6bangr

I've searched the forums for threads about people with similar issues, most fuel pressure issues I've read about seem to involve fluctuations and spiking or fuel pressure dropping while driving. My issue is that the car runs fine for about 15minutes then the pressure just drops to 20-25psi and the car sputters to the point of stalling while idling or driving pretty slow. So I thought I'd inquire to see what the solution was for other people who've experienced a similar issue.
The vehicle is a 2009 GT. I installed a whipple HO kit with the included dual fuel pump about 2 months ago everything else is stock. Added a boost gauge and an interceptor (no wideband). I relocated the IAT sensor but haven't wired it in up because I'm still using the provided frpp tune. The car has run perfectly with no issues since the install, never once did I see the fuel pressure under 40psi. I've probably put on about 6,000miles with the whipple.
Yesterday it was extremely hot out, I was idling in a parking lot for few minutes with the AC on taking a phone call and it started sputtering. I noticed the fuel pressure had dropped to 20-25psi and the vacumm pressure was down to 10psi so I shut it down. I checked under the hood and everything looked good, no leaks or loose connections, checked the gas cap too, had 1/2 tank of good quality fuel so I assumed that wasn't the issue. I waited about 15minutes then fired it up again and it was running perfect. After driving for awhile it started sputerring again, the fuel pressure and vacumm pressure dropped again (I didn't see it spike up or anything like that, it just goes from 40 down to 20-25). I pulled over and turned it off for a few minutes then went to fire it up as I was almost home and this time it started up rough because of the low fuel pressure. Turned it off, without waiting I cycled the keys a few times I could hear fuel pump driver priming up like the first time it was installed - then it started up and it ran perfectly once again. Just as I was pulling into the garage it started sputtering again and stalled right out. I haven't had a chance to check to see what codes it's throwing but the check engine light has been on steady since the second time the fuel pressure dropped. So it happened twice while idling and once when driving fairly slow in stop and go traffic on a very hot day. Based on what I've read I'm thinking it has something to do with a loose connection somewhere in the wiring harness or the 2nd fuel pump driver itself. I guess the part that confuses me is that it does start up and runs good but then it seems to consistently lose fuel pressure after about 15minutes. I've been running the povided frpp tune for almost two months without issue so I'm assuming the tune is ok, correct me if I'm wrong.
I'm going to check the codes, check the wiring harness, then I guess I'll have to start buying parts.
For those of you who have experienced a similar issue, what turned out to be the problem?
Would the fuel pressuer transducer have anything to do with it?
Any other suggestions would be much appreciated. I'll post the codes once I get them, though I'm guessing it'll probably come up with the classic P0191 fuel pressure code.

RyanzWhipple

Check the supercharger oil separator.

moosestang

I probably sound like a broken record, but I immediately want to blame your throttle body. They are notorious for failing and causing all kinds of idle problems. I would look at the tps position (on the interceptor gauge) next time it does it. The low vacuum and fuel pressure could both be a symptom of a malfunctiong throttle body.


It could be the wiring for the fpdm's, I'd check the grounds, make sure you sand the paint off.


Damn! Just noticed those are mods to your v6!!!!!! Since you don't have the BBK throttle body, I'd pull the vacuum line off the fuel pressure regulator and make sure it's dry. do this after idling for a few minutes.

You need to read the codes! The interceptor gauge can pull the DTC codes.

hammeron

i also, would suspect the Fuel Pressure Temperature Sensor.

6bangr

Thanks for the reponses - I deleted the v6 info from my signature, I didn't even realize that was still there. And yes those BBK throttle bodies are nothing but trouble.

Checked all the wiring connections and fuses - all looked good. Started it up and the fuel pressure was still down around 20. I checked the vacuum line on the pressure sensor as mentioned - bone dry. After yesterdays attempt the vehicle doesn't start anymore.
Got the codes:
P0191 - Fuel Rail Pressure Sensor (A) Circuit Range/Performance
P1233 - Fuel Pump Driver Module Disabled or Off Line (Fuel Pump Driver Module)

So I'm guessing the P1233 is probably causing the P0191. If the driver isn't working then I would assume the pressure sensor would probably throw a code as a result. Again, correct me if I'm wrong.
I already re-installed all of the harness connections (incl. grounds) and inspected all of the wires & fuses. However, I'm not ready to rule out the harness itself given that it's difficult to inspect and test every wire.
So am I correct to assume that I'll need to replace either a faulty fuel pump driver or the wiring harness itself?
Is it common for the fpdm to fail, has it happened to anyone else?
If you had to guess which part do you think is at fault?

moosestang

I would suspect the fpdm, but others have had bad wiring harnesses. Find one in a junkyard (fpdm), it's the easy thing to rule out and should be the cheapest. The problem here is that it should start and idle on 1 pump, at least I think it will. It's possible that if one fails the other will not work, but I didn't look that closely on how they are wired.

The FPR code is probably due to low pressure from the pumps.

hammeron

if you turn the ignition switch to ON, can you hear the fuel
pump(s) at all at this point?

if not, i would check the inertial fuel cutoff switch and also
the fuel related relays and fuses. Then start looking at harness,
driver and/or pumps.

moosestang

Yeah, mine make a really sweet sound with a full tank of gas. It actually sounds like SSSSSSSSSSSwwwwwwweeeeeeeeeetttttttTTTT.

hammeron

mine sounds the same!

6bangr

I could certainly hear the pump/pumps priming after the first few times it happened. In fact, initially I pretty much had to cycle the keys a few times just to get it start. It felt like it was priming up like the first time and that it just couldn't hold the pressure once it started running. I can still hear the hissing noise when I turn the key to the start position. It did actually start up today, but had the same fuel pressure issue and once again stumbled to the point of stalling.
I'll take a look at the inertia switch for the hell of it. I'm going to change out all the fuses tonight even though they looked good. Tomorrow I'm going after the relays and heading to the junkyard for a fprm, after that I'll start with some wire testing. And after that... to the dealership I guess. If there's anything else I should be checking in the process please let me know.
The P1233 code has me fixated on the harness or driver. I'm trying to convince myself that the pump is fine because I really don't want to pull that out again.
It was running beautifully for almost two months, now it's sputtering and I'm fiending for some boost...