Fuel Pressure

[chief153]

I recently put a fuel pressure gauge on my 1997 LeSabre, the pressure at idle was 42 psi, after setting for two hours the pressure had dropped down to 0 psi. Is this normal, or is the fuel pressure regulator defective? I have no problems with the engine or performance, just wondering if perhaps I need to replace the FPR or even the fuel pump. I am the third owner of this vehicle and the odometer is showing 132K miles, so I am sure all the components are original.

[BNaylor]

At idle what reading do you get with the vacuum line at the fuel pressure regulator removed? Also, what is the highest reading at fuel pump prime. Ignition to on but not start. How much does it bleed down after about 10-15 minutes or so?

Do you have any starting problems (long cranking) after letting it sit several hours or the next day? If not I would not be too concerned nor replace parts needlessly.

[chief153]

Originally Posted by BNaylor

At idle what reading do you get with the vacuum line at the fuel pressure regulator removed? Also, what is the highest reading at fuel pump prime. Ignition to on but not start. How much does it bleed down after about 10-15 minutes or so?

Do you have any starting problems (long cranking) after letting it sit several hours or the next day? If not I would not be too concerned nor replace parts needlessly.

Thanks for the reply BNaylor. The weather has turned for the worse here, so it may be a while before I can conduct any more tests. Thanks again for the reply

[happydog500]

I want to be sensitive about hijacking a thread, but this seemed like a relevent place to ask.

If I can find a fuel pressure gage, I need to see if my fuel pressure is good. Can you tell me a good process to go through to check?

Not knowing, I was going to relieve pressure, hook up the gage and turn the key on. Check pressure.

Spend a few minutes trying to start the car. If it starts, check the pressure when it's running.

After reading your post, I guess I would shut the car off and wait a few minutes, check pressure.

What should a 1997 pressure be at, at each stage of testing?

Would I need to do anything else?

Thank you for any advice,
Chris.

[chief153]

Chris,
I got my fuel pressure tester at Advance Auto for less than $40, this one has a pressure bleed off valve and discharge hose for safety measures.
All I did was hook up the gauge after the car had sat all night, then crank it up to see what pressure it would hold at idle. The weather turned off bad, so I did not get a chance to try different tests with the tester. The nest test I make will be with the fuel pressure regulator vac hose disconnected, if the weather ever breaks!!!

[HotZ28]

Originally Posted by happydog500

What should a 1997 pressure be at, at each stage of testing? Would I need to do anything else?
Thank you for any advice, Chris.

The proper (safest) procedure for testing fuel pressure, is to remove the fuel pump fuse and proceed to start the car. If the injectors enable, as they should, this process will bleed the fuel pressure from the rails.

Now it is safe to install your gage on the Schrader valve. Most people omit this process and use rags to soak up spilled fuel when attaching the gage. (Not a good idea)

Once the gage has been connected tight & secure, reinstall the fuel pump fuse and turn the ignition switch ON for the prime cycle to take place. After you here the pump shut off, turn the ignition switch OFF with a pause and back ON to initiate another prime cycle. Now you can check the reading for full prime pressure. Next, start the engine and take another reading @ idle. Finally, pull & hold finger over the FPR vacuum line for final reading.

Before removing the gage, pull FP fuse, and start engine as described above. (Don’t forget to install fuse after removing the gage from the rail.

Typical MPI Fuel Pressures:

Prime = 48-52 psig
Start idle = 46-48 psig
Vacuum Line Removed from FPR = 42-44 psig

[happydog500]

Thanks for the info in replys.

Right now if I had $40 I would buy food.

Still looking for a gage to use. Can't believe how many people I know who work on cars who have everything but a fuel gage.
Chris.

[happydog500]

Friend herd I needed help. He went out and bought a new gage and tested.

Prime was 2-5 psi (primed a few times). Running at idle was around 15-20 psi.

He said 99.9% chance it is a fuel pump.

He then asked if I wanted to get it and fix it. I told him I don't have any money until the 3rd of March.

He said, "Don't worry about it, I'll get it. Can you make it to my shop? I'll fix it tonight."

Thanks for all the replys,
Chris.

P.S. Looking at the procedures, looks like more of a job then I thought.

[happydog500]

Changed the fuel pump last night. I didn't want to lose any gas so I we did it with a little over half tank. Would of been a lot easer to have an empty one.

That screen that goes on the pump was really hard to get on. Hope we got it on all the way.

With back of the car on jack stands, we took a wheel off to get more room and noticed a lot of play in the wheel. Looks like I need a wheel baring for the Right Rear. Glad I found it, since it wiggles pretty bad.
Thanks for the replys, sorry for the hijack,
Chris.

[HotZ28]

Originally Posted by happydog500

Changed the fuel pump last night.

Does your engine start & run now?

[happydog500]

Yes, it runs very good. The fuel pump must of been slowly going out for a year. I haven't had this powerful motor for at least a year or more.

Leaving the garage I gave it gas and burned out down the street.

Thanks for the help,
Chris.