LarMan

1973 vette
DUI HEI ignition
Carter fuel pump
Small block
4 speed

2nd time out of neighborhood after fresh motor install. First time was last night. Motor was dropped in a few months back. After some initial work to rebuild the carb, get timing set, idle set, car has been running great. Couldn't be happier. It pulls well. New motor probably has 12-15 miles on it. (I'm slow and in no hurry.)

I drove this morning to gas up (3 miles away; 10 gallons, 93 octane ) and then a quick-lube place (1 mile from there) for a long overdue inspection. Pull into the inspection place and back into a spot. Turn the key to kill the car and it knocks and sputters a few times before shutting off. ???? I thought I was going to backfire. Seemed odd. Has NEVER done that before (new or old motor). Tried to start it. New starter spins the motor fine but it will not light off. Not even a pop. Nothing.

Seems to be spark, ignition related.
Fuel pump runs fine.
Can't image bad gas is the culprit.
Ignition wires and spark wires all look good. Nothing is obvious.

Any thoughts on where to start troubleshooting?

The is the really frustrating part of this hobby. Thought I had the car sorted out. But it is an opportunity to learn. ;-)

Thanks.

Larry
Houston, Tx

zwede

Sounds like it "dieseled" (run-on). Common with carbed motors especially if the idle speed is a bit high. My '71 had an "anti-dieseling" function where it would turn on the AC when shutting it off. The extra drag of the AC would kill it. Other ways are to shut it off in drive, or drag the clutch.

Once it dieseled it pulled raw fuel into the motor and wet the plugs which is why it wouldn't start. It's been an hour since your post so it probably started by now once the plugs dried.

SPCL FX

Check to make sure the wire to the distributor is still connected, if good there pull #1 plug find out if you have spark , if so then check to be sure your getting gas ! Best of luck ! Let us know how it turns out!! 😎

Kevin68

I'd start over again getting the timing set.

Mine will diesel if I turn it off the engine before it has returned to idle for a few seconds. But it always starts back up.

Recheck plug/coil wires?

How do you know the fuel pump is working? electric?

I don't think it could vapor lock in 3 miles. Try letting it sit for 20-30 minutes and try again.

Procrastination Racing

Gas, air, and fire - it takes all three.

Check spark is easy, pull a plug wire and hold it near some metal, especially with a paper clip in the end, and see if it sparks when cranking.

With the air cleaner off, pump the throttle or the accelerator pump plunger by hand and see if gas squirts in the carb.

Air cleaner plugged? (not likely) If you even question it, leave the lid off to start but have it handy in case a fire ball pops out of the carb.



Flooding can give you fits. If the car has been sitting, the float could have stuck or you could have the needle valve stuck open. Also, if you still have a Quadrajet on it, and it has the original type composite float, it could have dried and cracked and then soaked with gas. That means it sinks, opening the needle valve and flooding the carb. The dieseling could be a sign you shut off rich or flooded.

If flooding is bad enough, you will see gas flowing over the throttle opening from the fuel bowl.

If flooding is the issue, prop the throttle open and let it air out so the gas puddled in the intake can evaporate. After awhile, try to start without pumping the throttle. You may have to keep the RPMs up to get back home.




Is the Carter fuel pump electric? If so, it could be putting 10 / 15 psi on the carb. You only need about 4-5 psi on the street. If you have too much pressure, it will push open the needle valve and flood the carb.

If you have this, then disconnect the pump electric wire, start the car and run the gas out, and then connect the pump back. Go straight home and buy a fuel pressure regulator before getting stranded again.

LarMan

So after the car rests for several hours (5-6), I plan to start troubling shooting it. Before I do it, I try to start it one last time. Of course, it fires right off. Runs fine but the idle is now 1200rpms vs about 800-900. I've since turned it down to 800.

I'd rather it not have started than have fixed itself, only to leave me stranded later. :-)

Thanks for your help. This very well may have been what happened. By the way, it on sputtered a few times, less than a second.

LarMan

All connections look good. Please see my other response to the first reply.

LarMan

I very well might have blipped the throttle before killing it. Also, it seems the idle had crept up in the 10 minutes I was on the road from 8--900 to 1200.

Wires all seem fine. Fuel pump is electric and is working.

Thanks.

LarMan

Thanks. All very helpful. See other note about the car starting up fine after 5-6 hours.

This model of electric fuel pump only pumps out lower psi for carved motors. Built in regulator I suppose. I ran this set up on the old motor and this carb for a few months with no problems of flooding.

But if it was flooded, wouldn't it at least pop and sputter a bit? I cranked on it 10 different times over an hour and never heard it fire off even once.

Yes, it's a Quadra jet. Recent rebuilt it. Float is in good shape plus new needle, etc.

Thanks again.

StreetLegalH2R

I used to have this identical problem with a '69 on particularly warm days. It turned out to be vapor lock. I had an aftermarket Holley carb on it with a split fuel rail that set right above the intake. Moved fuel rail away from extreme heat source; problem solved.

C3 4ME

If it was flooded from the dieseling, which as I read was not confirmed, but if so, try mashing the gas to the floor when cranking and holding it there while cranking and obviously, let off immediately if it starts. That's the way I was taught to start a flooded car and have had success doing it that way.

Robert Thomas

Sounds like the timing's too far advanced to me. You might grab the distributor and make sure it can't be turned and recheck the timing.

bj1k

If the idle is too high it will definitely diesel and knock before shutting down sometimes flooding the engine.