"Ghost" engine stall

[classic60]

I've been having a mysterious engine problem since last year that I have been unable to have resolved.

THE FACTS:

1. Coach is an 2003 Bounder on an 2002 W22 Workhorse 8.1L.
2. June 2009, had it programmed with Ultra Power at RTS prior to a long trip from S. Cal. New fuel filter, Taylor wires and new plugs.
3. Approx 400 miles into trip, engine began to stall and lose power in hot weather and going up grade. No warning lights came on.
4. After sitting on side of road, continued on trip without additional problams.
5. On return leg, while going through Vegas, engine began to stall and lose power again. Sat on side of road again for a while. However, even after cooling down a bit, restarting would not "clear" the problem so I was towed to a hotel parking lot since this was a saturday evening.
6. Mobile RV mechanic came out Sunday morning and concluded that it was a bad fuel pump. It should be noted that after the engine had completely cooled down on Sunday and prior to the arrival of the mechanic, the engine once again appeared to be running fine.
7. Mechanic dropped tank and replaced pump. I drove about 300 miles and made it home with no further problems.
8. Since tank had been dropped and agitated, I replaced the fuel filter again with a Napa Gold filter as a precaution once I got home.
9. Drove the RV about 1000 miles from replacement of fuel pump/filter from June 2009 to June 2010.(No long trips during this period)
10. June 2010, while returning from a trip, about 1000 mile total, engine began to lose power and stall about 10 miles from home. The coach basically ran fine other than the fact it would only go about 50 MPH.
11. Took it in to Workhorse service center in San Diego. They could not replicate the problem and found nothing wrong with it. Since the problem appeared to start only after the Ultra Power programming, they suggested as a last resort, returning to factory specs which they did.
12. September 2010, drove about 100 miles from San Diego to Redlands. After exiting freeway, the "ghost" appeared. As I was "limping" towards my destination, I noted that the magical number that caused the loss of power was 3000 RPM.
13. The next day, coach once again ran just fine. Took it to Redlands Truck Service, where my coach currently sits, to see what they can find. To date, all preliminary diagnostics have not revealed an obvious problem.

I've become frustrated with this problem as I have lost confidence in my coach and feel that it's going to leave me on the side of the road at any moment. I find myself second guessing my decision to "mess" with the ECM since it was not until after the Ultra Power that the problem arose. Coincidence... maybe...maybe not...I probably will never know.

I'm concerned that I may now find myself in a situation where we begin to throw "parts" at the problem in hopes that one might actually stick.

I have searched this and other forums to see what I can find. I have found some similar stories but no difinitive solutions. I would appreciate any input from the "guru's or others who might have had a similar problem and found a solution.

Thanks in advance

2003 Bounder, 2002 W22 Workhorse chassis 20K miles

[Full-Timers]

I have a friend that had a similar problem. What it ended up being was the fuel returning from the fuel pressure regulator back to the fuel tank was hot enough to make the fuel pump fail since it dumps onto the fuel pump. He noticed that it would only happen when the fuel tank got to the low side. A temporary fix was to keep the tank at least ½ full. The final fix was something they did in regards with the return line and fuel pump.
I think Redlands Truck knows about this problem.

[oemtech]

Full-timers is probably right on the button.

In late 2003, I have a Dec 03 chassis with the 3 port filter, WH changed over to the 3 port filter. I suspect that is was for this very reason of hot fuel returning to the tank. Consider the following.....
1) Depending on the length of your coach you could have 80' of fuel line. 40' from the tank to the fuel rail and the return line of the same length.
2) The fuel lines run along the frame rail about 1' or so from the exhaust pipe.
3) The pump puts out about 90 psi and the fuel rail runs at 55 to 62 psi. One the pressure reaches say 60 psi any excess fuel is returned to the tank.
4) The return line probably dumps back into the fuel right on top or next to the fuel pump.
5) The fuel pump is COOLED by the fuel in the tank.
6) When you get to 1/4 or less your fuel pump is not getting cooled properly do to the hot fuel returning from the fuel rail.

The 3 port fuel filter eliminates 90%+ of the heat problem as the return line is probably less than 10' long. I have run my tank to almost empty (70+ gal on refill) and not had a problem.

The only down sides of the 3 port filter is...
1) Cost
2) Availability
3) A bad load of fuel will probably plug the filter quicker because the short return line.

[oemtech]

Quote:

11. Took it in to Workhorse service center in San Diego. They could not replicate the problem and found nothing wrong with it. Since the problem appeared to start only after the Ultra Power programming, they suggested as a last resort, returning to factory specs which they did.

classic60,

I doubt that UltraPower is the problem. The fact that you had it re-flashed to factory specs and still have a problem leads me to believe that you have some other gremlin.

I would suggest that you get a scan tool installed that continuously scans and saves the data so that when the failure occurs you have some data to review prior to the failure.

Generally speaking the last change to anything is usually the prime suspect when there is a failure.

Example:

I just did an UltraPower upgrade on 06 Class C a week ago... Got a call about 2 days later on how well it was performing. Customer was very happy. Got a call this am from the customer's wife, they were on the road, telling me that the coach would not shift into 5 gear. They wanted know if UltraPower could be the cause. I said no, but I would check with Brazel's. After about 10 mins, called them and asked of th OD switch was on ON or OFF... You know the obvious answer, it was OFF. Turned it on and it shifted into 5th.

[Max Hubrich]

Read this thread on fuel pump life--

Some folks don't agree that a submerged pump adds to pump life- --

[classic60]

OEMTECH et al,

Thanx for taking the time to provide your input.

I usually keep my tank at least half full and in the most recent episode, the tank was in fact half full or just slightly below. So let's say for a moment that the hot fuel returning to the tank might possibly be causing fuel pump problems, why would the coach continue to run?

During the prior episodes, I was too busy trying to pull over safely to the right of the highway to have noticed the RPMs. However, this time, the gremlin reared it's head once I was off the highway at which time I noted that the coach would accelerate until it reached 3000 RPMs at which time the pedal became unresponsive so I eased off the pedal and drove it home slowly.

The next day, with the coach running "fine" now, I noted that around 3000 RPMs is when the transmission shifts into the next gear...got me thinking.....might this be a critical clue to my problem?

[rgrstndgby]

classic60, alot of auto transmissions " interupt" engine power at the shift ( to provide smoother shifts). Tho I would be surprised if Allison does that, you might be on the right track. What happens at full throttle upshifts?....rgr...

[Full-Timers]

Another thing to think about, 3000 rpms is about all you will get out of it if you floor it in neutral.

[classic60]

Picked up my coach today from RTS after they replaced the neutral safety switch which they found to be "faulting intermittently". I am cautiously optimistic that the "gremlin" is now in the trash along with the switch. If so, kudos to RTS for finding what others couldn't. Unfortunately, I won't know for certain until next summer as this "gremlin" previously hibernated during the winter and only came out to play during the summer months.

Thanx all..

[Full-Timers]

Well I guess that makes some sense. Remember I said 3000 RPMs is all you will get if you floor it in neutral?

[DriVer]

Quote:

Originally Posted by classic60 I am cautiously optimistic that the "gremlin" is now in the trash along with the switch. If so, kudos to RTS for finding what others couldn't...

Did they mention if this was the NSBU on the side of the transmission?

[classic60]

They didn't specifically refer to it as a neutral start back up (if that what NSBU means) but rather the neutral safety switch on the transmission. If I recall correctly, they said something about their readings showed the transmission was still in neutral while it was actually in gear or something along those lines.

[classic60]

After researching what an NSBU module looked like and comparing what was replaced on my transmission, it appears that it was in fact the NSBU module. I also noted that one of my exhaust pipes runs within about 8 inches from the module...maybe the heat during long trips in the hot summer caused it to fault. If in fact the NSBU was the source of my problem, I should probably look towards finding a way to shield/insulate the new module from the hot exhaust pipe.

[George Z]

Full-Timers gets the cake. He lead the search for resolution in the proper direction.