Onan diesel generator cranking but not starting

[hokeweise]

Originally Posted by oceansailor

Hi, all -

I've got a QD 7500 (HDKAJ) genny that doesn't want to start. It ran fine a couple of months ago - in fact, since the power grid was down after the hurricane here, it provided all my power for several days. Fuel tank is ~1/2 full, so that shouldn't be an issue; oil and coolant are topped up, the air filter is clean, and the cranking speed seems good.

I was going to yank the cover off and start pulling injector lines, etc., but I figured I'd ask here first just in case. I'm fairly familiar with diesels in general, but not with these gennies, so I'm hoping someone who knows these beasties can offer a hint or two.

One odd item: I tried spraying a little bit of starter fluid into the air filter while cranking, and all it does is bog it down. Can't say I've ever seen that before...

Minimize using starting fluid. It does not take much to damage a small engine like that. If you do not have the service manual for it, and the wiring diagrams, don’t mess with it until you do. There are a lot of interlocks on that generator that will keep it from running, and you really need to know where they are and how to selectively and carefully go around them one at a time.

[oceansailor]

Originally Posted by hokeweise

Minimize using starting fluid. It does not take much to damage a small engine like that.

Fortunately, we're already done a few rounds on that upthread, with quite a lot more nuance than simply "DON'T" - so that issue doesn't need to be brought up again.

If you do not have the service manual for it, and the wiring diagrams, don’t mess with it until you do. There are a lot of interlocks on that generator that will keep it from running, and you really need to know where they are and how to selectively and carefully go around them one at a time.

I'm not sure what utility there is in posting anything like that, particularly when someone is asking what they can (rather than "can't") do. There are many basic diagnostic steps that can be taken - in fact, a number of them are listed in the troubleshooting section of the guide, and I and others have mentioned several more. All of those can be done by anyone with basic tools, and the overwhelming majority of all mechanical problems are simple ones (running out of fuel is MUCH more common than blown head gaskets.)

If you read the mission statement for this forum, it includes "thoughtful exchange of knowledge, values, and experience". Personally, I prefer to see that kind of self-reliant attitude fostered here - rational, inquisitive, and experimental - rather than fear-mongering or discouraging people from learning what they can do on their own, without expensive manuals.