[dt420]

Has Onan 218 (instead of Onan 220) and was running great for several years until tractor just stopped one day a few weeks ago after 30 minutes cutting grass. Would only restart after sitting for a while. When restarted the tractor was running somewhat roughly and the RPMs were very low. Changed oil and filter, replaced spark plugs and wires, new air and fuel filters. Still runs as before with RPMs not near where they should be and are very low. And as before, I can run the tractor for a while, shut it down, but it will not start back up until it has cooled again. What approach should I take to troubleshooting? Should I be looking for vacuum leaks, carb problems or governor/throttle adjustments? I have a 420 service manual as well as the Onan engine manual, but I am looking for advice on the best area to start investigating. I've already had to have someone else cut grass for me once

and I've got some dirt to move!

...and thanks Dave T. for pointing me in the right place to post this!!

 

[inspired_metal]

Hi David,
Welcome to the group. Here are a few things to check first. Isolate the fuel or electrical system. Run the tractor until it quits. Immediately pull out a plug and check for spark. You can also pull a fuel line from the fuel pump to confirm that you are getting fuel to the Carb. These two things will help figure out if its the fuel or electrical system. If they are both good then we have other issues.

I've seen old fuel lines deteriorate in the inside and create a flipper like bit of hose that will stop flow. If you haven't changed lines you may want to do that too.
Check it out and let us know what you find. Does your 218 have points and condensor?

Dom

 

[jdmaninlouky]

Dave -

Being as how you called it the 218 (Actually P-218) ; I'm assuming it is the (P)=Performer Series and will have electronic ignition .

Sooo..., not-withstanding fuel or mechanical issues first , I'm going to guess it has a weak/failing ignition pick-up coil (the one behind flywheel , or is running on one cylinder (broken rod) ? I would run a compression test first , to rule out mechanical failure . Then fuel , then ignition system .

Dave

 

[deaddeere420]

I agree with Dave, You need to run a compression test
The Onans are known for loosing valve seats. When that happens the valve seat rides up and down with the valve, seating and unseating itself until it finally beats the block bad enough that the seat wont sit in it properly at all.

 

[dt420]

Dominic, thanks for the welcoming! As Dave T pointed out, the Onan is the P-218 and it therefore has electronic ignition. I will definitely change the fuel lines, couldn't hurt since I do not know their age and I have read about cracks that can cause vacuum leaks.

Dave, how do I test the ignition coil pickup behind the flywheel? I couldn't find anything in the manuals unless I have overlooked it. I need to get my hands on a compression test kit and i will test for compression.

John, just in case, is a loose valve seat an easy fix?

A couple other observations...I have been getting a burst of black smoke upon start-up that quickly disappears. Also, I ran the engine without the air filter and I could see gas sputtering out of the carb (normal?). When shutting down I could see smoke hovering inside the carb.

 

[deaddeere420]

It depends on several things
how long its been loose & how much damage is done to the block
I opted to replace my block with another block.
A good machine shop can fix most but not all.

BTW Onan sells an over sized valve seat for them.

Mine did exactly what yours is doing. not running right and low on power and sputtering out of the carb. The most common valve seat to go is the right side intake seat

Know that there are a few things that can be done to prevent the issue.
Forum member JRL sells a replacement heat shield that seals off the engine to the firewall and improves fresh air flow to the engine.
Onan also sells a rubber grommet that seals the oil filter opening in the engine shroud to force good airflow to the right side of the engine.

 

[dt420]

I am going to start with testing the coil while I wait to get my hands on a tool to do compression and leak down test. The Onan manual does not provide a diagram of testing the primary windings. I assume these are just the terminals on the coil next to where the spark plug wire holes are located?

"2. Place a black lead on negative (-) coil terminal and
red lead to positive (+) coil terminal. Primary
resistance should read between 2.90-3.60 ohms."

I am still wondering how to test the ignition coil pickup behind the flywheel if anyone has any advice how to do this.

 

[chuckv]

David,

Testing the electronic ignition on a Performer series Onan engine is detailed in the TM1590 Service Manual.

Here are a few illustrations and steps from that manual that should help...

ignition timing test from TM1590.pdf (28.2 k)

Often these modules start to fail only at elevated temperatures, so your engine may fire up again when it is cold, and the above tests might check out OK when cold...so re-measure shortly after it quits if it does so again when hot.

Chuck

 

[dt420]

I tested the coil (part no. 166-0820) in my 80 degree garage last and it read 3.6 ohms for primary resistance and 21,800 ohms for secondary resistance. This is about 2,000 ohms above the range indicated as acceptable in the service manual. Is there any +/- variability in this reading? Is a new coil in order here?

 

[chuckv]

Your coil is very likely still good...there is some discrepancy in the Deere manual against the factory manual:

Onan manual illustration:

TM1590 version:

You quoted the Onan manual which you mentioned you had in your earlier post, and in general I believe it to be the more authoritative source. My experience is that the range could be a bit low for modern digital meters that use a much smaller sense current when measuring resistance than the analog Simpson meter illustrated, however. Your measurement is close enough to look for another root cause...

Of course, if the coil acts differently when the engine is up to temperature that is another matter. Elevated engine temperatures can also effect the condenser, as well as the ignition module which I described in my earlier post.

Have you done the hand rotation of the engine with the meter on the switched side of the coil to determine that the ignition module is working at room temperature? Has the tractor started and run now that it has cooled down from when it "quit"?

Chuck

 

[dt420]

Hi Chuck, I have not tested the ignition module, but plan to do that later when I can get a helping hand. The tractor will start and run, just the same low RPM condition as stated earlier.

I wonder which model coil the Deere manual refers to. I think the earlier coils had their own bolts and then the newer style have the bracket. Supposedly the newer style coil will have a little higher resistance reading than indicated in the Onan manual, around the 21K ohm range, but that's no where near what the Deere manual states!

 

[chuckv]

David,

there is another section on the earlier B-series coils with different ranges:

...Also, be cautious of applying voltage where it does not belong when testing your ignition system:

From your earlier post about some spitting back through the carburetor and the noticeable vapor -- have you checked your valve clearances? Maybe you have a loose seat (that should have shown up on the compression test...is that something you have done yet?)

Chuck

 

[dt420]

Chuck, I have not checked valve clearances yet. Also, no compression or leak down test yet, that's on the books to do though. Wanted to go with the easier things first until I can get a tool for testing compression.

 

[boomers_influence]

chuck, david and club.
the 166-0820 coils ( current model ) do test over 20K.
i have three new ones in stock.
20,500 is the lowest 20,800 is the next one.
i did not open the box to test the last new one.
i also tested two used ones.
one was at 20,600 the other at 21,200.
thank you. boomer

 

[chuckv]

Thank YOU, Boomer!!

...and have a GREAT 4th.

Chuck

 

[akaothermick]

Chuck that PDF file shows a flywheel screen on a Onan in a Hydro JD, I remember hearing that they don't come with both flywheel screens and belly screens. But that shows they can be equipped that way.

 

[chuckv]

Mick,

Yes there was some variation as I have heard as well -- I suspect that image was of a very early tractor. Maybe another member here with a unit that had the flywheel screen installed as a factory original can shed some light on when that might have occurred.

Chuck

 

[akaothermick]

Like my 89 318, original Onan Chuck,

(Message edited by treed on August 19, 2014)

 

[dt420]

Tested the ignition module this morning. Getting 12.46 volts and 0.9 volts. I assume this says the module is good?

 

[chuckv]

Yes...