Deere 318 Onan won't run

Ed in Va.

Member
Used this tractor all day long with a power blower cleaning up fall leaves.

Toward the end of the day, motor started acting like it was running out of gas, then died. The fuel level was ok however.

Seems to have spark at both plugs, at first I thought one side was not sparking. Removed one coil wire from the dual wire Onan coil, added a second 12volt coil for the left cylinder. added new plugs. Both sides sparking.

When I squirt fuel directly into carb, motor will not start, but may backfire slightly while cranking.

Seems to have good compression at both cylinders.

Fuel pump appears to be working OK.

Any suggestions on what I could look for next ?

Maybe a compression test to check actual pressure
at both cylinders?

Thanks Ed in Va.
 
Your engine may have jumped its timing. I would call your local JD dealer and see if they've seen this problem with the Onan engines.
We had those engines on generators at work and were very dependable. Hal
 
If eng has a trigger module for coil mounted on gearcase cover on pto side of eng,check that magnetic ring on crankshaft not loose or key sheared/missing for same,this will change ign timing.
 
Thanks Joe,

I have points, so that should simplify the process. I think I'll start by taking a look at them. Maybe they lost their gap or have broken down. I've run the tractor for a couple of years without messing with them. ET
 
Thanks ET,

That 18 Onan sure likes to work. They are dependable,Cummins has a lock on the replacement part business. Ebay has a lot of parts.

A new friend has been running one in a 317 Deere for 25 years. His original Kohler was replaced by the dealer fairly soon after he bought the tractor new. Dealer put the Onan in for replacement but never told the owner of the brand swap as far as I can tell.

He was convinced he was running a Kohler (cause that's what he bought new) up till this spring when we found it was a P218 Onan. I've got the B43

ET in Va.
 
I bought a JD 140 back in the 1980's with a blown engine. The connecting rod went out through the block. The owner thought his son had ran it out of oil, but that wasn't the problem. The engine was worn out and all they ever did with it was mowing. I installed a new short block and it ran like new. I had to replace the bearings in the JD rotary mower and I could only get them from a JD dealer. The Onan engines we had on generators were governored at 1800rpm's. We used diesel and gas engines. Hal
 
Thanks Hal...

As a matter of fact...I have a wiring diagram for the 318 as well...Courtesy of Mr.El Toro...you may know of him :) Thanks again...

I wonder if the point gap is on there, I need to reset the gap. When I first looked at the points this morning, I could not see them moving at all. I changed the gap then saw them moving and they have spark. My eye sight is not what it used to be,if you know what I mean. ET in Va.
 
I bet the 140 was a good machine. When I had inquired a few years back with the local dealer, he had suggested the 140 as I wanted something that would pick-up leaves.

If I remember right there were probably 4 or more JD machines at the time with a deep deck, which would gather up and shoot out leaves. He had probably mentioned the 318 as well. The other machines were using a shallow depth mower deck, which he described as not what I wanted.
ET
 
The very first thing I'd look for in a 300 series
JD is to see if the intake tube in the fuel tank has broken off.I have bought several 316's and
318's that it had happend on they get old and brittle and break.Very easy to pull the tank off and replace the hose be sure to get the old hose out and reuse the valve on the end of the hose
 
Point gap is .020. You need to also check the point push rod. If it is one of the plastic looking ones. Check the ends. Over time the rod will wear to one side which can change the timing. You can clean it up by sanding it back to level.

Both of your plugs fire at the same time. The points were the main cause of an engine running bad or not starting. If it has been awhile since you changed them. They are most likely worn out. Also be a good idea to check all lines for cracks. Older you get the more cracks you get.

Onan tech since 1980
 
Thanks Billy,
I checked the point push rod, it is the steel type. Cleaned off some carbon build-up on the side of the rod , seems to move better.

I still can't get motor to fire. I'll try replacing the points. I think my dual wire stock coil is only working on one wire (cylinder).

Right now I am using two seperate 12 volt auto coils, one per cylinder. Seems like it would run with two parallel wired coils, I'm getting spark, but seems kind of weak.

My compression is 90 psi on the right cylinder and 95 psi on the left. I wonder what compression the motor should have? 120psi ?

Thanks for the point gap...Et
 
I think that dual wire stock coil is a wasted spark type and the two wires are just both ends of one coil. It fires one cylinder on compression and the other on valve overlap then reverses the combination. I would also check the condenser.
Bryce
 
Thanks Bryce,

I have tried to start with the condenser completely out of the circuit.

From what I remember that was one way to check for a faulty capacitor.

The dual wire Onan coil looks like an ole standard auto coil but with two outputs. So I replaced it with a used coil I had on hand and added a second single wire coil for the second cylinder.

Thought if it works... I'll be sparking like crazy and save a trip$ to the local Cummins /Onan dealer.

So far all I got is more leaves piling up :) ET
 

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Back
Top