mep-802a no start from main start switch

[bhb116]

I have a mep-802a that wont start with the main switch, new relays, new crank relay tested all components all check, if I disconnect fuel stop solenoid and dead crank motor starts switch over to run and it runs ok. I have no voltage coming to x1 on crank relay in normal start but here is with dead crank. We have checked it over and over and were lost now. HELP!!!

 

[bhb116]

I have a mep-802a that wont start with the main switch, new relays, new crank relay tested all components all check, if I disconnect fuel stop solenoid and dead crank motor starts switch over to run and it runs ok. I have no voltage coming to x1 on crank relay in normal start but here is with dead crank. We have checked it over and over and were lost now. HELP!!!

Also we have just found we have no power coming to the k12 engine fault relay.

 

[CDR]

I had the same issue

 

[CDR]

Check my past posts I have like 40 hours in to finding that

 

[Triplecrush]

Did you ever find out what was causing it? I have the same problem. I disconnected the solenoid so it would run and I can manually shut it off by holding the lever with my fingers to shut off fuel but it would be nice to be able to start it from the switch and all that. Any help would be appreciated.

 

[CDR]

I responded to your question in the other tread. Hopefully I could be some help. Like I said it's not easy it's took me almost 40 hours to find that

 

[customload]

Not sure how this reply stuff works, so here it goes.
Bought an 802a. Wont start. New batteries, new starter that had new solenoid on it, replaced solenoid in other compartment, changed all 6 relays behind main panel, nothing.
Starter will not turn over on dead crank switch.
Jump across starter and it turns over.
When I use the main switch, the fuel pumps come on but when i turn to start, only the solenoid makes a clicking noise.
Changed out fuel solenoid on side of motor and nothing.
fuses are good. have fuel in tank, not up to engine yet.
Sounds like main switch works fine. even get a click noise on pre heat.
Any help would be great. trying not to turn this into a parts unit.

 

[kloppk]

Don't give up. You just have a simple electrical problem.
Do you have a voltmeter or 24 volt test light handy?

If so you may be able to narrow down the problem using the diagnostic connector.
You may need to use a small nail to stick into the pins on the diagnostic connector to make contact.

Connect your meter or test light ground to a suitable ground point..

Toggle the Dead Crank switch to Crank, hold it in the Crank position and check the following points in the diagnostic connector.
- Pin T should have power (~+24 volts) to it. If no power then the CR1 diode may be bad or the dead crank switch may be bad. If power at pin T then...
- Pin N should have power (~+24 volts) to it. If no power then the K2 relay is suspect. If power at pin N then...
- Pin X should have power (~+24 volts) to it. If no power then the started solenoid on the starter be bad.

 

[Daybreak]

Howdy,

Not to be smart, but.... push in and pull out your emergency stop button.

 

[Guyfang]

Perhaps you need to download the TM's and go through the troubleshooting. Changing parts is not the answer. If you can jump across the starter and it turns over, it ain't the starter. So what tells the starter to start? The start switch, (S-1) or the dead crank switch, (S-10). If it won't start from both switches, what do they have in common? Maybe the cranking relay, (K-2)? The troubleshooting diagram will tell you how to check it. If it's in order, (K2) then work back from X-1 terminal on K-2, to the S-1. And yes, like DAYBREAK told you, check S-17. The troubleshooting diagram will also tell you how to check it. You need to slow down, and take it step by step.

 

[customload]

Thank you All for the info. Let me provide more.
When I use the dead crank switch I get nothing.
I changed all the relays out with another 802-A that I have, so I dont think it is a relay.
Solinoid for the heater clicks when I push dead crank up, so solinoid is working, plus changed it out anyway.
Had one guy tell me that the speed switch was bad, thought he was joking because I cannot find anything on it.
found master switch was a DHR10 model not a CHR10 model.
All boils down to something not telling the starter to turn.
Yall have been a lot of help, please continue.
From Williamsburg Virginia

 

[customload]

So I looked on the wiring diagram to find the pins to test on the diagnostic plug and of course they are not lettered or marked.
How do I know which one is which?
also I did push and pull on the red main switch, and it works.

 

[customload]

How can I find the pins, they are not marked?
I do have a tester.
Is htere a machine on the market to hook up to the diagnostic port that someone could buy?

 

[kloppk]

Here is the pinout of the diagnostic connector. Doubleclick to enlarge.
There are pins with upper case and lower case lettering. Be sure to use the upper case pins in most cases when probing.
It can be found in TM 9-6115-641-24.
If you look closely at your connector you should see tiny letters molded into the plastic near each pin location.



Try going thru the test sequence I posted earlier and then post up your results.

From what I understand there is no machine on the market to hook up to the connector. Apparently it was designed in but the "machine" (diagnostic tester) was never made.



Here is the table from the TM about what each used test point in the connector is for and some notes about test conditions.
The pins in the table correspond to the letters in the triangles on the schematic.

 

[customload]

Grounded my meter to the generator ground , tested on battery got 12.4 volts.
pushed crank switch up to crank, got no starter movement, and no readings on any of the pins, T_N_X

 

[customload]

Also placed dead switch down, and master switch on and only got .2 v on the three pins.

 

[kloppk]

Grounded my meter to the generator ground , tested on battery got 12.4 volts.
pushed crank switch up to crank, got no starter movement, and no readings on any of the pins, T_N_X

Assuming you made contact with pin T then it's possible the CR1 diode is bad or missing.

Carefully probe MT4 on the bottom right behind the gauge panel. Does it have ~24 volts on it?

 

[kloppk]

If you get 24 volts there then probe both sides of CR1. It's located on a panel on the left side of the back wall behind the gauge panel.
There should be 9 parts soldered to the terminals on it.
It's the second component from the bottom. Measure the voltage on both sides of CR1. Should be 24 volts.

 

[customload]

24.9 on both lugs of mt4
crank switch in off position

 

[kloppk]

24.9 on both lugs of mt4
crank switch in off position

Good.
see post 18