Engine/Transmission (1998.5 - 2002) Possible FASS Problem?

[Midnite]

My truck stumbled and died like it ran out of fuel while it was idling in my driveway last week, and I'm trying to figure out what its problem is. I was hoping you guys might give me some ideas that I might not have thought of.



My gauge was showing zero fuel pressure, but I didn't trust it--it's a mechanical gauge with an isolator that looses glycol over time (found out later the rubber diaphragm had a small hole in it allowing the glycol to bleed back into the fuel line while the truck was off). Since I wanted a different gauge anyhow, I ordered and installed an electric gauge. It showed about 2 psi when I bumped the starter to get the FASS pumping. After changing the filter and verifying the regulator spring wasn't broken (and I stretched it a little bit, maybe a millimeter or two), I'm now getting about 3 psi.



JR2 has kindly offered to loan me his pressure test gauge, so that'll help me verify whether my new gauge and/or sender is good. If it turns out that 3 psi really is what I have, then I'll need to start troubleshooting the FASS. This coming weekend I'm planning on pinching the return line where the regulator spring is to see if that causes a bump up in fuel pressure. Doug from Smokindiesel.com suggested that one (awesome guy, by the way!)



Do you guys have any other troubleshooting tricks or hints I might try?



Thanks,

Mike

 

[BSander]

The gauge should go to 15 psi or so when you turn the key on, then swing back to "0" before you actually start it with the fass pump

 

[Midnite]

Yup, except that it just goes to 2 or 3 psi and then swings back to 0. Bump the starter and it goes to 2 or 3 psi for almost 30 seconds and then back to 0.

That just tells me that the computer is controlling the FASS as it should. My concern is whether the gauge is lying to me, or whether there's something that's not allowing the FASS to give me the pressure that it should.

Mike

 

[rjrkihap]

Boy, 3 gauges, all saying the same thing, I'd start checking into the FASS. Have you checked the pressure at the FASS test port? It sounds like an obstruction or failing pump. Are your rubber lines in good shape? Are you running Biodiesel in non Biodiesel lines?

Good Luck

Ron

 

[Crash&Burn]

Boy, 3 gauges, all saying the same thing, I'd start checking into the FASS. Have you checked the pressure at the FASS test port? It sounds like an obstruction or failing pump. Are your rubber lines in good shape? Are you running Biodiesel in non Biodiesel lines?



Good Luck



Ron

MIDNITE>>>>>

Do you have the Fass with the filters and pump together, or the pump by itself?

 

[Midnite]

Ron, no biodiesel here, and it's actually only two gauges, one of which I know was faulty--I'm just unsure of the new one I have in there now. The lines are in good shape. Where's the FASS test port? The FASS actually sounds okay and primed and filled my new filter quickly, so I'm hoping it is just a gauge problem.

Crash&Burn, it's an older FASS with the replaceable brushes and includes the filters.

 

[LowFly]

Ron, no biodiesel here, and it's actually only two gauges, one of which I know was faulty--I'm just unsure of the new one I have in there now. The lines are in good shape. Where's the FASS test port? The FASS actually sounds okay and primed and filled my new filter quickly, so I'm hoping it is just a gauge problem.



Crash&Burn, it's an older FASS with the replaceable brushes and includes the filters.

OK... . first thing you need to do is check and actually see if you have return fuel going back to the tank via the FASS. If you do, its a good assumption that you have fuel pressure to the engine as we hardly ever see a ball and spring fail. THOUGH we still need to test more. This will prove that the FASS is primed and it moving fuel.



Another good suggestion is to test for pressure at the FASS. This will let you know if you had a line failure or some major restriction between the FASS and your gauge tap. Its rare but it happens.



The test port should be on the fuel pressure manifold (Square block between motor and filter base where engine feed attaches. 1/8" NPT plug on frame side).

 

[Midnite]

Thanks Dan! I'll check both those things and post an update.

Mike

 

[Midnite]

Well, I took off the fuel filler cap and bumped the starter to see how much fuel was going back through the return line, and it was just barely dribbling out. Sometimes it stopped and then started flowing again, even though the sound of the FASS didn't change at all. I expected a much more vigorous flow.

I'm going to try to test pressure at the FASS's test port when I get home from work.

Mike

 

[LowFly]

OK... 2nd test... . pinch off the line going to the engine (With the engine off..... ) and see if the return flow increases. If it does... we might need to look at the injeciton pump for loss of resistance on the FASS. We need a dead head condition to build pressure... if that is lost... we dont make pressure and its moveing all its fuel though the injeciton pump.



But if the flow doesnt change... ... we need to check a few other things.

 

[JR2]

Mike - My wife is going to leave the test gauge hanging on the door knob to my garage tomorrow while she is out, otherwise she will be there and can give it too you.

If it turns out to be the VP you can use my garage if you want too.

John

 

[BRobertson]

Hi Mike and John!

When we put your pump in, I don't remember if we used your factory pickup line , or upgraded??

 

[rjrkihap]

I'm running the Fass HPFP with Eric (Vulcan's) 3/8 Bio approved lines.



By the way it was because of Diesel-Dan and his incredible support on this forum that I chose FASS.



Ron

 

[Midnite]

Thanks John--I picked it up yesterday afternoon. I don't appear to have a schrader valve on my VP44, so I took off the hose from your gauge and since the gauge itself was 1/8" NPT, I just threaded it into the tee on my fuel line. It worked great, and showed a steady 16 psi.

Hey Bob! I honestly don't remember what we did either, but I want to say that we reused the factory pickup line. I might be wrong though.

I remounted my sender in the tee again, but this time with a length of grease gun hose that I'd had with my mechanical gauge setup, and wired up my gauge a little differently. It now shows 16 psi! The way I had it before was a little male blade fitting jammed into the battery cable lug (hey, I was just trying to get juice to the thing temporarily! ) , and now it's wired up much better into a piggy-back add-a-circuit thing in the fuse block.

I fired up the truck and let it idle, and looked down the fuel filler neck, but there was no fuel at all flowing back there--that's not normal, is it? I should be seeing a steady flow going back to the tank with the engine running, right? I haven't been able to pinch any of the lines to or from the FASS yet since I don't have any decent vice-grips yet.

Dan, what do you think at this point? I'm thinking I mostly had a gauge problem, but I know something else is going on--a gauge problem wouldn't have caused the truck to stumble and die.

Mike

 

[nutter3]

Midnight, we should get together and have a lift pump party. . We could get John and Bob to come over too. See my thread on the fun I'm having with this thing.

https://www.turbodieselregister.com...5-2002/207089-lp-not-running.html#post1996638

I had the same issue with you on the mechanical pressure gauge. I could not get one end of the glycol line to seal. I just ordered an electric gauge. Currently using my test gauge to keep an eye on the lift pump.

 

[LowFly]

Well i saw that you mentioned that you had the older FASS with the serviceable brushes still. If you do, might check the return line splice to the filler neck... you might have the type that we tapped into the vent hose instead. You might not hear it as well if tapped into this line. (Mine was this way until i swapped it over to the newer style way in the filler neck so i could run my truck and fill up at the same time).



The best way to see if you have return fuel is to pinch off the line between your gauge tap and the VP-44... . so you don’t spike any pressure to the pump. Then run the FASS again and make sure you have pressure. Then, maybe with the help of someone else, slowly pinch off the FASS return line. The pressure should increase in a direct relation to how much you restrict the return line. If you have about 16 PSI…. i am going to assume you have fuel retuning…as that is where most of those older kits hit for pressure……

 

[Midnite]

I'll have to check--I can't remember now where the fuel return line is routed. I've picked up a bigger pair of vice-grips, so I'll try and pinch some lines and let you know what I see.

It seems to me that if I have a steady 16psi to the injection pump, then I should be safe to drive the truck, right? I mean, there shouldn't be any danger to the vp44?

How long typically to the brushes last in these older motors?

Thanks again,
Mike

 

[LowFly]

I'll have to check--I can't remember now where the fuel return line is routed. I've picked up a bigger pair of vice-grips, so I'll try and pinch some lines and let you know what I see.



It seems to me that if I have a steady 16psi to the injection pump, then I should be safe to drive the truck, right? I mean, there shouldn't be any danger to the vp44?



How long typically to the brushes last in these older motors?



Thanks again,

Mike

If your gauge is showing 16 PSI..... and its going to the VP... ... then yes, you should be safe as far as fuel pressure goes. Just keep an eye on your gauge.



The brushes are ware tested to 10,000-15,000 hrs. Add that to a modist 45 MPH driving average (What my GPS tells me at least), 450,000 to 675,000 mile life for the motor brushes. You do more hwy miles, your average will be higher.

 

[Midnite]

nutter3, I'd definitely be up for it. We've got a few other local members that might be interested too. I'm not sure when would be a good time though.



John, thanks again for the offer of your garage--I really appreciate it. I'm still crossing my fingers that my vp44 has some life left in it.



Mike

 

[BRobertson]

Mike

I would like to see everyone!

My truck is in pieces all over the garage, but we could meet here if that would work.

I had shoulder replacement surgery a month ago, so I am limited on what I can do for a few weeks.

Bob