MEP-804a No Crank from S1 Master Switch

[SLTRAM98]

I have an 804a Genset, 164 hrs. on the clock. New to me (2006 make); here is the run down and trouble shooting to date.
1) Fresh batteries, when using the dead crank switch (on side of engine compartment), engine cranks totally fine, no issues.
2) When S1 (Master Switch) is turned to start, you can hear the shutoff solenoid open, but no crank.
3) Pulled Magnetic Pick Up (MPU) it did have some metal shavings but in great shape, cleaned it put it back in.
3) Read through the TM, traced things back to poles 18, 19 and 20 on A5 Governor Control board.
- Tested Poles per the test scenario's in TM, 18 to 19 'should be' normally closed when genset is off, but they are not. Note: I did notice a difference from the TM schematic which shows reversed NO and NC switches from the white markings on the GC A5 Board, appears to me that the A5 white markings are correct when genset is off, I guess the TM switch confi. would be accurate when the machine is running.
- Pulled A5 board out, its spotless, no burns, I do understand that only means so much but was looking for a blown up part, nothing.
- I JUMPED 18-19 poles to test my theory that their is a failed NC (normally closed) switch and genset STARTED right up, purred like new using S1 (Master Switch), ran no problem. I only let it run for a minute since I am not sure about the following items noted below.
- In the manual the wire diagram shows S14, but again reading on this forum, sounds like S14 is built into A5? (Please confirm this.)
- Am I correct in my understanding that the purpose of NC 18-19 switch relay at start up, which then should open after genset starts, is to protect the starter from getting hit again and grinding the starter? Eg; what happens if I cant solve S14 (built into A5) and install a wire jumper permanently?
- Does anyone have the A5 board schematic - specific to A5 - so I can see what else is driven by poles 18 and 19?
- Only other item I can see that 'may have' failed would be CR4, HOWEVER, it would stop power from getting to 18 so my jumper wire would not work regardless, so pretty sure that has NOT failed.
- I could install an external relay that is NC until startup, that would be pretty simple however, again I would like to know if anyone knows what else A5 is reading from the 18 and 19 poles. If no objection a permanent jumper would be nice.

Thank you for the help!

 

[Guyfang]

Before you get too far along. Have you troubleshot the S1?

 

[LuckeyD]

Good Day: I use the B model as it is better drawn but has the same things in there. OK, using S10 dead crank switch you know the K2 is working as it cranks. Guy hit the starting point with the S1. Battle short switch in the down position so the K15 will work or it acts like what you have, Emergency stop pulled out, and you should have Battery, (B+) on S1 terminals 2,4,6,8 to chassis ground(I use the ground point in the control box that looks like a stud on the one side but any chassis point will do). S1 to run and B+ at terminal 3. The blue stuff has power on the attached. Now go to start and if K15 energizes you should have B+ at A5 terminal 19, and if the S14 inside the A5 is good you should get B+ at terminal 18 out thru a now closed K15 contacts to K2 and it should crank below 900 RPM. K15 not working it acts like what you have. Over 900 RPM the A5 switch S14 changes position from what is fed to it from the MPU locking out the starter and the K2. That is the start circuit and should get you on a path to success. Let us know how it goes.... The A5 is expensive so if you do not go to start while running grinding the starter teeth, you can use a short wire between terminal 19 and 18 till a new A5 is available if the S14 is faulty for TS purposes. I did use a toggle switch once so I had power from 19 to 18 and after starting I flipped it to the other position so I had power to terminal 20 after starting so AC production starts till a new A5 was available as everything was working but the s14 inside the A5. Again let us know how it goes..

 

[SLTRAM98]

Guyfang - [Before you get too far along. Have you troubleshot the S1?] Yes, pole 7 is hot and all other poles are hot in the correct S1 positions, S1 tested good when I was going through the TM.

LuckeyD - Thank you for the info, I will go through this and get back with you this weekend! I know Battle Short is working properly and I verified Emergency shutdown is also good. Again, will go through your process and let you know asap.