The car has basic bolt ons, evo 9 turbo and walbro fuel pump. IDC was through the roof when we went to tune and the car struggled to make 300whp on 22 psi which is where the car sits now and is as rich as the tune can be made... First thought was maybe a bad walbro so I replaced it with a new. Then moved to other parts of the fuel system and replaced them; stock injectors, stock fuel pressure regulator, hardwired the fuel pump, bypassed the release valve, replaced the fuel filter and basket, blew out the lines, etc.
Yesterday we finally got a fuel pressure gauge and routed it to the windshield so we could see it under boost. At idle the car was at 53psi and only increased 10 psi for 20psi of boost so then moved on to try ANOTHER fuel pressure regulator off of a known working evo, nothing. Then tried replacing the fuel pump and basket straight out of the same evo and still no luck. After this we pressurized the whole system and could get it up to 100psi no problem. Smelt and found no leaks, everything tested fine. Then just to make sure, we boost leak tested the car. End of the night the AFRs were still the same, which will obviously change being that the tune is so rich.
If anyone has ANY ideas please do let me know.

 

I've never heard of this before. The best I can tell you is that base idle fuel pressure should be 42-45 psi. Too rich and low fuel pressure under boost is an odd combo.

 

also seems like an odd issue,the high pressure at idle is probably from hard wiring the the pump, the low pressure under boost sounds like the FPR but you said you swapped that with a known good one. Is it possible you have a bad vacuum line at the FPR?

Have you taken your EGR equipment off the car? Have you recently had the injectors out? or another part of the system. I know you checked for leaks but about the only things that could cause a low pressure condition are the FPR, bad pump, or a leak somewhere.

 

No we checked the vacuum lines going to the fpr and made no difference. We swapped injectors and everything.

 

I tuned the car, and have been providing tech to my buddy Mike in GA who is troubleshooting the car... he has gone over everything and is just as stumped as I am on this issue... it is basically not providing a 1:1 rising rate fuel pressure ratio... however you take the vacuum line and compress it with shop air and it rises 1:1... It is like something is hampering flow from the hanger/pump assembly, however physically everything is good to go... Possibly the evap canister clogged causing to much vacuum for the hanger assembly to overcome???

 

if the fpr rises with shop air, can you confirm that the manifold tube that generally supplies its boost/vacuum source to the fpr is clear, replace the stubby line from the mani to the fpr & go from there.

iirc, that solenoid thingy on the side of the im is used for cold starts...not 100% certain, as i havent had that hooked up since ~2005.

GL

 

Aby, we have already verified that the small FPR nipple on the intake mani is open as we swappeed to the BOV barb... The FPR solenoid is not in the loop... new hose from the mani to the FPR...

 

Yup. Did all this the other night.

 

^ how can the fpr work with shop air & not with boost pressure from the turbo?

have you tried a different boost/vacuum source?

 

Not sure but why (as bad as it is and yes we tried it without it) would my boost gauge see boost accurately but the fpr doesn't. It's maybe an inch up the line from it. We did try it without the boost gauge line hooked up just to make sure there was no leak in that vacuum line.

 

update: Mike just texted me saying he bypassed the egr and evap and still no change... :/

 

Could it be an issue with the pump not being seated properly, I have head of that before when pressure begins to rise... Good luck guys!

 

What exactly do you mean by not seated properly? We did try a whole nother pump/basket set up.

 

sounds like the ecu is shot. but im guessing. my friend had the same exact issue on his turbod lancer and could never figure it out, turned out it was the ecu.

 

It sounds like you've got some smart people on it already. Desperate times call for desperate measures. I'd replace the feed line (it's cheap to do), and dump the return externally while testing.