Stock Fuel Pressure Quiestion

mustang8719 · Jan 13, 2006

What eaxctly is the stock fuel pressure supposed to be?
I have been driving around the last 2 days with my Guage connected.
At idle it stays at 32 Psi When I get on it then it jumps to 40Psi.

I know I need a new pump soon. When I shut it off all fuel pressure drops to Zero.

But I am chasing a problem with it running rich and Pinging when hot. When it is cold it runs strong. But drops off some and pings when hot.

The timing chain was done a couple of Months ago and is dead on. The balancer is good. I have to run Below 10 degrees on the timing to make the Pinging minimal.

I have more tests to do but wanted to get all the info I can about Fuel pressure.

Thanks for All Advise.

HISSIN50 · Jan 14, 2006

One should not drop below 30 PSI at any time. And the stock WOT pressure setting is 38-39 PSI.

Dont forget to make sure the tune-up parts and sensors are up to par - bad sensory input can contribute to pinging.

Good luck.

2002BLGT · Jan 14, 2006

I would dare to say that you have an injector that is bad , probably pinging on one cylinder that is not spraying properly and 40 psi is probably why its running rich ...should be about 38.....pull the plugs and see if one isnt white?? that will tell ya what cylinder is pinging due to that injector not working properly , leaking injectors would cause the fuel pressure drop when the engine shuts down , it should hold some pressure when you turn off the engine .....IMO replace the injectors and go from there ......and if you are holding fuel pressure at WOT then you probably dont have a fuel pump problem

HISSIN50 · Jan 14, 2006

The great thing about these forums is all the different perspectives and experiences that we have. I perceived this a little differently.

It can be quite normal for the pressure to bleed off pretty fast after shutting the car off. As pumps age, the check-valve in them will allow fuel to return quickly (it does not take much return volume to wipe out the static pressure in the line). And some FPR's (especially some of the aftermarket stuff) will return fuel once the car is shut down.

A cylinder balance test can show whether one cylinder is not contributing as it should be. That is a great quick and dirty way of testing.

If going with 2002's advice and pulling injectors and wanting to test them, JRichker has a really neat little test that he posts. He uses a cup of lightly sudsy (soapy) water and compressed air on the injector. If there are no bubbles, the injector is holding tight. See his post for all the specifics.
That could save some money (Injectors would not have been near the top of my list - just my opinion).

I would be leaning more toward ensuring that the stock temp gauge is not what is being used - it likely would not reflect how truly hot the car is running, if a cooling system component is on the outs.

Additionally, pulling the codes is the place to start - you might have a sensor (ECT, etc) out of calibration or just toast, that is causing some issues.

Just my random thoughts.

gt40_2003wes · Jan 14, 2006

HISSIN50 said:
The great thing about these forums is all the different perspectives and experiences that we have. I perceived this a little differently.

It can be quite normal for the pressure to bleed off pretty fast after shutting the car off. As pumps age, the check-valve in them will allow fuel to return quickly (it does not take much return volume to wipe out the static pressure in the line). And some FPR's (especially some of the aftermarket stuff) will return fuel once the car is shut down.

A cylinder balance test can show whether one cylinder is not contributing as it should be. That is a great quick and dirty way of testing.

If going with 2002's advice and pulling injectors and wanting to test them, JRichker has a really neat little test that he posts. He uses a cup of lightly sudsy (soapy) water and compressed air on the injector. If there are no bubbles, the injector is holding tight. See his post for all the specifics.
That could save some money (Injectors would not have been near the top of my list - just my opinion).

I would be leaning more toward ensuring that the stock temp gauge is not what is being used - it likely would not reflect how truly hot the car is running, if a cooling system component is on the outs.

Additionally, pulling the codes is the place to start - you might have a sensor (ECT, etc) out of calibration or just toast, that is causing some issues.

Just my random thoughts.

shut up lol.

mustang8719 · Jan 14, 2006

Today I was finally able to hook my scanner up and read codes.
I pulled a 21 coolant temp sensor code
I also pulled a 34 EVP voltage which im not sure what it is.

In the next day or so I will buy a new coolant temp sensor and install and see if the code comes back.

Michael Yount · Jan 14, 2006

"At idle it stays at 32 Psi When I get on it then it jumps to 40Psi. "

That's just how it should be. At idle (low vacuum) manifold vacuum causes the reg to reduce pressure. When you hit it hard, vacuum goes away and the pressure comes up as it should under load. 38-40 psig is what it should read max.

Sounds like your pressure is fine to me.

mustang8719 · Jan 18, 2006

UPDATE:Installed Temp sensor today seems to run a little better but still pings some. Haven't had time to clear the code yet but will tomorrow. I am also going to run Valve cleaner through it and then take it from there.

Stock Fuel Pressure Quiestion

mustang8719

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HISSIN50

"How long does it take to get help in here?

2002BLGT

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HISSIN50

"How long does it take to get help in here?

gt40_2003wes

I did sound a wee bit gay there.

mustang8719

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Michael Yount

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