New Member 803a fires but won't run.

[hooligan327]

Hi All. I'm new to the forum but I've been sifting through information around here for quite a while. I originally found this place when I was working on my Unimog 416. We live off-grid in Interior AK. We currently use a Honda 7k to charge our batteries in the winter but I recently acquired an MEP 803a. I would like to get this genset set up with a decent-sized fuel tank and put an autostart system on it, so that we could actually leave for more than 5 days in the winter. I bought it last winter from a guy who lives about three hours away. When I finally got down to pick it up he said that he had tried to start it that morning and discovered a bad fuel shutoff solenoid. He said that he had one on order and would mail it up to me when it came in. He did mail it up to me but it was the wrong solenoid. I ordered a new and put it in and it's still not working. The solenoid will open but not hold. If I hold it open the machine starts and seems to run fine, although at this point I haven't tested it much. I've spent a bunch of time searching around here trying to figure out what I'm missing. The batteries on the genset are all charged up. I've replaced the fuel shut-off solenoid. I tried to work my way through the TM but admittedly I'm not great with electrical stuff and I'm not entirely sure how to go about testing S1, which seems like it might be a problem from some of the reading that I've done. Any advice would be greatly appreciated.

 

[Guyfang]

Lets start easy. What are you calling a "fuel shutoff solenoid"? Do you mean a L5? Sometimes folks call things by different names, and it get confusing.

Do you get any idiot lights that come on, when you let S1 go?
Will the gen set run RIGHT, if you hold up S1, instead of letting it go?

 

[hooligan327]

Thanks for getting back to me. No idiot lights that this idiot could see. If I hold S1 for too long it sounds like the starter is grinding. I read here someplace that you're supposed to hold S1 for 5 seconds or something like that, but the starter starts making a pretty unhealthy noise in short order. The figure that you provided (L5?) is what I am referring to as "fuel shutoff solenoid", I will refer to it as L5 from here out.

 

[Guyfang]

STOP!!

You need to go to the MPU. Its damaged, or out of adjustment. When ever a TQG has starter grind, the MPU is at fault. And the MPU being bad will give the symptoms you describe.


Read the TM on how to remove, test and reinstall the MPU. If its ground off, dont screw with it, simply get another. DO READ the reinstall part at least twice, if not three times. Or you might just be buying another one.

 

[hooligan327]

Time to replace it I'm guessing...

 

[DieselAddict]

Oh yea, its toast.

 

[Guyfang]

Seen worse. And they all did not work! At least this is an easy fix. AND, you have a spare L5 that is good. Keep or sell.

 

[hooligan327]

OK... got the new MPU in finally. It's slow going getting things shipped up here. I'm still not getting any voltage off it. It's about 1/2 turn out from where it bottoms out and it's not registering any voltage. After my first attempt of screwing in until it bottomed out and then backing it off 1 1/2 turns, I took it all the way out and there was some rust and metal flakes on the end of it. So I cleaned it up. Tried again. Took it back out again and it was clean. I'm pretty nervous about screwing up the new MPU. Although I ordered a second one in case (a partially assuming) I screw up the first one. Any thoughts or ideas? Should I keep slowly turning it in or is there something else going on. I guess I'm wondering how close to the flywheel it should be before it starts sending a decent signal. Thanks in advance for any help.

 

[Guyfang]

Screw it in till it bottoms, then 3/4 out ad try it, adjust it from there! 2 turns is WAY too far out.

 

[hooligan327]

It's currently only a half turn out currently and not showing any voltage. Should it be showing some voltage at that point?

 

[Light in the Dark]

How and where are you measuring for voltage?

 

[hooligan327]

How and where are you measuring for voltage?

I'm measuring the voltage at the pigtails on the MPU with a multimeter. I've tried two different MPUs down to an 1/8 turn out. Still showing nothing.

 

[Daybreak]

Read the manual some more. You need helper B to complete the task.
The distance from the flywheel is about a hair.

 

[jamawieb]

Are you trying to measure voltage while not cranking? Like Guy said, bottom out and then 3/4 of a turn should be fine. It should start and not grind. You can fine tune it with the manual but not necessary. I usually do like stated above and then after its running, if I hit the start switch and it grinds, I know it needs to be closer in. Also make sure you have the solenoid hooked up correctly if the original harness has been spliced like I see alot. You'll have 1 wire that sends 24v to retract the solenoid when starting and then that one goes dead and number 2 wire holds it back with 24v while its running.

 

[kloppk]

Be sure your meter is set to AC volts

 

[hooligan327]

You got me, I was looking for DC voltage. I got the new MPU set correctly. Still getting a starter grind and it still won't run. Also when I spliced the original harness into the new solenoid (L5), I made a big assumption and just matched the wires up by color. I've got 15.5 v to red wire and 17.3 to the white. My batteries are probably a bit run down at this point. I will move the genset closer to the house and charge the batteries today (I have to charge our battery bank today anyway)

 

[kloppk]

On the new solenoid did come with instructions with what wire did what. There should be Ground wire, a Pull wie and a Hold wire. Need to match them up with the wire designation in the TM.

If the starter still grinds when it's running and you move S1 to start indicates that the starter lockout function isn't working. This involves the MPU, S14 Frequency Trip switch, relays K15 and K16. You have the MPU dialed in so it likely isn't that.

After you get the batteries charged we can tackle the starter grind problem.

 

[hooligan327]

Unfortunately, the solenoid did not come with any instructions to indicate which wire is which. From what I can figure red = HOLD, white = PULL, black = COM. The TM shows HOLD in Position #1, PULL in Position #2, COM in Position #3, this is how I've got everything wired up.

The batteries are all charged up. It's still doing the same thing. Got the starter grind going on and the L5 pulls but doesn't hold.

 

[kloppk]

Assuming the new L5 is wired correctly....
From looking at the schematic the hold signal comes from the K12 Engine Fault relay. If the set thinks it has an engine fault upon startup it will enable the K12 Fault relay and cause L5 to loose it's HOLD signal so that the engine shuts down. That would also explain the starter grind problem.

1) With the set not running but with S1 in PRIME/RUN push the test button on the fault panel and verify each of the lamps light up.

2) Start the set and release S1 to the PRIME/RUN. Leave S1 there. Check the Fault panel to see if any fault lamps are lit. If so which one?

 

[hooligan327]

I just figured it out. Pretty stupid on my part. I left the L5 pull adjustment in the same position when I replaced L5. Thinking about what could be keeping L5 from holding after it pulled, I thought that maybe it wasn't being pulled far enough to allow the hold magnet to take over. As it turns out, that was the case. It's outside purring away. Seems like it needed a new MPU as well. I really appreciate all the help from everyone here.
The next thing will be getting it wired into the inverter, set up w an external tank, and putting one of Kurt's autostarts on it. Looks like the weather might even give me a short break to get some of that done.