Small questions on AFPR!?!

[Pantera61]

I had leaking injectors so I installed them this weekend. Once I got the AFPR on I decided to see what the pressure is. At this time I had the runners and plenum off. I connected the battery and turned the key to "ON". The pump turned on throwing the needle in the fuel gauge up to 50.5, not bad for a guess. But then I watched the gauge drop quickly. This was the second day and my last chance to get it back together so I could go to work on moday. As the needle dropped, I couldn't tell which one fell faster, the needle in the gauge, or the tear falling down my face. I read and read and read some more. I finally found something that said there need to be vacum to hold any psi. Is this correct, I thought I had to have the vacum line disconnected in order for me to set it! What is going on? No one said anything about it falling off like that, and it was fast. I think that it finally held at about 20-25 psi. Some where in that area.

Thanks Guys,
Pantera61 :confused:

[ April 15, 2002, 09:52: Message edited by: Pantera61 ]

[WS6 VERT]

The vacuum varies the amount fuel pressure. With no vacuum, its generally around 50 psi. With vacuum, its usually drops to about 40.

The idea is that when under load (low manifold vacuum) fuel pressure increases.

If your loosing that much pressure w/ new injectors, it may be the checkvalve in the fuel pump.

[Pantera61]

I didn't hold anything above 20psi with the vacum unplugged! I did check it last night with the key on and the vacum line connected and it held 43psi. I started the car and it was holding at 50.5psi. Does this sound normal?
:cool:

[Skweezn87]

Well you might have had air in the lines.. I know when I open the system up.. I have to prime the fuel system a couple of times to get the fuel pressure up where it needs to be...

So are your running 50.5psi w/ the vacuum disconnected?? If you are.. thats high...IMHO

Rick

[WS6 VERT]

OK, something isn't right.

First off, if the key is on, and the car is NOT running, then the vacuum line makes no difference, since the car must be running to produce vacuum...

Second, the pressure should be higher with no vacuum then with vacuum. You said it was 43 psi w/ the car off, and 50 w/ it running. It should be the other way around. 50 psi is kinda high for a stock application. I run 50 psi, but my car isn't stock.

The correct way to set FP is with the car running, and the vacuum line removed (and plugged). This will set your MAX pressure. Once thats set, there is no more adjustments that need to be made to it. Once you put the vacuum line back on, the FP will drop, and that is your "normal" pressure, i.e. idling and cruising. Once you stomp on the gas, then it will go to "max" pressure.

[CraigSkiles]

Originally posted by BTripp:
The correct way to set FP is with the car running, and the vacuum line removed (and plugged).This I did not know, about the line being plugged. Cool.

[WS6 VERT]

You don't have to plug it, but if you don't, you'll just have a vacuum leak. Any time you pull a line for whatever on a running engine, you should plug the line, but its not necassary. It won't change your readings, just good practice.

[Pantera61]

That is what I was guessing. Tonight I will disconnect the line and plug it up. I will update tomorrow. Bernard is there a way to test that checkvalve without taking out the pump? Maybe that is the problem, if possible I will check it tonight and update tomorrow.

Pantera61

[ April 17, 2002, 09:58: Message edited by: Pantera61 ]

[Skweezn87]

You can turn the car on... get the FP up.. then pinch the return line and see if it drops..

If it does..then leaky injectors or AFPR could be the culprit... if it doesnt then possibly the check valve

Rick

[Pantera61]

Thanks, I will try to check it tonight and update tomorrow!!

[WS6 VERT]

Yeah, Rick nailed it. Crimp the return line and watch it. Just be careful what you crimp it with.

[Pantera61]

I think that Skweezn87 got it. I tested the fuel pressure and it was normal. idle was close to 41, and under load 50.5. I guess that was it. I will continue to check it. Also that is a good idea to always plug the vacuum line, thanks for reminding me. smile.gif

[Skweezn87]

Well I hope it all works out for ya... keep us informed..

Rick

[WS6 VERT]

Yeah, now your pressures look good. I'd be very happy with it.

[Pantera61]

I can feel the difference. I spent last night checking it again, then I took it for a spin. I can tell that it has a flatter torque curve!!!

Thannks Guys