MEP-802A. Won’t stay running.

[Generatorguy]

Cranks fine with main. Switch. Fuel solenoid pulls in and trys To start but solenoid falls out even with key still turned. Generator will run if i keep fuel lever held by hand. PLenty of oil pressure even when its cranking. It’s like it pulls the solenoid but then lets go immediately. any one ever seen this>?

Also. With Short switch on the genset will not even attempt to Crank.

any help would be great.

 

[Light in the Dark]

When the battle short is turned on, you will not be able to crank the set until it is reset. Have you referenced the -24 manual for 'ENGINE CRANKS BUT FAILS TO START' steps? The first step is to verify the battery charge... if your solenoid is not holding OPEN during crank, either your batteries are not properly charged (which this machine and all its accessories needs 24V at a minimum to operate)... or your solenoid is failing.

 

[kloppk]

When you release S1 from START to PRUME/RUN and the engine dies leave S1 in PRIME/RUN. Look to see if any of the lamps on the Fault Monitor are illuminated. If so which one?

If the Fault Monitor detects a fault, it will illuminate one of the lamps and cause the fuel solenoid to shut the engine down.

 

[Generatorguy]

When you release S1 from START to PRUME/RUN and the engine dies leave S1 in PRIME/RUN. Look to see if any of the lamps on the Fault Monitor are illuminated. If so which one?

If the Fault Monitor detects a fault, it will illuminate one of the lamps and cause the fuel solenoid to shut the engine down.

no fault lights. Doesn't even hold long enough to start. I can watch it. As soon as it starts cranking it pulls and then drops back out almost immediately. I can hold it open and it runs fine. Just won't hold it in almost like voltage it dropping off it immediately

 

[Generatorguy]

When the battle short is turned on, you will not be able to crank the set until it is reset. Have you referenced the -24 manual for 'ENGINE CRANKS BUT FAILS TO START' steps? The first step is to verify the battery charge... if your solenoid is not holding OPEN during crank, either your batteries are not properly charged (which this machine and all its accessories needs 24V at a minimum to operate)... or your solenoid is failing.

I wonder if I can unplug the solenoid and put 24v to it directly to see if it stays open. Im pretty sure it will. I don't see why it would pull fine when it first does and then just drops out. It's almost like it gets the initial voltage to pull
In but something is telling it to pull back before it even starts.

 

[kloppk]

If you have a hand held voltmeter watch the voltage on the middle terminal of the white 3 pin connector next to the solenoid. See if the voltage there drop out the moment the solenoid extends.

Does the starter drop out at the same time?

Also check for 24 volts on the pin on that connector to see if 24 volts is there as the set starts.

 

[pclausen]

I have a 802 with the exact same symptoms. It ran fine a few weeks ago, but when I tried to start it yesterday, as soon as it fired, the solenoid would cut off. If I manually hold the solenoid in the run position, it runs fine. There are no faults LED lit up.

I put a pair of Noco chargers on it overnight and tried cranking it again this morning, and same deal. So not weak batteries.

When I crank, the solenoid forcefully pulls back but as soon as rpms start to build, it shuts back down. If I keep holding S1 in the crank position, the engine keeps oscillating between crank, start to run, crank, start to run, etc. The starter never drops out, just the fuel solenoid keep going to start to stop during cranking.

I'll put a voltmeter on the middle terminal of the 3 pin connector going to the solenoid to see what I get, when I get a chance.

 

[kloppk]

While holding S1 in START watch relay K16 to see if it is moving each time the fuel solenoid changes position during the cycling.

 

[DieselAddict]

If I were going to place a bet it would be a set of dirty contacts on a relay.

 

[Light in the Dark]

The relays can often wiggle loose too, even with the hold down clips in place. I sold an 803 to a gent in TX and it would not start upon arrival... after some troubleshooting, it was determined that one or more relays had jigged about a bit in the ride down. All were reset and clips put back into position and no issues thereafter.

 

[DieselAddict]

Another thing I did back in the day when relays were everywhere is I had a buzzer box that would cycle the relay really fast for a few seconds. The contacts on industrial relays are self cleaning. They make contact with a slight wiping action that is supposed to keep oxide contamination under control. If they sit for a long time with no use the contacts can get dirty and stop working.

Making a relay tester/conditioner with an arduino would be a piece of cake.

 

[Guyfang]

That was one of the first things I made, after becoming a FMT, Field Maint. Tech for ITT. Got a socket, installed it on a tin can. Put two test points on it, red and black. Made two test leads, to go in the test points and the slave recpt. Had a switch on the side. Made it from junk parts from DRMO. Plug in the relay, got red lights for each normally closed contacts. Press the button, lights reversed. All red lights went out, the green lights came on when the normally open contacts closed. Simple, easy. Took 2 hours max. For me, it made sense. That was what I was doing 5-6 days a week. Generators. Even for a hobby gen mech, something to do on a cold winter night.

 

[pclausen]

I tried 3 different relays in the K16 socket and they all acted exactly the same. Here's one of them "dancing":

 

[kloppk]

OK, if K16 is doing that them it would appear that you may have a problem with S14 the Frequency Trip Switch. It's the leftmost item in the relay row. Looks like a relay but it isn't. What appears to be happening is that the S14 is "opening" and "closing" which causing K16 to open and close repeatedly. K16 is cutting power momentarily to the Fuel Solenoid and then restoring it when it's opening and closing. S14 gets its signal input from the Magnetic Pickup Unit (MPU) to determine when S14 should change state. S14 is supposed to measure the frequency of the signal from the MPU when the engine RPM is high enough to determine when to switch. My money is on a bad S14.
I have replacements listen in the classifieds section if you are looking for one.

 

[Guyfang]

Just for fun, check all the wires going to the S14 socket.

 

[pclausen]

I swapped out S14 from my parts 802 and same behavior. I then put S14 from the unit acting up into a good 802 and it started fine. I'll check the wiring going to the S14 socket next. The 802 acting up was running fine a few weeks ago when I last moved it around.

 

[Guyfang]

Is the MPU tight? Adjusted right? Not dirty?

 

[DieselAddict]

Check every screw on the wiring terminals and give each wire a little tug to make sure its not separated from the crimp connector.

 

[pclausen]

The MPU is not loose and the 2 connectors going to it are tight. I'll pull it when I get a chance to inspect it and make sure it is adjusted correctly. I do have a MPU from my spare set that I'll probably just swap in when I have it out anyway.

All the screws on the wiring terminals and by the relay bases are tight and do not come out when tugging on the wires. I went over this whole unit not 6 months ago and pretty much had it stripped down to just the block and gen head left on the base.

 

[kloppk]

If adjusting the MPU doesn't help then I'd suggest the following.
Watch relay K12 and see if it is also opening and closing with the behavior.
If K12 doesn't move then check to see if K16-A has 24 volts during the behavior. It should be constant voltage.