[SOLVED] HPFP Issue (in-tank pressure)

[Brado]

Keep in mind were not MSF that "donate or we won't help you Brownie" attitude isn't here

Unfortunately that's the exact first impression I got of these forums.

From this thread, a massive amount of shit was talked about DramaTuned, but all the reasons and supposed evidence are hidden behind the member section. I find this silly to be honest, especially when trying to convince someone the tune is the problem. Turns out the tune wasn't the problem and that thread is still the only place I've ever heard anything but good things about DramaTuned mentioned.

You're doing DramaTuned a service by hiding this information. If his tunes are that bad, share the info to the public and let the people decide.

Bad impressions aside, it's neither here nor there. I don't want to stray too far from the fueling issue I'm having!

 

[jdab555]

Providing another update. I've been waiting to post until I had fixed the issue or had something concrete, but you'll see that's not the case here.

So I swapped spill valves from the used HPFP assembly I picked up and unfortunately still saw the issue. I then swapped my CorkSport HPFP internals into the used housing that I picked up and the car ran great! There was still some hesitations during WOT, so I decided to swap the secondhand spill valve back over. With a secondhand HPFP housing and spill valve, I was feeling great as the car was running pretty well, but not perfect. Since I didn't spend any time cleaning the "new" HPFP as I was just testing it, I pulled the secondhand spill valve back out and cleaned that up. I threw that back in and drove around seemingly without issues until randomly at 70mph on the freeway my fuel pressure dropped to ~40 and then slowly rose back up as I coasted off the freeway.

I'm kind of lost as to what could be going on here, but I know the spill valve plays the most important role as it's the only thing electrical on the fuel pump.

How tight are you screwing on the top portion of the HPFP housing with the sensor plug / locking ring? I found that too tight or too loose will have a negative effect on fuel pressure across the range, has to be just right.

 

[Brado]

How tight are you screwing on the top portion of the HPFP housing with the sensor plug / locking ring? I found that too tight or too loose will have a negative effect on fuel pressure across the range, has to be just right.

I make sure it's pretty snug, but that's about as good as I can describe it. Without any torque specs it's impossible to say. It's definitely not on the loose end. I guess I'll try loosening it a bit and/or tightening it a bit in my troubleshooting.

 

[jdab555]

I make sure it's pretty snug, but that's about as good as I can describe it. Without any torque specs it's impossible to say. It's definitely not on the loose end. I guess I'll try loosening it a bit and/or tightening it a bit in my troubleshooting.

if you can read your actual HPFP on the AP, while your car is idling you can make a very small adjustment on that ring and watch the pressure go up or down, get it to the ideal (~400) at idle and it should be dialed in.

 

[Brado]

Going to update this and call it resolved. I think this issue was actually two separate ones. The 60psi drops were one issue and the ~1700psi limit was another. I haven't seen the 60psi drops since my last post, and the ~1600psi peak was the result of the PRV.

I purchased another PRV, this time used, and that solved the issue. Upon pulling out my PRV with the CorkSport stainless filter, I noticed that the filter was not in the PRV at all, and was actually sitting in the rail still. I'm not sure if the PRV was the culprit for the ~1600psi peak or if it was because the filter wasn't inside it at all. In any case, I can hold solid fuel pressure now.

While I'm glad the issue is resolved, I wish I had a more conclusive answer for the ~60psi drops. My spill valve still makes a ton of squeaky noise, so I'm still tempted to get another one that's not 15 years old.

 

[Brado]

Reviving this as I've learned more since my last post.

After near 1800 fun miles on the new motor/turbo, the fuel pressure dropped to ~60psi on a drive. Had it towed home and started troubleshooting the spill valve. Having two spill valves, I just found it unlikely they would both be bad. Among my testing, I found that if I wired the positive battery terminal to the spill valve, with the other to the negative, the spill valve would work seemingly just fine. If I hooked it up to the connector, there was almost always nothing, with a few intermittent periods of pulsing.

I'm hoping this isn't indicative of an ECU issue as I've load tested the wires already in a previous comment. Does anyone have any ideas?

 

[Awafrican]

Sounds like you've got an issue in the connector / harness I'd check it for cracks / shorts. Perhaps your connector is coming off just enough for poor contact?

 

[L337TurboZ]

It could be poor terminal tension. Are the pins in the spill valve connector spread?

 

[Brado]

So I forgot to mention but this last time the fuel pressure dropped it finally threw CEL P0091 which is low circuit for the spill valve.

Anywho, following the workshop manual for troubleshooting said DTC, I noticed that after replacing the spill valve, well the entire pump, the next big step was to change the PCM provided all the wires check out.

Before going the route of changing my PCM,
I decided to swap spill valves with a buddy who drove over with a working one. Sure enough, 1700psi right off the bat on a cold start. Turned it off shortly after and replaced it with mine and it failed to idle, dropping to ~60psi.

That said, I’ll be ordering a new HPFP assembly entirely to get this done and over with for good, but I wanted to update this thread in case anyone had any other thoughts.

 

[Brado]

For anyone who stumbles upon this in the future, here’s the diagnostic steps for DTC P0091 as an image and full resolution PDF.

DTC P0091: “Fuel pressure regulator control circuit low”.

 

[Brado]

Updating this one last time (hopefully) to say that my issue is fixed as expected. The new pump, and spill valve by proxy, are working as intended and fuel pressure is great and matches what's being desired by the tune.

Thanks everyone for coming to my TED Talk!

 

[Brado]

Let's revive this again as this is indeed a recurring problem!

I am back to ~60psi ITFP drops randomly, enough so the car cannot be driven even around town easily.

​

Current state of my internals:

​

My internals don't look bad to the point where this would happen, but let me know if that's incorrect.

Unfortunately the service manual just wants you to replace the entire fuel pump, which I have done once before with new OEM.

​

I have tried wiggling the wires, checking for obvious connection issues, etc. Nothing is jumping out. I'm leaning towards taking it in as I've just been through this so many times and can't pinpoint it this time.

Lastly, I've attached the datalog above along with some others that illustration the issue.

 

[Easter Bunny]

I would look over the wiring more especially the connectors. It still seems like the problem is there

 

[Brado]

Big update, with some good troubleshooting and good news.

TL;DR: Something about the HPFP housing I had was giving me the issue.

Troubleshooting step 1: Pressure Relief Valve

Despite my thoughts, some people recommended trying another PRV, to which I did. No luck or change with that.​

Troubleshooting step 2: Spill Valve

Next I wanted to make sure my spill valve was indeed getting a signal. I took a multimeter to it and drove around while monitoring the voltage. Our spill valve seems to operate from 0v to ~1.57v, which was neat. When my fuel pressure dropped to 60psi I noticed my spill valve immediately jumped up to the full voltage, meaning the car was at least telling it to do it's thing. This ruled out any electrical issue.

Here's a picture showing my low fuel pressure drop and the voltage to the spill valve. Very cool to watch how that all works.
​

Troubleshooting step 3: Refurbished HPFP Housing

Having ordered a refurb HPFP for another spill valve to try, and it having no difference, I had the housing and internals that I decided to try next. To my luck, on the refurbished unit with OEM internals, the car drove as a stock car would. Not once did I see the 60psi drops.​

Troubleshooting step 4: Refurbished HPFP Housing w/ AutoTech Internals

With this testing done I took the AutoTech internals (piston and sleeve) and swapped them in, no pressure drops!​

So the housing has an issue, whether that's an o-ring, seal screw, etc I am not sure. I would like to figure out what about a housing can cause these issues, as it would be good info to have. I've read about someone having issues with the housing once before, but it's just a bunch of drilled holes and fixed pieces, with the exception of the seal screw and o-rings. Maybe the exit check ball?

In any case, the issue has been fixed and I was really happy to go through the troubleshooting process and dwindle it down!

 

[Awafrican]

Glad you got it sorted! I think this is around 3rd or 4th pump housing I've heard of failing over the years and it's always weird trying to diagnose it, thanks for keeping us updated.

 

[Brado]

A strange issue, to say the least! Do you have any recollection of what was wrong with the previous housings you read on?

 

[Awafrican]

A strange issue, to say the least! Do you have any recollection of what was wrong with the previous housings you read on?

I unfortunately do not, I don't think anyone's figured out what is was either as they didn't see anything visible from what I recall

 

[SyntheticAtmosphere]

First Ive heard of anyone hooking up a multi-meter to it and taking a drive. Kudos, good skills!!

 

[AndrewC08MS3]

I have a similar issue to the OP that I’ve been trying to troubleshoot for the past week, scouring the forums and I really have run out of solid directions to go in.
When I do a cold start up, I have solid 1500psi that slowly drops down during warm-up as it should. if I blip the throttle once coolant gets above 100°F, fuel rail pressure drops down to tank pressure 50-60.
Once this happens, restarting the car brings me right back to tank pressure unless I let it sit for a while.
HPRV was replaced shortly after the built engine block two years ago, along with injector cleaning and bench testing courtesy of injector RX. HPFP internals were also replaced at that time because the autotechs had sent debris downstream and clogged everything (plastic screens were torn).

initially, I started by checking the two fuel pump relays and then moved onto disassembling and inspecting the HPFP. Nothing out of the ordinary there.

I then checked continuity from PCM pins from 2F and 2G to the spill valve on top of the HPFP. And NOTHING! this was tested with both ignition on and off. At this point, I was pretty confident that I had a break somewhere between the Bill valve and the PCM. Last night I ran jumpers between those two expecting promising results, only to find tank pressure right out of the gate on startup. I then reverted back, and I’m back to where I started. At this point, I’m hoping some of you OG guys may be able to help point me into another direction as you have before!!

Thanks so much.

Also, my signature should have most of the current modifications on the car. Let me know if it’s unable to be seen or if more information is needed

 

[Brado]

I would definitely try swapping with another spill valve and/or swapping with OEM internals if you can. These will give you solid troubleshooting info!

I have spare pumps at this point, but the parts have proven useful countless times for troubleshooting purposes. You can pick one up on eBay for around $100.