This may be a stupid question, but please don't flame me. I already searched for the answer but nobody has asked this particular question (that I can find).

I have installed a permanently mounted fuel pressure gauge according to the instructions I found on the forums. BTW, I have a TBI engine.

How do you check the pressure at WOT?

Obviously the engine is going to be spinning a lot faster with the car in park and no load on the engine. It's also kind of hard to look at the gauge while going down the road!!! Not to mention, holding the car at WOT with no load on the engine would not be very healthy to the engine.

Any help is very appreciated; even if you point out something stupid that I'm not thinking about.

 

Fade,

you don't need to check your fuel pressure at WOT because it won't change with engine RPMs.

Remember: You have an electric fuel pump and thus the pressure should (and most probably will) stay the same, regardless of the RPM of your engine.

Hth,

Andreas

 

That makes sense. Thanks.

 

OH ...... Wait a second! I forgot to add that I'm using a VAFPR. So the pressure should change at WOT .......... correct?

 

Yes the FP should change at WOT. That's what the fuel pressure regulator does.... raises the fuel pressure when the engine load increases (based on the vacuum).

You can disconnect the vacuum line going to the FPR, and that will simulate WOT, except that the flow will be very low.

Otherwise, mount the gauge where you can see it; like, duct tape it to your windshield or something. Then go do a WOT run and see what it does.

If it drops during the run from whatever it is idling with the vacuum line disconnected, you have a fuel delivery problem.

You should probably see something like 12 psi idling with vacuum connected, and 15 psi idling with the vacuum line disconnected.

 

Yes, it should. To see fuel pressure at WOT, you usually have to run a long fuel line from the T-fitting, test port, etc. to the fuel pressure gauge, route the extra fuel line up towards the windshield away from heat and moving parts and make sure not to pinch it when closing the hood, and then tape the gauge to the windshield (I know it sounds odd, but you really don't want pressurized fuel in the passenger compartment). Drive around and watch the readings.

I'm sure there is probably a better way to test it, but that's how I've always been told how to do it.

And, actually, a slowly dying electric fuel pump can produce lower pressures at WOT. An engine needs a lot more fuel at 4000 RPM than it does at 700 RPM, and if the pump is starting to go out it can't keep up with the demands of the motor at higher RPMs, and the fuel pressure will decrease. This doesn't always happen, but it can.


EDIT: RB83L69 pretty much covered it.