MEP 803a Starter wont crank using S1.

[benjcallahan]

MEP 803a. Fuel pumps run. Starter will not turn over using S1. Dead Crank operates normally. No power at terminal 7 on S1 when in start position. No voltage at starter solenoid post 2 when starting. No power at common posts 6 & 8 on S1. No voltage between pins F and J on diagnostic connection points.

I am getting no continuity at CR1 (Reverse Battery Diode) but I have anther machine that is operating properly that shows the same reading, probably operator error.

My latest idea is the voltage regulator is bad. I will swap with the machine that is functioning in the morning.

Machine did tip onto its back when moving into the garage as it is on a trailer that is back heavy. Run great last summer. Any advice would be greatly appreciated!

 

[kloppk]

Looks like you do not have power to all the S1 input terminals since you indicated the fuel pump runs but no voltage at S1-7 when in the start position.
S1 should have ~24 volts DC on terminals 2,4,6 & 8 with the Dead Crank in "Normal" and the Emergency Off switch pulled out.
You need to determine why S1-6 & S1-8 don't have 24 volts on them.

Don't bother with the regulator swap.

Can you post up pictures of the wiring on S1?

 

[Guyfang]

Look at this simplified schematic. If you have no power at S1-6, then trace it back to CB-1-1. If CB1 is closed, then through the CB to terminal 2, and on to S17. Through S17 and on to S10-3. That means you have to have the S10 in the normal position. Then from S10-3 to S10-2, and on to CR1. Though CR1, to MT4. I suspect you have a switch out of place, S17 is bad, or the CR1 is bad. Maybe a wire broke, but thats a long shot.

 

[benjcallahan]

Attached are a couple photos of the switch. We have traced power through CB1, S17, S10, CR1, and MT4. Back to thinking it is the S1 switch. Swapped S1 with an old switch but didn't actually verify proper function.

 

[benjcallahan]

Jumpering S1-2 to either S1-6 or 8 allows it to crank normally. I know this sounds like a stupid question but I should have continuity between all the even terminals on the S1, correct?

 

[kloppk]

Yes, all even numbered terminals on S1 should all be electrically tied together. That connection is indicated by the vertical thick black line running thru 2,4,6 & 8 in the TM's switch schematic in your post.

 

[Guyfang]

This S1 you have, is Mark 2 version.
Have you ever seen it work right, Start I mean?

 

[benjcallahan]

Yes it has worked for the last two summers. After opening the switch up there is no physical connection between terminals 8/6 and 2/4. Installed a jumper between terminal 4 and 8 and everything is working as it should. Any way this is not a switch issue? Any recommendations on where to buy a new S1. Green Mountain says they are out of stock.

 

[Guyfang]

Have you or anyone else worked on this set? There are suposed to be small copper jumpers that connect all the even numbered contacts. Thats why I am asking. Sometimes the jumpers fall out when someone removes the switch. I have often found that to be the case, so I simply made my own jumpers. Try it.

 

[kloppk]

Jumper circled in RED on one version of the switch. I believe this is a version 1 switch.

 

[Guyfang]

Kurt, thank you. There are times I could scream. I dont have a set to take pictures of, and these jumpers are not in the TM. Good show!!

 

[benjcallahan]

THANK YOU! Deff. noting that in my manual. Obviously fell out at some point. Thanks again.

 

[Guyfang]

Now I will tell you a funny story. In about 2006, 0r maybe 2008, I went to a unit because all the MEP-802A's would not start. About 15-16 sets. It was a commo unit. When I arrived, the Motor Sgt. and Platoon Leader were frantic. They were suposed to be loading up for a deployment. It was about a 4 -5 hour trip, on a good day. And it was sure not a good day. Anyway, got there and could not beleve my eyes. All the sets would not start! I went to the first one, and it had a brand new Mark two switch in it. So I mesured the voltage on pin 7 at start up. No VDC. Normally I would say get a new switch, but went to the next gen set. Tested, same deal. No VDC at pin 7. And a new switch! Some young soldiers was trailing along behind me, the Motor Sgt. behind him, and the Platoon Leader behind him. So I asked the young soldier if he had done anything to the sets. Proud as he could be, he told me he had gotten rid of the old, bad and unreliable Mark One switches, and installed the new ones. So I asked him about the jumpers. "What jumpers" was the reply. So I explained. Well, he had done the work late one afternoon, and to speed up things, had loosened up all the screws on the switches, and tossed them into his canvas tool bag. He then walked around to each set, and very carefully removed each switch, and replaced it with a brand new Mark Two switch. And all, or almost all the jumpers had fallen out of the switches. We got his tool bag and dumped it out. I had never seen so many jumpers before in my life. I always had a hand full in my tool box, but this was in another league. So I spent the rest of the day walking around and helping this poor young man remove and replace the jumpers on all the switches. I laughed till my head about busted!

 

[benjcallahan]

Found the S1 jumpers from both machines on the garage floor. Too many hours went into chasing down this stupid thing. Thank you everyone for your help.