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Still got problems...

21K views 180 replies 22 participants last post by  mastercurt14 
#1 ·
Still having a problem with my 76. I have owned it since Feb with no problems until about a month ago. After about 20-30min of running it sputters & shuts down unexpectedly. Let it sit for a few minutes and I’m on my way running smooth. I thought it was an electrical problem – replaced plugs, wires, cap, rotor, and ignition module. Still have an issue.

Today after changing the radiator hoses and belt, I let it run in the driveway with the hood up. Outside tmep in the 80’s, water temp ~190deg. Car stopped after about 25min. I don’t think this is temperature related.

As some of you thought earlier, I now think it is fuel related. Can a rich running condition cause a shut down after about 30min? It has an edlebrock 600cfm manual choke carb. I replaced the air filter awhile back with a shorter, larger diameter one for hood clearance. Could this have caused a rich A/F condition?

I followed the edlebrock owner’s manual instructions on setting the A/F mix screws and idle speed. The car idles smooth at 500rpm. If I lean out either of the screws it seems to run worse. The idle speed screw is currently not touching the throttle lever (min speed position on linkage).
The weather is GREAT here now but I don’t want to drive it in this condition. Advice is GREATLY appreciated! I want to fix it this weekend.
Thanks,
Mike
 
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#2 ·
the size of air cleaner would have no effect.. why is the idle adj screw not touching ? look into the bores while running when it starts to stumble and die..if you see fuel dripping , its flooding. float adjustment or needle and seat not shuting off fuel..how much fuel pressure do you have. too much will overpower the needle and seat. If you replaced the module, its probably not electrical.
 
#3 ·
The car idles nice at ~500rpm which is the fully max forward location of throttle lever. The screw is just backed out a little farther than the max position (so just a slight gap between screw and lever). If I run the screw in further the idle rpm increases. I thought 500rpm sounded pretty good.
 
#5 ·
is it a manual or auto trans? auto usually needs a little more idle rpm..that it idles smoothly for awhile then suddenly dies, sounds like a flooding issue, or possibly the opposite, its running out of fuel,have you checked the fuel filters?.. bad modules can do that after they get hot, but you replaced it. I would turn the adj screw til it touches. good luck..let us know what you find.
 
#14 ·
Yes, fuel pumps can work good then not work good. Then work good again. My fuel pump on my '71 454" has been acting up for about a week now. I finally took it off and cut it apart to see why it's acting so funny. The rod seal inside was coming apart and causing the lift shaft to bind; getting only a partial stroke. So yes, they CAN fail intermittently.
 
#8 ·
It sounds like lack of fuel.If it was flooding out the plugs would foul and then be hard to start back up.(especialy after a couple of tries).It's probably the fuel pump or the filter(in carb if quadrajet). fuel pumps are fairly cheap so I would change both at the same time.
adam
 
#11 ·
A little more info...

I had it idling again today in the drive way. All is good and smooth until ~30min then shuts down. I have one of those "see-through" fuel filters that I was watching when the motor died. The filter was filled solid with fuel flow when the car stopped. The fuel then slowly started emptying back into the fuel pump until the filter was completely empty. The longer I leave it sit (after konking out) the longer it will run before stopping again. The last time I had it running today, the fuel did not fully empty from the fuel filter - it stayed about half full. Does this say anything about the pump? I also monitored the carb while running. I am not sure what I am looking for to diagnose the trouble. When I had the car running at ~2000rpm, there was a steady gas drip out the center of the 2 forward venturis. Is this what is supposed to happen? Not sure how to tell if my floats are stuck, etc. Anymore info or links on this subject would help. - Thanks!
 
#13 ·
Reading you post I would have to agree with the fuel pump being the issue. It would be an inexpensive part to replace so it can be eliminated if the problem persists. Another possible problem would be if you have a seperate coil. I had a charger that would also do what you have discribed and it ended up being that the coil was getting hot due to a lack of cooling oil.
 
#16 ·
I just remembered another similar problem I had with another car where the carb was flooding slightly and over time the gas diluted the oil which would heat up or loose pressure and cause the engine to shut down. Check your dipstick and if the oil is high and smells of gas, the fuel pump may be leaking gas into the crankcase where it is mounted to the block.
 
#18 ·
Have you checked for a vapor lock condition?
 
#19 ·
I recently had it running with the hood up and cool weather outside. Engine coolant was around 190deg. I was getting liquid fuel dripping into the carb when throttling it to about 2000rpm. I don't think it has a vapor condition. I was considering it though a couple of months ago when the outside temp here was over 100deg.
 
#25 ·
Got the fuel pressure gauge installed. Looks like a new fuel pump is in order. At start up, with car idling at ~500rpm the car was running 3-4psi. After 10min - down to 2psi, after 20min - between 1-0.5psi. No fuel dripping into carb during idle. I plan on ordering a new pump on Monday. Hopefully this will fix my problem.

Check the before and after pics below... It previously had 6 hose clamps between the pump and the fuel filter using 3pcs of hose, steel line, and filter. I cleaned up the plumbing a bit.

Before pic...
Auto part Fuel line Engine Automotive fuel system Vehicle

After pic...
Auto part Motor vehicle Fuel line Engine Vehicle


Thanks for everyones info - once I install the new pump, I'll give an update.
 
#27 ·
STILL got problems!!

New update / information...
I installed a new fuel pump and fuel lines (pump to rail supply & vent lines). This makes all new components from the frame rail lines to the carb.

Nothing has changed. At idle ~600rpm Fuel pressure starts at about 3.5psi and then continues to drop. After about 15min. it's down to 0.5psi. After 20min at idle needle is at 0psi. This is the same situation I had before replacing the pump.

What is going on here. Is there a carburator or vacuum adjustment I should be looking at? I did not see any fuel dripping into the carb at idle. I did not even see any dripping at ~1500rpm. Do you guys think the pressure is being lost at the carb? (not giving back pressure).

I do not have any experience in checking for carb issues. I need some advice - not sure where to go from here.

Thanks,
Mike
 
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