Help; Loss of power

[J. Morgan]

Cummins will use a lift pump, in pickup trucks it is inside the tank, motor home I don't know.

Fungus can grow in the tank and plug and or take out the lift pump.

If the lift pump goes, or if fuel is otherwise restricted, the much more expensive injection pump will fail as the excess bypass fuel is what cools the injection pump.

I have seen pounds of biomaterial growing in diesel tanks.

This may not be the issue, and chances are it isn't the issue, but be aware just in case.

[J. Morgan]

On review, a 91 may not use a lift pump, I am not for sure, but fungus may still be an issue,

[Protagonist]

Originally Posted by J. Morgan

Fungus can grow in the tank and plug and or take out the lift pump.

I have seen pounds of biomaterial growing in diesel tanks.

Algae, actually. Algae only grows in diesel tanks that have water in them from condensation, and only if the fuel sits long enough for there to be a water/fuel separation. It doesn't matter if it's biodiesel or regular diesel; same thing happens in both cases.

Two general solutions to prevent this from occurring: (1) add a biocide to the fuel to kill any algae. Which leaves dead algae in the tank to clog your filters, and does nothing to get rid of the accumulated water; and (2) a recirculating pump to take fuel from the tank, pass it through a fuel-water separator and a filter, and dump it back into the tank. Which removes the dead algae and any water.

Algae accumulation is common in diesel tanks that aren't used often, and almost unheard of in tanks that are regularly used.

[wxbuoy]

Thanks for all the suggestions!

Was unable to remove the filters. Tried with a filter wrench and both wouldn't budge. So after much consideration and the location of the moho (fenced in storage lot with no room to get a wrecker in to pull it out) I decided the only viable option was to leave well enough alone. If I somehow mess up the filters during removal or something else it is dead in the water with no way to move it. At least this way I can pull it out of the lot to where a flat bed can get it.... I also find it hard to believe it is the filters. I drained the water separator again and it is clear and bright. I would also hate to be an hour into the trip and have it crap out again because I bumped a solenoid, or connection enough to get it to run O.K. for a little bit.

If there was a Walmart close enough I could get to by doing 20 mph I would almost consider driving it there and try changing the filters again. That way if I mess something up then the wrecker can get it.

I am on a time restriction with getting time away from work due to the only two other folks in my department being transferred in May and I will be on my own till July. So it either gets fixed and delivered in the next two weeks or it has to wait.

So the only choice is to take money out of the reno budget for the repairs.... Besides beds and chairs are over rated.

Air filter wasn't bad but replaced it anyway since I had to get something done. It is a bad work day when changing the air filter is your only accomplishment.

[J. Morgan]

It may be true that the funk that grows in the tanks is not fungi, it is my understanding that algae as a plant requires sunlight to grow. So without exercising the benefit of research I decided to go with fungus. I may. E mistaken , but the general gist is crap can grow in the tank, and it seems that by the op description that fuel may have been in there for a long time.

I doubt it would show in the filters unless poisoned, but it will block the hell out of a pickup sock.

[tony6373]

I think I'm having the same or similar problem with my Isuzu. Some times it runs fine but when I first put a heavy load on it after a rest stop it will bog down and may even quit. After holding it at 2000 rpm for a couple of minutes it will clear up and run ok... usually. Changed the little fuel filter (PF13) and it ran great until the first rest stop. I'm in Florida (1150 miles from home) and need to find the problem. Water separator looks fine and both filters were changed before leaving home. Could a clogged filter be intermittent? This is an '85 and I don't know if it has a lift pump in the tank? Should I change the PF13 again? Or change the Racor water separator filter again? It got very few miles in the last 8 months before this trip... just driving it to and from places for service.

Any help would be greatly appreciated.

[J. Morgan]

My guess on the Isuzu might be that air is getting in the lines after a hard run and stop.

Just a guess though. Could be a "hot leak", very small, but enough to let a little air in the lines.

If your Isuzu has rubber return lines on the injectors I would start looking for small cracks there, and or the ends of the lines running to filters etc.

[Smartstream]

Originally Posted by tony6373

I think I'm having the same or similar problem with my Isuzu. Some times it runs fine but when I first put a heavy load on it after a rest stop it will bog down and may even quit. After holding it at 2000 rpm for a couple of minutes it will clear up and run ok... usually. Changed the little fuel filter (PF13) and it ran great until the first rest stop. I'm in Florida (1150 miles from home) and need to find the problem. Water separator looks fine and both filters were changed before leaving home. Could a clogged filter be intermittent? This is an '85 and I don't know if it has a lift pump in the tank? Should I change the PF13 again? Or change the Racor water separator filter again? It got very few miles in the last 8 months before this trip... just driving it to and from places for service.

Any help would be greatly appreciated.

That definitely sounds like an air leak. Since you just changed the small filter with no change I would look at the Racor. Let it sit for awhile and remove the cover of the Racor and see if the fuel level is all the way to the top or if there is a small air pocket. The engine will clear a small amount of air at start up, run ruff until the air runs through the system. Check the cover gasket and make sure it's seated well and make sure the o ring on the cover "T" handle hold down is in good condition. Also next time you park for while like at a rest stop, before you start reach down and pump the hand priming pump on the side of the engine. If it starts out soft and stiffens up after several pumps you just cleared the air and are pumping straight fuel. Pump several more times to make sure all the air is clear and screw the pump handle down snuggly, this can also bleed air. Now start the engine, if it runs normally you found the problem.

[DaveFL]

Originally Posted by J. Morgan

My guess on the Isuzu might be that air is getting in the lines after a hard run and stop.

Just a guess though. Could be a "hot leak", very small, but enough to let a little air in the lines.

If your Isuzu has rubber return lines on the injectors I would start looking for small cracks there, and or the ends of the lines running to filters etc.

Transition from metal to rubber at joints usually, but I once found instead of rubber looking tubes they had used wire braided over rubber and the rubber split with age and fuel couldn't be seen while sitting, but wire mesh got damp with fuel when I pressurized fuel with an electric pump.

[streamquest]

Dave,

I'm voting for a clogged fuel filter. I've got the Cummins/Allison in my 325 as well. The maiden voyage was going well until a total loss of power put me on the side of the road. Of course I had no tools, so took off my belt, and with a sheet metal screw between the leather and filter just to get some bite, managed to remove it. The filter was jammed with all sorts of stuff. Shook it out, flushed it with fuel, shook it some more, filled her up, re-installed it, and the engine came back to life. Had to repeat the process about 100 miles later, but made it home. My first major investment was a new aluminum fuel tank.

Charly

[wxbuoy]

Charly,

Thanks! I am starting to lean that way as well or the lift pump. The only issue is where they are located I can not get enough torque on them to get them loose. I mean I was starting to crimp the filter. Where did you get the aluminum fuel tank?

[tony6373]

Thanks Dan and J. I'll start looking for cracked fuel line on the filters and pump. Will also check the Racor seals. I have noticed that the hand primping pump doesn't feel really firm like it once did. Also the pump drips a little while priming. I may have a worn out priming pump.... has anyone change out one of these?

It's all part of the great adventure of owning and using a 30 year old machine.

[mayco]

Tony6373,
You may already know this but there is a bleeder screw just in front of the primer pump on the isuzu. If you crack that screw open just a tad while you are pumping the primer, if there is a bit of air in the line after your upper filter change, it will sputter a little then straight fuel will start to come out. Then quickly tighten the bleeder. It may have a lock nut on it i cant remember. It worked for me.

[streamquest]

Originally Posted by wxbuoy

Charly,

Thanks! I am starting to lean that way as well or the lift pump. The only issue is where they are located I can not get enough torque on them to get them loose. I mean I was starting to crimp the filter. Where did you get the aluminum fuel tank?

Hi Dave,

I had the tank custom made at at friend's shop. That was a few years ago and I want to say that the cost was in the $700 range, but it will never rust out.
The fact that the filter is so tough to remove might be an indication of how long it has gone unserviced. It's gonna have to come off one way or another, either whole or in pieces.

Charly

[bkahler]

Originally Posted by wxbuoy

...Air filter wasn't bad but replaced it anyway since I had to get something done. It is a bad work day when changing the air filter
is your only accomplishment.

Oh I don't know. I've had days where just having time to change the air filter makes it a good day!

[wxbuoy]

Brad, Good Point! I seem to have those as well.

[tony6373]

I called Hamilton Engine Sales yesterday and there suggestion was to replace the high pressure fuel pump and the check valve in the top of the final fuel filter. But they wanted the engine serial number which I did not know. It's stamped into the bottom edge of the block on the exhaust side near the front. I can't see that area. After several hours of crawling under (in the rain) and looking with mirror and flashlight I finally got smart and stuck a small digital camera down from the top. Bingo! 6DB1-######. I'll call them back today and order the parts if they are available.

So word to the wise... know your engine serial number!

[tony6373]

Okay, lift pump and check valve on order. Tried to leave today but M/H would not make it up the first hill (in Florida!) then suddenly it ran fine. It's just not dependable enough to drive.

[dirigible25]

I just bought a tank for a 1937 Chevy Pick Up street rod that I am building. I bought a universal tank, and they also build custom tanks to your specifications. The company is Tanks Inc. www.tanksinc.com

[wxbuoy]

Originally Posted by dirigible25

I just bought a tank for a 1937 Chevy Pick Up street rod that I am building. I bought a universal tank, and they also build custom tanks to your specifications. The company is Tanks Inc. www.tanksinc.com

Thanks!!