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Onan L423 diesel won't start


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  #41  
Old 11-17-2011, 05:18 PM
fromthefifties fromthefifties is offline
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Default Re: Onan L423 diesel won't start

Update on my l423 diesel that won't start.

Took off inspection plate on the injector pump and cycled engine manually looking for the correct timing mark. I did finally find it, it is very faint and it took a strong light to see it. While the mark was aligned on the injection pump, I checked the timing on the engine and it was no where close to 15 degrees BTDC, so the timing was definitely way off.

Removed the injector pump gear cover and removed the injector pump gear.

Manually cycled the engine to 15 degrees BTDC on the compression cycle, manually rotated the injector pump shaft to align timing mark with stationary mark and then re-installed the injector pump gear. Cycled the engine manually several times and checked to ensure that when engine is at 15 degrees BTDC on compression stroke that the marks are still aligned on the injection pump.

I won't get the injectors back until tomorrow as they had to be rebuilt. According to the rebuilder one was stuck open and the others were clogged and not putting out a full spray.

Hopefully, once the injectors are re-installed it will start. Will know this week-end.

Thanks for all the help and I'll let you know when it starts.

Neil
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  #42  
Old 11-23-2011, 04:00 PM
fromthefifties fromthefifties is offline
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Default Re: Onan L423 diesel won't start

Finally got my injectors back and they were completely rebuilt $$$, not cheap!!

Brought the flywheel to 15 degrees btdc and aligned the rotating mark on the injector pump with the stationary mark.

Tried to re-install the injector pump gear sprocket and I can't get it to seat down all the way. Both injecter pump shaft and the gear sprocket are tapered. Tightening the nut doesn't pull the pump gear sprocket down to full mesh with the crankshaft gear. It is as if the gear on the sprocket and the gear on the crankshaft don't match. I have removed and rotated the gear sprocket several times and retried but can't seem to get it to mesh all the way. Scratching my head as to what is holding it back. Any ideas??

Neil
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  #43  
Old 11-23-2011, 04:08 PM
bobbyz72 bobbyz72 is offline
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Default Re: Onan L423 diesel won't start

well we know they do match because you just removed it, so thats out of the question. This may sound stupied, but you do have the right side of the gear going on first, one side has a larger hole then the other side, it may not even go on all if it was backwards. Make sure the shaft and gear taper are smooth.
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  #44  
Old 11-23-2011, 04:29 PM
fromthefifties fromthefifties is offline
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Default Re: Onan L423 diesel won't start

yes, the larger hole or end of the taper is going in first. I have even greased the shaft and the gear. Both are smooth. I did remove it a few days ago, but did not notice if it was completely meshed before I removed it.

That was also my first thoughts, that I had it on backward, but as you said, it will only go on a little if it is backwards. On frontwards it goes on a ways, but just does not fully mesh or bottom out on the crank gear and tapping on it with a small hammer and socket does not drive it on any further. Tightening the nut does draw it down a little but not much.

Neil
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  #45  
Old 11-23-2011, 04:46 PM
bobbyz72 bobbyz72 is offline
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Default Re: Onan L423 diesel won't start

Thats as far as it goes, it does not bottom out.
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  #46  
Old 11-23-2011, 07:48 PM
bobbyz72 bobbyz72 is offline
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Default Re: Onan L423 diesel won't start

Well..... lets see the video of the smoke blowing out it....
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  #47  
Old 11-26-2011, 09:47 AM
fromthefifties fromthefifties is offline
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Default Re: Onan L423 diesel won't start

I got a few hours to work on the generator yesterday and it appears that it is almost running. It is puffing white smoke for sure and is popping like it will start any second, but it just won't catch and fully run just yet.

After aligning the injector timing marks while at 15 degrees btdc and re-installing the rebuilt injectors, it has started sounding like it is almost ready to fire off and go.

I removed all of the glow plugs and tested them with a 12 volt source to make sure that they are all heating and they are. I also checked the preheat circuit on the generator and it does supply the 12 volts to the glow plugs when pre-heat is depressed. While each glow plug was out, I checked compression on the cylinder and have 180+ on three cylinders and 225 on one after several revolutions.

I am hoping that it is just air in the lines at this point. With the injector lines loosened and cranking the engine, I am seeing alot of fuel getting to the injectors but it does still have some air bubbles. It doesn't hit any better with sprayed ether, wd40 or sprayed diesel fuel.

It may be a few days before I can get time to get back on it again, but it does sound like it is getting close. When I do get back on it, I plan to crank it until the air bubbles are gone and then if it still won't start, I will change the timing to 17-20 degress btdc.

Thanks to everyone who has contributed input to my problem, I wouldn't be this far along without all your help, it is very much appreciated.

Happy Thanksgiving to you all.

Neil
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  #48  
Old 11-26-2011, 10:13 AM
Wayne 440 Wayne 440 is offline
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Default Re: Onan L423 diesel won't start

Your compression numbers seem low to me. That it won't hit on ether is not a good sign.
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  #49  
Old 11-26-2011, 12:58 PM
David C David C is offline
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Default Re: Onan L423 diesel won't start

I second Wayne's comment. I have no info on the L423, but the spec for the DJC is around 390 psi. Does the compression tester that you are using have the check valve at the fitting that screws into the head? If a hose was rigged up for an extension, your readings will be low.

Make sure you are cranking at the correct speed, as too low of speed will low the compression readings.

Had friend of a friend add an extension (without check valve) so he could check the compression on a motorcycle. He ended up pulling the engine apart a couple of times trying to find the problem that he did not have. He was not a happy camper when he found out his problems were self induced.

David
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  #50  
Old 11-26-2011, 01:31 PM
bobbyz72 bobbyz72 is offline
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Default Re: Onan L423 diesel won't start

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Originally Posted by Wayne 440 View Post
Your compression numbers seem low to me. That it won't hit on ether is not a good sign.
Mine also would not hit on ether when i was working on it.

MAKE SURE the throttle is set right, at the rebuild shop they may have set it all the way to a very low- too low idle, i dont know. I think if you could just get it going, it would be ok. When i bled my lines, i kept thinking it had air left in them, but i bled and bled, got tired of bleding and thought no way is their still air in them and i hooked them up and it took off.

Take a heat gun, maybe even a hair dryer, and blow HOT air into the air intake while you spin it over.

If you generator is like mine, it automaticly turns the glow plugs on when cranking, but they really should be on 10-15 seconds before you start cranking, but with mine i cant manualy turn them on.
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  #51  
Old 11-26-2011, 05:27 PM
Gunny Gunny is offline
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Default Re: Onan L423 diesel won't start

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Originally Posted by bobbyz72 View Post
Mine also would not hit on ether when i was working on it.
Let you in on a secret.

You can ether a diesel engine all you want and unless it is getting fuel, it will not even try to fire. About the same as ethering a gasoline engine with no spark.

Ether, unless you know what you are doing, can be a very bad thing. Most folks use way too much and inappropriately, usually resulting in undesired results.
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  #52  
Old 11-26-2011, 06:25 PM
Billy J Shafer's Avatar
Billy J Shafer Billy J Shafer is online now
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Default Re: Onan L423 diesel won't start

You mean like heads blown off. Or pistons with holes in them.
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  #53  
Old 11-26-2011, 08:24 PM
Tony Rye Tony Rye is offline
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Default Re: Onan L423 diesel won't start

oil the cly. i thnik you need 350lb. to fire diesel. if the eng. is not wore out and the cly are wash down you will not have comp.
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  #54  
Old 11-27-2011, 09:19 AM
fromthefifties fromthefifties is offline
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Default Re: Onan L423 diesel won't start

I didn't know what the compression should be on a diesel. The 180-200 would have been okay on a gas engine (the difference between 180 and the 240 on the one would have been the concern on a gas engine). The engine shouldn't be worn out but I did buy it used 8-10 years ago from a friend who had connections with Onan and it had only about 400 hours on the hour meter then (but who really knows if the meter was correct or if it had been changed). The generator has been run very little since I have owned it. It was always a little hard to start but with a couple squirts of ether and a little patience, it would usually start.

The compression tester I used is a good one with the threaded adapter. I threaded it into the glow plug holes. With the starter, I cycled the engine several times and recorded the highest numbers for each cylinder. I did have to use an additional adapter on the three cylinders (1,2,3) under the intake manifold as they were too far under the manifold to check without the additional adapter and they were the 3 cylinders that registered 180+/-. Number 4 registered 240 so I may have not had the adapter tight enough on the 3 hard to reach cyclinders

It is getting plenty of fuel into the cylinders as the glow plugs are really wet with fresh fuel when I pull each of them.

I assume the diesel works the same as a gas engine in trying to determine if the rings or the valves are where the compression is being lost, example if I put oil into the cylinder to be checked and then check compression and it increases, a broke or worn compression ring is the problem and if it doesn't increase compression, then the problem is in the valves (cracked or not seating correctly). Am I right on this??

I was thinking that if I moved the timing to 20 degrees btdc that it would get the fuel in there a little earlier and maybe this would raise the compression a little, am I thinking right on this??

Ain't ready to give up yet!!

Neil
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  #55  
Old 11-27-2011, 10:12 AM
Tony Rye Tony Rye is offline
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Default Re: Onan L423 diesel won't start

if the cly. are washed down the oil will put the film back on the cyl. walls. once you get the eng.running that oil film is kept on the cly.walls by the eng.oil most of the tine if the upper cly is wet with fuel the cly are washed down .gettin the oil film back sometimes take a little work.if the inj. pump is out of time it will not affect the compression .if the compression is good an the pump is out of time a little you should get a lot of smoke
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  #56  
Old 11-27-2011, 11:05 AM
fromthefifties fromthefifties is offline
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Default Re: Onan L423 diesel won't start

Quote:
Originally Posted by bobbyz72 View Post
Mine also would not hit on ether when i was working on it.

MAKE SURE the throttle is set right, at the rebuild shop they may have set it all the way to a very low- too low idle, i dont know. I think if you could just get it going, it would be ok. When i bled my lines, i kept thinking it had air left in them, but i bled and bled, got tired of bleding and thought no way is their still air in them and i hooked them up and it took off.

Take a heat gun, maybe even a hair dryer, and blow HOT air into the air intake while you spin it over.

If you generator is like mine, it automaticly turns the glow plugs on when cranking, but they really should be on 10-15 seconds before you start cranking, but with mine i cant manualy turn them on.
Bobby,

You mention to make sure the throttle is set right. I had left it set where the rebuilder set it. How can I know if it is set right?

Quote:
Originally Posted by fromthefifties View Post
Bobby,

You mention to make sure the throttle is set right. I had left it set where the rebuilder set it. How can I know if it is set right?
You also mentioned that the glow plugs turn on during starting, I haven't checked that. I do know that they come on allright when the pre-heat button is held down.

Neil
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  #57  
Old 11-27-2011, 11:50 AM
bobbyz72 bobbyz72 is offline
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Default Re: Onan L423 diesel won't start

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Originally Posted by fromthefifties View Post
Bobby,

You also mentioned that the glow plugs turn on during starting, I haven't checked that. I do know that they come on allright when the pre-heat button is held down.

Neil
Disregard that, Mine does not have a preheat button, and only turns the glow plugs on when the engine is actully trying to start.
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  #58  
Old 11-27-2011, 01:30 PM
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EricWood EricWood is offline
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Default Re: Onan L423 diesel won't start

1. Your engine is a 21.5:1 compression ratio. I would think you should have readings at least in the 350-390 range. (I did a tired Volkswagon Rabbit diesel years ago w/21.5:1 ratio, and the "tired" cyl was still at 300psi)

2. Unless I missed it, I didn't see your Spec letter for the engine model. You got the 108900--seems to me its one digit too many. Could the last digit actually have been a letter "C" perhaps? If so, Spec A-C used solid lifters, with .020" intake and .030" exhaust. Spec D was hydraulic lifters.

3. How much pre-heat time are you giving the plugs initially before cranking?

4. Hows your cranking speed rpm's? Spinning over at a good rate?

5. On the injection pump, on the side facing you, the lever with the front and rear screw stop adjustments, loosen the rear screw, and rotate lever counterclockwise as you crank, this would be towards a more "full fuel" position. Front screw is low idle stop, and for some pump-governed gensets, this screw is used to set the no-load running speed. (about 1845 rpms/61.5 hertz). Note, that some pumps utilized this way may use the rear screw for set speed, with a spring attached to the lever to hold it backwards.

eric
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  #59  
Old 11-27-2011, 11:20 PM
Tim0477 Tim0477 is offline
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Default Re: Onan L423 diesel won't start

Fromthefifties,

You said you wanted to try setting the timing 17-20 degress btdc instead of 15btdc. I think you are going the wrong way. The closer the piston is to TDC, the more compression (and heat) should be developed to fire the fuel. I would try closer to TDC, not further away from it. Maybe Gunny or one of the diesel experts can comment on this.

Tim
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  #60  
Old 11-28-2011, 12:00 AM
Jim Rankin Jim Rankin is offline
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Default Re: Onan L423 diesel won't start

Injection should begin before TDC, how far before depends on fuel rate, rpm, compression ratio etc. Sometimes it's recommended to increase timing by a few degrees to compensate for wear in the drive train of the injector pump. Just changing it a few degrees isn't going to magically make it run, but it might make it run better or might make it run worse once you get it started.

As others have pointed out, the compression values you found are seriously low. Try putting some motor oil into the cylinders and then cranking it over to check the compression. It can restore the oil film on the cylinder walls as well as taking up some space in the combustion chamber, so compression should be a bit higher as a result.
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