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Open Roads Forum  >  Class A Motorhomes

 > Cummins 8.3 ISC fuel inejction pump bad?

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jejb

Rogers, Arkansas

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Posted: 01/28/10 09:56am Link  |  Print  |  Notify Moderator

Got some bad news yesterday. Our 03 Winn Ultimate Advantage had been missing under load on the last couple of trips. Like when climbing hills. It also has a surging idle when we go to high idle after coming off the road. Tryed some fuel conditioners and ran several tanks of fuel through it, but to no avail. I change the fuel filter yearly using Fleetguard parts, and the filter on there is pretty fresh. It has the 8.3 Cummins ISC 350hp motor with just 46k on it.

So we took it to a local diesel truck place and they finally diagnosed it yesterday. They tell us the fuel injectiion pump is bad. The pump alone is just over $3600, and that's a reconditioned one!! Labor is likely to run at least another $1000.

I'm somewhat stunned by this. First, how can a fuel pump cost that much? Holy cow! Second, how can a major component like that for something that was designed for the commercial truck market, where a million miles or more is not unusual, go out with just 46k miles on it?

I called Cummins today and also a Cummins part place and they said those pumps do go out, so not a shocker. But they would not comment on the low mileage of mine going out. I've also just done a couple of hours of searching in here, and find some history of it. But I've also found some saying this same kind of problem was cured with a lift pump change. So I'd love to get input from others that have seen this issue. We've probably driven it 3000 or more miles with the issue as it's not horribly bad, and it's not left us stranded or anything. Just the surging idle and missing at high loads things.

I was a big believer in the advantages of diesel motors in an RV. Now, I'm not so sure.

Thanks


John B
2003 Ultimate Advantage 40K
2003 Winn Adventurer 35U W22 (gone)
1995 Coachman 29' Class C (long gone)

Economical Handyman

S. California

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Posted: 01/28/10 10:17am Link  |  Print  |  Notify Moderator

Sorry to hear of the problem.

We had two replaced in less than 3000 miles, one in Memphis and before we completed the trip the problem resurfaced. We placed second one after we got home.


DeWayne & Judy
04 3810 Dutch Star
ISL 370
Frank's autoformer
01 Sahara Jeep-toad
Blue Ox Aventa II
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This is not the "GOLDEN-YEARS", it is the "RUSTY-YEARS" !


mpfireman

Cook County Il

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Posted: 01/28/10 10:24am Link  |  Print  |  Notify Moderator

Check the pressure on your lift pump. It should be at lest 5 PSI. Getting below the 5 PSI can cause your injector pump to experience fuel starvation, overheating, and premature ware due to this low amount of diesel fuel flowing through it. The newer ULSD fuels can also cause this type of ware, but the fuel companies say that there is added safeguards to these newer fuels to prevent this type of premature ware. But I usually add 1/2 Qt of 30 weight oil to my fuel tank every fill to insure adequate lubricity. If you had the newer, 07 and up diesel, I would not add this oil. But the older diesels run just fine with this added oils. My tank is only 34 gallons, thus the larger tanks could use 1 Qt every fill.


1998.5 Dodge Ram Quad Cab Cummins
1998 Sunnybrook 27RKFS Fiver

bsprague

Milton, WA

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Posted: 01/28/10 10:48am Link  |  Print  |  Notify Moderator

Change the fuel filters before you do anything more expensive.

My 8.3 ISC started surging ("missing") under load about two years ago. For yet unknown reasons the ATC light flashed every time it surged. Technicians went to work trouble shooting with testers and computers. Five hours and $500 later a "good ole boy" said "Let's change the fuel filters and see what happens". The fuel filters only had about 2,000 miles on them. As soon as the filters were changed the problems disappeared. The engine has been running well since.

Good luck!


Bill Sprague
2004 Beaver Monterey, 8.3 ISC 350 Cummins
2007 Ford Edge AWD
9 ft Quicksilver inflatable boat w/ 15 hp Suzuki

P Kennedy

Alberta

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Posted: 01/28/10 10:56am Link  |  Print  |  Notify Moderator

Cummins makes the components but truck, bus and rv manufacturers place them on the chassis. Research will show this was a big injection pump failure issue on some Dodge 5.9's. So lets go back to basics, the injection pump is designed to "push" fuel at high pressures to the injectors not bring it from the fuel tank. The lift/transfer pump is designed to push it to the injection pump. In the Dodges it was mounted high up against the engine block not too far from the injection pump, solution mount a pump in the fuel tank. In reality the same thing is accomplished by mounting the lift pump below the fuel outlet if possible and closest to the source-tank. This allows the pump to stay primed and push not suck up hill. The farther the pump from the I pump the stronger it must be SOOOOO.... now you can see the basic engineering flaws with these systems. Use a cheap small pump where it is most convenient on the chassis and hope it makes it past warranty. Solution check out sites like Geno's Garage who have applied logic check out a lift pump solution kit= higher volume pressure mounted properly. Most of these kits were designed for lame Dodge 5.9's but the 8.3 is very close for fuel needs. Most fuel tanks now feed from a suction tube drawing from the bottom out the top..... so a fuel pump mounted mid level of the fuel tank allows for some auto siphoning and protection from road hazards.

* This post was edited 01/28/10 11:07am by P Kennedy *


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bsprague

Milton, WA

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Posted: 01/28/10 11:20am Link  |  Print  |  Notify Moderator

I am certainly not a mechanic. But, when my 8.3 lift pump failed I learned that it is supposed to only run for about the first minute after you turn the key. I am 99 percent sure it does not pump fuel to the primary pump while the engine is running.

A lot of Cummins 8.3 lift pumps have failed. Many think it has something to do with "O" rings shrinking from ULSD fuel. I don't think Cummins ever publicly agreed. The primary symptom is watching fuel drip during the first minute after turning the key. If the "O" rings are shot, the primary fuel pump could be sucking some air in through the lift pump and that could cause surging or missing.

deandec

Northern CA

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Posted: 01/28/10 11:37am Link  |  Print  |  Notify Moderator

We replaced a Bosch injection pump at 50,000 miles. Also replaced was the mechanical lift pump (C8.3L Cummins). The engine died and would not restart so we were towed.

The cost 5 years ago was about $4,000 at Cummins Rocky Mountain. I have always suspected that the lift pump was the real problem not the injection pump.

Although the injection pump failure is considered routine, you might want to shop for a second opinion. A diesel injection specialty shop might be a good place to visit vs a Truck shop. These are the folks who actually repair and rebuild the injection pumps that the truck shop installs.

I personally would have the lift pump replaced first to see if that corrected the problem. If not, then move on to replacing the injection pump.


Dean
95 CC Magna, Jeep GC


pmy4104

Central Pa.

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Posted: 01/28/10 11:43am Link  |  Print  |  Notify Moderator

Had the same problem with a CC magna with 8.3 cummins and found out that the water seperator filter had never been changed out for one thing and that the lift pump was also weak, it has to feed your high pressure pump in order for it to fire the injectors, Carter makes a rotary vane fuel pump, the one with 1/2 inch hose fittings (gas) but will work OK with diesel that pumps about 7 psi and is a version of the same pump that is used on the Dodge pickups for a lift pump. We installed it in the line feeding the filters right from the tank 2 years ago and it runs better than it ever did.
Its available for around 100 bucks from any auto parts store that handles Carter products, I would also change all fuel filters every spring with all the******that is in the fuel nowdays. Its worth a shot!

jejb

Rogers, Arkansas

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Posted: 01/28/10 12:00pm Link  |  Print  |  Notify Moderator

Dean,
I'm also wondering if I should just have them change the lift pump first and see if that fixes it. Seems some say it should be changed at the same time as the I pump anyway, so why not do it first? But if what bsprague says is true about it not being needed after starting, maybe it wouldn't make any sense?

I have changed the fuel filter since this problem first started. Thanks for the suggestion, but it did not help. And the filter on our motor has the water seperator built in.

deandec

Northern CA

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Posted: 01/28/10 12:15pm Link  |  Print  |  Notify Moderator

John, I am no expert on fuel injection. In your case, the lift pump may not be the cause since your engine starts and runs although not to satisfaction.

So, I would still try to find a Diesel Injection Specialty Shop that would look at your problem before replacing the $4,500 injection pump. They might be able to minimize the cost or determine a different cause to your problem.

On my Cummins there are two fuel filters. One at the rear of the engine compartment and easy to replace. That one is the Fuel Water separater. The other fuel filter is on the passenger side engine block. I have to hang from the bedroom access to the engine compartment to change that filter.

Perhaps you have a second filter that needs changing?

See filter in engine picture

* This post was edited 01/28/10 02:38pm by deandec *

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