Use of Cummins 5.9 manual priming pump?

[Elliot Naess]

Seems my circa 1992 Cummins 5.9 has a deteriorated fuel hose that is letting air
into the system. The injection pump “loses prime” and I have to crank a long time
before the engine starts.

So I need to use the manual priming pump. (Of course, the hose will get replaced soon.)
The priming pump is awfully difficult to reach in this cramped Forward Control engine
compartment. I fiddled with it once, and found it hard to tell if I was operating the
pump correctly. Can somebody describe the correct use of this priming pump?

[the_experience03]

I would imagine our pumps are very similar being that they are both inline Bosch units so I will paraphrase what my owners manual says.

1. fix all leaks. (duh)
2. unscrew the pump handle and pump approximately 50 times
3. open the bleeder on the fuel filter assembly and let the system back bleed for a minute or two
4. close the bleeder and pump an additional 20 times
5. crank the engine with the accelerator fully depressed (may take 15 seconds)
6. run the engine with your foot on the floor. It may die after 10 seconds
7. crank with the pedal depressed for an additional 10-15 seconds
8. if it still doesn't run, start over again (this will give the starter time to cool)


Now here's my instructions.

1. pump until the handle gets firm. It may be 10 pumps, it may be 200.
2. if it was more than 20 pumps or so, crack the bleeder and watch it just like a brake bleeder. Once you get more fuel than air, close it. Pump it a few more times.
3. crank it without touching the pedal. Eithre it's going to start or it's not and I don't like the idea of it firing at full fuel without oil pressure if it's been sitting.
4. listen while it runs and feather the pedal as necessary, but watch that oil pressure
5. if it still doesn't start, pump again, but I think it should go just fine for you with just a few pumps. I know my cold engine that had been sitting did. It took just a few pumps to get firm pressure. I don't think that's bad bleed back for sitting 3 months.

As Jason stated a long time ago...an electric fuel pump sure saves a lot of trouble when it comes to priming that thing. I know my primer is a pain to get to and I have a flip front hood! Even after you replace that line, it wouldn't be a bad idea to put a pump on there. I know a few of the private bus drivers I've talked to up here have done it on their VE44 rotarty pump fuel 5.9's just to aid the weak lift pumps, especially in our cold climate where the fuel can thicken up a little after sitting.

[Elliot Naess]

Follow-up:

I finally got around to replacing the hoses. Then I used a 24" two-by-four to pump the primer
button -- from underneath, using the frame rail as a fulcrum. I must have pumped it
a thousand times without the button getting any firmer. Of course, I forgot to even
look for a bleeder! (The big trucks I've primed didn't have any bleeder and the
pump became firm after a while.)

It started right up anyway. And purred like a kitten.

[sportyrick]

I just turn my electric fuel pump on to fill the carb, pull the choke handle and she starts right up; OH, mine is gas Looks like you have the advantage right now with diesel .40 a gallon cheaper than gas. sportyrick

[Elliot Naess]

What happened to all the gasoline that (presumably ) WAS in that carbonator
from the last time you drove it?

But yes, I AM interested in an electric pump -- even if only for backup/priming.

[lapeer20m]

Originally Posted by the_experience03

I would imagine our pumps are very similar being that they are both inline Bosch units .

i'm pretty sure the priming pump on phills 5.9 is significantly different than the pump on my dt360 even though they are both bosch inline injector pumps.

the dt uses a knob that you have to unscrew then manually pump up and down. If i remember right, that cummings 5.9 has a button you push down and it is spring loaded so it returns by itself.

They both accomplish the same thing, but are somewhat different. Phill ran out of fuel (sometime after i ended up in the ocean) and called me for help. I tried to describe the primer pump on his engine over the phone, assumming it was just like mine. He ended up waiting hours for me to arrive to help get her primed. I found the primer, but it wsa different from my dt360.

[Elliot Naess]

Yep, my Cummins 5.9 has a spring-return button with a rubber cover over it. Like on my chain saw.