Onan diesel generator cranking but not starting

[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...

[hilgert]

Perhaps fuel pump not working properly?

[oceansailor]

Originally Posted by hilgert

Perhaps fuel pump not working properly?

If that was the case, wouldn't the starting fluid fire it up for a few seconds?

[tmw188]

Replace the fuel filter, push down on the start switch to prime it real well then try to start it. No matter what you need to start there.

[hilgert]

Start with any fault codes. Onan's will have a series of blinks which indicate fault codes.

Page 45 of your RV Generator Set Operating Manual starts the Troubleshooting section, which describes how to get the fault codes. This is a link for your QD 7500.

From there you will have a starting point. If the codes are indeterminate then I'd start with a new fuel filter (just a guess given other symptoms).

[oceansailor]

Originally Posted by tmw188

Replace the fuel filter, push down on the start switch to prime it real well then try to start it. No matter what you need to start there.

I did a full service on it about 7 months ago, and have only run it a couple of times since. Again, though - I'd expect at least a little fire from the starting fluid, even if there was no fuel at all, and that's not happening.

[oceansailor]

Originally Posted by hilgert

Start with any fault codes. Onan's will have a series of blinks which indicate fault codes.

Right, thanks for the reminder! Just tried starting it - still nothing, but also no blinks. That's starting to sound like an electronics problem.

Page 45 of your RV Generator Set Operating Manual starts the Troubleshooting section, which describes how to get the fault codes. This is a link for your QD 7500.

Awesome - I appreciate that! I'll take a look at it.

[twinboat]

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...

Either is bad for diesels , it dries out the cylinders and can bog it down if not cranking fast. It's firing off before the piston is up enough. It can blow a hole in a piston if to much is used.

Use WD40 in place of starting fluid, it will run on that.

If it does run on WD40, you have a fuel problem. Besides, it's almost always a fuel problem on diesels.

[oceansailor]

Originally Posted by twinboat

Either is bad for diesels , it dries out the cylinders and can bog it down if not cranking fast. It's firing off before the piston is up enough. It can blow a hole in a piston if to much is used.

I appreciate the warning; I'd hate for some new user to flood their engine with a gallon of ether and then blame this thread for "making" him do it. Yes, actually having liquid ether pouring into your cylinders would be a problem. That's why I specified - and used - only a little bit.

It's also worth noting that many large diesel engines - including the deuce and a half I used to drive and the diesel generators that I was responsible for in the US Army - come with an installed ether injection system. That doesn't play well with the "ether is bad for diesels" story. Too much ether certainly is... but that's true of almost anything.

Use WD40 in place of starting fluid, it will run on that.

While that sounds reasonable, it also requires caution.

https://www.baltimoresun.com/news/bs...113-story.html

Quote:

"Leon Fields was squirting WD-40 under his Winnebago camper to stop corrosion, one of the advertised "1,000 uses" for the spray lubricant, when the can touched a live wire and another piece of metal and burst into a fiery ball of oil and propane.

"It just spread like napalm," said Fields, a 58-year-old mathematics teacher who was burned over 24 percent of his body in the accident in 1994."

I'll also note that I've actually tried using WD-40 for this kind of thing several times, and it's nowhere near as good for diagnosis as a little squirt of ether. With ether, if there's ignition, you'll know right away.

If it does run on WD40, you have a fuel problem. Besides, it's almost always a fuel problem on diesels.

I can't disagree there; in my experience, it's almost always fuel or air. I do find it a bit annoying that there's no easy access to the engine in this thing - seriously, Onan? You couldn't have installed an access hatch, or maybe used clamps instead of a dozen bolts? - which is why I was asking for "local knowledge" here, just in case someone was super-familiar with these and had an easy answer. Guess it's back to the basics...

Thanks for giving it a shot.

[twinboat]

Originally Posted by oceansailor

I appreciate the warning; I'd hate for some new user to flood their engine with a gallon of ether and then blame this thread for "making" him do it. Yes, actually having liquid ether pouring into your cylinders would be a problem. That's why I specified - and used - only a little bit.

It's also worth noting that many large diesel engines - including the deuce and a half I used to drive and the diesel generators that I was responsible for in the US Army - come with an installed ether injection system. That doesn't play well with the "ether is bad for diesels" story. Too much ether certainly is... but that's true of almost anything.



While that sounds reasonable, it also requires caution.

https://www.baltimoresun.com/news/bs...113-story.html

Quote:

"Leon Fields was squirting WD-40 under his Winnebago camper to stop corrosion, one of the advertised "1,000 uses" for the spray lubricant, when the can touched a live wire and another piece of metal and burst into a fiery ball of oil and propane.

"It just spread like napalm," said Fields, a 58-year-old mathematics teacher who was burned over 24 percent of his body in the accident in 1994."

I'll also note that I've actually tried using WD-40 for this kind of thing several times, and it's nowhere near as good for diagnosis as a little squirt of ether. With ether, if there's ignition, you'll know right away.



I can't disagree there; in my experience, it's almost always fuel or air. I do find it a bit annoying that there's no easy access to the engine in this thing - seriously, Onan? You couldn't have installed an access hatch, or maybe used clamps instead of a dozen bolts? - which is why I was asking for "local knowledge" here, just in case someone was super-familiar with these and had an easy answer. Guess it's back to the basics...

Thanks for giving it a shot.

Either injection systems are metered thru a small orifice, sized for the engine displacement and installed on engines primarily used in sub freezing conditions. I've installed them.

I don't see any relevance in the WD40 story you dug up. You don't spray the outside of the vehicle with lubricant to start it.

[oceansailor]

Originally Posted by twinboat

Either injection systems are metered thru a small orifice, sized for the engine displacement and installed on engines primarily used in sub freezing conditions. I've installed them.

We rarely had freezing conditions at Ft. Lewis, but starting the trucks in the winter usually required using ether. Oddly - with hundreds of trucks and thousands of such starts - I don't recall any explosions, flying pistons, or anything of the sort.

I don't see any relevance in the WD40 story you dug up. You don't spray the outside of the vehicle with lubricant to start it.

The relevance should have been obvious: anything used improperly can be dangerous. The stories about the "dangers" of ether - that it will wash off lubrication, or blow holes in pistons - presume improper use.

The secondary point - which may be a bit more subtle, but also obvious to anyone interested in facts rather than scare stories - is that the existence of these systems (also supported by the explicit statement of "for diesel engines" on many ether cans) is that there's nothing wrong with using ether for diesels when used properly.

Hope that clarifies it.

[twinboat]

Originally Posted by oceansailor

We rarely had freezing conditions at Ft. Lewis, but starting the trucks in the winter usually required using ether. Oddly - with hundreds of trucks and thousands of such starts - I don't recall any explosions, flying pistons, or anything of the sort.







The relevance should have been obvious: anything used improperly can be dangerous. The stories about the "dangers" of ether - that it will wash off lubrication, or blow holes in pistons - presume improper use.



The secondary point - which may be a bit more subtle, but also obvious to anyone interested in facts rather than scare stories - is that the existence of these systems (also supported by the explicit statement of "for diesel engines" on many ether cans) is that there's nothing wrong with using ether for diesels when used properly.



Hope that clarifies it.

I don't think military equipment is built specifically for Ft Lewis climates.

We are clear.

[txcpl]

Our generator takes a while to crank over and start. I have had to hold the start switch down for nearly 1 minute to get it to start once. Without fault codes to begin your search, I have no other ideas.

[Argosy]

Originally Posted by oceansailor

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...

It sounds like it's bogging down because the ether detonates before TDC. It's firing, just not when it should.

The engine is a 3 cyl kubota. My experience with them is a few seconds of glow plug is a lot better than a few seconds of cranking. They're small and normally aspirated, any heat you can put in the head or cylinder does a lot of good to get them to fire off, even in fairly warm weather.

Originally Posted by oceansailor

(also supported by the explicit statement of "for diesel engines" on many ether cans) is that there's nothing wrong with using ether for diesels when used properly.

At one time ether was the only way to start a cold diesel. But it was really painful listening to them crank, you knew something bad was happening inside.

Manufacturers (of the engine, not the ether) knew it too, glow plugs and air heaters were developed. It's really hard to say there's a proper way to use ether to start diesels today. Make sure the glow plugs are working and use them.