varying fp (fuel pressure)

[ThikStik]

I havent many miles on car lately as its just become drivable after a year. I was charging AC with hi idle (things wer toasty)and notice that fp was 22!! So that was like 28 line off. I set it to 45 per the translator/extreme chip instructins and it varied back down. I remember this happening before car was parked and i did take aprt the billett fp reg, and all its internals seem clean and fine. I do think the f pump may have a bit of a scream to it...more than i remember. It is a Walbro bought just before the bad batch came out. Car does have knock beyond 12 psi. I am going to let car cool then recheck, and i bet it will be 10 psi higher after sitting! Have yall seen this, where the pressure drops alot after heating up, and is it usually f pump or reg? thanks

 

[ThikStik]

Oh yea, did a cold start, and f pressure was 55. Thats after settoing it hot to 45psi. Nice pig rich mixture helping to harm my engine until warmed up, then too lean. So I get a 10 psi difference cold vs hot, do yall think its the pump?

 

[Mr.Spool]

replace the pump,change the fuel filter,sometimes troubleshooting requires replacing parts.then check to see if fp rises 1/1 with boost

 

[pacecarta]

change the gauge

 

[ThikStik]

Yall are saying-Question everyting....sound advice. I can say that my billett reg has always leaked down in about 25 minutes. Ive been out of touch for awhile as car has sat, so can yall say what is the best fuel pump to buy ? tia

 

[Chuck Leeper]

Chances are good, that it's the pump check valve leaking down, not the reg....

 

[ThikStik]

I should be flogged for not checkig this all along. I got out a manometer and with 20 psi chuked in, damn thing only went to 48psi from the 45 base. That was with car idling so i imagine if fuel was being used, pressure could be worse! Both reg did this, so i guess its pump. So thats a bad walbro bought 5-6? years ago, and a bad billett regulator (bleeds sdown). Cant win with these garbage parts!!

Is the only option the Supra Denso pump?

 

[kidglok]

deatschwerks pump should be good to the tens, allegedly

 

[Chuck Leeper]

You have some fixation with the reg being bad??

 

[ThikStik]

You have some fixation with the reg being bad??

You have a good point....most likely the reg probably is ok here, it cant "regulate" low incoming pressure caused by a bad f pump. The billett does bleed down faster, so i guess thats a sign of a bad needle/seat. Actually, given my crazy luck, watch me put in a new pump and it turn out to be 2 bad regulators! Ok, im obsessed with regulators....i need help.
Chuck, have you heard of Hydrophi in Doraville? There is a guy there who has his dyno there, they rent it from him tuning big rigs, etc for mpg. His name is Forrest, and a heckuva tuner. Hows your fi business?

 

[ThikStik]

i put a gauge on windshield. fp was at 45 on a cold car, then stayed at 44 after warm up. Drove and it tracked , if anything, alittle higher than 1:1.
Get back home , car sat for 20 minutes and get this-fp went up to 55 sitting. So i turn motor off and jump pump on, and i hear a swishing sound at reg.
So now im back to thining i have 2 bad regulators. The gauge does flutter alittle with the sound. Ill try the other one later and if it flutters, ill think it is pump. Thing is, pump was able to go to 70psi on the drive..of course i still got knock.

 

[HouTX87]

I have a liquid filled gauge and I can't trust it when it warms up. It's always accurate at ambient temps but pressure drops as engine temp rises.

 

[chopped39]

Do you still have the pulsator between pump and sender? If so get rid of it. You can have 55 psi and no volume which will cause issues. Hook up a good fuel pressure gauge with a dump port and see what volume you have. A stock pump will fill a 20 pop bottle in 20 seconds. A better pump will do it faster, how much I dont know.

 

[ThikStik]

dont have a plsator, but will try and dig up volume numbers. PaceCarta, HouTX87, yall nailed it....gauge has a 11psi variation ambient VS whatever my hairdryer heated it too. I also got a 2 psi drop on pump after 25 minutes , and i heated regulator (to appease my obsession) and it dropped only 1psi. Billett regulator bleeds down to 0 in 15 minutes, *235 reg holds alot longer. May go to 0 in an hour or so. So , at least i havent been doing anything bad except turning fp up to 55psi during those times that a cold gauge read 35psi. Car ran no better with knock past 15 psi boost and 940 o2's. This, even as the Translator WOT spark is set to 6 which pulls 6.6 * timing at 5400rpm, and more as rpm goes up. Only thing i can think of is my intercooler scoop (stock 24 row intercooler) doesnt have the duct wrapping between scoop and body of icooler. OR , K is very possibley from false 93 octane. It is very common here. Anyone have a preferred service station here in the overgrown South?

 

[HouTX87]

I'm in Houston, Tx and I prefer Chevron.