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P0090. Intermittent start. Possible bad HPFP harness??

19K views 23 replies 4 participants last post by  6.4_Piper 
#1 ·
Been searching and can't find any definitely answer. So here it is.

08, 6.4 93k miles. DPF delete straight piped. Bought with the delete but I have no tuner (not sure if that matters)

So I just finished installing my upfitter switches along with an auxiliary pump and strobes to the switches. I believe it's completely unrelated but I went driving shortly after and the truck just shut off.
First thing I did was check fuses. All okay. Sat for about 20 minutes while I waited for someone to bring me my eBay code scanner and it said N/A for 4 codes.
Was able to start the truck up and it wanted to bog down at higher RPM.
Now the truck won't start again and I'm getting a P0090 code.
Can someone point me in the right direction for my next troubleshooting step?


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#2 ·
ALSO! One of the things I did today was check the filters.
this is the horizontal. It was filthy after less than 10k miles.The one on top of the engine was super clean. With the exception of TINY metal shavings. I'm talking about the size of a grain of sand.


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#3 ·
You should google the p0090 code. It's a fuel pressure regulator control circuit code. Lots of info and most of it points to a problem with the HPFP. Based on some of what I read it's a circuit fault, not a sensor fault so it could be related to your recent wiring of the upfitter switches. I would recheck everything I touched on that work and make sure you have not caused the issue with a bad ground or chaffing....but the metal in your fuel filter is a big problem....
 
#5 ·
You can test for shorts at the 4 pin connector, next to glow plug control module. That is the connector for hpfp cover gasket/harness. Vcv and pcv
 
#6 ·
Alright. So I did what you suggested once I got back from work. I had continuity on both sides. I got a scanner with live data and my pressure looked good. Around 5k at crank up and up to around 14k somewhere around WOT. I took it for a drive and as soon as EGT got up there a little bit it stalled out again. Now I'm getting 0 pressure KOEO and only 300 when it's cranking. Now I only have continuity at 2 of the pins. My best guess would be that the wiring is crapped and once everything warms up, the insulation expands and breaks what little connection I had. I'm not too familiar with the 6.4. I'm okay with gassers so I'm kinda learning as I go along. But does this make sense? I'm almost 100% it's the harness.
Thanks!


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#7 ·
Pretty much exactly what you describe..... When you tear into her make sure you check for metal in the hp fuel system before wasting the time to go further though.
14kpsi at wot is low though..... Very low.

Very possible you have a combination of problems here... hpfp might be coming apart and the harness might be shorting out.
 
#8 ·
Yeah after I posted I looked at the live data again and it was somewhere around 27k near WOT. 14K was only around 50%. I was reading the scanner and driving at the same time, my bad. Does that seem right though??
Thanks for the help. At least I know I'm on the right track.


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#9 ·
Also. I've had an incessant P132B turbo actuator code. And EGR is not operating. So, I'm going to try and get these issues fixed (or at least accurately diagnosed) while I've got the turbos off. I'm not overly concerned about EGR working since I plan on doing the delete soon anyways UNLESS the EGR valve sticking is causing the P132B. Any advice there?
Thanks again!


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#11 ·
Wow. That news makes my whole week right there. So, even though the P132B was going on a good while before the P0090 do you you still think they're related? Now I just gotta get my extended warranty to cover the repair. Even though I'll be doing the work myself. I plan on seeing about having them pay somehow.


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#12 ·
Just throwing this out there...

While the cab is up do 2 things: 1. Yank the valve covers and replace rocker arms. 2. drain fuel from the hp system and check for metal.

If you have the time and money get a set of up pipes without the egr tube and do your egr delete when its easy.
 
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#16 ·
Just throwing this out there...



While the cab is up do 2 things: 1. Yank the valve covers and replace rocker arms. 2. drain fuel from the hp system and check for metal.



If you have the time and money get a set of up pipes without the egr tube and do your egr delete when its easy.

Yeah ideally that's what I'd do. Looking at the price on the rocker arms I'm convinced it'd be best to do that too. My only thing is I'd need a tuner and custom tune to do the EGR delete properly, right?? That's been the only thing holding me back from doing it. Just the extra cost of tuner/tunes.


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#14 ·
Don't want to give you a hard time, but don't ever expect a 6.4 to make life easy. Whenever the cab goes up for something like this expect the worst. Don't be surprised if you end up with a grenaded hpfp and have to replace the entire system and flush the lp lines/tank.

Just keep that in your mind and make sure you do everything you can to check while its apart the first time.....
 
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#17 ·
@kaya when I get back from work I'm going to check the filter again and post up pictures of the black cap test. @ Crazy I'm optimistic but ready for the worse. TBH I think I'm leaning towards replacing the High pressure system while I'm there. It just makes sense right? Do the replacements tend to last longer than the factory ones? Also, I'm planning on doing this cab on without lifting the cab. I think I've seen a couple Youtubers do this. We'll see how I feel about that once I get started.


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#18 ·


Alright. So here we go. See the tiny specks that look like specks of dust? That's what I was referring to as "shavings" same in the fuel bowl next to that glob of what looks like some sort of acrylic sealant? No bigger than that. But at 93k. Is this normal wear and tear type stuff? Or is it cause for concern? Either way I'm tearing into her tomorrow. Just gotta re-organize my tools and clean my nasty *** workbench.


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#19 ·
Check out dieseltechron's channel. He has a good video on tilting the cab without the need for a lift. When pulling turbos its completely worth it........
 
#21 ·
Yea it's hard to say. Those specs could easily hang an injector. You really can't be too cautious with these piezo injectors.
You're going to pulling the rails to do the rocker arms anyways. While they're out, pull the plugs off the ends and drain the fuel into a black spray lid. Metal likes to collect in them.
See what you find in there. But really, just with what you've got, I'd probably be dropping the tank, flushing the system draining and flushing the rails, and replacing the hpfp.
It only takes microns.
If you've ever had one of these hang an injector and run away on you, you know what I'm talking about.
I'm not saying you won't be fine without doing all this. But there is a chance.
If you do go through with it, drop the tank before doing any work. Pump the diesel out, clean that tank right out, reinstall, use fresh diesel to flush the system by removing the return line at the hfcm and running that into a pale. Then, go ahead and do the work. The idea here is not to contaminate any of the new or thoroughly cleaned parts.
It may sound like Overkill, but like I said, there's no such thing with these fuel systems
 
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#22 ·
Hey I found this spring on my floor while swapping out the drive gear on the HPFP. Problem is my garage floor has a bunch of junk laying around. Does this spring belong on the new one? Also, the old pump has a snap ring and the old one doesn't. Should I swap this over as well?
Thanks guys!



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#23 ·
Just in case anyone was curious I ended up swapping the HPFP, harness, and the jumper harness that leads to the connector by the GP module. Went ahead and did the complete EGR delete and some up pipes from Rudy's. I think I've driven close to 300 miles now since the repair and feeling pretty good about it. Also. When I got to the old pump the harness had been replaced but the jack wagon that did it apparently didn't care for the zip ties and the connectors were not as secure as they should've been. (I used the zip ties) When I compared the two pumps the old one was certainly harder to spin the gear. The new one was nice and smooth. Anyways. Shout out to all that helped with good solid information.



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