Fuel pressure not rising on boost

[Alex1gdsm]

Having an issue where fuel pressure is not rising with boost have an upgraded fuel pump 340lph and 1250cc injectors on e85 have a fuel lab pressure regulator and fuel lab fuel filter installed also any tips on what to look at to fix this issue any help will be appreciated.

 

[diambo4life]

How did you determine this? That's a quality AFPR so I am inclined to blame user error until I am convinced otherwise. Take a photo or show a video of your setup.

 

[Alex1gdsm]

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[1990TSIAWDTALON]

If you have access to an air compressor, add 20 lbs to the fuel regulator vacuum line and see if the pressure goes up.
Other things are clogged fuel filters. On E85, I've had that issue a couple times now. Narrowed it down to a stuffy 10 micron filter. Replace yours if you think it may be a similar issue. With air pressure on the fuel regulator, if it doesn't rise, it could be that or a faulty diaphragm in the regulator itself. You can test that by sucking on the vacuum hose and see if it holds the vacuum.

 

[Alex1gdsm]

I did do that test and fuel pressure does rise on the regulator with adding air to the vacuum line to the regulator. do you know if the fuel lab filter has an element that can be replaced instead of the complete filter itself?

 

[diambo4life]

Yes, the element can be replaced. I don't like the fuel flex sensor between the fuel rail and the regulator. I would do it after the regulator. Are you planning on running E85? I would change those rubber lines to PTFE. Also, don't run worm clamps on fuel lines please. I missed how you determined the AFPR is not working. Remove the sensor and mount a manual gauge and see whether vacuum changes the reading with the car running during idle and the throttle is intermittently opened and closed.

 

[Alex1gdsm]

I did install a gauge on the regulator and when I added psi to the regulator it did rise on the gauge. And it is now running on e85 runs well but my tuner had me install a electronic fps to see if pressure was rising and he is telling me it’s not and need to fix before he can finish my tune. I also took apart the fpr and seems ok so not really sure what to check next. When doing a log I noticed fuel pressure drops when I’m driving it hard don’t want to ruin my engine that’s why I’m reaching out for advise.

 

[1990TSIAWDTALON]

Are your AFRs rising as the pressure doesn't go up?
I have been where you are at and my car completely quit logging fuel pressure so my tuner advised the same and I understand why.
If the AFRs are rising (above any safe level, 12s, 13s on E), then something is not working.
Change the element in the filter housing.

 

[Alex1gdsm]

Not sure what he’s seeing he just said your fuel pressure is not rising under boost and it’s leaning out so need to get that fixed. I did have the vacuum source teed to my boost gauge so I fixed that and have a dedicated line to the fpr but he said it’s acting as if the vacuum sourced was not hooked up

 

[diambo4life]

Where do you have the AFPR vacuum/boost signal sourced from? Can you take a photo showing where? We know the regulator is working, the issue is why it's not reflecting in the log.

 

[jdxnc]

Make sure the o-ring on the fuel pump is properly seated if using the stock hanger, it's common for them to leak back into the tank if it's not perfectly situated.

Also from past experience with Fuelab, if the adjustment screw is out too far, it won't rise either with boost. Yours looks very far out.

 

[Alex1gdsm]

I’ve adjusted the regulator to like 42psi while car running as seen on some threads on how to adjust the fuel pressure. Also noticed fuel pressure bleeds off pretty quick after I shut engine off and has a hard start issue sometimes have to crank it a couple times for it to start not sure if it’s related. I’m gonna take out the fuel pump and check it make sure that it looks ok and that oring is in its place thanks for the help.