Diesel starts then dies

[mudpie]

I'm trying to get help someone else get their mower running. It's an Exmark Lazer Z XS with a diesel engine. They tell me it ran great, mowed great, but it started to shut off at random. It will restart, but then dies. They've had to restart it 4 or 5 times just trying to get it on a trailer, or sometimes it will run for 4 or 5 minutes before it dies, but that's the longest it will run before dying.

We were initially thinking maybe a safety switch somewhere, but my experience generally is that electrical switches are either good or bad. It would either start or not start. Now I'm thinking maybe a fuel delivery issue, but I'm just guessing. I've never heard it run.

Any thoughts on what to start checking would be appreciated.

 

[gainestruk]

First make sure fuel is clean no water, I would replace fuel filter, if you have never worked on diesel you will need to fill new filter with fuel before putting it on, and I mean full take it all the way to top of rubber gasket.
I'm guessing it has an electric shut off on injector pump you should be able to hear it click when turning key on.
But if it will restart after it dies that sounds like fuel starvation, dirty filter air in system, check around injector pump for a primer pump that will help getting air out, you can crack loose the injectors and spin engine till you get steady flow of fuel info no primer, with primer loosen nut on injectors and hand pump till good flow.

 

[mudpie]

Thanks for the suggestions. We had a chance to work on it today, and initially it started and ran for just a couple minutes. We verified that the fuel pump was running, and drained a bunch of water from the separator. We also pulled the thermostat. Apparently they had another identical mower that was getting hot and also dying, and when they pulled the thermostat that mower ran fine, so they decided to try the same with this mower.

We started it back up and it ran for 4 or 5 minutes before dying. We cracked a fuel line to verify fuel. Nothing dripped out, which I thought was odd, but as soon as they cranked the motor there was fuel, and the engine did run on the other 2 cylinders. We shut it off and reconnected the line and it fired up and ran for several minutes.

At this point we've got 4 people staring at it, and someone noticed that the plunger on the fuel cutoff solenoid moved when it died. It restarted immediately and ran another 3 or 4 minutes.

Initially I thought it was a fuel supply issue rather than an electrical issue, but it appears the engine isn't necessarily dying from lack of fuel but rather something is telling the solenoid to shut off. Technically that is a lack of fuel, but you know what I mean I'm sure.

I did some searching online and found a suggestion that it could actually be the solenoid itself that's bad, so I'll test that on Monday and see what happens.

Again, thanks for the help.

 

[cpurvis]

Diesels need two things to run--enough compression to heat air above the ignition point of diesel fuel and a correctly timed injection of fuel.

Barring an internal mechanical failure of valves, pistons, etc., compression will not be an issue, especially to an engine that was already running. It will also not be an intermittent problem.

Fuel supply is by far the most common problem. Fuel filters will normally give some warning that they are reaching a clogged condition because a gradual loss of power will be noticed. This has to be checked under load, as a diesel running at full throttle but not under load ("high idle") will seem to be running fine.

The next time you have it running (under load) and it dies, be sure to pay attention to the way it dies.
--If it slowly loses power until it stops, it is being starved of fuel slowly, as a clogged fuel filter or fuel line will do.
--If it dies abruptly, as if you've "turned off the key," it is most likely an electrical issue causing the fuel shutoff solenoid to close.

Pay attention to "how" it dies and focus your attention on whichever scenario matches it.

Good luck.