Cliff's Quadrajet Parts and Rebuild Kits
Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: 67elco on September 24, 2024, 07:31:58 PM
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Hi everyone, I come from the LS platform, haven't had a carb'd car in almost 20 years so pardon my ignorance.
67 El Camino, 327, 4 speed, engine is bone stock. Previous owner put this carb on but was missing all the choke components. When I bought it, it ran fine, until one day it left me stranded and fuel was gushing out of the choke mechanism on the passenger side. I spoke to Cliff and bought one of his kits and installed it. I set the float at 1/4" below the max height. Idle mixture screws are about 2 1/2 turns out, choke mechanism parts are all installed and adjusted per the book. Did the bushing kit on the primary blades, made sure everything was indexed correctly, very minimal gaps around the blades when held up to the light.
Car turned over on the first crank, but ran very poorly for about 15-20 seconds and then shut off. I did not see any major dripping when looking down the choke plate at the boosters, but a tiny bit of fuel on them. I also noticed the gasket was damp with fuel. Tried to restart 3-4 more times, with no luck, wouldn't even sputter a bit like it's trying to catch. Made sure the fuel tank has fuel in it as well.
I have not messed with the timing as it ran fine prior to the rebuild. I did replace the plugs as they looked fouled. I don't want to keep trying to crank it over as I don't want to wash out the cylinders with fuel. Running out of ideas on what to adjust to get this thing running correctly.
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Sounds like the choke pull-off is not working.
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I replaced the choke pull off, hose, and the rods with all new parts. This has a divorced choke, and I also l replaced the coil on the intake manifold.
What testing can I do to ensure it's working properly?
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The p-o should open the choke blade about a quarter of an inch at lower (front) edge at cold start.
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I hooked up a vacuum tester to the port on the pull off and it retracts fully. I had to manually move the lever though to get the cam to engage and open the choke about 1/4". I then cranked the car over and it started and ran for a few minutes. It was running super rich and adjusting the idle mixture screws did nothing. It was idling a bit high, and as it was getting warmer I was adjusting the idle down when it stalled and wouldn't restart.
The previous owner had a small spacer between the carb and intake manifold which I did not re-install originally. I added that back on, as I was thinking that maybe there was vacuum leak and it still wouldn't crank. When it did run, the gauge wasn't moving (plugged into the passenger front port).
I did notice that when you press the throttle down, it does not set the choke at a 1/4". If I manually move the lever it'll set, but the moment I press the throttle, it'll shut the choke completely. I've attached some photos of the linkage on that side, I'm assuming something must be wrong in how I have everything routed.
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Starting a cold engine with carb beginns with pushing the throttle once, then remove foot.
This settles the choke in closed position.
Turn the key and engine starts and p-o opens the choke blade 1/4". Three minutes later the choke is fully open by the bimetal spring in choke on manifold.
I noticed on your last pic there is a vaccum tube missing in the front piedestal for the p-o bracket. This is a vacuum leak if not corrected.
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In the last photo if you look closely, you can see that hose was disconnected for testing the break and the clear hose is attached. Once I was done, the line was reattached.
When depressing the throttle pedal once, the lever is not moving the choke into the correct position. Based on the photos I attached, is my linkage assembled wrong? And if so, what can I adjust to fix that? I'm not sure that's the entire problem with it running poorly, but I'll try anything at this point.
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In this pic you can see the vacuum tube your carb is missing.
HTH
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I may be wrong but it looks like the rod from choke to carb is too short.
When choke is closed the rod should be at the bottom of its travel moving upwards when heated.
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Fortunately I have a spare quadrajet (same model # as mine) I was able to transfer that tube over and I capped it with a plug. It cranked over pretty quickly, but it ran way worse (didn't think that was possible), but with my vacuum gauge plugged in, it was showing near 5 inches/hg, whereas before it wouldn't show any vacuum at all.
Again, screwing in the idle screws down to 1.5 to 2.0 turns did nothing. With the choke closed, it won't restart, but if I wedge a screwdriver in the choke flap, it did crank over and fire after a lot of cranking, but again, ran horribly.
I really don't want to hurt this motor, should I pull the carb back off and go through it again? Any benefit in using a smoke machine to look for vacuum leaks that are not from the carb since I can't run the motor?
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You may have fuel inlet system issues. If lift clip on inlet needle is used it should be hung from behind on float arm, NOT in one of the holes in float arm as this will bind the needle and cause flooding.
I always turn the carb upside down, connect the vacuum pump to inlet fitting to check it holds vacuum before mounting the carb.
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I pulled the top off the carb just now and verified the clip on the needle was hung correctly on the float arm. I adjusted the float height lower slightly as well. Needle was moving smoothly in and out of the seat.
I removed the old spacer as I found it was causing a vacuum leak, so now it's just intake manifold, gasket, and then carb.
I installed a fuel pressure gauge between the pump and carb, and it's consistently reading between 8-9 psi.
I swapped in a new fuel filter as the old one looked like it had been in there for a long time. Old one wasn't clogged, but it was dirty.
I also adjusted the choke flap rod to be slightly less curved. It still is not setting the choke flap in the proper position on one pump of the accelerator pedal.
The car turned on, but ran like it was on 7 cylinders. It ran for maybe 2 mins at most, but afterwards I used my IR thermometer on the exhaust manifold and noticed cylinder 1 was colder than the others. Pulled the spark plug out and it was slightly wet with fuel, double checked the gap and it was a bit wide, so I gapped it down .035.
Checked the plug wire on #1, it was fine. Checked the distributor cap, looks very clean and inside and the rotor looked almost new, very clean as well.
Tested the ignition coil resistance and it was around 12.3 from the side posts to the center, and roughly 1.5 from side post to side post.
Pulled the left valve cover and lash on the #1 cyl rocker felt the same as all the others, no indication of a mechanical problem.
Car still won't run unless it's sat for 4-5 hours, and then runs once, very poorly and won't stay running.
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If it has 8-9 lbs. fuel pressure it could be flooding.
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I ordered a regulator, hopefully that will help. The fuel pump on the car is aftermarket, but unknown what brand.
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Fuel pressure isn't the issue, that carb will EASILY take 7-8 psi if not a tad more w/o issues.
You mentioned "stock" engine. Did you use the correct gasket and stainless steel shim gasket, then the carburetor?
Those parts are REQUIRED in that order or the engine will not run well, if at all due to a HUGE leak at the hot-slot allowing butt-loads of exhaust gasses into your engine.........
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Originally, the car had a thin gasket, stainless gasket that had rtv on it for some reason, and then what appears to be a 1/4" spacer. I did not reuse the stainless gasket as it was damaged. I tried running the car with the new gasket from your kit and the spacer and it ran horribly.
I'm assuming the stainless gasket will need to be replaced and then reattempt.
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Is your coil reading 12.3 ohms or 12.3 K (Thousand) ohms? If it actually is 12.3 ohms from the center to either side of the coil, It is shot. 1.5 ohms from side to side sounds about right.
Off the top of my head you should see 5~8 thousand ohms from the center post to either side.
Just had a bad coil myself this past week. My fathers 54 Jaguar would start to act up and die after 30 min or so of driving. Then it would re-start after a cool down. Ended up being the coil, I brought a spare along and swapped it on the side of the road and it fired immediately.
The old coil would gain 1000 ohms from cold to hot. No good.
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With the heat shield installed, and the old spacer, it finally ran decently. I was able set the idle, and the fast idle also appeared to work correctly and kick down. With the vacuum gauge hooked up, it was showing around 18-20 under light throttle.
It seemed happy to idle at around 850-900 rpms, but I did notice that at idle it was still running rich. Adjusting the idle screws in further did not appear to make any difference.
On a hot start, it cranks over with no throttle input, which is nice. On a dead cold start, one pump of the accelerator would set the choke about 1/4" open, but it would not crank over well at all. If any one has pointers on setting up a divorced choke, please let me know.
I have some bad belt squeal when revving it more than 50%, which I suspect is due to the alternator being misaligned with the other pulleys.
I'm embarrassed about not knowing about the hot slot, but here we are.
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One pump on accelerator with cold engine should set the choke 100% closed, no more no less.
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If you are using a 1967-69 SBC cast iron intake with the "hot-slot" the slotted gasket goes against the intake, then the steel shim gasket, then the carburetor.
No need for any additional gaskets or spacers and adding them will make the divorced choke rod too short and you may have leaks on the long side of the exhaust slot.
I would return to the stock set-up under the carb and start your testing over. I stock those gaskets if you need one, they are discontinued by many manufacturers and getting difficult to find......
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Got it, I will definitely do that. The spacer the car came with is really old and it's also not giving much thread engagement on the studs. And yes, it's still the original cast iron intake.