Hi

Just finished rebuilding my mild powered engine. After running in, tried WOTing and was SHOCKED to see the fuel pressure dropping! During normal driving, part throttle, everything was fine and fuel pressure was maintained and did not drop. I noticed that only at WOT will the pressure go south.

Anyone having this similar problem??...any idea how to solve it??....

I have changed fuel filter just a couple months ago, upgraded my fuel pump to walbro 255, with RC 440cc injectors and stock fuel regulator.

 

Usually that problem can be traced to the fuel pump. We have seen a few of the Walbro's demonstrate spotty performance.

 

Hi

Would actually assume its my fuel pump.

But before my mild built, I had a 13 comp engine with the exact same fuel system as now. There was no such problem. Could it be something else as the problem only comes at WOT and not at any other situation?

 

Anything is possible, but at WOT the fuel delivery system is stressed to it's limits. That's when a plugged fuel filter or a pump that can not deliver enough fuel will make their presence known.

 

...or a leak in the system somewhere.....make sure all the lines and the rail and the injectors are all dry....

 

Make sure your getting full voltage to the pump.If your getting a voltage drop the pump will not maintain pressure.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by cyrix12 &raquo;</TD></TR><TR><TD CLASS="quote">Hi

Would actually assume its my fuel pump.

But before my mild built, I had a 13 comp engine with the exact same fuel system as now. There was no such problem. Could it be something else as the problem only comes at WOT and not at any other situation?</TD></TR></TABLE>
it doesnt matter if it worked great one hour ago, five minutes ago, or even the last time you started your car.. it needs to be checked... to me it sounds like a fuel pump problem ..

 

Change the fuel pump.
its just low fuel pressure,

 

if it was me i would test a second fuel pressure regulator sicne that is easier to change than a pump. I ahve seen stock FPR's go crappy as well over time, and chances are it has a lot more miles on it than the pump.

 

pump

 

Hi Everybody

Finally got my fuel pump changed to the exact same model of Walbro.

The problem still persists. My fuel pressure still drops and I could not go beyond vtec and there was no enough petrol which cause knocking.

by the way, have changed the fuel regulator again to the same one as my previous..but still....

Anyone??

 

have you changed your fuel filter recently?

 

hi

my fuel filter was change not even 2 mths ago...

was tinking abt changing again..by come on...2 mths...

so not plannin to change tt..

the weird thing is...at say 75% throttle...my fuel pressure was ok...stayed strong north...but only when WOT..the problem arises..

 

have you tried a different F.P. regulator

 

hi

tried a second one..though its the same type as the previous one using...nevertheless..its a 2nd F/P regulator...

 

shot in the dark here cuz this is a weird one ..but possible low voltage to fuel pump ...??

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by cyrix12 &raquo;</TD></TR><TR><TD CLASS="quote">

the weird thing is...at say 75% throttle...my fuel pressure was ok...stayed strong north...but only when WOT..the problem arises..</TD></TR></TABLE>


The fuel system is working hardest at WOT, so if there is an issue with inadequate pressure, its most likely to happen then. Like chris says, check voltage and wiring to the pump.

 

whats the injector duty cycle at WOT? what A/F ratio and where are you tapping your gauge from?

 

there is a vacuum line that goes on the fuel rail or the the regulator that is connected to the intake manifold make sure its not pinch or clog.

 

ive actually seen this caused by a clogged return line believe it or not....triped me out...used a air compressor to blowout whatever was in there and it was fine ever since???

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 2k.civic.si &raquo;</TD></TR><TR><TD CLASS="quote">ive actually seen this caused by a clogged return line believe it or not....triped me out...used a air compressor to blowout whatever was in there and it was fine ever since??? </TD></TR></TABLE> very good point artie!!

 

if a return line clogged the car would have excessive fuel pressure.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by mike_belben@yahoo.com &raquo;</TD></TR><TR><TD CLASS="quote">if a return line clogged the car would have excessive fuel pressure.</TD></TR></TABLE>

tell that to the two people i helped swap out new fuel pumps fuel filter fuel rail etc....both had clogged return lines and had the same problem....cars ran great around town under light throttle but the fuel pressure droped to almost nothing at wot...i have datalogs of it
cleaned out the return line problem gone

 

I don't see how that can cause the pressure to be too low, no return will build up pressure at all times. I have pinched off the return line before to max out or "deadhead" the pump for diagnosis reasons.

 

the only thing i can think of if that were true, and i doubt this is reasonable but i cant come up with anything else.. the tank might need to "breath" in return fuel in order to allow the pump to siphon more, sort of like a gascan has the vent and it will flow with the vent open or chug really slow with it closed.

the fuel pressure regulator is a controlled return line clog, so i dunno, i suppose it's possible.