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Author Topic: Engine continually cuts out - 75 C3 350  (Read 18918 times)

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Offline jimandemma

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Engine continually cuts out - 75 C3 350
« on: March 19, 2017, 05:51:31 PM »
Hi guys and gals,
                           seem to have a problem with the engine cutting out at idle after about around 2o seconds of running and when driven, intermittent coffing and spluttering then stalls when you come to a stop. I originally thought it may be a blocked fuel filter, but after inspection, appears fine. Fuel pump all good also. When it does cut out at idle, it's instant, so doesn't appear to be fuel related. Car has been running like a clock with no evidence of a problem before this started. Could this be an electrical problem, maybe the distributor? I can't see any arcing around the cap or from any of the plug leads. Any help or advice would be greatly appreciated.

Cheers, Jim
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Offline bfit

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Re: Engine continually cuts out - 75 C3 350
« Reply #1 on: March 19, 2017, 06:12:59 PM »
Hot wire the engine to start , that will by pass all the electrics then you will know  where to start to look.
isolate the problem to engine bay .
Bfit
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Offline jimandemma

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Re: Engine continually cuts out - 75 C3 350
« Reply #2 on: March 19, 2017, 06:30:33 PM »
not sure how to hot wire to start BFIT
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Offline Vettech

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Re: Engine continually cuts out - 75 C3 350
« Reply #3 on: March 19, 2017, 09:14:08 PM »
When you say "checked the fuel filter" - on my 78 350 Quadrjet there is a small inline filter on/in the carby body where the fuel pipe enters. You need to remove fuel line (use two spanners) from memory it is paper, I assume your 75 would be the same, maybe "bfit or sirfixalot" could comment. Also check "bowl" for water. Not unusual for tanks to fill with water, fuel floats on top. Sorry if I'm preaching to the converted, sometimes little items can be over looked. Good luck.
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Offline Vettech

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Re: Engine continually cuts out - 75 C3 350
« Reply #4 on: March 19, 2017, 09:37:11 PM »
When you say points, I assume it is a basic points systm (no electronics) check points, if in doubt I allways change leads, cap, CAPACITOR and points. That leaves nothing to chance and will ensure long life. Oh! Nearly forgot - the Ole COIL  v8's can be notorious for crossfire, start the car in the pitch dark and look for cross fire at the plug, leads and cap and coil. Be aware you can (on some cars) see the plugs fireing down in the cylinder.
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Offline jimandemma

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Re: Engine continually cuts out - 75 C3 350
« Reply #5 on: March 20, 2017, 09:24:42 AM »
Vettech, took fuel line off this morning from carb (Holley 650) but no fuel filter there. Re-assembled, started motor, all good now. Not sure what the hell is going on, but running fine now.

Jim
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Offline MY081

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Re: Engine continually cuts out - 75 C3 350
« Reply #6 on: March 20, 2017, 12:45:10 PM »
Welcome to the mysterious world of the Corvette.
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Offline Vettech

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Re: Engine continually cuts out - 75 C3 350
« Reply #7 on: March 20, 2017, 01:00:12 PM »
Ummmmmm. That is the worse fix, did you pump any fuel out of the line when it was off?. I hate intermittent faults which clear with no know cause being found.
Hate to say it -  but it may come back. Sorry but I'll look forward to hearing about this again here on the forum. Ever the pessimiss. Happy cruising.
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Offline bfit

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Re: Engine continually cuts out - 75 C3 350
« Reply #8 on: March 20, 2017, 08:00:45 PM »
Mmm vapour lock on a cold day unusual.
Did u take the fitting out of the carby to look for the filter
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Offline jimandemma

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Re: Engine continually cuts out - 75 C3 350
« Reply #9 on: March 21, 2017, 12:47:32 AM »
Pumped fuel out of the line, no problem there. Found no filter at the carb when the fitting was off. Haven't driven the car yet, but is idling fine now without cutting out and back to easy starts. No idea what it was, but went away as quickly as it came.
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Offline Vettech

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Re: Engine continually cuts out - 75 C3 350
« Reply #10 on: March 21, 2017, 01:10:02 PM »
Maybe some blockage which came out with the fuel. Would not need to be very big. Well I hope that is that. Happy Cruising.
I know the Quaddy has the filter, not sure on the Holley !?!?!?!?....
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Offline bfit

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Re: Engine continually cuts out - 75 C3 350
« Reply #11 on: March 21, 2017, 03:09:52 PM »
Quote from: Vettech on March 21, 2017, 01:10:02 PM
Maybe some blockage which came out with the fuel. Would not need to be very big. Well I hope that is that. Happy Cruising.
I know the Quaddy has the filter, not sure on the Holley !?!?!?!?....

every Holley I have word on has a sintered bronze filter.
something like this
https://eb9239d2b3c1bda1d53d-6b4eb896915f5ae433f1eefb2b932a4d.ssl.cf1.rackcdn.com/230107.jpg
It's in there to hopefully keep the crap out of the needle valve. But some people do leave them out
with the idea it will flow more fuel.
questionable  at best that idea. When one want to flow more fuel its best to go up a size in needle and seat.
 Time will tell if the problem will crop it head up again
Bfit 
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Offline jimandemma

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Re: Engine continually cuts out - 75 C3 350
« Reply #12 on: March 23, 2017, 01:23:28 AM »
Well, it did crop up again today. I think I know the problem. The last week I have been jacking one side up (LHS) to check the brakes, this is when the cutting out started when back on the ground. When I checked the fuel line on the carb the other day, the caar had been on the ground for a day or so and started and ran fine. Yesterday I jacked the car up one side at a time to put it on jack stands to bleed the brakes. Started to cut out again, so I'm now thinking the float in the carb is sticking at an angle when 1 side of the car is jacked high enough causing it to cut out after 15 to 20 seconds. Thoughts?
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Offline bfit

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Re: Engine continually cuts out - 75 C3 350
« Reply #13 on: March 23, 2017, 08:08:59 AM »
Which type of bowl does the carby have , side pivot or centre pivot.
Any thing is possible
Bfit
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I have seen too many instances where people continue to pursue wrong courses of action because they do not take the time to think critically about what has happened in the past.’’
Winston Churchill

Offline sabre

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Re: Engine continually cuts out - 75 C3 350
« Reply #14 on: March 23, 2017, 04:26:20 PM »
Put a gauge on the fuel line. Had the same symptoms a few years back. Turned out to be a dicky valve in the pump. Should be between 2 and 5 psi.
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Offline jimandemma

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Re: Engine continually cuts out - 75 C3 350
« Reply #15 on: April 02, 2017, 05:51:26 PM »
Todays update. Fitted a 7PSI Carter electric pump and new filter, Holley fuel pressure regulator and fuel pressure gauge at the Carb. STILL cuts out after about 20 - 30 seconds with trouble starting again. I have fuel pressure at the Carb of 6 PSI but engine sounds like it is slightly missing. By chance, checked the battery and was only 10.7 volts. I currently have the battery on charge to see if it holds voltage, could this be the problem? If not, I have new leads and a complete new HEI dizzy to replace the current factory HEI dizzy.
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Offline jimandemma

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Re: Engine continually cuts out - 75 C3 350
« Reply #16 on: April 02, 2017, 05:55:07 PM »
With a bad battery, can too low of a voltage while running, load the alternator enough to cause a stall?

Jim
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Offline bfit

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Re: Engine continually cuts out - 75 C3 350
« Reply #17 on: April 02, 2017, 06:37:39 PM »
It you have more than 10.5 volts while cranking it should run.
What's your vacuum like
Is this an automatic.
Bfit
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Offline sirfixalot

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Re: Engine continually cuts out - 75 C3 350
« Reply #18 on: April 02, 2017, 07:22:57 PM »
Hei ignition is not a lover of low  voltage 10.5 v  is way too low i'd investigate why it is that low car will run on alternator without battery. Voltage when running should be about 13 volts 
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Offline jimandemma

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Re: Engine continually cuts out - 75 C3 350
« Reply #19 on: April 02, 2017, 07:50:47 PM »
Car is automatic.

Not sure on vacuum yet

Haven't checked alternator output yet as car doesn't run long enough.

I'll check battery in the morning and go from there whether it is stuffed. If not, alternator next I suppose.
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