Duramax Fuel Pump - Where?

[Tim Martin]

We are trying to locate the fuel transfer pump on a 2005 Chevy K3500 with a duramax diesel engine. It is a no start situation and we are not getting fuel into the filter. Mitchel 1 says there is a pump on the left frame rail. We have examined every inch of the left frame rail and there is no fuel transfer pump to be found. Parts books also all show a pump mounted on the frame rail. What are we missing?

[ricmorin]

Tim,

I think only the dual tank units have a frame mounted pump. No transfer pump for single tank? Sounds weird.

[steven kiser]

don't confuse the transfer pump with a fuel filter. i've had a few times where the "filter" was replaced and the truck still didn't start. the customer had never seen a filter with a plug before and assumed it was a heater. if the gauge is reading 1/2 full the fuel isn't being transferred to the front tank. the front tank is the primary and has the lift pump in it. the fuel should be supplied to the injector pump (from what i've been told) at about 1 gallon in 90 seconds. check for signal at the pump plug on the front tank.

[Tim Martin]

This truck is only a single fuel tank. So does that mean that the injection pump on the engine is what draws fuel out of the tank?

[steven kiser]

should be a lift pump. if you have the fuel filter bleeder open it should push fuel with key on.

[ricmorin]

This truck is only a single fuel tank. So does that mean that the injection pump on the engine is what draws fuel out of the tank?

According to what I read, yes. I could not find a lift pump on this model.

[Tim Martin]

Strange that no one's service info tells us that.

What then are the test proceedures for checking fuel pressure? Or doesn't that apply to this model?

[ricmorin]

Strange that no one's service info tells us that.

What then are the test proceedures for checking fuel pressure? Or doesn't that apply to this model?

Ummm. After reading what I have it doesn't really apply. But I do have some info if you want me to send it your way?

[Tim Martin]

Well well. Come to find out there is no fuel transfer pump on this vehicle unless it has dual fuel tanks. So. We installed a Raptor electric pump and the engine fired right up and runs fine. Another one of GM fine ideas to depend on the injection pump on the engine to do the entire job. We live and learn, do we not?

Thanks guys for your input on this frustrating issue!

[steven kiser]

if the pump helped i think there may be a leak in line that's sucking air and i hope it's on the tank side of the pump you installed ................................

[ricmorin]

If I were a betting man, my money is on the main pump. My concern is how the pump will handle this pressure and whether there will be any liability for this modification.

[steven kiser]

in my many years in this field (helped smooth out the stone wheel ) i've either seen or done many modifications with great sucess. i've also seen many failed modifications with disastrous results. if i were to look deeply into this situation i would suggest keeping a close eye on this. i can see a situation where the high pressure pump being overpowered and possibly causing another issue. i would ask the customer to come by for a chat. i agree with ric about the possibility of the high pressure pump being the culprit. again, i've learned to be on the side of caution in the newer engineered and designed vehicles. changes are more and more constant with updates and changes. the lift pump installed may be a great fix and will save customers big bucks, but also you may have created a situation where collateral damage may occur. i would make sure the customer is on the same page as you and is well aware that there is an amount of risk. ultimately, until g.m. comes out with an update that uses your pump idea your way is incorrect and if the motor fails and the pump can be tied into it the cost may be on you.

[Tim Martin]

My fellow men! I appreciate your input. Always have. But getting back to the issue at hand. May I explain a bit why we chose to install an electric transfer pump. On this same truck with dual tanks, GM installs an inline pump on the inside of the left frame rail. the same injection pump is used on the Duramax engine regardless if there is one fuel tank or two. The inline pump is used because to depend on the injection pump on the engine to pull fuel from two tanks does not work well. So I see very little issue with installing an aftermarket pump with the same fuel pressure specs. Or am I wrong? So far as leaks, there is none that we could find. What we have found is that the suction side of the injection pump up on the engine loses its suction ability and consequently the engine becomes a no-start. I agree with the risk of too much pressure if the wrong pump is installed but to replace the main injector pump on the engine is a rather costly operation, especially if a less costly option is available. So far as an update from GM ?????? not likely.

Thanks again for your reminders. There is some rather sharp minds in this field!

[ricmorin]

My fellow men! I appreciate your input. Always have. But getting back to the issue at hand. May I explain a bit why we chose to install an electric transfer pump. On this same truck with dual tanks, GM installs an inline pump on the inside of the left frame rail. the same injection pump is used on the Duramax engine regardless if there is one fuel tank or two. The inline pump is used because to depend on the injection pump on the engine to pull fuel from two tanks does not work well. So I see very little issue with installing an aftermarket pump with the same fuel pressure specs. Or am I wrong? So far as leaks, there is none that we could find. What we have found is that the suction side of the injection pump up on the engine loses its suction ability and consequently the engine becomes a no-start. I agree with the risk of too much pressure if the wrong pump is installed but to replace the main injector pump on the engine is a rather costly operation, especially if a less costly option is available. So far as an update from GM ?????? not likely.

Thanks again for your reminders. There is some rather sharp minds in this field!

My sources say the inline pump is used ONLY to transfer fuel from the secondary tank to the primary tank and does not supply any pressure to the main pump. That is why I'd be concerned about liability for altering the system.

[Tim Martin]

What you are saying about transfering fuel from one tank to another may be true but if we follow the fuel line from the output side of the inline pump, it goes to the CP3 fuel injection pump on the engine.

[Tim Martin]

By the way, Dodge also uses this same CP3 injection pump on their 5.9L diesel engines with an electric lift pump.

[ricmorin]

What you are saying about transfering fuel from one tank to another may be true but if we follow the fuel line from the output side of the inline pump, it goes to the CP3 fuel injection pump on the engine.

Interesting. I thought the vehicle you had there was a single tank. So you have a dual tank vehicle there also?

My source clearly says balance pump, so I wouldn't expect it to go directly to the main pump.

The repair may be ok, but I always worry when modifications from the original design are done.

[Tim Martin]

No, the truck we had that was a no-start was a single tank truck. Most of these Duramax diesel Chevy pk tks we have seen are dual tank units. We have had dual tank units with a no-start that the inline pump was at fault. We were looking for the inline pump on this single tank truck and it's not there. Turns out from the factory it doesn't have one. And yes, my info source, which is Mitchell1 also calls it a balance transfer pump which can be misleading, especially in diagnosis but when it fails the engine will not start.

Admittedly, if I installed a pump that had fairly high pressure, say 50psi or more, then there likely would be a risk element as you men are suggesting. The pump we installed is a low pressure pump.

[Tim Martin]

Regarding which Dodge trucks used the CP3 pump, without looking, I think they started it in mid 1998 and used it till they went to a common rail fuel design which was about 2003, something like that.

[steven kiser]

please don't take my questioning as anything but that. if something can be tweaked i've probably done it. i just want to remind us all that, in my opinion, any modification should be done with the blessings of the customer. i naturally accepted that you used a low volume pump, it never crossed my mind that you didn't. however i did think about a bypass back to the tank. i'm wondering if this will cause any evap or emission issues if only at the state or federal standards. i'de like to be kept updated on this subject because this is something i would defiantly use in the future.