fuel pressure not stable - Team Camaro Tech
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post #1 of 8 (permalink) Old Nov 27th, 18, 05:41 PM Thread Starter
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ken
 
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fuel pressure not stable

hi I have a 427 with a mechanical fuel pump it shows 6psi when it is cold but as the engine warms up the pressure slowly drops to almost 0. is this a vapor lock problem-fuel pressure gauge-gas cap venting can I add a electric fuel pump by the gas tank to aid the machinal fuel pump? the fuel line is single I put a temp sensor on the input line it reads about 78 deg f thanks for looking ken
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post #2 of 8 (permalink) Old Nov 28th, 18, 03:24 AM
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Re: fuel pressure not stable

if the engine runs as it should when warm, I would first start with the gauge
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post #3 of 8 (permalink) Old Nov 28th, 18, 03:37 AM
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Re: fuel pressure not stable

Agree, replace gauge and/or spray the gauge with a can of keyboard duster, its CO2.
You could also remove gas cap when the gauge reads close to zero and observe if pressure comes back up.
And you should be able to suck on cap in testing vent, and it is a one-way valve - pressure in, no pressure out.
As Kevin suggests, if engine runs as good when warm as it does cold, throw away the gauge - problem solved.
A short test of mechanical pump is see if it will fill a qt bottle in about 15-20 seconds, +/- 10, maybe 15, at idle speed.
Mech pumps only provide a volume of fuel, not pressure.

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post #4 of 8 (permalink) Old Nov 28th, 18, 04:55 PM Thread Starter
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Re: fuel pressure not stable

THANKS FOR THE INFO IT SURE IS NICE HAVE ANSWERS THAT WILL HELP SOLVE PROBLEMS WITH OLDER CAMAROS KEN
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post #5 of 8 (permalink) Old Nov 28th, 18, 05:34 PM
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Re: fuel pressure not stable

I had a similar issue with a fluid filled Russell pressure gauge. As the engine warms the pressure in the gauge builds as there was no vent. I drilled a tiny hole in mine and it's been fine, but according to Russel, you shouldn't use a fluid filled gauge under the hood. Switch to a dry one will likely solve your problem.
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post #6 of 8 (permalink) Old Nov 29th, 18, 05:51 AM
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Re: fuel pressure not stable

Where is your gauge mounted? If it's under the hood, don't trust the pressure reading when it's hot. I ended up biting the bullet and getting a fuel isolator and moving a gauge inside the car so I could rely on the reading.

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post #7 of 8 (permalink) Old Dec 1st, 18, 02:30 PM
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Re: fuel pressure not stable

I had the non fluid filled one and it bounced all over the place. I then switched to the fluid filled one and it reads low when the engine is hot. If you really want it to be accurate you need to get the gauge out of the engine compartment. I was going to get an electric fuel pressure gauge but they are really expensive and I don't like having them mounted on the cowl, so i just let it alone for now. Good luck.
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post #8 of 8 (permalink) Old Dec 2nd, 18, 08:57 AM
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Re: fuel pressure not stable

Yes, with a mech pump, gauge will bounce because of the stroke of mech pump.

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