CRXtoRX7

Car history and mods:
Just finished rebuilding my j-spec s4 TII engine, streetported, and put back in. Drove it for about 75 miles before my problem started happening, so I am still breaking it in. I have a T04b hybrid, and all of the basic bolt-ons.
Fuel Mods:
RP fuel pump (not rewired)
Greddy 720cc secondaries (rewired for high imp)
Stock 550cc primaries
New fuel filter(problem before and after new filter)
SAFCII (untuned)
FCD

Problem:
Its kind of hard to describe, but I will do my best. One day, I was accelerating in 1st, and it seems like the fuel just fully cut. That was about when I hit 2500 rpm or so, on about 20% throttle, no boost. Then, a few miles down the road, it started doing it more, through 2nd and 3rd as well. Now it progressed to me barely being able to drive it a mile on residential streets. I give it gas and it randomly cuts out, like the engine died, but the rpms stay the same, since im in gear. I found that if I leave the gas pedal exactly where is was, no blipping, when it falls back down to ~2300rpms it catches again and i keep speeding up. Its really weird, and my only conclusion is that the fuel pump is bad. I tested its volts with the car just in the acc position and it read about 10.3v. I can't check it with the car running because I am by myself and the car doesn't idle. SOMEONE HELP ME PLEASE! I have no car to drive because my daily driver's timing belt went out. I need something to drive!

TIA,
Ben

WAYNE88N/A

did you look at the low pressure (in tank) fuel filter? that's what was causing my problems when mine was doing what you're describing...

CRXtoRX7

no I haven't, ill check that out tomorrow, maybe it has gunk in it, since the gas sat for 8 months. any other things i should check while im in there?

pip

If it does have gunk in there make sure none of it is clogging up that new fuel pump.

DAN CARWIN

FC fuel pumps rarley go out, it can happen but rarely, I would check for electrical shorts or vacuum leaks. could be dirty fuel filter or injector problem. you just have to narrow it down by trouble shooting.

CRXtoRX7

the previous owner put the rp pump in, so its not thattt new. I think the problem is that the car was sitting for 8 months, so the gas is probably bad. I bet all that gum and chunks are in the intank filter. Tomorrow I will check it out.

I had another question though, when checking the voltage on the pump, is the reading with the car just in the acc position the same as it would be with the car on? 10.3 seems pretty low. I am going to do the rewire sometime, but thats just a bitch and takes a good amount of time.

-Ben

pip

The rewire is a pita but in the long run its way worth it because you will never have to worry about it again.

WAYNE88N/A

you should get about a 2 volt higher reading with the car running...after all, the system voltage jumps from 12v to 14.4 or so with the engine running...

NZConvertible

The fuel pump only runs when the engine's running, so there should be no voltage at the fuel pump when the key's in the ACC position.

Don't forget that all Turbos and S5 NA's use a dropping resistor to lower the fuel pump's voltage at low load and idle. 9-10V is pretty normal. Under load (i.e. boost) the resistor is bypassed and the pump receives full battery voltage.

The rewire is a very good idea, as it eliminates most of the voltage drop caused by the long route the fuel pump circuit takes through the factory loom.

CRXtoRX7

are you sure the pump has no voltage in the acc position? because i can hear the pump running, and i got a reading of 10.3 volts. I hope the pump isnt the problem. lets see whats in that filter tomorrow.

NZConvertible

The fuel pump is fed power from the IG1 circuit (i.e. ignition), not the ACC circuit. There's no way it could run with the key at ACC unless someone's done some seriously dodgy rewiring...

Rotory Nut

I'll agree that the pump doesn't receive voltage until the motor is turned. I just finished checking my inj.'s manualy and just replaced my fuel pump. With the hoses off the pump, no fuel spits until you try to turn the engine over. My 7 sat for over 5 years. The gas had clogged my injectors and runied the pump.

Rotory

iTrader: (1)

umm if he has the fuel pump check connector in the passenger side of the engine bay jumpered his pump will run at the ACC position

CRXtoRX7

I thought there was a whole priming the fuel system thing when you turn the key. Ill check that jumper, but I the wiring is all stock looking, i have no interior, and I can see it go right into the wiring harness. Is there anything else that could be making a whirring noise in the gas tank when i turn the key? well anyways, enough discussing, im going to go start working on it.

thanks,
Ben

SureShot

Ya know what esle can give random fuel cuts??

The TPS.

Pull the TPS connector off.
Get an analog (needle type) VOM set to the 1K scale.
Connect it to the pins for the orange & green wires.
Open the throttle enough so you can test the TPS plunger through its full stroke.
As you work the TPS plunger in & out, the meter needle must swing smoothly from ~0 to ~5K ohms.

As the TPS wears, it can give non-linear or inconsistent signals to the ECU.
A worn out TPS may give 1K ohms at idle, but have a drop out or short further up the scale.
A drop out at mid scale will tell the ECU to idle at that point & give a fuel cut hesitation.
I had one go open at the top which made the ECU go nuts, giving random fuel cuts.

CRXtoRX7

I only have a digital mm, but I will go see what its doing. Maybe its because i have it set so high, it is set to about 2v for idle, but my car still doesn't idle. Any way to get a new rebuild to idle, should i try the idle set screw?

SureShot

Before you try to adjust the TPS, make sure it's not worn out.
It should read near 0 ohms with the plunger in, and increase smoothly to about 5K when fully out.
The idle setting is near 1K, so for example, if it dips below 1K at half stroke, the ECU will cut fuel.

CRXtoRX7

alright, I will check that, but if this matters, the car doesn't cut out when i rev it in neutral or with the clutch in.

SureShot

With no hesitations in neutral it may not be the TPS, but I'd sure test it anyway.

Mine drove me nuts for 2 weeks because it was so intermittant. When it got worse, I found it.

It's possible "elfking" in that other thread is having a similar problem.

CRXtoRX7

ok. tested the tps, seems fine, but its hard to move the throttle, hold the two testers in and watch the tps at the same time. I figured out that i meant in the "on" position, not the "acc" position before. However, without jumpering that cable, the pump stays on with the car in the on position. I listen back there, and it doesn't sound right. Kinda like its sucking in air, and making little noises, not just a constant whirr. So I opened it up(im a little high off gas fumes right now...) and i pull it out. in the little can thing in the tank that the pump assembly goes in, lies a ~2x2 inch piece of floating black rubber. looks like it has a little bit of something written on it. so i pulled that out. now is the fuel pump supposed to be connected at the bottom rod? the rod is just hanging loose. The filter is kinda bent up and a little orangish brown. Do local parts stores carry those? how bout the dealer? and what do i do about the pump always being on? I tried jumpering the yellow connector in the bay, and nothing changes. any help appreciated
-Ben

CRXtoRX7

Alright, I figured out that the black rubber piece is what holds the bottom of the pump in place on the assembly. So i put that on and washed out the in-tank filter. The pump is still always on, but I don't see why it is a problem. Anyways, I drove it around and it seems that the little black piece was the culprit. Now, it doesn't cut out. My only problem now is that my car won't idle. The tps is set to 2.3 volts. I am going to adjust the throttle cables to get rid of a little slack, then I might adjust the idle set screw. Any other ideas?

thanks for all of your help,
Ben

Josepi

TPS should be set to near 1v.

NZConvertible

Go back and read my post again. The fuel pump is not fed from the ACC circuit.