Cummins Marine Diesel 450 HP Will Start But Not Stay Running

Well, if you can't find anyone on the premises that knows how to do it, then you are better off getting in the local service representative from Cummins to sort it out before anything gets damaged, Boss. That's what I would do, then, I'm funny that way.

There are a few things to check, but first some questions.

How old is the fuel? Does it have any anti-fouling/anti-bacteria additives?

Did you let the tank run dry?

Not sure of your setup but it sounds like you have a fouling somewhere. Usually when the engine starts but won't continue it's because fuel has seeped past the blockage when the engine is off so there's enough for a start but not enough can get past at normal running flow. If you let the tank run dry then you're correct, the system is air-bound, usually there are multiple bleed valves that have to be opened in the proper order to get all the air out. You should also collect some fuel from the valves and see if there's water in it. If all else fails it's time for a competent (and expensive) mechanic to take over.

Well I finally read the first complaint that will be an every day occurance .The new enviromental fuel has a thing in it that has an addetive that is made from corn .And guess what corn does when it sits for awhile ,IT mildews ,And mildew plugs up a fuel sytem like you wouldn't beleive .For engines that sit for awhile there is going to be nothing but trouble ..This is going to be one big problem till we get rid of this addetive and a few enviromental people that have made a fortune on this one

An air leak in your fuel line may give you those symptoms.

Some generators have a fuel starting spray injected at startup. This is a possibility also. The starting spray will allow the engine to run for a short time without diesel fuel.

#0 Are you low on fuel? Low fuel + Air leaking (sucked) into a fuel line from a crack, etc.... can play havoc with starting... My truck does this on a low tank....... (I'm too lazy to fix it, I keep it over 1/4 tank and park it facing down hill)

#1 if you've changed your filters, then make sure the lines aren't blocked or rotten...

#2 What lift pump are you running? Mechanical or electrical, and is it functioning properly?

#3 You can crack an injector line and bleed the air out while cranking in some cases...

#4 Air in fuel lines is bad... Should I repeat that??????

#5 Starting fluid is bad for a diesel... Use WD-40 if necessary...

Cummins PT system (is it your case?) have the problem to need more fuel tresspassing the filters (much more) than it needs to inject,even more when it is idling.So don´t put filters with lower capacity: even clean filters and reliable trademarks fails for that reason.If your cummins is not a pt system like a 855 (14l) i don't know what to say.-

Not a pt case

Ok have cleared all fuel ines and taken racor apart, cleaned and degunked all putting back together and trying again. I am sure that we will run till we get more sludge that looks like a tumor into the line agai and restricts everything.

I was looking and not linear inj.pumps for that large engines in Cummins, so or PTsystem or common rail.. if so, harder terms about quality and purity of fuel :normally the injectors switch have a so small calipered pass to work: if closed it won't work.-

Thks got it fixed

Time to backflush the entire system starting from behind (after) the major blockage all the way back to the tank. You might be able to get away with the installation of a temporary separator followed by a high flow filter setup right after the tank, plus lots of biocide and algicide clean up chemicals like ValvTect. There's a noticeable difference in performance in my friend's dual Penta setup when using VavTect treated diesel fuel.

http://www.valvtect.com/

You did not state if the engine would stay running or not before you changed the filters.

If yes:

You need to bleed the air out of your fuel rail and injectors or keep cycling/starting the engine until the air purges out and it operates/runs smoothly.

If no:

Follow the many good suggestions in the postings.

I would add:

Verify the master fuel shutoff solenoid is staying energized when the ignition key/star switch is returned to the "RUN" position and if it is not, you most likely have a bad switch. Most marine engines are designed to shutdown with loss of voltage to the fuel shutoff valve and/or engine controls to prevent/limit fire and explosion.

Verify status and operation with VOM.