MP-803A - Will not Crank from S-1

Maestro said:

I finally had some time to get back to debugging the electrical issue.

I have verified all the correct voltages are on S1, depending on position of switch. I have 24V on S1 - 2,4,6,8 when S1 is in the start position I get 20V on pin 7, I followed that to K12 (Engine Fault Relay) pin 8 to pin 2 (N/C) should have 20V, and this is where the first problem appears. When I go through the start sequence the first time, from off to prime to start I get 19V at pin 2 to but no start, as soon as I release I get the oil pressure error light and K12 is energized and no power at pin 2. I clear the error, but it does not de-energize K12. I have to put the S1 back in off position and start over again.

K12 get power on Pin A which comes from S7-pin 7 as well as Pin 4 of K12 which is normally open until K12 is powered. Obviously the power is not coming from S7-7 so it coming from K12-4 which creates a lockout condition thus the reason you have to remove all power to reset. Pin 4 is connected to Pin 7 which is connected to S14-7 (crank disconnect switch), K19 (fuel level relay) pin A ( Power for relay)

In order for power to get to the starter L4, the power signal also goes through K16 (Crank Disconnect Relay) and K2 (Crank Rely) I know K2 works since S10 Dead Crank works. Looking at K16 the only way the signal gets through, it has to be energize when switch S1 is turned to start, this relay does not energize until after the S1 is released. Which means the power to A and B pins on K16 are not getting power at the right time. Pin B (ground) is connect to S14-1 and Pin A (positive) is connected to K20-4 K20-9 (oil pressure relay), and K12-1 so any of those relays can provide 24V.

I am at the point where can someone tell me how do you check S14 that it is working properly. I looked at it and do not see any obvious failures. Since the fuel level relay is in the circuit, how much diesel must be in the tank, I only put in a couple of gallons, did not want to fill it until I new it was running. The other possible fault is oil pressure, I put enough oil in it and check it a couple of time and it all the way up on the dip stick. As said before if I dead crank it for a little be before trying to start it do not always get the oil pressure fault light. Lastly, and you might have noticed the voltages, going through S1 the voltage drops from 24 to 20V and as the signal goes through the relays it drops to 19volts. This definitely is not normal. not sure of the drop in S1 it could be due to the diode across pin 7 to pin 1. can someone verify what is correct.

Just an FYI, I put a starter button on the L4, while holding S1 in the start position I pressed the stater button and the engine turned over but did not start. this tell me something is disabling the starting.

Any insight where to look next.

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Maestro said:

Just jumpered S1-7 to S1-2 and it did not turn over, still only hear K18 engaging. I am leading toward the S14 and tried reaching out to @kloppk to get his opinion since it make replacement S14. For some reason the website would not allow me to start a conversation with him.

@peapvp I plan to reach out to you later once I get this MEP running and installed I want to put your auto start system on this generator. I do have quick question about it, can you start the generator with contact closure, would like to tie it into my home automation system if all possible.

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BeStihl said:

I’m pretty sure S1 pins 3 & 7 have to be hot to start. S1-3 should send voltage through a NC contact of K12 to K16 coil in RUN it’s grounded through S14 NC contact, START should allow voltage from S1 pin 7 to reach the starter solenoid through the NO switch of K16 after it closes.

You said K16 was only energized after you released the start switch. Does K16 have power to the coil when in RUN?
Possibly losing its ground connection through S14 NC contact if faulty.

I’m curious if you grounded the coil of K16 temporarily in RUN then attempt to START either with switch or earlier mentioned jumper to S1-7 would the set start?
If so you would have to remove K16 coil ground ASAP after starting to release the starter and flash the gen head Then move back to RUN position to remove field excitement. In theory this would work if S14 is bad, I think but I do get things wrong sometimes.

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Maestro said:

Looking at K16 the only way the signal gets through, it has to be energize when switch S1 is turned to start, this relay does not energize until after the S1 is released.

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