Generac starts but won't stay running

[RoyW]

I have a 3 cyl. diesel Generac NP75D. It has 950 hours and is equipped with a glow plug button that you hold down for "a maximum of 30 seconds" and then release before starting. It starts readily but won't stay running and immediately dies unless you push the glow plug button and hold it down. Let go of the glow plug buton and it immediately dies. It had this problem a couple years ago and was diagnosed by a tech (at a $300 cost!) to be a $20 low pressure oil sensing switch. This fixed the problem, but it is recurring. So, I put in a new low oil pressure switch and this didn't fix the problem. The trouble shooting guide in the owner's manual suggested the high temp sensing switch, but the unit is cold and bypassing this switch didn't help, either. The manual also suggested a circuit board problem. Another $300 for a new circuit board and the problem persits. HELP! And, many thanks.

[BTPost]

Sounds like you need a Genset Tech, and, or, a Wiring Diagram for your unit. We have a few Resident SmartGuys, that live, and work in the Seattle area, and maybe one of them would be interested in helping you out.

[Isaac-1]

Have you checked the low oil sensor wire to make sure it is not grounding out against the frame somewhere? (the same for other normally open sensor switches)

Ike

[pegasuspinto]

When you say 'bypass' the temp sensor, I assume you mean you disconnected it, and insulated it from ground....

If you ground out the wire, that is the indication of being overheated.

Robert

[RoyW]

At this point I'm willing to PAY a smart guy to fix this problem once and for all. The unit is in my RV and I could even bring it to them if you know someone. Or, they could come out to beautiful Seabeck on Hood Canal for the weekend and stay for free (I'd still pay them for the fix) and have fresh oysters off my beach, too!

[Onan boy]

Hey Roy

I'll be please to go there and fixe your probleme, if i can stay there for the weekend for free i'm willing to do it for free too... as long as you pay for my plane ticket ??

Does your genset produce any voltage when it's turning ?

[Onan boy]

I forgot

I would look for sure around the glow plug button. Look at the schematic, there is something you bypass when you push the glow plug button that keep you engine running. As pegasuspinto said, look if the wire for the oil pressure aren't short somewhere between the board and the sensor, that will cause the same probleme.

For the temp sensor, if you have the reading for the sensor, it is easy to use a multimeter in Ohms to test it. If you bypass the temp sensor, that doesn't mean it will work. This sensor is a variable resistance so as the heat go up and down the resistance change.

[Kimbra Dean]

Don't suppose it could be a fuel related problem do you. Just a thought.

[RoyW]

Well, I have a tech out there (in the rain) with the $$ meter running as I type this. He's been on the phone half a dozen times with Gererac. Thought it might have been the starter selenoid. So, we just put in a new one. Didn't help. She starts just fine and will stay running as long as that pre-heat/glow plug button is pressed down.

[Billy J Shafer]

You might have him take a look at the manual auto switch. I have had a lot of problems with them. Seems to be a weak spot with Generac units.

[Attakapas24]

Did you get it running? I have a NP75D that the genhead is dead.

[Kevin Henshaw]

Did you find out what the problem was? I have a gas powered 5000xp
that is doing the same thing. I would guess that it's a simple fix and pretty common. If I had a book I'm sure I could track it down. Guess what, I DONT HAVE A BOOK! Arrrg!!!!!