Hey guys,

I recently installed a fuel pressure gauge to try to figure out what may have caused my issue coming back to school at the end of December. You can read the issue and thoughts I had at the time here.

Anyhow, installed the gauge and went on a test run and I can pull the pressure down to 40 psi pretty easily, and regularly pull it down about 5 psi under normal driving acceleration. Generally takes the truck a bit of driving to bring it up to 65 psi at idle/easy cruise, otherwise it likes to sit at about 60 psi. This is with the FRx installed with the 61-65 psi spring.

So far the steps I have taken are new filters (fuel bowl and frame rail, OE from clay in fuel bowl and Napa 100 micron on the frame rail mount), rebuilt fuel bowl (it was leaking and convenient to do when I installed the fuel pressure sending unit). I have also tested the gauge, at an idle I have 14.5 volts from power wire to ground, and 5.0 volts on the sending unit power wire to ground.

My next step is to swap out my FRx spring with a stock spring which, according to Clay, should provide stock pressure as long as it is not worn out. If that doesn't yield anything noticeable I plan on probing around the fuel pump with my multimeter. I am worried about "throwing" a fuel pump at it though because of what I have read in this thread. This thread. For those that don't know, in that thread ExPaCamper was having very similar issues, replaced his pump and had no change.

So, what are everyone's thoughts? Am I going about this the right way? Is there a step I have missed or something else I should do?

To add on to this, here is a video of my fuel pressure following startup the other day.


Thanks,

Baatzy

 

Have you dropped the tank and cleaned/gutted/removed the screens in there?

 

Jump to about 3:40 in this video . . .
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I don't think your problem is in the spring (FRx) or the fuel bowl. Do you have a way to remove the 100 micron filter on the frame? Perhaps plumb a short piece of injector hose into it and see what your fuel pressure is. If that does not work, leave the filter off and drop the tank to inspect the sending unit for debris/algae.

I don't think you have a fuel pressure problem, I think you have a fuel restriction/supply problem.

Sharp looking gauge and pod though.

 

I had the tank down in Fall of '13 and Hutch and Harpooned it. I am thinking of swapping in the Racor PS120 instead of the filter I have there, and I haven't filled up in awhile, so I could possibly drop the tank again.

I can work out a way to plumb around the filter I think. I might stop by work tomorrow and throw something together if I have the time.

I watched that video last week, it's interesting. Of course I have the plastic tank, so the lining hasn't been coming off. Also when I H&H'ed my tank I never had that much junk on my little filter things, a little bit of junk, but nothing like what was shown there.

Thanks on the gauges, ISSPRO gauge in an autometer pod. Plan is 2 EGT gauges and build a driver side extra pod to throw in a boost gauge at some point in the future, as long as the truck hasn't gone down the road.

Thanks guys,

Baatzy

 

I didn't know you had dropped the tank already. I would eliminate the 100 micron filter and see how the truck runs. If it goes to normal fuel and pressure then you know what the problem is. I am very happy with my Racor PS120, it flows freely and still provides the protection that the in tank screens originally provided.

When you are under there, have a look with a bright light at your lines going from the tank to the pump, make sure they are not kinked or something simple.

 

I think it is interesting that the pressure shot up when the glow plugs turned off. Have you checked your system voltage and ground connections? I haven't had chance to read the whole thread to see if you covered this, but I am wondering if there is a low voltage condition to the pump causing it build less pressure until the voltage stabilizes?

Again, apologies if you have already covered this, just had a couple of secs to skim through the forum.

 

I really don't think the 100 micron filter is the problem, as long as it isn't plugged. Is it cleanable, or is it a spin-on element? FWIW, I run a 30 micron filter pre pump and it's never been a problem at all.

 

It's a spin on element, only a couple months old(in use). I can't imagine it would be too dirty yet, if at all.

I haven't conducted any voltage tests at the pump yet, planning on it, but hasn't occurred yet. However, that approximate 5 psi rise that occurred isn't always so plain, and it doesn't automatically settle at 65 psi right away either, pretty common to idle between 55 and 65.

Baatzy

 

That doesn't look like a tank issue - unless the riser tube has a compromised vacuum. I see either voltage fluctuation at the pump or vacuum fluctuation in the line between the tank and the pump. Fuel loss to the pump can be from restricted flow, or air leaking into the fuel line. You ran a new fuel hose and fuel injector hose clamps with that H&H?

What happens on the road, when you're really demanding fuel?

 

Yep, it got new fuel line and new clamps, but it looks the kit I used (Driven Diesel Kit) used worm clamps for the lines, so if I do the Racor I will probably switch those out.

Also, I haven't been able to get in any situations that "really demand the fuel", just some short (1/4 mile or so) WOT runs due to traffic. Pretty well in any of the last 4 gears I can get it to 40 psi or maybe slightly lower, and in the last 3 gears its pretty easy to pull it down to and hold it at 40.

Baatzy

 

Until you get this resolved, set that ISSPRO warning light to 45 psi. That way you'll get a warning light when you might not be focusing on the gauge. 43 psi is the magic number you don't want to go below.

That electrical issue has me stumped. The GP's pulling the power down enough to affect the FP. When it's pulling down like that do u still get the 5V reference signal?

 

Picked up some fuel injection clamps from the store today and did some testing in between classes. My multimeter only has a tenth of a volt resolution, but the 5v reference voltage nevered changed, except for a brief second when I started the pickup it dropped to 4.9v. Tried to program that warning light, but couldn't figure it out, may have downloaded the wrong software.

Baatzy

 

should look like this:

Attribute Programmer

 

Finally figured it out, got the gauge programmed to come on at 45 psi. Tomorrow I might be able to do the fuel line clamps and see if that helps. Otherwise kinda at a roadblock right now.

Baatzy