Too high fuel pressure causing issues????

[Strokersace]

Ok, so talking about the 97 in my sig...

I've had the motor back in and running for a week. Up until yesterday, I'd put maybe 400 miles on it and it's been flawless. Smooth crisp startups, idles nice, runs down the road great, etc, etc.

Yesterday, however that all changed. Pulled into a parking lot in town and put it in park. As I did, the engine started romping horribly and the factory oil pressure gauge was flickering badly as well. Pressed on the throttle and it smoothed out and was fine. Shut the truck off and end into the store. Upon startup after coming out it was fine. I immediately put it into gear and it did the same thing all over again. I watched the scangauge and the oil pressure would fluctuate but never below 500, duty cylce was never extreme (12ish at idle, 20ish while driving).

Did this off and on throughout the next hour or so while in town. Approx. 20 minutes after the initial "romping", I happened to look down at the fuel pressure gauge and it was maxed out at 100psi. Never changed the entire rest of the day. I assumed the sensor was bad again.

Had to drive to a job interview in the afternoon and when I got into that town and got to the 1st stoplight, the engine died as I was slowing down. Started right back up and kept driving. Upon coming home I noticed that it wasn't starting as smoothly as it had been. It was taking more cranks to fire. Also noticed that when I was sitting there idling, the rpms would fluctuate 100 or so in both directions and you could hear it in the motor (not just the gauge moving). It'd drop into the low 500's and jump up to 750ish. Died again when I was close to home slowing down to turn the corner.

Parked the truck today and just had time to work on it this afternoon. Checked the codes and the only one was the CPS code. Thought I'd change that out with an extra one I have. The one in it was a blue CPS, replaced with a new (from last year) IH black cps, one of the good ones.

Decided to rule out the sensor for the fuel pressue gauge being bad. All I had for a mechanical gauge is a 160psi air pressure gauge. When I turned the key on the pressure is reading 130psi at the regulator!!! What the hell could be causing this??????


My fuel system is as such: Both tanks w/ 3/8" line into the factory selector valve, 3/8" to 1/2" line into an AirDog1 with 10micron filter, 1/2" into a Walbro, 3/8" line into a 2micron post pump filter, 3/8" to ITP bowl delete block, into front port on heads, out the back port into the regulator, then 3/8" return line back to selector valve then back to each tank. The regulated return is setup in the same fashion that ITP/Strictly Diesel does theirs. The return for my AD is y'd into the stock return line right before the selector valve.

Are my rash of symptoms related or not??? And what the hell could be causing my fuel pressure to be so dang high, just out of nowhere?

 

[Big Bore]

Bad regulator?

 

[Strokersace]

Good question. I guess that's always a possibility.

I did try adjusting the pressure and had the adjustment screw almost completely backed out and it didn't change a thing.

 

[twelch3]

Did you try to tighten it down to decrease fuel pressure?

 

[Blowby]

Clogged filter will cause this if it's after the pump. Not sure if you still have the OEM filter, or where your reading pressure since it's your RR fuel system.

 

[Strokersace]

Did you try to tighten it down to decrease fuel pressure?

On the regulator, if you tighten the screw down, it increases pressure, loosen it, it decreases.

Clogged filter will cause this if it's after the pump. Not sure if you still have the OEM filter, or where your reading pressure since it's your RR fuel system.

No OEM filter. It's 2micron Baldwin spin-on after the pump. Pressue is read right at the regulator, after the fuel comes out of the heads.

 

[dave186]

Must have a restriction in the return side somewhere.

 

[Strokersace]

That's what I'm wondering Dave. Going to pull the return line from the selector valve and drain into a bucket. If that drops my pressure back to normal, then I know that the selector valve is the issue. I can swap tanks and it doesn't change anything.

 

[Dieselboy.]

AE software ? I had similar symptoms but don't have an in cab fuel pressure.

No where as severe either. Icp or ipr ? I'm not sure how the guts of the regulator look but perhaps something is stuck open. Ball valve etc. :s

 

[Strokersace]

I have an Aeroforce scanguage, no AE though. Have a separate in cab Isspro EV2 fuel pressure gauge to monitor fuel. To rule out a sending unit failure on the gauge, I put in a mechanical gauge to know how much I was reading.

 

[Strokersace]

Background info:

I'm running a BTS dual HPOP system. Every sensor on the motor and also the MAP are brand new. IPR's are Motorcraft, IPC is Ford, MAP is Motorcraft. Installed all new when I reinstalled motor.

Oil is 5w-40 fully synthetic Schaeffers.

I took it for a little drive (10 minutes maybe) right after starting this thread yesterday evening and it died again while slowing down to turn off the highway. So the CPS is not the issue with that.

The regulator is an Aeromotive unit. The black/red one with -10AN inlet ports, -6AN return.


BTW- I had a similar issue over a year ago where the pressue spiked, but I was able to get it to adjust slightly with the set screw. It ended up being a restriction in the return side of the selector valve likely caused by some crap in the fuel that f-d up the supply side shortly before that. Went from no fuel pressure 1 week, to too much the next. Replaced the selector, made sure there was no trash in the lines and no issues since.

At that time though, it never effected the idle or driveability in any way.

 

[Strokersace]

UPDATE as of this morning:

I disconnected the return line between the "y" of the factory return/AD and the selector valve and ran the line into a bucket. Pressue at the regulator when I did this was 30psi. I tried to adjust it up and it would not go over 30, however, would adjust down below that. I then hooked the line back up going TO the selector and the pressure was back up to the 130ish mark.

This tells me a couple of things - the selector has a restriction, causing HIGH pressure "backfeeding" to the regulator. It also tells me that I have a supply line issue as well when there is no restriction of the return. As for the filters: the AD water sep and 10micron fuel filter as well as the 2micron Baldwin spin on post pump filter were brand new out of the plastic approx 600 miles ago. They've had 3/4 of a rear tank and 1 full front tank ran thru them before this started on Wednesday. The Walbro has about 18K miles on it and is 1 1/2 years old. The regulator is close to 3 years old and has around 30K miles on it.

So a few things are going thru my mind: Either my Walbro has crapped out and the only thing supplying fuel at the lower pressure is the AirDog; the filters are clogged, or the regulator is going bad.

Thoughts?

 

[Dieselboy.]

Seems to me you have an issue on both sides (feed/return)

By basically taking out the selector and only get 30psi something tells me you have a feed issue as well. However something in that selector or after is causing a huge restriction to spike up 100psi.

Im not familiar with the OBS fuel system on the dual tanks So I cant really comment too much on that, however can you rig up something to bypass one filter at a time ? Both filters ? and the walbro ?

If pressures start changing when you bypass a single component of your fuel system it could narrow the feed side issue down to a single piece.

One suggestion just too rule out the return side if you could throw a ball valve in place of your return selector. Maybe you have a plugged selector. Im just throwing out ideas here.

On edit: Something else to consider. When I wired my fuel system up I used a fuse on the main line and one fuse for each pump. Maybe an electrical issue caused the walbro to shut down ?

 

[Strokersace]

All good thoughts and options.

I actually just crawled back out from under it. Checked all fuses and they're all good. I had bought another Walbro last year when I was having some problems only to find out at the time in was not the pump. So I've had it as a spare in the toolbox.

I just installed the new Walbro and with the return dumping into the bucket with no restriction, the pressure at the regulator was easily adjustable up and down. I set it back to 65psi as my previous adjustment attempts had it set at around 45. So I've figured out the supply issue being the Walbro crapping out. The return side still have the issue and it has to be the selector causing the restriction because it doesn't matter which tank I flip to, it's still the same. If it where in one of the lines that was tank specific, it'd only have high pressure on that one. So it's gotta be the selector on the return side.

I'm thinking for now, I'll just keep running on the front tank and I'm going to by-pass the return side of the selector. Just tie the return line from the motor directly to that tank. I'll still use the supply thru the selector until I can figure out what I want to do. I called the local salvage yard that I use and they don't have any on the pickups they've got, and I can't imagine those selectors are very cheap through ford. The aftermarket ones I've seen aren't cheap either.

What I may end up doing is just tying the tanks together and making them 1 big tank, like the semi's have. I've heard of OBS guys doing this as well but have never really liked how it was done. My just use a sump setup to tie them together, then only pull from one of the tanks. I've got an aux tank in-bed as well, so basically all 3 would be tied together but I could fill them seperately.

 

[genuineford]

All good thoughts and options.

I actually just crawled back out from under it. Checked all fuses and they're all good. I had bought another Walbro last year when I was having some problems only to find out at the time in was not the pump. So I've had it as a spare in the toolbox.

I just installed the new Walbro and with the return dumping into the bucket with no restriction, the pressure at the regulator was easily adjustable up and down. I set it back to 65psi as my previous adjustment attempts had it set at around 45. So I've figured out the supply issue being the Walbro crapping out. The return side still have the issue and it has to be the selector causing the restriction because it doesn't matter which tank I flip to, it's still the same. If it where in one of the lines that was tank specific, it'd only have high pressure on that one. So it's gotta be the selector on the return side.

I'm thinking for now, I'll just keep running on the front tank and I'm going to by-pass the return side of the selector. Just tie the return line from the motor directly to that tank. I'll still use the supply thru the selector until I can figure out what I want to do. I called the local salvage yard that I use and they don't have any on the pickups they've got, and I can't imagine those selectors are very cheap through ford. The aftermarket ones I've seen aren't cheap either.

What I may end up doing is just tying the tanks together and making them 1 big tank, like the semi's have. I've heard of OBS guys doing this as well but have never really liked how it was done. My just use a sump setup to tie them together, then only pull from one of the tanks. I've got an aux tank in-bed as well, so basically all 3 would be tied together but I could fill them seperately.

When I do a fuel system on my obs that is what I plan on doing with mine. I have the steel tanks and I was going to weld a bulkhead fitting in each tank and run a hose between them.

 

[Strokersace]

Bypassed the return side of the selector and going straight into the front tank. Working great for now. Pressure is holding at 65 better than it has in quite a while. My guess is the original Walbro I had in there was being limped along by the AirDog for quite some time and finally just decided to go.

Still don't know what could have caused the restriction on the return side of the selector. Starting to wonder if it has something to do with the volume going back thru it since I have the fatory line from the motor and the AD return "y'd" and both are going through it together. Shouldn't make a dang bit of difference I'd think, but I've had this same issue to some extent twice now. Of all the OBS diesels I've had, this is the only one I've had problems with the selectors on.

Also made another interesting observation tonight... Since installing the new Walbro today, it is a TON quieter than the other one EVER was. The 1st one was always louder than a stock SD pump and I could always hear it whining. This one I have to put my hand on it to even know if it's working.

 

[Dieselboy.]

So we concluded you low pressure problem was due to a failed pump. But I'm still curious too know what in the selector caused it to spike 130 psi. That's one hell of a restriction.

I don't see how stage IIs could cause that much flow. WOT maybe but not at idle.

Is there possibly something after the selector that could cause a problem ? Does switching tanks make a difference ?

 

[Strokersace]

Switching tanks makes no difference. My thinking is it may be how I have my AD return line Y'd into the factory return right before the selector valve. I'm wondering if that isn't causing the return side problem. Not sure why, and really have no way to prove that theory, but that's my guess. Have never had an issue with selectors before until this setup.

 

[Tree Trimmer]

my only comment, is if you tie both tanks together, but are not able to shut one off in some way, if you park uphill or down hill, the uphill tank will drain into the lower tank. gravity will take over. the upper tank will drain down to a level even with the lower one. so if the two tanks are full.......

 

[Big Bore]

I seem to remember there being a problem with a batch of Walbro's, or that there were two different part #'s, one good and one bad. I have one on the truck that has over 50K on it and doesn't seem to be loud at all except right at key on, and I'm not sure if thats actually the AD or the Walbro to be honest. Glad you've got proper fuel pressure and figured it out, lot's pf good trouble shooting info posted.