416-8 Onan Runs for 3 Minutes and Quits

[RJ Hamner 1,025]

This originally started with the engine surging with help from @Ed Kennell, @lynnmor and @Bill D The carb was cleaned,new intake and exhaust gaskets. 

A check of the coil found that it was bad and replaced.

Got everything back together and found that the fuel pump had bit the dust.

While waiting for parts I replaced the 9 pin connector with an 8 pin Packard 56 and rewired the engine.

Still waiting for parts I did a compression check (cold) and found I have 115 forward and 120 aft. (Probably unrelated but I did it anyway)

Fuel pump showed up today and before I installed it I blew out all the fuel lines even though they were new.  (gas is fresh and is corn squizings free)

With the new fuel pump installed it fired right up and ran for approx. 3 minutes then shut down.

On the off chance that I had a faulty coil I checked it with the engine cooled, fired it up again and it ran for another 3 minutes and checked it hot.

It checked good.

I did have a thought about the two piece intake manifold.  If it got hot and opened a seam would that cause anything like this???

I 've gone through the checklist multiple times checking for anything I might have missed.

I have run out of ideas at this point.  Anyone have any ideas????

[rmaynard 15,936]

Only thing that crosses my mind is that the vent in the gas cap is plugged. Take the cap off and see if it keeps running.

[Bill D 2,103]

If you have another ignition switch try swapping it out.  Also check the seat switch and PTO switches.  The power to the coil runs thru them.  If they are failing the current passing thru the contacts may make them hot and cause them to open the circuit to the coil.  When it shuts down is there still 12V on the positive terminal of the coil?  If 12V is still present then you may need a new ignition module.  Bill

[RJ Hamner 1,025]

12 minutes ago, rmaynard said:

Only thing that crosses my mind is that the vent in the gas cap is plugged. Take the cap off and see if it keeps running.

Well...I had my fingers crossed.....but...3 minutes on the nose and she quit

[rmaynard 15,936]

Just now, RJ Hamner said:

Well...I had my fingers crossed.....but...3 minutes on the nose and she quit

Well shoot 

[RJ Hamner 1,025]

7 minutes ago, Bill D said:

If you have another ignition switch try swapping it out.  Also check the seat switch and PTO switches.  The power to the coil runs thru them.  If they are failing the current passing thru the contacts may make them hot and cause them to open the circuit to the coil.  When it shuts down is there still 12V on the positive terminal of the coil?  If 12V is still present then you may need a new ignition module.  Bill

The ignition switch is new.  The seat switch is bypassed (yeah I know).  The PTO switch was working before the surging started so??

But let me get this straight in my head.....(1) get it started again, (2) wait till it quits, the (3) see if I have 12V on the positive terminal of the coil (switch still in the ON position)????

[Bill D 2,103]

Correct.  If you still have power to the coil then the ignition module is probably bad.  It's possible you could have a bad ignition switch even if it's new.  The PTO switch could have failed.  Welcome to the wonderful world of Onan.  My local dealer refers to them as Onan the Barbarian.  

[RJ Hamner 1,025]

11 minutes ago, Bill D said:

Correct.  If you still have power to the coil then the ignition module is probably bad.  It's possible you could have a bad ignition switch even if it's new.  The PTO switch could have failed.  Welcome to the wonderful world of Onan.  My local dealer refers to them as Onan the Barbarian.  

I have 9 volts on the positive post of the coil

[johnnymag3 2,559]

TIME for a KOHLER>>>>>>>>>>>>> Right Bill !!!!!

[gwest_ca-(File Mod) 11,266]

52 minutes ago, RJ Hamner said:

I have 9 volts on the positive post of the coil

Where did the other 3-1/2 volts go?

 

Garry

[Bill D 2,103]

What is the voltage across the battery terminals?  If it's more than 9 volts you have a voltage drop somewhere.  Most likely a set of hot contacts in a switch.  Does it stay running if you run a jumper from the battery positive to the coil positive?

[lynnmor 7,588]

1. Check the voltage at the ignition switch with it turned on.

2. Check the voltage across the battery terminals, it should be the same as 1 above.

3. Check the voltage at the + terminal of the coil, should be the same as above.

4. The kill relay is one place you can lose power, try swapping the relays around.

5. Running a jumper as Bill D said is a good test.

6. Whatever the problem is, blame Onan, even a flat tire.

[Bill D 2,103]

@lynnmor I don't think he has a kill relay.  He is working on a 416-8, not a 520.  Bill 

[lynnmor 7,588]

3 minutes ago, Bill D said:

@lynnmor I don't think he has a kill relay.  He is working on a 416-8, not a 520.  Bill 

I see, we should state the model in each thread to make things easier.  The seat relay is still a suspect even if the seat switch was bypassed.

[RJ Hamner 1,025]

5 minutes ago, gwest_ca said:

Where did the other 3-1/2 volts go?

 

Garry

Did you ever think one thing and type another

 

6 minutes ago, Bill D said:

What is the voltage across the battery terminals?  If it's more than 9 volts you have a voltage drop somewhere.  Most likely a set of hot contacts in a switch.  Does it stay running if you run a jumper from the battery positive to the coil positive?

See response above

 

4 minutes ago, lynnmor said:

1. Check the voltage at the ignition switch with it turned on.

2. Check the voltage across the battery terminals, it should be the same as 1 above.

3. Check the voltage at the + terminal of the coil, should be the same as above.

4. The kill relay is one place you can lose power, try swapping the relays around.

5. Running a jumper as Bill D said is a good test.

6. Whatever the problem is, blame Onan, even a flat tire.

I am going to do what Bill said -  AKA your #5.  But FIRST I am going to sit down and have a frosty beverage and have a discussion with myself about the $400 for a new module and ring vs.A shiney Red Garden Tractor turned into a Rural Mail Box

[Bill D 2,103]

My Onan powered tractor is an 1989.  It doesn't have a seat relay.  What year is this tractor again?  Jacks has the best price on modules and you may not need the ring.  Bill

[lynnmor 7,588]

The early rings were black in color and did fail, the newer gray ones rarely fail.  The price quoted is about double what it should be, contact AZ Tractor.  Before buying anything do the tests above and also those in the Onan Service Manual.

[RJ Hamner 1,025]

11 minutes ago, Bill D said:

My Onan powered tractor is an 1989.  It doesn't have a seat relay.  What year is this tractor again?  Jacks has the best price on modules and you may not need the ring.  Bill

The one in question is a 93. The”dog” is a 91

 

3 minutes ago, lynnmor said:

The early rings were black in color and did fail, the newer gray ones rarely fail.  The price quoted is about double what it should be, contact AZ Tractor.  Before buying anything do the tests above and also those in the Onan Service Manual.

I know that the 91 tractor runs pretty good. What I may do is run the tests on the 93 to make sure that the module is good or bad then run some tests on the 91 to see if it’s worth swapping the engine or just rob the parts. If I go the used parts route I might as well use the ones I’ve already paid for. 

[DennisThornton 4,771]

My Onan might start, might run long enough to mow the lawn, might run for a couple minutes.  I found this info online and have ordered an ignition module.

 

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This test is for the P series Onan engines. P216, P218 & P220 etc. with electronic ignition. First thing to do is confirm you are getting Battery voltage to the coil.

Connect a jumper lead directly from the positive battery terminal to the positive (+) coil terminal (smaller diameter of the two threaded posts). Crank engine over while watching for spark. If spark occurs, the problem is in the low oil pressure cut out switch (if equipped) or related wiring, the lubricating system (low oil pressure), or in the other circuitry bringing voltage to the coil. If no spark occurs it's time to test the ignition module.

Connect positive side of voltmeter to negative (-) coil terminal (larger diameter of the two threaded posts) and negative side of voltmeter to engine ground. Leave the jumper from the + battery terminal to the + coil terminal connected and rotate flywheel slowly by hand while observing voltmeter. Voltage should switch between battery voltage and 1-1.5 volts for each revolution. If voltage does not switch properly, replace ignition module.

Module is behind the flywheel mounted to the gearcase cover.

 

I'M NOT SURE ABOUT THIS!!!

"Another thing I have been told you cant test spark in the conventional manner on these onans, they have resistive spark plug wires, don't put any thing else but those in the onan. "

[RJ Hamner 1,025]

2 hours ago, DennisThornton said:

 

 

_______________________________________________________________________________

 

I'M NOT SURE ABOUT THIS!!!

"Another thing I have been told you cant test spark in the conventional manner on these onans, they have resistive spark plug wires, don't put any thing else but those in the onan. "

You can definitely check for spark with real wire plug wires

[DennisThornton 4,771]

11 hours ago, RJ Hamner said:

You can definitely check for spark with real wire plug wires

Makes sense to me but I was only passing only what I gathered with a "Notice!" that I doubted what I read.  Thanks for your input!

[Bill D 2,103]

I made a new set of solid core wires for my P216.  They work fine.  Bill

[RJ Hamner 1,025]

The only reason that suppression type wire would be required would be avoid interference with computer controlled electronics or interface with radio/stereo reception 

So......unless you have the latest surround sound stereo installed on your Wheel Horse......good old copper wire is what you should use. 

[RJ Hamner 1,025]

I ran across a post that had a step by step narrative on how to replace the ignition module. 
As I read back through the post I found that he experienced the exact same problem that I am having now. He attributed it to the failure to blow out the “crud” that gets sucked in around the flywheel when mowing. All the dirt, grass and moisture gets packed in the area behind the flywheel where the module is located. This can create a heat sink and over time damages the module to the point that it fails from excess heat. He replaced the module and solved the problem.

 I am keeping my fingers crossed. 

[lynnmor 7,588]

4 hours ago, RJ Hamner said:

I ran across a post that had a step by step narrative on how to replace the ignition module. 
As I read back through the post I found that he experienced the exact same problem that I am having now. He attributed it to the failure to blow out the “crud” that gets sucked in around the flywheel when mowing. All the dirt, grass and moisture gets packed in the area behind the flywheel where the module is located. This can create a heat sink and over time damages the module to the point that it fails from excess heat. He replaced the module and solved the problem.

 I am keeping my fingers crossed. 

 

Later models have a gasket like material behind the module, perhaps to reduce heat from the engine block.  Be sure to clean the often plugged up narrow space under the engine to allow air to cool the oil sump.