12v fuel pump

[cgoodwin]

One of the conversions I did on a 12v cummins (94-98) had a strange issue I could nto sort out, it ran fine on diesel but would die in just a few minutes on VO. Eventually I replaced the mechanical lift pump and the problem was solved. It seems that the pump could move VO without a problem but could not move enough VO to maintain pressure.

Recently my own 98 Cummins began stalling on the switch to VO, I checked everything but still every time I ran VO I could drive in the city on flat ground but if I tried to stomp on it or go faster than 30 or up a hill it would die. I replaced the lift pump and the problem was solved. Not sure what goes on with these pumps but this one was on the truck when I bought it and has been running VO for 4 or 5 years now.

Other notes on these pumps:

Don't buy cheap pumps, I have seen some really crappy chinese knock-offs.

Some motors were fitted with a fuel preheater/strainer, this shoudl be plumbed around as it is a very common fuel leak and does nothing. The bracket that hlds the strainer/heater is about 1/4" thick, if you remove the bracket than the pump will mount 1/4" closer to the engine and the push rod that actuates the pump will be too long, when you start the engine the push rod will break the pump off the motor.

ALWAYS check the length of the rod that came out of the pump you are replacing to the length of the rod on the new pump, if they are not identical, use the rod from the old pump with the new pump.

[dougz]

I am trying to trouble shoot my problem sounds similar to yours I have bought a 1996 5.9 12v cummins dodge which already has the frybrid system installed.

When the engine gets up to temperature I I get a drop off in the fuel pressure gauge and it will loose power and stall but if I press the button to force the vegetable oil it will start to build pressure again and then it will be fine. It only seems to do this on the first switch to vegetable oil of the day if I stop and purge and the engine cools down starting on normal diesel it will be fine when it switches back over to veggie oil when it gets back to temperature.

Any other possible thoughts before I tackle replacing the fuel pump?

Cheers
Keith