SamGrant951

Ok, heres the skinny:

-Adjustable FPR unit installed for many years, all is well - dial up to 3 bar for bigger turbo / mapping and car boosts strong and AFR's safe/good.

-Pickup car and get on it - goes lean, check fuel press gauge -> shows low...figure adjustable FPR has failed as Dan said it was acting a little wierd when he was adjusting it. Tested a 3-bar FPR I borrowed from a friend tonight. Gauge still shows 23-24psi. Vacuum connection to FPR looks great - no kinks, pull off line and it bumps fuel press up just a few lbs. Its reading about 20psi low for the regulator thats installed from what I can tell...

Heres where we stand fuel wise:

-55 Injectors, balanced/cleaned a few thousand miles ago
-Fuel filter 1-2 years old, 4k miles max
-Pauer fuel lines/Pauer fuel gauge
-Fuel pump replaced 40k miles ago in 1997.
-Fuel pump check valve is known to be bad - could this have failed in some other strange way causing low pressure? It sometimes takes awhile to build pressure but it always starts...

Thinking fuel pump and/or check valve. Plan on replacing both but was just seeing if there was something else Im missing...

thanks,
Sam

TRP951

the check valve wont affect it when the car is running, maybe its the FPR again

introuble

Did you say that your only running 23-24psi of fuel pressure? I am running a Super 61 with 55lb injectors and my pressure is at 47 static and it runs fine.

xsboost90

after the motor was assembled i started the car and it had low fuel pressure 30psi. I adjusted it on the FPR and it was about 45psi and the car ran great. After he picked the car up a day or two later at least, the fuel pressure was back down around 20-30psi again somehow. Adjusting the reg did nothing so he installed a new 3bar regulator and still only 23psi or so.

SamGrant951

I actually didnt even try adjusting the FPR once I noticed how low the gauge was reading - I just swapped in a known/good 3-bar regulator and still low 20's on the gauge.

dand86951

The easy thing may be to change the filter to make sure it isn't blocking the flow. If it is blocked it will reduce the flow and thus the pressure at the rail.

I had a AFR do the same thing, ie start being variable on the output at idle so I changed it out and in my case it was just the FPR. Either your pump is losing efficiency or the suction is blocked or the filter is blocked. Let us know what you find.

Mike Murcia

Is your rail powder coated? If so, is there any chance some sand/debris is causing some clogging of the injectors, in the rail or the gauge?

xsboost90

possible although he said he cleaned the poop out of them beforehand. It was running bad once and i turned the fuel pressure up- she ran great- then pressure goes back down and she runs like poop again. Gunk in the regulator would make it rich-stop flow back to the tank- and gunk should not be in the dampner- guess its worth a look.

Bri Bro

Pinch off the return line and see if the preasure shoots up.

TRP951

it might be the fuel pump then thats starting to crap out

Judson951

I was thinking the same thing tonight. Switch your rails around real quick.

xsboost90

swap the rails? Pinch off the return and if you still dont get much pressure i would say its the pump. I talked to Pauertuning and he said he could get the Walbro pumps which are big time in the supra community. They take an adapter to fit into the 944 but they are awsome pumps. Im thinking of that or a big bosch pump for my car sometime soon.

MM951

The walboro 392 pump is ~95$ +10 shipping on ebay. I bought one but havent installed it yet

btw: got the parts , thanks again Dan

TRP951

Yup they are pretty affordable, they dont support as much as the 044 something like 500-600 in between there but not many people are in that range here.

SamGrant951

Yes its coated...I cleaned the living crap out of it before it was ever installed onto my car...and it was installed on the old motor for awhile before it was swapped onto the new motor so although I cant say for sure, I doubt thats the problem - but ya never know...

I will try this, thanks all.