803 Pre-heat run-away

[pclausen]

I picked up a 803 a few months ago in good condition with a little over 5,500 hours on it. Runs good and I load tested it last weekend and it held a 12 kW load without breaking a sweat.

Fired it back up yesterday and ran it for a few minutes and then shut it down again. Temps were in the 40's and I didn't bother using the pre-heat before starting it.

Anyway, after about 5-10 minutes, I noticed a burnt smell in the pole barn type building the unit was stored in. I then noticed smoke coming from the 803. Opened the doors and a lot of smoke came out. I then noticed all the paint had burned off the intake manifold and it was still way hot. Got a 1/2" wrench and disconnected the battery and the intake manifold finally started to cool down.

It is almost as if S1 had somehow gotten stuck on the pre-heat position, but it was definitely in the OFF position and the spring loading back to OFF is working. My S1 switch is the blue plastic style as opposed to the "open style". Is this switch prone to this type of failure? I suppose it could also be K18 that somehow flaked out.

I'll disconnect the output wires from K18 to ensure the heating elements don't come on again when I reconnect the batteries to troubleshoot the issue further.

Also, given that the heater elements were on for a good 5+ minutes, should I pull the intake manifold to make sure they were not damaged and potentially broke and dropped pieces that might get sucked into the engine when starting it back up.

Is there anything else I should look at before starting this unit back up again?

 

[Ray70]

It probably would be a good idea to pull the manifold and / or the heaters to verify none of them melted and dropped any fragments in the manifold.
I think I would start by looking at the K18 solenoid, my money says it got stuck in the on position.
I believe the K18 is energized when cranking the engine, even if you don't use S1 to preheat before cranking.
I know the air cooled machines work that way, and I bet the liquids do as well.
Start by checking K18 as-is to verify the contacts are open.
With the heaters disconnected, try energizing the solenoid a few times and check to see if it sticks on after power from S1 is removed.
If it does not, reattach the heaters and try again. I have seen solenoid contacts get welded together from the arc created by the load.

 

[nextalcupfan]

The preheat relay is energized when the S1 is in the start position.

The Blue style S1 switch is known for it's contacts sticking internally seemingly at random.

I recommend you undo the main wire to the heaters (116A) and use a volt meter to determine if you have voltage.
Start at the output of the S1 (1) and work your way to K18.

I also agree with taking the intake off before cranking to check them, won't hurt to test each ones resistance value while you are there.
It's alot cheaper to do that than rebuild an engine.

 

[loosegravel]

The preheat relay is energized when the S1 is in the start position.

The Blue style S1 switch is known for it's contacts sticking internally seemingly at random.

I recommend you undo the main wire to the heaters (116A) and use a volt meter to determine if you have voltage.
Start at the output of the S1 (1) and work your way to K18.

I also agree with taking the intake off before cranking to check them, won't hurt to test each ones resistance value while you are there.
It's alot cheaper to do that than rebuild an engine.

Just curious. If the preheat relay is energized with S1 in the crank position is this feature temperature related? As in will K18 only pull in at ambient temperatures below a specific threshold?

 

[Guyfang]

Just curious. If the preheat relay is energized with S1 in the crank position is this feature temperature related? (NO) As in will K18 only pull in at ambient temperatures below a specific threshold?

Is the switch a round, or square S1?

 

[loosegravel]

Is the switch a round, or square S1?

I've been seeing a mix of round and square S1's. I've just always "assumed" that the glow plug operation on these units was strictly manual, turning the S1 to the pre-heat position.

 

[Light in the Dark]

No preheat is energized during cranking as well.

 

[loosegravel]

No preheat is energized during cranking as well.

That's good to know. Thanks!

 

[nextalcupfan]

If you look at the back of the switch you'll see a diode. It's jumping pin 1 and 7.
That powers the preheat during cranking no matter the ambient.

 

[loosegravel]

If you look at the back of the switch you'll see a diode. It's jumping pin 1 and 7.
That powers the preheat during cranking no matter the ambient.

Perfect! I guess where I was going with this is that this is probably a good reason to NOT use starting fluid on these units, unless the glow plugs are disabled. It could be a problem!

 

[Light in the Dark]

If you look at the back of the switch you'll see a diode. It's jumping pin 1 and 7.
That powers the preheat during cranking no matter the ambient.

Bingo

 

[pclausen]

Thanks for the suggestions. I'll be sure to pull the intake to make sure none of the heaters dropped any fragments.

Good to know pre-heat always come on during cranking, that would explain how K18 closed in the first place. I guess that means the heaters stayed on while the set was running and kept going after shutting down.

My S1 has rounded corners. Here it is:



And yep, it has the diode between 1 and 7.

I'll start by checking K18 after disconnecting the heater wires.

 

[Guyfang]

This is the so called Mark 1 switch. It had serious problems. Unreliable. The blue Squire switch, the Mark 2 was better, but still unreliable. The round Porzellan switch, Mark 3 is the best, and I have never seen one go bad, that was not abused. Like beat on. So yes, I would check the S1 also.

Good to know pre-heat always come on during cranking,

TM?

 

[pclausen]

I just checked S1 again, and what do you know, it will get stuck in Pre-Heat is not careful. It also feels real mushy. See below:

So when I shut it down yesterday, it more than likely got stuck on the Pre-Heat position.

So I'll start by swapping it out with the S1 from my spare set, which I believe is a Mark 3:



If it turns out I do have an issue with K18 as well, can I swap in the one from my spare set? (shown below)



I know a 803 has 4 heaters instead of 2 and when compared to my 802s, the wire coming from the starter solenoid feeding K18 is much thicker and there are 2 wires coming from K18 going to the heaters on a 803 compared to a 802:



So I wasn't sure if K18 in a 803 has a higher Amp rating compared to a 802, or if the wiring was the only thing that is beefed up in a 803.

Yes, I need to study the TMs some more, especially about the differences between a 802 and 803.

 

[nextalcupfan]

So I'll start by swapping it out with the S1 from my spare set, which I believe is a Mark 3:

Yes that's a Mk3.
You got lucky, those Mk3's can be tricky to find and expensive. I had a Mk1 in my set and replaced it with a Mk3 last year, I think it was nearly $200.

 

[Guyfang]

Yes, I need to study the TMs some more, especially about the differences between a 802 and 803.

 

[Light in the Dark]

I assume the leads on the 10k will be heavier as they have to pass current forward for 4 manifold plugs instead of 2.

 

[kloppk]

The Pre-Heat relay K18 is different between an 802 and an 803.

 

[Guyfang]

I assume the leads on the 10k will be heavier as they have to pass current forward for 4 manifold plugs instead of 2.

Yes, I need to study the TMs some more, especially about the differences between a 802 and 803.

 

[asloan5]

The same thing happened to me with the junk blue S-1.. purchased 2x of the better ones from a member here and s***canned the old ones. I’m sure I could’ve sold them on eBay but I wouldn’t do that to somebody