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Onan L423 diesel won't start


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  #1  
Old 11-02-2011, 04:28 PM
fromthefifties fromthefifties is offline
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Thumbs down Onan L423 diesel won't start

Onan 20kw Diesel Generator Model L423d-I/108900 S/N D873208109

This diesel generator hasn't been started in a couple years due to personal health reasons.

I installed a new hi-amp battery and even though it cranked over very good, it wouldn't fire even with ether sprayed into the air filter intake. I drained the fuel tank and added new fuel, but it still wouldn't fire. I checked and wasn't getting fuel to the injectors when cranking engine, so I removed the injector pump (DB2-4086 Stanadyne) and had it rebuilt. Now getting diesel fuel to injectors but engine will still not fire. The injector pump is aligned on the mark when the timing is at 15 degress BTDC. Anybody have any ideas as to what I need to look at now.

Thanks,

Fromthefifties
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  #2  
Old 11-02-2011, 06:04 PM
Andrew Mackey Andrew Mackey is offline
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Exclamation Re: Onan L423 diesel won't start

Old fuel may have gunked up the injecters. Are you getting fuel into the fuel supplt to the injecters? You may still be air bound. Try loosening the fuel lines at the injacters and see if you are getting fuel to that point.
Andrew
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  #3  
Old 11-02-2011, 06:12 PM
fromthefifties fromthefifties is offline
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Default Re: Onan L423 diesel won't start

Quote:
Originally Posted by Andrew Mackey View Post
Old fuel may have gunked up the injecters. Are you getting fuel into the fuel supplt to the injecters? You may still be air bound. Try loosening the fuel lines at the injacters and see if you are getting fuel to that point.
Andrew
Andrew,

I have loosened each of the fuel lines at the injectors and fuel does get there and I have cranked it 30 seconds or so with them loosened trying to get all the air out.

Shouldn't it at least fire on the ether? It doesn't even try to fire.

Scratching my head.

Fromthefifties
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  #4  
Old 11-02-2011, 06:15 PM
David C David C is offline
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Default Re: Onan L423 diesel won't start

Are you getting any smoke from the exhaust? If you have fuel to the injectors, you should see a sign of white smoke from the exhaust, if fuel is making its way into the combustion chamber. If you have no smoke and the pump is working correctly, you still have air that is not getting purged or all 4 injectors are stuck. Pull the glow plugs (make sure you get out the copper gasket, if this model is so equipped) and spin it over. You should get a good vapor cloud of diesel blast out of the glow plug hole. Make sure you have no open flames around when you do and keep your face away. It makes it easier on the starter, plus you know which cylinders are getting fuel.

Check the glow plugs will they are out. Check for any blockage in the intake or exhaust system.

David C.


David C.
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Old 11-02-2011, 06:21 PM
Gunny Gunny is offline
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Default Re: Onan L423 diesel won't start

Any chance you got it timed wrong? It'll give a lot of white smoke but won't go.

Careful with that ether.
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  #6  
Old 11-03-2011, 07:02 AM
fromthefifties fromthefifties is offline
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Default Re: Onan L423 diesel won't start

Quote:
Originally Posted by David C View Post
Are you getting any smoke from the exhaust? If you have fuel to the injectors, you should see a sign of white smoke from the exhaust, if fuel is making its way into the combustion chamber. If you have no smoke and the pump is working correctly, you still have air that is not getting purged or all 4 injectors are stuck. Pull the glow plugs (make sure you get out the copper gasket, if this model is so equipped) and spin it over. You should get a good vapor cloud of diesel blast out of the glow plug hole. Make sure you have no open flames around when you do and keep your face away. It makes it easier on the starter, plus you know which cylinders are getting fuel.

Check the glow plugs will they are out. Check for any blockage in the intake or exhaust system.

David C.


David C.
David

Yes, I do have white smoke coming out from the exhaust when attempting to start. I will pull the glow plugs this morning and try that. Do the glow plugs only come into play during pre-heat or are they acctivated during the cranking?

You mention blockage in the intake or exhaust. I have removed the exhaust pipe down to the exhaust manifold and shined a light down in there to see if there was any blockage but didn't see anything. Where would I check for blockage in the intake manifold?

Thanks for the ideas.

Neil
Fromthefifities

---------- Post added at 06:02 AM ---------- Previous post was at 05:55 AM ----------

Quote:
Originally Posted by Gunny View Post
Any chance you got it timed wrong? It'll give a lot of white smoke but won't go.

Careful with that ether.
Gunny,

I think that it is timed right. With the flywheel timing mark on 15 degrees BTDC, the injector pump mark is right in the middle of the inspection window. I did cycle the engine around manually several times and the injector pump mark is centered everytime the flywheel is at 15 degrees BTDC.

Thanks,

Neil
Fromthefifties
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  #7  
Old 11-03-2011, 09:38 AM
Jim Rankin Jim Rankin is offline
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Default Re: Onan L423 diesel won't start

With any 4 cycle diesel, the engine at 15*BTDC can be either on the exhaust stroke or the compression stroke. You could be one whole turn off.

Most(all?) Stanadyne/Roosamaster pumps will happily spline up either way. Other engines like CATs usually have the pump drive tang offset so they won't spline up until the engine is timed correctly.

To check if you're on compression stroke,

either....
pull the injector on #1 cylinder (on opposite end from the generator) have someone put a finger OVER the hole and turn engine until it pushes air out as the piston is coming up on compression stroke, stop at the 15* mark and install the pump

or
remove the valve cover and watch the valves on #1 as you turn the engine over. When both valves are closed (no movement of rocker arms and tappet clearance can be felt by rocking them back and forth) that cylinder is coming up on compression stroke or has already passed TDC and is going back down on the power stroke.

This still doesn't explain why it won't even pop on ether. Compression must be very low. Ether does work better when there's fuel being injected than when it's not, but it should at least try to run. You don't mention if you checked the intake for blockage.

You can also check the valve clearances at the same time while you have the valve cover off. If you find some with no clearance, you may have valves sticking open which could explain the failure to start.
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  #8  
Old 11-03-2011, 11:00 AM
fromthefifties fromthefifties is offline
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Default Re: Onan L423 diesel won't start

Quote:
Originally Posted by Jim Rankin View Post
With any 4 cycle diesel, the engine at 15*BTDC can be either on the exhaust stroke or the compression stroke. You could be one whole turn off.

Most(all?) Stanadyne/Roosamaster pumps will happily spline up either way. Other engines like CATs usually have the pump drive tang offset so they won't spline up until the engine is timed correctly.

To check if you're on compression stroke,

either....
pull the injector on #1 cylinder (on opposite end from the generator) have someone put a finger OVER the hole and turn engine until it pushes air out as the piston is coming up on compression stroke, stop at the 15* mark and install the pump

or
remove the valve cover and watch the valves on #1 as you turn the engine over. When both valves are closed (no movement of rocker arms and tappet clearance can be felt by rocking them back and forth) that cylinder is coming up on compression stroke or has already passed TDC and is going back down on the power stroke.

This still doesn't explain why it won't even pop on ether. Compression must be very low. Ether does work better when there's fuel being injected than when it's not, but it should at least try to run. You don't mention if you checked the intake for blockage.

You can also check the valve clearances at the same time while you have the valve cover off. If you find some with no clearance, you may have valves sticking open which could explain the failure to start.
Jim,

Raining here today and the generator is outdoors, so I probably won't try to work on it today.

When the rain stops, I was going to try David's suggestion of removing the glow plug at each cylinder to see if fuel was making it through the injectors. It's possible that one or more of the injectors is plugged up.

I have removed the air cleaner and housing and looked down into the intake and found no blockage at that point. Is there any other place to check for blockage as this is very possibly my problem. This generator was in a side shed to my barn for most of its life, but a storm this past year blew the side room roof off and I had to completely dismantle what was left of the side shed so now the generator is totally exposed outside with a tarp covering it. When I first started trying to start the engine a couple months ago, I removed all of the covers for the electrical controls and the generator housing and found that dirt-daubers and mice had taken up residence in this area. I thoroughly cleaned and removed all of their work and inspected everything for chewed or broken wires, finding none. But the chance of them getting into the diesel engine has been in my mind ever since it wouldn't start.

You mention pulling an injector. This is something that I have never done before and my question, is that a special deep set socket required to unscrew the injector?

Thanks for your help and ideas.

Neil
Fromthefifties
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  #9  
Old 11-03-2011, 12:28 PM
bobbyz72 bobbyz72 is offline
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Default Re: Onan L423 diesel won't start

Im working on this same generator, but per injector pump shop, my pump is trash from sitting too long. My generator WOULD NOT hit on starting fluid at all!! Dad thought to put diesel in a windex spray bottle, and mist it into the intake as i turned it over... it started and ran, as long as he pumped the spray as fast as he could. LOTS OF SMOKE. Recommend pulling all your injectors and having a good shop look at them... they say i have one or more bad ones and thats what trashed my pump.
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Old 11-03-2011, 12:48 PM
David C David C is offline
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Default Re: Onan L423 diesel won't start

Neil,
No need to pull the glow plugs to check for fuel. If you have white smoke out of the exhaust, you are getting fuel through at least one of the injectors. I would double check your timing per Jim's recommendation. I would pull the #1 glow plug instead of the injector to check for compression on # 1 cylinder. If there is a preheat switch on the instrument panel, use it for the recommended time. The engine should fire up if the glow plugs and related wiring and solenoids are working properly. If you have a valve stuck, it will only shut that particular cylinder down. It still should run on 3 cylinders.

David C
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Old 11-03-2011, 02:27 PM
Jim Rankin Jim Rankin is offline
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Default Re: Onan L423 diesel won't start

Quote:
Originally Posted by Jim Rankin View Post
You can also check the valve clearances at the same time while you have the valve cover off. If you find some with no clearance, you may have valves sticking open which could explain the failure to start.
As "power" pointed out to me in a private message (thanks! and your pm folder is full, so I couldn't reply to you directly) the above quote from my earlier post in this thread isn't accurate. Valves with NO clearance at TDC compression stroke can be HELD open by the valve train, but valves with EXCESS clearance could be STUCK open. Either way, no/low compression.

With glow plugs in the engine, you can pull a glow plug to check if the #1 cylinder is on compression stroke instead of exhaust stroke. Probably easier to do than removing the valve cover unless you want to check valve clearance anyway.

Anytime someone sees something I have posted that is wrong or is confusing, do not hesitate to correct me.

One thing that may have a bearing on this engine is how much white smoke is coming out of it while cranking. I've seen engines that will make a bit of white smoke while cranking even with fuel shut off. If it's going to run, it should crank with LOTS of THICK, white diesel "smoke".
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Old 11-03-2011, 02:45 PM
bobbyz72 bobbyz72 is offline
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Default Re: Onan L423 diesel won't start

I dont think you have to adjust the lifters... ever.... i think they are hydro
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  #13  
Old 11-03-2011, 03:27 PM
fromthefifties fromthefifties is offline
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Default Re: Onan L423 diesel won't start

Quote:
Originally Posted by Jim Rankin View Post
As "power" pointed out to me in a private message (thanks! and your pm folder is full, so I couldn't reply to you directly) the above quote from my earlier post in this thread isn't accurate. Valves with NO clearance at TDC compression stroke can be HELD open by the valve train, but valves with EXCESS clearance could be STUCK open. Either way, no/low compression.

With glow plugs in the engine, you can pull a glow plug to check if the #1 cylinder is on compression stroke instead of exhaust stroke. Probably easier to do than removing the valve cover unless you want to check valve clearance anyway.

Anytime someone sees something I have posted that is wrong or is confusing, do not hesitate to correct me.

One thing that may have a bearing on this engine is how much white smoke is coming out of it while cranking. I've seen engines that will make a bit of white smoke while cranking even with fuel shut off. If it's going to run, it should crank with LOTS of THICK, white diesel "smoke".
Jim,

It has some white smoke when it is being cranked, but I wouldn't say a lot. As you and David suggested, I will pull the glow plug on #1 in the morning and cycle the engine to make sure that it is timed on the compression stroke.

Also, I do hear the solenoid kick in when I push the pre-heat switch but I haven't checked to see that I do have voltage at the glow plug at that time. I'll check that in the morning when I remove the glow plug.

Thanks,

Neil
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Old 11-03-2011, 08:46 PM
Jim Rankin Jim Rankin is offline
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Default Re: Onan L423 diesel won't start

a quick test of a glow plug is to take a 12 volt test light probe, clip the "ground" wire on the positive battery post and after removing each glow plug wire, touch the glow plug terminal with the sharp probe. If the test light lights up, the glow plug is probably good. You must remove the wire from the one you're testing or a single good one will make them all test good.
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Old 11-04-2011, 04:38 PM
fromthefifties fromthefifties is offline
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Default Re: Onan L423 diesel won't start

Jim, David,

I removed glow plugs and cranked engine and there was a puff of fluid vapor from each glow plug hole as the engine cycled through. I reinstalled the glow plugs and tested with the 12 volt test light probe as you mentioned and each one lit the test light. I also ohmed them and they were about 1 ohm of resistance on each one.

I cycled the engine around while checking for compression at no. 1 cylinder to ensure that the injector pump was timed correctly. Stopping the flywheel at 15 degrees BTDC on the flywheel during the compression cycle, I removed the inspection cover on the injector pump and the alignment marks are very close. (maybe off 3-4 degrees). Is this enough to cause it not to start? I will try to load some pictures that I took of the injection pump when flywheel is at 15 degrees BTDC.

I also removed the vavle cover and cycled the engine several times manually and it appeared that all valves are cycling as they should. It didn't appear that any were stuck open.

After puting it all back together, I attempted to start the engine and nothing has changed. I didn't see much, if any white smoke, even when I squirted raw diesel into the intake.

I did disconnect all fuel lines at the injectors and cranked the engine for 30 seconds or more and did see some air in the fuel. I cranked it for 30 more seconds and the air bubbles seemed to be less. I reconnected the fuel lines and attempted to start engine without success. Do I still have air in the fuel lines?

Any more suggestions at this point as I am scatching my head.

Neil
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Old 11-04-2011, 05:07 PM
Isaac-1 Isaac-1 is offline
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Default Re: Onan L423 diesel won't start

My guess is you still have air in the system, you may also want to disconnect the fuel return line where it connects near the injectors and see if your getting return fuel flow.

Ike
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Old 11-04-2011, 05:11 PM
fromthefifties fromthefifties is offline
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Default Re: Onan L423 diesel won't start

Here are (2) photos. One is flywheel setting at 15 degrees BTDC and the 2nd is where the injector pump is setting at that time.

Neil
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IMG_2173_1.jpg   IMG_5550_1.jpg  
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Old 11-04-2011, 06:46 PM
Jim Rankin Jim Rankin is offline
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Default Re: Onan L423 diesel won't start

You must get rid of all the air, unless you can get it to run on something you spray in the intake. They'll usually clear out if you can get them running, but you have to get it running first.

Keep cranking it with the injector lines loosened at the injector until you get nothing but fuel out of them all. Probably have to stop and let the starter cool for 10-15 minutes after cranking a minute or two.
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Old 11-04-2011, 07:02 PM
bobbyz72 bobbyz72 is offline
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Default Re: Onan L423 diesel won't start

Id stop right now! Pull the injectors and have the shop inspect them. Im having problems with this same generator, and I trashed my pump due to back injectors..... If the injectors test good, great, go from there, but your risking messing out your fresh pump on bad injector/injectors.
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Old 11-04-2011, 10:41 PM
sorenson2009 sorenson2009 is offline
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Default Re: Onan L423 diesel won't start

It would probably be best to have the injectors tested and cleaned so that you can eliminate that possibility. The pump and injectors work as a set so it's always a good idea to have them done with the pump rebuild anyway. If it wouldn't start on ether or mist of fuel there are probably other issues though.
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