GMC Duramax Ambulance

[BamaChief600]

I usually post on the 6.5 boards and dont know that much about the duramax other than the normal diesel stuff. A friend of mine has an ambulance company and one of the ambulances is a gmc duramax. Im not sure of the year so Ill throw out the problems its having: Sometimes when running it loses power and will only run about 30 mph. It only happens when the fuel is under half a tank. They can stop and sit for a few minutes and it will run fine then repeat some miles down the road. The shop has swapped out the turbo (no idea why imo),cleaned the fuel tank,replaced the fuel pumps, and maybe thats it. To me it sounds like a fuel delivery problem but they have changed the filters and pumps. Any ideas?

[More Power]

Would be helpful to know what codes are being set. The symptoms you're reporting could be due to a fueling issue or even a transmission issue.

When was the fuel filter last replaced?

Jim

[Mark Rinker]

30 mph could be a bad thing for an ambulance!!! What year is the cab/chassis this is built on? What is the 8th digit of the VIN?


The Duramax ECM has a 'limp' function that is usually associated with codes, setting the SES light.

Does the 30mph limit back to normal function come and go like a light switch? If so, its probably a limp code, and they have cycled the key a few times, resetting it.

I'd have them dig deeper for codes, and ask if anyone has installed an aftermarket programmer or power tune. If so, have it removed - with the weight of that work body, and a heavy foot, they are probably limping it with transmission slippage protection.

[Kennedy]

I usually post on the 6.5 boards and dont know that much about the duramax other than the normal diesel stuff. A friend of mine has an ambulance company and one of the ambulances is a gmc duramax. Im not sure of the year so Ill throw out the problems its having: Sometimes when running it loses power and will only run about 30 mph. It only happens when the fuel is under half a tank. They can stop and sit for a few minutes and it will run fine then repeat some miles down the road. The shop has swapped out the turbo (no idea why imo),cleaned the fuel tank,replaced the fuel pumps, and maybe thats it. To me it sounds like a fuel delivery problem but they have changed the filters and pumps. Any ideas?

I have been in contact with an Ambulance Company with same complaint, and I also think from GA. Last I heard they were installing my twin lift pumps which should correct the problem. If this is not the same Company then we'll have to look to getting them set up provided the fix works.

[BamaChief600]

One of the NEW fuel pumps was bad. All is well....thanks folks.

[DmaxMaverick]

What fuel pump? The HP fuel pump, in the engine valley? Aftermarket lift pump(s)? What year? Is this a chassis/cab, or a van (van has an electric primer pump)? Inquiring minds want to know.

[BamaChief600]

2004 and I think it was aftermarket. They do there own work. I believe it was just the lift pump not the IP.

[More Power]

Chassis cabs and some special applications use two fuel tanks. There is a factory ECM-controlled electric fuel transfer pump between the two that works to maintain fuel levels. There have been a few problems reported by owners in the past, but not recently.

Jim