DoodleBee

Hope everyone is having a good weekend.

My truck has never had any fuel issues - solid starts every time. All of a sudden while driving home, the truck starts to die. I am pushing the pedal and it is like someone is turning the fuel off. It's a slow progression and then it completely shuts down. I managed to get it to the side of the road. First thought is that it's the FSS. The truck has a new fuel filter. My pump has a Denny-T delete. I have read that when the pump is turned up, the FSS can fail.

I order a new one - install (PITA, made a special wrench). It appears I have the stock lift pump. It might even be the one that came with the truck. I am able to pump the lever on the lift pump and I feel resistance like it is actually pumping fuel. The lines are of course filled with air and I have to crack them to get it started. Boom -- we are in business. I drive it around in the subdivision and it appears that all is well.

I take it out yesterday and driving on the highway I get 10 minutes from the house - it does the same thing and dies. So this time I gut the FSS - hit the lift pump leveler about 20 times and crack the lines and finally get it started. This time is only runs for a few minutes and dies. I have to tow it back home again.

I assume the lift pump is the issue? I don't have a gauge to test the pressure. My understanding is that if the factory type lift pumps go bad, there was enough pressure to draw fuel in to keep the motor running? Maybe not at highway speeds. Is that an accurate statement?

I am new to these trucks - is there another piece to the fuel system I am missing that could be causing the issue? The truck has fresh fuel and new filter with less than 100 miles on it and up until the fuel issues, has been solid.

Truck specs are in my signature.

Thanks for any help.

cheers
Doug

1320Fastback

Diaphragm lift pump certainly do go bad. They will either leak a little fuel out of a weep hole or if the seal ruptures start filling your crankcase with diesel.

How is your oil level?
If it is high, thin and smell like diesel it's most likely your issue.

How did your old FSS look?
Was the tip still there?
Could be clogging part of the injection pump if not.

DoodleBee

Thanks 1320Fastback for the response - I will check tonight.

I am going to the Cummins shop tomorrow and pickup a new pump.

I put in a new FSS and it still did the same thing.

cheers
Doug

1320Fastback

Make sure the FSS is getting 12V with key on also.

If Cummins wants your first born for a pump call a Case dealer.
Should be much cheaper but same thing.

DoodleBee

Cool thanks again - I believe the correct part number is 068130135 - I was quoted $116 for the pump.

I will check the FSS for 12v.

cheers
Doug

oliver foster

Genos sells that lift pump for under $50.
I am not sure if it is a genuine Cummins part though.

maybe368

Not only just that the fss has 12 volts, but that the connection is good. Mine used to sporadically die, then go, then die, etc., as I was driving. It was a loose connector at the fss. Some guys put an "eye" terminal on the wire for a more secure connection...Mark

samiam4

I think i've got a similar issue.

Mine I replaced the ignition switch and now it cuts in and out at 70+ mph. Kinda feels like someone hitting a switch. Lift pump is 5+ years old.

Probably time to do a piston pump upgrade and replace the switch with a NOS switch.

Michael

maybe368

Before you do that, make sure that the fss wire is connected nice and tight...Mark

DoodleBee

Thanks for the responses everyone -

Ok, an update to my ongoing issues - so I decided to replace the lift-pump. That work is complete.

I also purchased a new FSS. I ordered one from VW. I read those are suppose to be better. I replaced it.

The truck does the same as before. I pump the lever on the LP then crack the injector lines. I start at "one" and work my way back. I only need to get to number 4 and it finally will start. It runs for about a minute then dies again. When it dies it is not a sudden shutdown. It just slowly dies. You push the pedal and it slowly dies. Once it does this - it appears there is no more fuel coming in. In order for it to start you have to pump the lift and crack the injector lines.

What am I missing? It has a new fuel filter. I also checked when I had the FSS out and pumped the lifter, lots of fuel came out very easily.

I have also tried with removing the pin from the FSS so it is free flowing. Same issues. I did not check if I have 12v at the FSS.



Thanks again for any help - and happy 4th everyone.

cheers
Doug

DoodleBee

One more item I should state - on the number two injector I don't get anything coming out of it.
Number 1 3,4 all have fuel coming out when I crack them and crank the engine. I have never opened 5 and 6.

Comment? Hope that makes sense.

j_martin

I think you're sucking air somewhere between the lift pump and the bottom of the fuel pickup in the tank.

patdaly

Yep, losing prime.

oliver foster

You could try running a new fuel line into a jug of diesel on the ground, or bed of the truck from the lift pump.
If it runs well on the new "fuel system", you KNOW the problem [sucking air] is between the factory lines from the lift pump to the fuel pick up in the tank.

DoodleBee

Thanks everyone for the help - I did check the power at the FSS and it holds right at 11v when you turn the key on.

Oliver - I am going to try your suggestion.

Happy 4th everyone.

cheers
Doug