Fuel Pressure Drops when Car Heats Up??

[Blakboost]

Has anyone ever experienced this?


When I first start the car up when it's cold the "new" rail-mounted fuel pressure gauge seems to read a good 6-10psi higher as to compared when I check it after I have been driving it for a few minutes. I will set my FP to @45psi line off when it's cold and by the time I check it after a few minutes of driving it shows in the 30's. I have recently replaced the fuel pump, FP Gauge, and regulator.

Should I be setting my static pressure after the car has heated up?

Thanks for the help!

 

[Squid4life]

You shouldn't have to set it with the car (and pump) hot. It should not change when it warms. Swap your regulator back out and see if the pressure stays the same from cold to hot, then try a different gauge. In other words, try one thing at a time.

 

[ThikStik]

Me too, by about 6 psi. And , the gauge drops upon sitting within 2 minutes, its draining at pump. Reg is only 3 years old and is billet. I took fp out to check my hose connections and they were fine, so it must be fp....dont really know how bad this is. Good luck

 

[Squid4life]

Has anyone ever experienced this?


When I first start the car up when it's cold the "new" rail-mounted fuel pressure gauge seems to read a good 6-10psi higher as to compared when I check it after I have been driving it for a few minutes. I will set my FP to @45psi line off when it's cold and by the time I check it after a few minutes of driving it shows in the 30's. I have recently replaced the fuel pump, FP Gauge, and regulator.

Should I be setting my static pressure after the car has heated up?

Thanks for the help!

Thik, his is draining while the car is running, are you talking about yours dropping after you shut it off? Two different issues. :biggrin:

 

[mikec1969]

If it's a liquid filled gauge then thats why the pressure changes when the motor is hot. I'm removing the gauge under the hood, capping the outlet off with a AN steel cap. I'm then going to attach the gauge to a -4 braided fuel line, so I can still check fuel pressure from time to time. I had a fuel gauge fill with fuel and leak once and since then have heard they can blow the dial cover off and leak fuel into the engine compartment-not good.

 

[Brer Rabbit]

I think this is ur problem

As crazy as this sounds I had the same problem when I first fired up the new motor. Ur problem is the coil pack and/or module. but I suggest u replace both. By a Delco coil pack and module along with the gasket that goes between them, and ur problem will be gone. By the way, I had mine tested at autozone and it checked out fine. The problem is they cannot simulate the heat that builds up causing the failure. Specifically, I would start my car and drive it about 3 miles away then the car would start starving for fuel. I jumped out and checked the fuel pressure gauge and noticed it was dropping to about 30psi, which is where the car would start to stumble real bad under acceleration, then die out. U have to borrow a known good working coilpack and module to test my theory, cuz the delco stuff will put u back about $260.00. Good luck.

 

[ThikStik]

Squid,
Mine drops after car is off. I also have liquid filled rail mount gauge, so may be thats why its differing hot/cold. But yes, it is symptomatic of fp check valve with me. No starting problems.

 

[Lee Thompson]

I bet

It is the liquid gage.

 

[Dwayne]

It is the glycerin in the gauge causing the fluctuation in readings. I have a liquid filled gauge mounted on the hood. On initial startup, the gauge will read whatever I have the pressure set to, then after a drive in the sun, it will drop off. It is even worse if the gauge is mounted under the hood due to the trapped heat. As long as your pressure goes up when building boost, you'll be okay.

 

[Blakboost]

The gauge is brand new and it did this with the old regulator as well.

So should I just set the Static FP when the car is cold?


How does the coil/module affect this? Curious.

 

[Brer Rabbit]

Couldnt tell U...

But that fixed the problem. If ur in Chicago I will pull mine off for u to check it. I know mine is good.

 

[Welby]

Mine does the same thing, I have a Marshall underhood mounted FP gauge, brand new Walbro 340/hotwire, and a new Accufab regulator (Well, they were all brand new when I put them on last year). Once the car was warm it would (and does) read differently. So, should I adjust it cold or hot? I'm cornfused....

 

[Dwayne]

cool and/or cold

 

[turbopaul]

read this..... http://www.turbobuick.com/forums/general-turbo-buick-tech/170952-fp-drops-after-while.html

#8 in particular


Paul

 

[bison]

If its a liquid filled autometer then ther is a screw in the top of the guage. I just back off the screw slowly until it equalizes. Then i leave the screw right where i just moved it to and continue with the guage install.

 

[QUIP'6']

mine did the same thing mounted under the hood then i put it on the glass under the blade and it stay where i set it and yes it was a liquid filled used to drop 5 to 6 psi after getting warm