i reinstalled my new FP gauge (autometer ultra-lite 0-100psi) today with a new, non-leaky stainless hose...i go out for a test to see what kind of pressures i'm actually getting under boost. starting from 0 mph, first gear pull, 5psi of boost, as soon as i hit full boost the fuel pressure drops all the way to 10-20psi (from idle 40psi) and the EGTs (obviously) skyrocket to 1600...

how in the hell can i even be maintaining boost if the pressure is dropping so low when it should be doubling idle pressure? what should i check? i am clueless. it's almost like the gauge needle is moving the wrong way.

Does it rise at all?

nope..at the onset of boost it dips a little, and during that quick period when boost jumps to full, it dips all the way down...never goes above 40. never thinks about going above 40. i mean, it really does behave exactly like the needle is moving the wrong way. but i dont think thats possible

Where is the FP gauge reading from? It should be reading from BEFORE the FMU not on the return line... just a thought.

What are you using to regulate fuel. If FMU, maybe hooked up backwards?

FMU, but its correct, the gauge read properly last week, and now its doing this.

it's reading from the same port that i was taking readings from with the HRC gauge that comes with the kit. like i said, it read correctly last week, the only thing i changed today was the stainless line, and i changed the broken ignition coil to an MSD coil. i'm about to leave for work, so i'll get a better test drive now, and see how it behaves, but the EGTs are way too high.

No leaks are there. Does the car pull the same as it did before this problem?

Did you touch your fpr?
Your egt's match what your FP reading are, might want to open that baby up and make sure she's still in tact. Is it the vortech fmu?



Nick
97RS

no, its the craptech...which is probably the problem itself. SFMU is one of the next things on the list...i just dont want to be left stranded again in the meantime. yes, EGTs indicate that i really am losing pressure under boost, but it still seems to pull the same under boost (which at 5psi, is to say, not much).

But the plot thickens...i just pulled the CEL code, and in addition to the expected code 15 (speed sensor), i got a new one to add to my collection...code 21, which means something is funky with one of the O2 sensors...just great. i think that code went off on my way home, because all of a sudden the car was hesitating bad, almost to the point where i couldnt get up a hill in 3rd or 4th gear. it was hitting a wall at about 4000 rpm and wouldnt accelerate past that point...does that sound like an O2 related problem that the ECU was compensating for?

Hesitation? Are you using the Fuel Cut defender from hahn, or a missing link ect?

Also I'm not expecting you to have a wideband (even thoug I should), but do you have a narrow band air/fuel gauge?, Because that might at least give you a hint of what your car is trying to do under boost, then look at your egt's.

Also you might want to check the vac lines going from the FMU to where you sourced it. Any small holes might cause the FMU not to rise the pressure like it should.

nope, i found the problem today when i noticed my car was idling a lot more quietly than usual...because the inline fuel pump isnt working anymore...i dont know why...haven't had a chance to look under the car. maybe a loose wire (hopefully), or maybe its shot completely. can anyone confirm whether the lack of that extra pump would cause a drop in FP under boost? i assume that it would. also, i dont have a wideband...i was consindering buying one with the SFMU...any suggestions? i will search for topics on widebands but while you're here you might as well throw some out there. i do have a narrowband, but it (along with several other not-so-critical gauges) are currently not hooked up.

Originally posted by cyan
nope, i found the problem today when i noticed my car was idling a lot more quietly than usual...because the inline fuel pump isnt working anymore...i dont know why...haven't had a chance to look under the car. maybe a loose wire (hopefully), or maybe its shot completely. can anyone confirm whether the lack of that extra pump would cause a drop in FP under boost? i assume that it would. also, i dont have a wideband...i was consindering buying one with the SFMU...any suggestions? i will search for topics on widebands but while you're here you might as well throw some out there. i do have a narrowband, but it (along with several other not-so-critical gauges) are currently not hooked up.

My buddy's inline pump quit and that is exactly what it would do, FP would drop seriously under boost.

time to fix it then...hopefully it's the wiring under the car, cause it's a pain in the ass to get to the wiring under the seat because my amps are mounted there.

glad you found the culprit, as far as the O2 sensor problem, mine did the exact same thing, felt like it was hitting a wall, pulled a code 21 for upstream O2 sensor, got a new one from autozone for 50 bucks, solved the problem. As far as the wideband, there are many ways you can go. I have the zeitronix Zt-2 wideband as do several other members on this bord. www.zeitronix.com