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

peapvp

peapvp

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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.
Click to expand...
S1 2, 4, 6, 8 should have 24V as soon as S10 is in "Normal" Position AND S17 E-Stop is Pulled Out AND CB1 is not tripped.

Further, S1 Pin 7 will be technically at the level of the Battery during crank. Since you are measuring 20V and you have a no crank condition, the Voltage should be higher, around 24V or whatever your system is at based on battery charge status.

This sounds to me more like an issue with S1

I would do the following:

Set S1 to run prime and make a momentary jumper from S1-2 to S1-7

If starter engages, remove jumper and set S1 back to OFF => S1 is your problem

If starter does not engage then the problem is somewhere else
 
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M

Maestro

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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 he makes 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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peapvp

peapvp

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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.
Click to expand...
Yes, it is possible and its designed for this purpose.
 
BeStihl

BeStihl

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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.
 
M

Maestro

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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.
Click to expand...
Actually, I said K12 energized after S1 returns to the run position and it stays energize even after the fault is clear. I just checked K16 and it to only energizes after the run switch is released, otherwise it does not have power and stay energized after fault being cleared. S3 does have power on it in the run and start position, it is 23.5V, my batteries are at 25.2 volts so there is some significant voltage drop from connection to connection.
 
BeStihl

BeStihl

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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.
Click to expand...
Incorrect, K16 gets power in RUN from S1-3, & in START from S1-3 & S1-7.
I think as GuyFang suggested you need to start at S1 and trace power in the RUN & START circuits, ie. S1-3 & S1-7. Maybe this color coded schematic will help, good luck.
 

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BeStihl

BeStihl

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Hopefully S1 is dirty causing his voltage drop (from 25V to 20V)which could possibly be letting K16 drop out during Start which would also stop current from reaching K2 through K16 NO contact.
High Impedance volt meters sometimes lie and make you think there is 20 when it could be 5, know what I’m saying?
 
M

Maestro

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Again, Thank you everyone for your help, With the help of @kloppk I was able to determine I had a defective S14. It would not allow K16 to energize. I got a new S14 and now it cranks using S1.

I now have a new problem and I will start a new thread since it an engine problem not electrical. The engine will not start it turns over and only start with starter fluid.
 
M

Maestro

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Figure out why it will not start and run and have to thank @Guyfang, read another thread about a MEP-803 not running and he suggested to look at the MPU and when I went to look at it, it was missing. Earlier on I saw two wires not connected and could not figure out what they were for, just thought they were extra or for a feature the generator did not have.

Off to buy an MPU. I hope this is the last thing.
 
M

Maestro

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I am going to wait to get the MPU before starting a thread it will not run, however, I do have quick question.

When I first tied starting it and would not run I check to see it fuel was getting up to the injectors, the lines were dry so I tried bleeding the line. I also gave a squirt of starter fluid to help it along. The engine fired up but immediately stop even though fuel was in the lines. I am assuming this is due to the missing MPU? Can someone confirm this make sense it started on starting fluid.
 
M

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@Guyfang, how does the MPU control fuel? From what I can see the fuel pumps are mechanical there is no direct electrical connection to the fuel supply other than the low pressure pumps. My understanding is the MPU measure RPM and is used to ensure RPM is maintained under load and will shut off the engine if there is problem.

When trying to start I observed the fuel supply solenoid, pulls back when starting which releases external start/stop lever, but the level does not move on its own it stays in the same position, I manually rotated the bottom of it forward towards the radiator and it still no start. Should the arm rotate once the solenoid pulls back. I am thinking this may need to be adjusted.

As previously said this unit has had some work done to it, originally I indicated the water pump, I was wrong it was the Gear End Cover, that was removed, there is gasket scraping in the bottom of the unit and they used RTV as gasket for the Gear End Covered. I wondering if something was not installed correctly related to the external start/stop lever and it not engaging the mechanical mechanism for the injector pumps. Looking at the drawing there are clock springs on the shaft of the start/stop lever. If the spring is missing or broken are there replacement for it.

Any thoughts

Screenshot 2025-09-12 121126.png
 

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LuckeyD

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Good Day: Just sitting there, all off the S14 should have a closed contact between 1 and 8. This changes at about 900 RPM as this contact set controls the k16. What is supposed to occur is as you rotate the s1 to run; K16 energizes closing a contact set where you could take a multimeter from S1 terminal 7 to the K2 X1 and it should be a closed circuit at about 0 ohms. I attached 2 docs that should get you some help
 

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M

Maestro

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The only way to find out is to open it up and I do not want to do that if there is possible something else going on.

Here are two pictures of the fuel shutoff solenoid and stop/start lever. The first one is with solenoid energize, it is pulled in, the stop/start lever did not move to the stop on the lower position nut. The second picture is when the solenoid is push out, and the stop/start level only move a bit and did not go to the upper stop position nut. I removed the solenoid lever and tried moving the stop/start lever by hand and as best I can tell it not moving through its full range of motion, I expect it should move between those two stop nuts. It definitely does not have any resistance as if it was connected to a spring as the drawing shows.

I have very limited experience with Diesels, I am trying to determine what is normal operation for this part. Right now without the engine running it only move about 1/2". Will it mover more if the engine is running. As you can see the front cover has been removed. I am assuming you have to remove that to see what is going on inside the governor control. Other than that work the engine is clean the oil you see there is from me bleeding the line. The pin on the engine and around the exhaust show little signs of use.

MEP-803 Fuel Shut off 1.jpg
MEP-803 Fuel Shut off 2.jpg
 
peapvp

peapvp

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Maestro said:
The only way to find out is to open it up and I do not want to do that if there is possible something else going on.

Here are two pictures of the fuel shutoff solenoid and stop/start lever. The first one is with solenoid energize, it is pulled in, the stop/start lever did not move to the stop on the lower position nut. The second picture is when the solenoid is push out, and the stop/start level only move a bit and did not go to the upper stop position nut. I removed the solenoid lever and tried moving the stop/start lever by hand and as best I can tell it not moving through its full range of motion, I expect it should move between those two stop nuts. It definitely does not have any resistance as if it was connected to a spring as the drawing shows.

I have very limited experience with Diesels, I am trying to determine what is normal operation for this part. Right now without the engine running it only move about 1/2". Will it mover more if the engine is running. As you can see the front cover has been removed. I am assuming you have to remove that to see what is going on inside the governor control. Other than that work the engine is clean the oil you see there is from me bleeding the line. The pin on the engine and around the exhaust show little signs of use.

View attachment 953829
View attachment 953830
Click to expand...
if I see this correctly then the linkage moves but it does NOT move the lever to open fuel supply
 
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