Ms6 fuel rail pressure loss past 5000rpm

[Rogi]

My ms6 is having a fuel rail pressure loss past 5,000rpm. A little background of the car:

built engine with around 600 miles.
6262 turbo.
return style fuel system with aeromotive fuel pressure regulator,
base pressure set at 40psi with rising rate,
Walbro 525lph ITFP with new stainless steel strainer, fuel pump has hardwire kit installed ,
Fuel pump resistor bypassed,
autotech HPFP internals,
6AN fuel feed line with stock fuel line as return,
radium venturi pump,
BeCuse injector seals with cleaned injectors,
New OEM FPRV,
damond Port injection with focust st manifold,
ngk 6510 spark plugs gapped at .022 per freektune recommendation,
compression test: 186, 185, 183, 186.

Currently the car is getting tuned for Direct injection only currently by freektune, it will hold steady 1700ish psi and then steadily dip down 700psi by 6000rpm. i have rebuilt the hpfp with reys ethanol safe seals along with taking the autotech internals and swapping them into a donor housing, new OEM FPRV, KOEO test showing fuel rail pressure climbing and holding psi. still having the same issue. Car runs great below 5000rpm, idles and start up normally with no issues. I am running out of ideas on what else could cause this issue, ordered a new autotech internals kit and going to swap them in once they arrive. i have attached some data logs of the issue. any feedback is greatly appreciated .

 

[DISIFTW]

How's the hpfp being fed fuel and do you have a boost reference going to the FPR?

 

[Rogi]

How's the hpfp being fed fuel and do you have a boost reference going to the FPR?

Hpfp is being fed from a y split in the engine bay. Setup is 6an line from ITFP basket to engine bay, 6an to double 6an y split, one line goes to hpfp feed, the other goes to the PI fuel rail, exit side of fuel rail has the fpr, exit of fpr goes to the ethanol sensor and then the factory feed line which is my return line now.

FPR is boost referenced, have a line from the intake manifold hooked up to it.

the pictures i attached with the different marker colors on it go as such:

Green- 6an feed line from the ITFP
blue - 2 feed lines both coming from the 6 an y split, one goes to hpfp feed line, other goes to pi fuel rail
purple- return line from the fpr that goes through the ethanol sensor then through factory feed line which is now return.

 

[Easter Bunny]

Have you done the test of the prv with a hot motor?

 

[Rogi]

Have you done the test of the prv with a hot motor?

Yes, pressure climbing up slowly.

 

[Easter Bunny]

What is the pressure when it releases?

 

[Rogi]

What is the pressure when it releases?

pressure built up to 1750 psi and still slowly climbing before I stoped monitoring it. It did not release the pressure. I’m assuming it’s because the relief pressure is at 1850psi for the fprv.

 

[Easter Bunny]

should build to 1850 and crack there

 

[Rogi]

I

should build to 1850 and crack there

I don’t believe it is the fprv, freektune got back to me this morning. He believes it is due to the itfp either starving of fuel or leaking at one of the connections. Am going to summit currently to pick up a hydramat to ensure the fuel pump stays submerged. That seems more plausible as I currently have a stainless mesh strainer on the fuel pump pick up and the pump could be emptying out the basket when doing a pull / fuel sloshing to the back of the tank. Will report if this will make a difference with logs of course

 

[Enki]

I know you've already done this, but pull the HPFP and clean it with naphtha (lighter fluid), then lube it with Redline injector cleaner. Inspect the internals for visible wear markings; it could be a friction issue or the new o-rings could be too tight. Note that the ring in the retention nut is actually an x-ring not an o-ring. This is kind of important.

During reassembly, put it back on the car with the spill valve loose and just before you button that up, fill it to the bottom thread with Redline to "prime" it then lock it down.

Worst case, you've inspected and cleaned your pump. Best case, you find the problem.

If your torque is relatively flat before and until it starts dropping fuel pressure, then that suggests to me that it's probably not a flow issue from the ITFP (though that's a bit of a vague/inaccurate test). The HPFP only needs a few PSI to be "fed," and at the higher RPMs, it seems more likely that the internals are simply not retracting via spring force fast enough for a full-stroke. I have had this issue before.

 

[Easter Bunny]

Does it still do it with a totally full gas tank?

 

[Rogi]

Does it still do it with a totally full gas tank?

got a 3x15” hydramat installed in my itfp, still having the same issue. Filled up the fuel tank fully and did another 3rd gear log, no changes based on datalogs. Am going to pull the hpfp off again, I have a brand new auto tech internals set coming tomorrow and going to swap them out as the set I have in my hpfp currently, I purchased used. Will upload pictures of the internals that is in the car currently.

 

[Rogi]

I know you've already done this, but pull the HPFP and clean it with naphtha (lighter fluid), then lube it with Redline injector cleaner. Inspect the internals for visible wear markings; it could be a friction issue or the new o-rings could be too tight. Note that the ring in the retention nut is actually an x-ring not an o-ring. This is kind of important.

During reassembly, put it back on the car with the spill valve loose and just before you button that up, fill it to the bottom thread with Redline to "prime" it then lock it down.

Worst case, you've inspected and cleaned your pump. Best case, you find the problem.

If your torque is relatively flat before and until it starts dropping fuel pressure, then that suggests to me that it's probably not a flow issue from the ITFP (though that's a bit of a vague/inaccurate test). The HPFP only needs a few PSI to be "fed," and at the higher RPMs, it seems more likely that the internals are simply not retracting via spring force fast enough for a full-stroke. I have had this issue before.

I actually came across your post in other forums of using naphtha fluid to clean/ redline to prime it and followed that procedure when rebuilding the pump in a spare hpfp housing with Rey’s ethanol seals. Only thing I reused was the auto tech internals from the pump and put them in a spare hpfp housing to rule out a bad housing. I have a brand new set of auto tech internals arriving tomorrow so am going to install that and report back. Will also take pictures of the current internals and post them here.