MEP-802A. Won’t stay running.

[zarathustra]

Y'know, I've managed to install S14 backwards and got some pretty odd results. Some of the later S14's are 'murphy proof" but some of the earlier ones weren't.

 

[Guyfang]

Don't feel alone!

 

[pclausen]

Finally had a chance to work on the unit some yesterday. I removed the MPU and cleaned off the little bit of rust stuck on the tip. Re-installed and adjusted and I still get the same thing. I remove the MPU from my spare set and noticed the connectors on the ends were gone. Anyone know if a good source for a male and female connector like these:



Anyway, if I leave the MPU disconnected, the unit actually starts up and runs fine. The one downside is that I have to let go of S1 once it gets going since the starter won't disengage automatically like it normally does. Perhaps that is indicative of another issue?

Once I get some new male and female spade lugs, I'll try the spare MPU, but I have a feeling that's not the issue.

I did not see K12 opening and closing with the behavior. Didn't get a chance to monitor K16-A for constant 24V, but I'll try that next.

 

[kloppk]

Having the MPU disconnected prevents S14 from detecting that the engine has started. With that case the starter won't be disabled automatically and the gen head field won't get flashed.

A good hardware store should have those crimp on connectors.

 

[pclausen]

Been a while. So I have now sold all my spare 802s except for this one that won't stay running unless the MPU is disconnected.

I measured the resistance of both the spare MPU and the one in the unit. Both are right around 141 Ohms. So I really don't think that's the issue.

Here they are:



Other than needing crimp connectors on the unit on the left, they both appear in great shape physically.

On adjusting the MPU, I screwed it in until it bottomed out against the flywheel, then back out 1 turn. Upon reading this:



It looks like I should check for 2-3 VAC. Looking at the referenced diagram, it appears to be this relay:



So is item 35 the K16 relay and that's where I should look for 2-3 VAC across terminals 3 and 6 while dead cranking?

 

[kloppk]

Yes
Also make item 35 is not a relay like the others in the row. 35 is a Frequency Trip Switch. You should be able to see a small circuit board inside it.

 

[pclausen]

Yep, I know exactly what "relay" that is. Thanks!

 

[zarathustra]

It seems as if the speed sensing ciruitry is cutting the starter on and off. You could try simply disconnecting the speed sensing unit and starting the gen. If it runs and doesn't oscillate then something is akilter in the circuitry that shuts off the starter motor. If S 14 is known to be good that'll make it simpler 'cause there aint much left to go bad. If it still oscillates when the sensor is disconnected, well, that's a whole new kettle of fish. If that is the case I'd vote for a dodgy socket on s14. The 802a vibrates a lot and sometimes problems appear in a dynamic mode and look OK in a static mode.

 

[pclausen]

Turns out it was the adjustment of the MPU. I put the original back in, backed it out 1.5 turns and got about 0.9 VAC dead cranking. Turned it back in 1/8 turn and I was at 1.6 VAC, did another 1/8 turn and was at 2.3 VAC, tightened up the nut and it runs great now.

 

[kloppk]

Thank you for the follow up. Great to hear it's running!

 

[Guyfang]

Best setting is between 2.5-3.0 volts, AC. But if it works, don't fool with it!

 

[Will H]

Thank you for the follow up. Great to hear it's running!

Hello,

I have an 802a that is doing the same exact thing. I did everything thing in the above post and it still surges. When I disconnect the MPU it would run, but only with the S1 held on run. Any other ideas on what it could be. It did take the entire top off and checked for lose wires.

thanks

 

[Guyfang]

It would be best when you start your own thread, then its possible to help you better. All the comments to your thread concern you, and only you. If you need help starting a thread, say something. While the problems sound alike, there is a good chance they are not the same.

 

[ALB39055]

Cranks fine with main. Switch. Fuel solenoid pulls in and trys To start but solenoid falls out even with key still turned. Generator will run if i keep fuel lever held by hand. PLenty of oil pressure even when its cranking. It’s like it pulls the solenoid but then lets go immediately. any one ever seen this>?

Also. With Short switch on the genset will not even attempt to Crank.

any help would be great.

Been working on a 802 I recently acquired. It is doing the same thing, cranks then solenoid cuts it off. The connector was cut off of the set side for connecting to the solenoid. Tested power and spliced it together. Couldn't figure other 2 out, both had continuity. Tried it, cranked then solenoid cut out. Switched the white and ground and it cranked and ran. Does not crank with battle short. One of my questions is am I by passing a safety if I have switched the ground and white on that connector? I see from reading posts from this thread to check power on white while cranking. I will test that to help ensure I got white and ground correct. Another odd thing with this set was a wire was disconnected from the inner most upper starter bolt. Three wires connect there for a ground. Looked at my other 802 and verified. I reconnected the free wire back to that ground. Wondering if that was an attempted fix or an attempt to by pass a safety from its time in the units?