Fuel delivery problem - Team Camaro Tech
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post #1 of 14 (permalink) Old Dec 10th, 05, 12:22 PM Thread Starter
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Exclamation Fuel delivery problem

Everything should be fixed now. Intake sealing, valve guides and newly refurbished carb. I still have idling problems. Now it appears that there is a fuel delivery problem. I put a clear in-line filter to protect the carb because I have not dropped the tank yet. The car will die and there is no fuel in the filter. There is fuel in the carb up to the sight plug when it dies. I used screw clamps on the rubber line up to the fuel pump. The line to the tank is open because when I remove the rubber hose fuel siphons out. The fuel pump is a new Delco for this stock engine. Could the pump be bad? Any thoughts? Vapor lock at 50 degress outside?

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post #2 of 14 (permalink) Old Dec 10th, 05, 12:55 PM
 
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Re: Fuel delivery problem

Make sure all fittings and clamps are tight. Check hose and parts for breaks a air leak in the line will cause it not to pull fuel.

This is just one area to check to eliminate questions.
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post #3 of 14 (permalink) Old Dec 10th, 05, 01:09 PM Thread Starter
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Re: Fuel delivery problem

I think I have eliminated hose leaks with the screw clamps. After it sits for a while the clear filter fills up.

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post #4 of 14 (permalink) Old Dec 10th, 05, 01:19 PM
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Re: Fuel delivery problem

Those clear filters often look empty. The solid ones probably do too, we just can't see em. If the bowls are full to the sight plug, it is not dying because of no fuel.





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post #5 of 14 (permalink) Old Dec 10th, 05, 01:33 PM
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Re: Fuel delivery problem

Quote:
Originally Posted by JimM
Those clear filters often look empty. The solid ones probably do too, we just can't see em. If the bowls are full to the sight plug, it is not dying because of no fuel.
Yeah, I agree with these statements 100%. How can it possibly be fuel delivery problem (to the carb) if the float bowls are full? It's gotta be something else.

You mentioned "newly refurbished carb". That would be a prime suspect in my book. It's real easy to use incorrect gasket or leave a small orifice clogged up or maybe a check ball fell out. Lots of ways to mess up a carb overhaul. Maybe try a carb swap, just for a test.

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post #6 of 14 (permalink) Old Dec 10th, 05, 01:51 PM Thread Starter
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Re: Fuel delivery problem

The fuel pump checks out at 7psi. The carb was fixed and tested by JM. I just took it off and re-adjusted the secondary butterflies to just barely cracked open. Full bowls with no fuel in the filter is odd. I test drove it and after it dies it is hard to start almost like vapor lock. Sometimes on the test drive coming up to a stop sign it will just die like it is starving. I am basically back to where I was months ago. ARRHHHHHH!

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post #7 of 14 (permalink) Old Dec 10th, 05, 02:01 PM
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Re: Fuel delivery problem

next test drive, hook up a vacaum guage, tape it to the windsheild, and do not take your eyes off it for a second. It will tell the tale.





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post #8 of 14 (permalink) Old Dec 10th, 05, 02:43 PM Thread Starter
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Re: Fuel delivery problem

Quote:
Originally Posted by JimM
next test drive, hook up a vacaum guage, tape it to the windsheild, and do not take your eyes off it for a second. It will tell the tale.
What to look for?

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post #9 of 14 (permalink) Old Dec 10th, 05, 03:06 PM
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Re: Fuel delivery problem

bouncy needle would be a sign of misfire or vac leak, gradual drop off at idle or constant speed would indicate the motor was "loading up."
You should also check the plugs... tan is good, oily is bad, black is rich, white is lean.
Hook a timing light to each cylinder in turn, make sure they all firing steady. If the vac guage needle has a regular bounce, shine the light on it, one cylinder at a time, will tell you which cylinder has a problem.
How bout some more ifno about when/where it has problems.
What is the temperature where you are?
When the motor is cold and the choke and fast idle are on, will it idle well?
if you kick the choke off right away(manually push the fast idle link down), does it keep running or stall?
Does it run OK at 1500 rpm?
does it run ok at 1500 under load (in gear, moving)?
I'm gonna go reread some of your older posts in the meantime.





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post #10 of 14 (permalink) Old Dec 10th, 05, 03:25 PM
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Re: Fuel delivery problem

ok done reading. This is the Z with the bad valve seals. Been a problem motor for a while, but should be fixed now.
Been questions before about vac guages, too.
The best place to connect for this kind of troubleshooting is someplace that see's both sides of the plenum, the only place that does that is the passage where the pvc connects. If it's only on one side (with a dual plane manifold), it only see's 4 cylinders.
The guage lets you "see" the air moving in the engine. At idle, with a fairly radical cam, reversion will cause the needle to move around some, but it should be even, one move for each cylinder, very regular and fast. If the engine idles slow enough you can count the ticks as each cylinder fires.
When you increase the rpm, the airflow increases and smooths out, the needle gets steady. If it doesn't, something is wrong.
If a cylinder is misfiring, that cylinder won't pull the same vacaum as the others, and the needle will move.
The "point the timing light at the needle" trick can help you find which cylinder is the problems, but remember the timing... the cylinder is firing nearly 180 degrees after the intake valve closes, and a closed intake vavle has no effect on the needle.

Since you just had this all apart again, I'd think about resetting your valve lash, and I'd wonder about your basic tune. Did you set idle speed, mixture, and timing using your vacaum guage?

Your post from the 27th indicated it fired right up and idled stable for 10 minutes, and ran fine. What's changed since then?





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post #11 of 14 (permalink) Old Dec 10th, 05, 04:16 PM Thread Starter
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Re: Fuel delivery problem

Jim, thanks for your patience. I did start it on the 27th with a used carb. It turns out it really was doing the same thing, dying at idle after I posted. It actually sat and idled for about 10 minutes then, started acting up. At that point I said I will wait for my good carb to arrive back to me. I installed the good carb this week. The vacuum gage acts as you say. Jumps about 1-2" range at close to idle, say about 1000 or so. Reving it up smooths it out. I am checking the vacuum on the full vacuum port for the choke hold back. I made John Z's vacuum advance mod, but changed it back until this is figured out. The downside to his mod is with 15 deg of advance, if you lose enough vacuum the lack of timing will kill it anyway. My mind tells me vaccum leak, but the last gaskets before changing the head looked like it was sealing. No water leaks either. With 1.52 roller tips I use .030" gap. They are a little tough to get adjusted with the roller, but obviously I had to reset the gap after installing the heads.

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post #12 of 14 (permalink) Old Dec 10th, 05, 08:21 PM Thread Starter
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Re: Fuel delivery problem

Quote:
Originally Posted by JimM
bouncy needle would be a sign of misfire or vac leak, gradual drop off at idle or constant speed would indicate the motor was "loading up."
You should also check the plugs... tan is good, oily is bad, black is rich, white is lean.
Hook a timing light to each cylinder in turn, make sure they all firing steady. If the vac guage needle has a regular bounce, shine the light on it, one cylinder at a time, will tell you which cylinder has a problem.
How bout some more ifno about when/where it has problems.
What is the temperature where you are?
When the motor is cold and the choke and fast idle are on, will it idle well?
if you kick the choke off right away(manually push the fast idle link down), does it keep running or stall?
Does it run OK at 1500 rpm?
does it run ok at 1500 under load (in gear, moving)?
I'm gonna go reread some of your older posts in the meantime.
I missed this post because of 2 in a row.
1. Plugs are good. Tan. #3 looked a little black.
2. Won't idle cold. The fast idle is not adjusted corectly. The choke works. I need to find the procedure for adjusting the fast idle cam. Bend the tab forward against the cam?
3. Temp was warmed up. T'stat open.
4. Runs fine at 1200 rpm and up. Like a bat outta heck. Idle and under load.
5. It really acts like it is loading up, but no blue smoke or smell.
6. After it quits it can be hard to start like it is flooded or out of fuel. Won't idle very well after that. No indication of flooding. An engine usually misses for a few seconds after it starts when flooded.

I will try the timing light on the vacuum gage if I can tomorrow.

Thanks.

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Last edited by Gary L; Dec 10th, 05 at 08:38 PM.
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post #13 of 14 (permalink) Old Dec 10th, 05, 09:41 PM
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Re: Fuel delivery problem

If you have a leak at the manifold/head junction, you would see it on the guage.
With the guage hooked to the carb port, you are only seeing half the engine (assuming you have a stock type or similar true divided dual plane.)
How much initial are you running? 302's with stock 11:1 compression can be tricky with todays gas, may very probably ping if you put in as much initial as it wants.
You might try up to 20 degrees initial, but get an adjustable advance can, limit it to 10 degrees, and hook it to the choke plloff for full manifold vacaum.
Set your mixture screws for best lean idle using the vacaum guage.
Been forever since I messed with the choke on a holley, but I think you do have to bend that tang to set the fast idle.... unless you can find a screw to do it. My edelbrock has a screw.
Your descriptions 5 & 6 sound very much like it is loading up.

Do your idle mixture screws respond like they should? They should end up about 3/4 turn out for best lean idle, and bottoming either should kill the motor.





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post #14 of 14 (permalink) Old Dec 11th, 05, 05:18 PM Thread Starter
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Re: Fuel delivery problem

OK, I had a little break thru today. It turns out that the primary float level was low and it made a huge difference. Just so you know I was using a temp front bowl because I stripped the inlet fitting from my 35 year old bowl. My replacement will be here Tuesday. I can get a fairly stable idle about 1100 rpm, but it won't make the transition down to full idle at 900.

The timing is set at a conservative 6 deg. The distributor is curved for 36 deg total at 2800 rpm with 28 deg built in. I am not hearing any missing and it runs good 1100 rpm up. I would think it should idle with less timing. The idle screws are out about 1 turn. They won't go less. I may have made a mistake by cracking the seconadry butterflies open. I will try the timing light on the vacuum gage this week when I have more time.

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