Thread: Fuel Pressure Prime Question

Ok so i'm trying to figure out the rough idle, sputter, and dying issue i'm having with my DET. First off most of the time i start it I have to sit there and rev it a few times (when it gets close to dying off) until it warms up and the idle evens out, then after that sometimes itll idle ok but other times the idle will get rougher and weaker until it dies. Theres no leaks on the car, it has a Walboro pump that i can hear the pump prime and even hear the gas slosh around inside. After I did this I hopped out of the car and looked at my Fuel Pressure gauge, and noticed that in about 10-15 seconds the gauge drops back down to 0. In my research i've found that some people say this is normal and others saying its not and should hold the pressure for a few hours at the least. It was suggested I may have a leaky injector but was told by someone else if that were true I would have hard starting issues and it would prob hydrolock. Also the plugs would be wet from fuel (as i've mentioned nothing seemed wet or anything like that). I'll grab some pictures and even footage of a start up and try to check it die out on me. The car also has a Calum RT Ecu that came in it and I know nothing about tuning so im not sure if maybe a bad tune could be causing the issue but when I first bought it I drove it 10 hours with no issues. I'd like to rule out everything else while i look for someone who could help me figure out the tune. Its a bluebird highport T25 in a 95 B14 running N62 MAF. I just replaced the fuel filter (z32) to rule out a clog, but like i said, seems to be getting up to around the standard 40ish pressure mark right after prime. Just wanted to be sure the rapid falling pressure was normal or not. I also sprayed starter fluid and the like around the engine to check for Vac leaks and turned up nothing. Gonna try again later and maybe run some smoke or something into a vac line to see if it comes out anywhere (car off of course lol)

In my cars a use the Z32 Fuel Pumps - They hold pressure for days. I used the Walboro once and didn't care for it. IIRC there are 2 difference versions on the 255lph Walboro fuel pump.




Smoke test is more accurate. Starter fluid can be hit-or-miss.



What fuel rail are your using?

What injectors are you using?

What fuel pressure regulator are your using?

Where is fuel pressure gauge located?


Do you have the ability to see what % of the IACV/AAC is being used when you have rough idle?


Pics ALWAYS help.

Far as i know everything is stock bluebird U13 swap. Here is a video of what sounds like air leaking from somewhere near the fuel pressure gauge, not sure of the brand, but everything else is stock. Gauge is located back by the fire wall above the fuel filter


Sorry, fixed the link so you can view the video

The static pressure(engine off)should never drop to 0. long cranking and/or hard start will result. The fuel pumps have a built in check valve to prevent bleed down.
The sound you hear is probably the fuel leaking back to the tank past the check valve.

That "air leak" sound in the video seems to be coming out of or around the fuel pressure regulator. Are you talking about that sound being the fuel leaking back in teh check valve? That sound (i assume which would come from fuel pump area) would be down by the fuel pump, no? Would that do with the check valve?

I should note even with this problem i do not have an abnormally long cranking or hard starting.

In this video (or sound clip) i placed my phone right on the fuel filter under the fuel pressure regulator to better hear the sound. As you can see (when the camera moves) pressure does go into the line [that hose right in front of the phone is the fuel line that runs out of the top of the fuel filter] cuz the line kinda moves the phone when the pressure builds up [causing the phone to refocus a little]. Then you can hear the air leak from what i think is coming from the fuel pressure regulator. Suggestions, ideas? I'm hoping fixing this issue will get my intermittent sputtering problems and shit i've been having under control.

The leaking sound could be resonating up the fuel lines from the check in the pump, or through the regulator itself.
Unfortunately I have no experience with the after market pressure regulators.
I have heard this sound on customer's vehicles with a check valve issue.
Hopefully I am not "speaking out of school" here and not helping the issue

I think I recognize your FPR as a POS one (no offense). Do you have a Techtom or OBD data viewer?

Also - as a side note, are the fuel lines that you are using standard fuel line or "fuel injector fuel lines" ? If you are not using "Fuel Injector Fuel Line" they will eventually fail in a bad way.


Next step. Prime the fuel pump and clamp off the return line 1/2 way through the prime. This will help determine if the problem is in the regulator or the pump.

No offense taken, previous owner put it on and the BOV was a cheap Type RS ebay knock that i've replaced with a real one, so its prob also an ebay special. The Fuel line is Good Year Fuel Injector Fuel Line. I have one of those Data Scan tools that plugs into that port in the fuse box, the ECU in this car is a Calum RT also.


Here are some pictures of the area so you can check it out.

Actually that FPR looks like the ISIS now that im researching. The gauge doesnt match the ones im seeing on ebay but it matches the ISIS one. Now i just gotta figure out which things to clamp to diagnose it.

When someone gets a chance can you explain which line to clamp and should the pressure hold when said line is clamped what that would mean? I've "labeled" this picture below. From what I assume the YELLOW line is the return line pre FPR, the WHITE line is the return line post FPR, the RED line is the feed line and the BLUE line is the vacuum line from the manifold that splits going into the FPR and the plastic hard line goes to my boost gauge...