Onan Marquee Generator wont crank with plugs installed?

[Class_A_DP_1]

Hi, The starter on my Generator will crank and spin the engine freely with the plugs out. When I install the plugs it has good compression but will only spin the motor a 1/2 revolution or so then stop. It sounds like the starter cannot overcome the engines compression. If I repeatedly bump the starter the engine will hiss a bit as compression releases and then turn about another 1/3 revolution and stop the same way again.

I have replaced the starter, starter solenoid, and the battery. As a test, I have connected good 12v (with good amperage) to both the starter terminal right on the starter and also to the starter terminal side of the starter solenoid (hard to get to). Both of these tests resulted in no change at all.

Is there supposed to be a compression release of some sort on these engines? Cant figure this out. ANY help is appreciated and thanks very much.

[long_hauler]

This Onan Manual might provide the information you're looking for! I found a lot of helpful tips and facts for my issues!

[Sam_Spade]

wolfe10 wrote:

I keep coming back to "it takes more amps to turn over an engine with plugs in (because of compression) than one with plugs out." Back to voltage drop issue SOMEWHERE.

The problem has been solved. OP reported that it was a bad connection on one of the main battery cables; "It was a bad wire from solenoid to starter! "

[Class_A_DP_1]

Special thanks to EVERYONE for the assistance.

Wes, right on. I had not much to lose so I have been running the genset a few hours and I believe the smoking has all but subsided on its own just like you have said here.

I did throw a couple parts at it but it needed them anyhow. Thanks!














Uh-oh... Now my desk chair is squeaking.

[Wes_Tausend]

Class A DP 1 wrote:
It was a bad wire from solenoid to starter! Which is strange cause I had checked it with 200 amps straight to the starter prior to this. Anyhow it is running now. Smoking a little more than I remember from last time it ran. It also is spitting a little oil into the air cleaner housing for some reason and this may be the reason its smoking? I had sprayed a touch of WD40 in the cylinders as a pre lube but I would have thought that would burn out in just a few minutes.

All electric motors run on amps. If the motor had no torque, it had little or no amp flow.

Amp flow is the sole basis for electromagnetism (thus torque) and it does not matter what the voltage is other than to "pressurize" enough amp flow at the motor terminal to meet crank needs.

Think of a battery like a pressurized water supply. Amps are the gallons per minute and voltage is exactly comparable to water pressure. A bad wire and/or connection is exactly like a high-resistance kink in the hose and restricts flow, whether that be coulombs/sec (amperes) or gallons/min of water. Trivia: One coulomb = 6.242x10^18 electrons.

When the starter is not energized, a full 12v will appear on the switch (solenoid) before the starter terminal. With a bad wire, as soon as the starter kicks in (draws), the pressure will drop very low, if either the hose is kinked, or in this case, the electrons cannot flow through a high resistant bad connection. But you knew this and fixed it.

WD-40 lubes great for the way in which you used it. If the engine is having blow-by issues, it is possible that the dry cylinder walls sat so long as to accumulate a bit of surface rust on them. The rings normally scrape this off, but the debris tends to work it's way into the ring grooves (piston lands) and sometimes the rings stick. They may clean out on their own after a few hours of running but may tend to stick indefinately if too bad. Usually they stick in at the furthest squeeze (usually the little worn bottom of cylinder) and then leak compression towards the more worn upper cylinder thereafter.

It is hard on gas engines to not be regularily driven and very few people mothball them with extra cylinder oil before long term storage. Diesel engines tend to be naturally oily and fair better in neglected storage.

Wes
...

[wolfe10]

Let's see if we can get this thread back on track!

If voltage at the starter is not dropping below 12 VDC, that eliminates both positive and ground. And, yes the ground path, particularly if generator is on a slide is often the issue.

I am struggling to see what mechanical issue could be causing the "stop rotation". Can think of a number of them, but, not that would change between no spark plug and spark plugs installed.

I keep coming back to "it takes more amps to turn over an engine with plugs in (because of compression) than one with plugs out." Back to voltage drop issue SOMEWHERE.

[Westcoasting]

Sam Spade wrote:

Westcoasting wrote:

It is not sticky, where do you come up with this bs?

It is not BS.
Do you know the history of WD ??
If not, look it up.
If you think you remember......look it up again because your memory is failing.

If oil would have worked in the application they were working on, they would have just used oil. It is purposely made to STICK to stuff and repel water.

As for sticky, spray a half an ounce of the stuff into a shallow glass container and then let it sit for about a week. A warm temp helps speed up the evaporation. At the end of a week, dip your finger into what is left and see if it feels nice and slick or

I quit.

You should quit as you have no clue you just like to read you're own words arguing

[Sam_Spade]

Westcoasting wrote:

It is not sticky, where do you come up with this bs?

It is not BS.
Do you know the history of WD ??
If not, look it up.
If you think you remember......look it up again because your memory is failing.

If oil would have worked in the application they were working on, they would have just used oil. It is purposely made to STICK to stuff and repel water.

As for sticky, spray a half an ounce of the stuff into a shallow glass container and then let it sit for about a week. A warm temp helps speed up the evaporation. At the end of a week, dip your finger into what is left and see if it feels nice and slick or sticky.

Or ask a gunsmith or locksmith or clock maker like I originally suggested.

I quit.

[Westcoasting]

Sam Spade wrote:

Class A DP 1 wrote:
Sam have you ever sprayed WD40 on a stuck bolt or nut?

Whatever good that does is because of the powerful SOLVENTS that are in it, not because of any real lubricant properties.
In some situations, WATER is a lubricant.

And when it dries it absolutely IS sticky and not slippery. Where DO some of you come up with these wild guesses ????

It is not sticky, where do you come up with this bs?

[Class_A_DP_1]

Sam Spade wrote:
Where DO some of you come up with these wild guesses ????

Sam, I didn't invent "Water Displacer 40" but, more than a wild guess.. I know that OIL repels water also.

The only thing left to ask on this thread is.. Who else here slept in a Holiday Inn Express last night?

[Sam_Spade]

Class A DP 1 wrote:
Sam have you ever sprayed WD40 on a stuck bolt or nut?

Whatever good that does is because of the powerful SOLVENTS that are in it, not because of any real lubricant properties.
In some situations, WATER is a lubricant.

And when it dries it absolutely IS sticky and not slippery. Where DO some of you come up with these wild guesses ????

[Westcoasting]

Sam Spade wrote:

cwit wrote:
Please read the info on the wd-40 can. It s a good lubricant and one of the only ones that will not hurt a finish.

IT IS NOT A GOOD LUBRICANT. When the solvent dries, it leaves a sticky film that repels water....and gets stickier the longer it sits.

It was designed as a "Water Dispersant" and the claims of lubricating properties are just a marketing claim (lie).

Like I said, ask an expert......like a gunsmith. They won't let WD anywhere near a good gun, except maybe on the OUTSIDE of the metal parts to help prevent rust.

Not the best lubricant... But it certainly is one. It also does not leave a sticky film at all.

[Class_A_DP_1]

Sam have you ever sprayed WD40 on a stuck bolt or nut?

[Sam_Spade]

cwit wrote:
Please read the info on the wd-40 can. It s a good lubricant and one of the only ones that will not hurt a finish.

IT IS NOT A GOOD LUBRICANT. When the solvent dries, it leaves a sticky film that repels water....and gets stickier the longer it sits.

It was designed as a "Water Dispersant" and the claims of lubricating properties are just a marketing claim (lie).

Like I said, ask an expert......like a gunsmith. They won't let WD anywhere near a good gun, except maybe on the OUTSIDE of the metal parts to help prevent rust.

[cwit]

Please read the info on the wd-40 can. It s a good lubricant and one of the only ones that will not hurt a finish.