HELP!..Motorhome cranks but will not start

[bullydogs1]

3 weeks ago...all fine...motorhome started and ran fine..full tank of diesel....go to start it and it cranks but will not start...generator is fine..and runs fine...tried to turn key and let fuel pump run..several times..still cranks but will not start...not even close...was about to head out on Thursday and now?????...is there a fuse for the Cummins fuel pump..?... (ISL 400)..

[Terryallan]

Could also be that the valve that allows fuel to flow to the engine is stuck, and is not opening.. the valve should open when you turn the key on, and close when you turn the key off. Diesels need no electricity to run. Starving them of fuel is how you shut them down. Could be since it ran fine a few weeks ago, and the valve worked when you shut it down. the valve has frozen shut.

[Peralko]

I had a similar situation. Turned out to be a fuse holder running power to the ECM. Had a couple of shops flummoxed for a while, including our Cat dealer.

[Artum_Snowbird]

I copied this off another forum:
First thing is, you do not have any glow plugs. Your motor has a grid heater somewhere in the air intake system that heats air as it is inducted into the motor. IIRC, my wait to start light stays on for about 10 seconds. You can check the operation by watching your voltage gauge. When you turn the key you will see a voltage drop and when the heater cycles off, the voltage will rise.

Another thing is you could have a bad lift pump and be loosing prime. Cycle your ignition on and off 4 or 5 times waiting 10-15 seconds from the time you turn it on till you turn it off, then start over again.

Your motor should start within 5 seconds of engaging the starter.

[Roman_Duck]

Diesels ignite fuel by compression not spark, you probably know this already.
A discharged battery or one that's tired will crank the engine over, but not fast enough to squeeze the fuel to create combustion. Try charging your batteries.
Another thing to check for: to make sure there's power to the solenoid on the injector pump.
Turn on the key and put a 12 volt test probe to the connection at the solenoid. Should be power to operate the solenoid if not then's there's your problem. I still charge the batteries, make sure you have a full 12 to 13.5 volts good luck, keep us posted

[Ivylog]

Not sure about where there may be a fuse but you should be able to hear the lift pump running after you turn the key on. Mine runs for one minute before it shuts off so plenty of time to walk to the back of the MH and listen for it.