Piston transfer pump or diaphram which is better?

[T. Baker]

I want the most reliable tranfer- lift pump. Is the piston or diaphram style more reliable? Sombody please answer!

 

[A Johnson]

Since you are posting in this forum I will assume you have a P7100 injection pump. The diaphram lift pump won't supply enough pressure/volume for the P7100 pump.



If you actually have a Bosch VE rotary pump, then that is a different situation, and Cummins makes the piston type pump to replace the diaphram style. I assume they came up with the piston style as it must be more reliable as Cummins doesn't seem to do anything unless it is cost driven, in other words there is less warranty costs associated with the piston style pump. This is purely speculation on my part.



If you do convert to a piston style pump then be aware that the conversion entails more than the pump. I believe you will need a new fuel outlet line, as well as a spacer plate between the block and the pump, also the piston style lift pump itself is different depending on whether you have a P7100 or Ve style injection pump.



Also in future posts, if you give some indication of what engine you have or what you are trying to do , you may get a better response to your questions. AJJ

 

[T. Baker]

Thank you AJJ. You have answered more than one question for me. I will be recieving my '96 engine this tuesday for my engine conversion and I really did not know that the inline pump came only with a piston style transfer pump. I am thinking about getting a high flow electric pump in the system as a back up. I have read about so many people having problems with the transfer pump. Too bad Cummins didn't use a gear transfer pump like the one on my Nissan diesel. I will put up a signature when I get a little futher into the project.

Treven.

 

[Dieselnerd]

I doubt you will need a backup lift pump on a 12 valve. The lift pumps giving problems all seem to be associated with the 24 valve engine. While they can spring a leak from time to time, they are not known for sudden failure.

 

[Joseph Donnelly]

Sickly uses the stock fuel transfer pump and lines, stock fuel filter. No extra feed pump. 12 valve fuel system rules

 

[A Johnson]

T. Baker, most Cummins engines do use a gear style transfer pump. Here again I think it is a cost oriented thing. To my knowledge only the B and C series engines use a non-gear type transfer pump.



I'm with Mr. Donnely and DIESELNERD in saying don't waste your money on an electric pump. While the piston style pumps will ocasionally break an internal return spring, or screw up a check valve, it is a rare thing to be left high and dry because of it. In my experience the symptom of a failed piston type pump shows up during a fuel filter change or running out of fuel situation, where it is hard to get the air out of the fuel system. This is normally at a time where you have a few tools around to fix things. I would be more concerned of the electric pump failing and causing problems. AJJ

 

[T. Baker]

Thanks for the replies. I feel more reassured about the reliabillity of the Cummins tranfer pump. On other vehicles I have installed a back up electric pump and the main pump pumps most of the time. The main pump pumps through the auxillary pump. The beauty of this system is that if anything seems funny I can flick the switch and if the problem goes away I have a start on diagnosis and It might get me home without having to do anything else. If you mount it somwhere near the tank the fuel system goes from vaccuum to presure up stream of the auxillary when it is on. It is easier to find a fuel leak than an air leak. It is also usefull when bleading the system. I'm not sure that a regular gasoline electric has big enough fittings to use with the Cummins though. I guess I could put a check valve in the inlet line then mount the pumpt to pump from one side of the check valve to the other. I could then use a small electric without restricting the flow. Anyway it does not seem like a big priority right now with all the other work I have yet to do. My '96 engine will be here tomorrow!!!! I'm not sure yet if it is a 215 or a 180hp engine. I'll know tomorrow hopefully.

Treven.