Onan motor will not run or spark HELP Please.

[tyoungbauer 1]

I have an old bolens that has not been running in a while.  It has an Onan 18HP XLS motor I think P218.  It will turn over but not fire or spark.  I thought it may be a bad coil so I ordered a new one but same result.  I then figure it had to be a bad ignition module.  So I decide based on age I should just replace these parts.  I also replaced the battery and plugs.  The only things I have not replaced are the plug wires but they seem to test fine with the test meter.  The other piece is the ignition rotor. I have the whole thing out of the frame on the bench.  The rotor magnets will stick to other metal so I think it is OK, although they are not strong.

 

So I need help.  I have a few hundred into this and would like to get it running.  I have the motor on the bench and it will turn over but I see zero spark on the plugs.

 

I actually think I did not need the new coil or ignition module but I have 2 sets now.  I cannot figure out why I am not getting spark.  Oh I also got a new condenser.  I have that on the positive side of the coil too.

 

Any ideas?

 

Thanks in Advance. 

[gwest_ca-(File Mod) 10,498]

Do you have this Onan service manual?

 

Garry

[tyoungbauer 1]

I do have that.  I wonder if the brand new coil is bad too?  Here is how I am testing.

 

digital multi meter.  Black cable in Common port, Red cable in volt/Ohm port.

 

Setting to 200

 

I touch black to neg post on coil and red to pos post.  I get a reading of 3.4 on the old coil and the new coil.

 

I change the setting on the meter to 2K.

 

I put in the probes into the spark plug openings and I get a reading of 1.0 on both.  I am expecting 15k to 20k reading.

 

I am thinking both the old and new coil are bad?

 

Comments?

 

Thanks

[tyoungbauer 1]

Additional info.  If I set the ohms meter to 200K I do get a reading of 21.6 on both coils.  I get 1 if I go to 20K

[km3h 543]

Set the meter to the 100 scale and you should see 14,500 to 20,000.

[km3h 543]

So you have the engine out of the tractor and on the bench. Are you feeding voltage to the ignition system? Simply attaching one cable to ground and the other to the starter does no feed voltage to fire the system. Sorry for asking a question like this but you never know a persons experience level. You also have to be careful because this system does not like to be used without a battery hooked up properly. You might burn out the regulator if it is not feeding voltage back to the battery.

[bowtieguy 334]

Just spent 3 days looking for same problem on a 416 w.Onan...replaced fuse block, condenser, switch and relay...still a problem.....finally tore the plastic connector apart,,the one in the wiring harness between the engine and the rest of the wiring harness....found one wire that was "rotten" inside the male pin....ordered a new pin from Toro (4 bucks each..whew)

 

The ole Onan came to life with that soft Onan purrrrrr!~~~funny what ONE wire can do or not do!...now have spare "electrical parts" for the next job!!

[wallfish 15,919]

I'm not very familiar with the Onans but could it possibly be a low oil sensor switch cutting off the voltage to the ignition system? Just a shot in the dark since I don't even know if your engine is even equipped with one or if the voltage you are supplying to the ignition is bypassing it or not.

[Martin 2,130]

Nick and Frank both touched on good points here. check the wiring thoroughly at the connectors and go to the trouble of hooking up the entire engine harness with charging system if you are trying to run it. all the ignition components can be tested on the engine individually without running it or having it hooked to battery. do you have a copy of the demystification manual? it is great for individual testing of components.

 

John, these engines as far as i know didnt ever have a low oil sensor.

 

here is a link to the manual, there is a note saying the file is broken, but I've never had problems with the file.

 

 

i would test the individual components thoroughly first and make sure they are ok. make sure to hook up the ignition module correctly when you are ready to apply battery voltage, you can fry them if not hooked up correctly, not a cheap item to replace.

 

some of us can probably help out a little more with more info from you regarding wiring condition, how you have tested the individual components etc. already.

you mentioned the coil, but testing the module and rotor in position to make sure it is sending signal to the coil is important too.

 

I've never had new ignition parts that didn't work out of the box, it can happen i suppose, but I've also replaced old parts with new in the past that ended up being another issue such as wiring etc and the old stuff was working as it should be. 

[tyoungbauer 1]

I agree with everyone, except I have the motor of the frame and am trying to get it running without al of the switches etc.  I can get it to turn but zero spark.  Two experts told me to replace the ignition rotor as they do go bad on that model.  Since I replaced all the other parts this seems to be the only part not replaced, so I am going to do that while it is on the bench since it is so hard to get to.

 

Once I do that I will update.

[km3h 543]

I hate to say this but just changing parts is not the answer. If it were me I would hook all connecters and switches. Then I would start at the beginning and test every switch and wire in the starting circuit until I found the answer. I don't know what it would do to the circuit on the Onan engine but you can hotwire it just like the old car thieves did. Run a wire from the battery to the positive side of the coil and then crank the engine. Works on the Kohler engines in my Case 444. That will bypass all the safety switches.

 

I am not telling you to try this. I do not know what it might do to the rest of the circuit. Maybe someone else will jump in and say something about it. 

Edited August 17, 2014 by km3h

[WH nut 553]

"Two experts told me to replace the ignition rotor as they do go bad on that model."

 

 

Sounds like I want them working on my tractors.

[tyoungbauer 1]

I agree I am not one for just changing parts until I find the solution.  I thought the coil was my issue but that did not fix it.  I already the motor out so I figure the module was probably next.  The only other part is the rotor.  I am not sure any other electrical wiring is the issue since the motor shoudl run all by itself.   I am jumping the starter.  The coil only has connections from the condenser and the ignition module and the starter.  So I am jumping the starter to the battery and it all turns over but no spark.  The motor is 20 years old so new electricla parts probably not a bad idea and I have replacement parts if they are good but die later.

 

Since it is already on the bench another $10 to replace the rotor won't hurt me.  I will get that put it all back together and test.  

 

Thanks everyone.

[Martin 2,130]

but do you have 12 volts to the + side of the coil?  this was one thing that Nick asked you earlier in post #6.

 

might also help to ground the block with the neg battery cable so the ignition can complete its circuit.

[km3h 543]

So have you solved this problem or what?

[Martin 2,130]

good question Nick. an update would be great. might just help somebody else out in the future.,....

[km3h 543]

Always helps when the solution to a problem is posted. I suppose the two experts he got advice from solved the problem for him.

[tyoungbauer 1]

Sorry work has kept me away.  I have not had a chance to get back to it.  I will post once I know something.

[546cowboy 301]

Some experts. I have had probably 10 Onan P-series engines and never heard of anyone having to replace that rotor. It is the grey plastic piece on the crankshaft you are referring too? If it isn't damaged and fits tight on the crankshaft it is OK.

Since you have already replaced the hard parts to get to, I would suggest you put the engine back in the tractor and hook all your wiring back up, make sure your battery is fully charged and it is grounded at one of the engine mount bolts.

Now turn the key on and see if you have 12 volts at the red wire on the coil. If you don't have power to the coil, you won't have spark either.

As mentioned you can run a jumper wire from the battery to the coil and you should have spark. That does eliminate all the safety switches as far as I know. In case you didn't notice the two terminals on the coil are different sizes as are the connectors from the module so you can't put them on wrong. If they are not, where did you get the module?

There is one thing that will keep it from starting that no one has mentioned and it has happened to me. That is the PTO handle not pulled to the rear or not staying there ( it has a spring as I recall ) or a faulty switch. Actually there are two switches together there. Also there is the 9 pin connector and the fuse block that "ARE" known problem areas.

It is extremely hard for someone else to diagnose a problem from afar when someone jumps too far ahead in the diagnosis and skipping steps. It is a common problem with the way mechanics are trained now days and also the reason repairs cost more than they should. Seems we now have a generation of parts changers instead of real mechanics who understand how a system works. It also has to do with being paid on commission by a labor time guide but we don't want to get into that here.

Edited August 30, 2014 by 546cowboy