I don't think that changes the fact that they are a pain to deal with. I always had good luck with Hollies and Webers. Never could get Qjets to run right - they always seems to run rich. Likely lack of knowledge on my part.

Thanks DJRENO. I'm looking at replacements as we speak, and have read both good and bad about the QJets. Was surprised to learn about the Carter version as I assumed they were all Rochester also. But sure enough it says "Carter" GM replacement on the side. Go figure. Holley makes a spread bore (#4165) 650cfm that is supposed to be a direct replacement on the existing Qjet manifold but it's $650!! Was really hoping to not have to spend that much right now.

 

[Dr Smash]

I have rebuilt many of those carbs. If it pops through the top of the carb “ stack fires” that’s a lean condition. The first place I would start is check the flow out of the tank. The pick up in an older vehicle might have a plastic strainer in it that has crumbled and the pieces have clogged the tube. Next check your fuel filter from the tank and there is a small one at the fuel inlet at the carb. Put up a picture of your carb.


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[ManNamedJed]

Don't have much to add other than I recently rebuilt a carb and it was easier than I expected. If its older, that would certainly reduce the number of things that could be going wrong.

Also, GM TBI systems are simple and work really well. I have one on my CJ (inline 6) and it always fires right up, passes smog, etc. Looks like you could get something for just a bit more than that new carb.

CHEVROLET Legacy Complete TBI Kit – Affordable Fuel Injection

affordable-fuel-injection.com

 

[wrund]

I used to work on QJets all the time, excellent carb when properly set up. Send me a text 775-737-one six four two

 

[87FrYJ]

I used to work on QJets all the time, excellent carb when properly set up. Send me a text 775-737-one six four two

Thanks wrund! Text sent!!

 

[87FrYJ]

Don't have much to add other than I recently rebuilt a carb and it was easier than I expected. If its older, that would certainly reduce the number of things that could be going wrong.

Also, GM TBI systems are simple and work really well. I have one on my CJ (inline 6) and it always fires right up, passes smog, etc. Looks like you could get something for just a bit more than that new carb.

CHEVROLET Legacy Complete TBI Kit – Affordable Fuel Injection

affordable-fuel-injection.com

Thank you ManNamedJed. I think the engine had TBI in it's old life. It appears to be sitting on an adapter plate of some sort rather than being mated directly to the manifold. I am currently researching every engine and part number I can today to see what my options are. Thanks again for the link.

 

[87FrYJ]

I have rebuilt many of those carbs. If it pops through the top of the carb “ stack fires” that’s a lean condition. The first place I would start is check the flow out of the tank. The pick up in an older vehicle might have a plastic strainer in it that has crumbled and the pieces have clogged the tube. Next check your fuel filter from the tank and there is a small one at the fuel inlet at the carb. Put up a picture of your carb.


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Thanks Dr Smash! It has an aftermarket 23gal tank with an external Carter electronic fuel pump P/N 152-875 which I read is pushing up to 8psi max. It has a cheapo inline fuel filter that looks clean but haven't checked the inlet filter at the carb but will do that tonight. From the numbers it looks to be a 1977 chevy 4bbl for an auto trans, even tho its a manual T176 4speed. Will keep you updated on my progress and thanks again for the info!

 

[Dr Smash]

I had one of those clear filters on my old truck and it looked clean as well but was clogged inside.


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[87FrYJ]

Want to thank wrund for helping on this one! Turns out it was somewhat of a carb issue and a timing issue.
Due to his expertise regarding the Q'jet, he noticed that the adjustment screws on all sides weren't even close to being right, the timing
was off and it was sitting on square bore manifold adapter instead of a spread bore so the secondaries couldn't open if they wanted to.
We replaced the Ignition module in the HEI to be safe, re-timed it and ditched the manifold adapter and it came to life! Still a little fine tuning
to be done but damn what difference. I can't believe I drove it like that for a year thinking it was just a tired 4.3.

Anyway wrund, I can't thank you enough for taking time out of your schedule to come over and help a Brother out. I owe you bigtime.

 

[Superlucky]

One other thing to check.
Take some carb spray and spray it around the throttle plate shaft on both sides. If the idle speeds up, you have a vacuum leak. These carbs are known for wearing out the throttle shaft bushings, causing a vacuum leak and a lean condition.

 

[wrund]

Happy to help, Seth. As mentioned above it had an ignition module going out which was causing a no start / backfire through carb issue. The initial timing was also off a fair amount, the carb was way out of adjustment, and it was sitting on the wrong adapter which prevented the primaries and secondaries from working correctly. The carb itself was fine.

Seth has a nice Jeep, will be great to have him on any upcoming trip.

 

[DJRENO]

Totally off topic, sorta, but still relevant - wrund invited me to check out his rig (and even let me drive it) when I was considering some mods. I took most of his advice (though I didn't go to 5.38s) and am happy as clam in sand. Great member. I'm looking forward to a group run soon.

 

[wrund]

Looks great. Oh, and I want your driveway.

 

[87FrYJ]

Totally off topic, sorta, but still relevant - wrund invited me to check out his rig (and even let me drive it) when I was considering some mods. I took most of his advice (though I didn't go to 5.38s) and am happy as clam in sand. Great member. I'm looking forward to a group run soon.
View attachment 59757

Nice Rig DJRENO!... and X2 on what wrund said. Nice driveway.