MEP-804A, Cranks on dead crank switch but not on master

[BigIron69]

Hello,

I have a MEP-804A and I have changed all the fluids and filters per manual. I go to start it and at first nothing on the front panel, I set the dead crank switch to normal and reset the 7.5A breaker behind the panel (it was out), now I have instrument lights, needles didn't seem to move on the panel, but I am not sure if that is normal. When I go to prime/aux, I can hear the aux pump run, prime and run, nothing, turn to start, and no crank. Dead crank switch works but does not light up the instrument lights when cranking so I am not sure that the correct systems are getting voltage.

I tried reading dc volts on the wire circled in the photo while the master was in crank position, nothing there.

Thank you in advance, this forum is a wealth of knowledge.

 

[Guyfang]

Put the S1 in the run position and see if you have 24 VDC at S1. contacts 2-4-6-8 &3. Then if you have voltage to all those pins, have someone hold the S1 in the start position and measure at S1 again, but on pins 2-4-6-8-3 & 7

If you have 24VDC to all those positions, take the top off and look for K2, the crank relay. Pins X1 to ground, & X2 to ground, for 24 VDC when the S1 is in the start position. If you have 24 VDC there, measure from K1-A1 to ground & and K1-A2 to ground. Tell us what you got!

 

[SLTRAM98]

BigIron69
Depending on what you find, from the upfront voltage checks Guyfang recommended; consider the below thread. I had what sounds like a similar issue on an 804a as well. Worth checking the A5 board pins. If the S14 relay does not receive power it will not connect the starter. Just an idea based on your symtoms.

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www.steelsoldiers.com

 

[LuckeyD]

Guy hit the nail on the head. I attached a file you may read and it includes how it works.