My 518H dies after running for 20 min

[Jess 29]

I'm only talking about my 518 H  it dies . I had no spark

 

 

I thought the ignition module was bad that is when I pulled the fly wheel and tried to test it and started looking for a way to bench test it. SaveOld Iron had a post on how to do this , but I could not get it to test right. So I ordered a module and installed it . The tractor started right up ! So I thought I had it licked. It ran for 20 min and quit again? That is where all my headaches began. I went through all the wiring many times had almost the whole machine apart. I started replacing things as that is what the local dealer told me he would do any way if I brought it to him.

 

 

No matter what I do the tractor will not run for more then 20 min or so and die and will not reassert until I let it sit for 1/2 hr.

 

 

So I ordered the Hurley coil to see if that would work , thinking the coil was heating up.

 

 

This is where I'm at ! I have replaced the ing module, ing coil, key switch, starter solenoid, gas filter .Have dismantled the carburetor completely and cleaned and checked inside and out . Have taken all micro switches off cleaned every switch and contact and all wires and contacts several times .Rang each wire to clear. Checked and cleaned all grounds .

 

 

Changed all fuses . And the machine still will not run more the 20 min at a time. At one point I ran a hard wire from the positive side of the battery to the positive side of the coil and disconnected the wiring harness and I got the tractor to run for over an hour , but I could not make it happen again. Don't know if it was just a fluke or what.

 

 

So now I just use the machine for 20 min and put it away. I have it down to a point that I know when It is going to die (NUTS) so I run it back in the shed !

 

 

[gwest_ca-(File Mod) 11,393]

This tractor is likely 25 years old so here is what I would do. Get the tractor high enough that you can remove a fuel hose and let gravity put the entire tank of fuel into a spare fuel can. It should flow at a decent constant speed until the tank is empty. You should start with a couple of gallons in the tank if you can. Leave the fuel cap on the tank. If flow slows remove the cap and continue.

 

Garry

[km3h 543]

Jess

I am going to ask this question again. When it dies, is there 12 volts at the positive side of the coil with the key on?

[Geno 1,929]

Do the test Nick recommends first. 

 

Could also be a connection heating up at the engine connector and loosing contact.  When it dies I would feel the connections to every connector you can get to and see if any of them are hot.  Also, when it dies, pull the wire off the coil and see if the inside connector has any oil in it. 

[bmsgaffer 2,052]

After that do the fuel tank thing like Garry recommended... (or just remove or loosen the gas cap when you are nearing your 20 minutes)

 

Sounds like it could be a symptom of your gas tank not venting properly. (pulls enough fuel after 20 minutes to starve engine of fuel)

 

That one time you got it to run so long you may have left the cap off or a little loose...

 

Just my

[ericj 1,579]

i would loosen the gas cap and run it for 20 minutes if it dies then check the connector like said above. pay special attention to the 9 pin connector

 

 

 

 

eric j

[Jess 29]

Jess

I am going to ask this question again. When it dies, is there 12 volts at the positive side of the coil with the key on?

I have been running it with a jumper from the Bat pos to the coil pos when it dies and it wont restart. I have poored some gas (Small amount) into the carb and it still wont restart once it dies like always. I also can see the clear fuel filter when its running and it always has fuel and still dies. I know I sound like a broken record but other then all of the new parts and time I have invested in it nothinh has changed .

   Thank you for your time

[km3h 543]

How many hours on this engine?

[Geno 1,929]

You mentioned in your 1st post "no spark", is this correct?

[km3h 543]

I am finding it hard to understand how you can be without voltage and spark while using a jumper wire from the plus side of the battery directly to the coil, unless the ignition module is acting up when hot. You are by-passing everything in the circuit when you do this. Have you replaced the ignition module?

 

 

Read this page, 4th paragraph on right side. It would appear that if the oil pressure sensor reads low, it turns off the ignition module.

 

 

 

The only other thing I can recommend and this is just a theory, is that there might be so much debris under the tins that after running it for a while it overheats to the point of shutting everything down. But electronically I can so no way for this to happen.

 

I am stumped on this one.

 

 

 

 

Onan Engine Manual 25.pdf

Edited November 9, 2014 by km3h

[Geno 1,929]

Could be the coil or condenser heating up and quitting also Nick. 

[bmsgaffer 2,052]

In addition to the electrical, try the gas cap still. It wont run fuel out of the lines (theres just a vacuum in the tank not letting the fuel "move" forward).

[km3h 543]

You said you are running it with a jumper from the battery to the coil. So please answer the question, have you measured the voltage at the coil when it stops? Is there still 12 volts there? 

 

He said that he put a new coil on the tractor. Not likely a second one would go bad in the exact way the first one did. Also if he is not getting a spark, it makes no difference how much gas gets there.

 

None of this makes any sense to me. Look at the information I have posted from the Toro Demystification Guide.

[546cowboy 302]

So from what you said in your post since you had no spark you assumed the module was bad without checking to see that you had 12v. to the coil. Is that right?

 

Once you run a jumper wire from the battery positive to the red wire on the coil you have eliminated the safety switches and the ignition switch wire, so you have eliminated all of those possible malfunctions. Then there are three other things that can cause no spark. The coil, condenser or the module. Since you have replaced the coil that should be good?

I have never used a Harley coil but I have read here that there are two different coils and one of them will not work for these engines.

 

Of course if your assumption was correct about the module then you need to check your work.

Did you also replace the insulator that goes between the module and the block?

That is a separate piece that does not come with a new module, or did you use the old one?

I am assuming that you bought a new module or did you get a used one?

Did you make sure those wires were routed correctly before you reassembled everything?

 

You don't say if you have checked for spark when it dies now. Have you?

 

You know everyone here would like to help you but without the right information you get all kinds of shots in the dark. That's why there is the demystification guide in the manuals section. So you can make a systematic diagnosis before you start replacing parts that won't fix the problem.

 

I was a GM mechanic for 20+ years and did electrical repairs all the time. I also saw others who disregarded doing all the steps necessary for a thorough diagnosis only to spend hours or days on something simple to fix if they had followed the manual.

Edited November 10, 2014 by 546cowboy

[Geno 1,929]

He said that he put a new coil on the tractor. Not likely a second one would go bad in the exact way the first one did. Also if he is not getting a spark, it makes no difference how much gas gets there.

 

 

New does not mean good.  Especially if made in China.  

[Jess 29]

Could be the coil or condenser heating up and quitting also Nick. 

Both are new as well as the ing module

I am finding it hard to understand how you can be without voltage and spark while using a jumper wire from the plus side of the battery directly to the coil, unless the ignition module is acting up when hot. You are by-passing everything in the circuit when you do this. Have you replaced the ignition module?

 

Demystification Manual_Page_473.jpg

 

Read this page, 4th paragraph on right side. It would appear that if the oil pressure sensor reads low, it turns off the ignition module.

 

Pages from Onan Engine Manual-2.jpg

 

Onan Engine Manual 31.jpg

 

The only other thing I can recommend and this is just a theory, is that there might be so much debris under the tins that after running it for a while it overheats to the point of shutting everything down. But electronically I can so no way for this to happen.

 

I am stumped on this one.

Everything is clean and yes ignition module is new

[Jess 29]

So from what you said in your post since you had no spark you assumed the module was bad without checking to see that you had 12v. to the coil. Is that right?

 

Once you run a jumper wire from the battery positive to the red wire on the coil you have eliminated the safety switches and the ignition switch wire, so you have eliminated all of those possible malfunctions. Then there are three other things that can cause no spark. The coil, condenser or the module. Since you have replaced the coil that should be good?

I have never used a Harley coil but I have read here that there are two different coils and one of them will not work for these engines.

 

Of course if your assumption was correct about the module then you need to check your work.

Did you also replace the insulator that goes between the module and the block?

That is a separate piece that does not come with a new module, or did you use the old one?

I am assuming that you bought a new module or did you get a used one?

Did you make sure those wires were routed correctly before you reassembled everything?

 

You don't say if you have checked for spark when it dies now. Have you?

 

You know everyone here would like to help you but without the right information you get all kinds of shots in the dark. That's why there is the demystification guide in the manuals section. So you can make a systematic diagnosis before you start replacing parts that won't fix the problem.

 

I was a GM mechanic for 20+ years and did electrical repairs all the time. I also saw others who disregarded doing all the steps necessary for a thorough diagnosis only to spend hours or days on something simple to fix if they had followed the manual.

There was no insulator between the ing module and the block? And this is the first time my machine has ever been taken apart. It just had 2 small bolts and washers and bolted right to the block.

And I bought a new ing module , the Harley coil was recommended to me by another member and it works . There is a new ing module , new coil, new condenser, new key switch, new starter solenoid new gas cap , new gas filter and oil/filter changed . Took off all pans as well as seat pan , pressure washed and cleaned motor and anything else I could .

It just wants to die after 20 + min ?

Thank you

[bmsgaffer 2,052]

Have you followed the steps that people have provided here?

 

All of the steps were responded to with "I know its good because of (something other than what was mentioned)"

 

These guys know what they are talking about, if you want help it is best to follow the steps asked and give a response to the test, otherwise we cant really help you.

 

I think you are making a lot of assumptions and I think that one of these tests will at least lead us to another clue. You have to remember we are trying to help based SOLELY on your descriptions, none of us have seen the tractor or can read your mind. There may be some small detail that's being miscommunicated.

 

[bmsgaffer 2,052]

 

There was no insulator between the ing module and the block? And this is the first time my machine has ever been taken apart. It just had 2 small bolts and washers and bolted right to the block.

And I bought a new ing module , the Harley coil was recommended to me by another member and it works . There is a new ing module , new coil, new condenser, new key switch, new starter solenoid new gas cap , new gas filter and oil/filter changed . Took off all pans as well as seat pan , pressure washed and cleaned motor and anything else I could .

It just wants to die after 20 + min ?

Thank you

 

 

Was this before or after the 20 minute problem? High pressure water can do all sorts of nasty things to electrical stuff including causing intermittent problems as well as heating/resistance issues from corroded wiring...

[bmsgaffer 2,052]

Have you replaced any of the relays? I think there is a relay that is on when the engine is running (having to do with the safety switches) that may be heating up and failing. (Thats from a 520, I cant tell you for sure it is the same with the 518)

 

Although that wouldnt have an effect if you have jumpered the coil...

Edited November 10, 2014 by bmsgaffer

[Martin 2,133]

Jess, i still have not seen you respond to the 'is there 12 volts at the coil + when the engine dies?' even if you are jumping the wiring to supply power to the coil, have you measured to see if you are loosing power at the coil? ignition switch on still from when it was running.

i want to know if you are indeed checking the coil for power immediately after the engine stops? i have yet to see your response with a voltage measurement to the repeated question from Nick and others both in this thread and the other one..........

[Geno 1,929]

Both are new as well as the ing module

Everything is clean and yes ignition module is new

 

I run into this fixing what other mechanics failed to fix.  New does not mean good. 

 

Testing is the only answer, my motto at the shop -

[546cowboy 302]

I surrender!

[km3h 543]

Ok, here is a test for you. There is a 9 pin connector coming from the engine to the tractor. Disconnect it. This will remove all other circuits on the tractor from interfering with the engine.

Use a jumper from the battery to the coil. On the starter solenoid there is a small wire, usually blue, that actuates the solenoid when the key is turned to start. Take another jumper wire and pick up 12 volts from the large wire coming from the battery and tap the connection the blue wire was on. The engine should start and run normally. If the engine continues to run past the usual cutoff period, we know for a fact that nothing in the tractors electrical system is a fault and it is within the confines of the engine or its electronics.

 

I am beginning to wonder if internal heat or low oil pressure is your problem.

 

   

I would still like an answer to several questions.

 

1. When the engine quits, is there 12 volts at the coil?

2. How many hours on the engine? 

3. Have you ever removed all the engine tin and cleaned it?

 

When I or anyone else here ask questions, we do so from a need to know so that we can go to the next diagnostic step.

[Save Old Iron 1,571]

Guys,

 

let's give Jess some breathing room here.

 

Maybe too many cooks in the kitchen at this point?