MEP 804b wont crank

[expeditionnw]

Ive got a 1000hr 2008 model 804b.

it wont crank over with the master control switch.

I have run thru all the diagnostics found in the TM. all relays test out good, starter is good, master/dead crank/ emerg.stop switches, and al three breakers test good.

I can apply 24v to the starter solenoid and fuel relay and it will start immediately.

When I turn the master switch to start, i hear the relay clicking under the panel.

In inspecting everything, I have found the Cranks sensor be be pretty banged up. I wouldnt think this would cause it to not crank.


Has anyone had this problem? Ive reached the step in the manual that reads " notify next higher level of maintenance"

Also, Does anyone have a crank sensor for this unit?

 

[robertsears1]

When you say the “crank sensor“, do you mean the MPU (magnetic pickup) found inside the left door at the flywheel? My 804a would just click at the solenoid when I first got it. I kept wiggling and tapping things and it finally started working correctly. You can get the MPU from eBay, search MSP6729 3/8-24unf-2A, around $25.
It may be ok since you can get it to run. That is usually the problem when it cranks but no white smoke from the exhaust after a few seconds of cranking, like it isn’t getting fuel. You also need to check that your’s has the fuse modification installed and if not, do that first. In the picture, it is right of the blue box. Search “quad fuse”.
I have both an 804a and b, but I got them to power 3 phase equipment. You do realize that they only make 3 phase, not designed for single phase? You can finagle and get single phase but is not good for the set long term. I have seen more threads lately on MEP 804s, 805s, 806s, 004s, 005s, 006s than the smaller sets that can switch between single and three phase output. Is it because they are available and relatively cheap? The older 004,5,and 6 can be reconfigured to put out single phase since they have a 12 wire gen head but the newer ones either only have 10 wires or the other 2 are buried up inside. Either way, you will not get full output amps.

 

[Guyfang]

When you see the " notify next higher level of maintenance" comment, you need to go deeper into the book. There is another troubleshooting section. Yes the MPU will prevent it from starting. Have you ever seen it run right? Or is the set new to you?

 

[expeditionnw]

the unit is new to me. No experience with it functioning.

I ohmed thefuse show. test good. In this photo-is this the quad fuse seems an odd name for it.

With the s1 in start, i am getting .03 volts thru the fuse. (Pole7 of s1 is outputting 24v nom.)

 

[Guyfang]

Slow down partner. You need to hit the books. The -10 manual tells you how to properly start the set.

The fuse has nothing to do with starting. Its to protect the main generator from being damaged when the volt regulator, (the box to the right of the fuse) goes bad.

Tell me whats not working. Will the starter engage the motor? Or will nothing happen when you turn the S1 to the start position?

 

[Guyfang]

Its 00:00 here, so I only have a little more time.

 

[expeditionnw]

Slow down partner. You need to hit the books. The -10 manual tells you how to properly start the set.

The fuse has nothing to do with starting. Its to protect the main generator from being damaged when the volt regulator, (the box to the right of the fuse) goes bad.

Tell me whats not working. Will the starter engage the motor? Or will nothing happen when you turn the S1 to the start position?

My fuse comment was replying to Roberts “search quad fuse” comment.

anyway,

S1 only clicks K21 when in start position. It will not power starter. It will not power the fuel shutoff solinoid.
(S1 itself tests good, outputting correctly in all positions)

the 3position dead crank switch will spin the starter, but not power the fuel shutoff solinoid.
(Dead crank switch also tests good)

starter obviously tests good. Fuel solenoid tests good.

when the starter solinoid and fuel shutoff solinoid is jumped, the engine cranks and runs immediately.

 

[nextalcupfan]

I would check both the input and output of the S1 switch to see if you have 24V (on the 803a output is terminal 7 and all even numbers are input).

If you're getting 24v on terminal 7 on the S1 I would Trace along where that power goes using the wiring diagram until you find where it's disappearing.

I would like to give you exact wires and terminals but I can't seem to find an 804b wiring diagram.

 

[Guyfang]

If your MPU is chewed up, you need a new one. It tells the governor what to do. No signal, no start. Get a new one and then read the procedure in properly install it, of you will wind up buying another. Then try starting again.

 

[expeditionnw]

If your MPU is chewed up, you need a new one. It tells the governor what to do. No signal, no start. Get a new one and then read the procedure in properly install it, of you will wind up buying another. Then try starting again.

The mpu is chewed up, but shouldnt prevent it from cranking right? Only whether it fires?

 

[expeditionnw]

The mpu is chewed up, but shouldnt prevent it from cranking right Only whether it fires?

it wouldn’t even be able to generate a signal unless engine is spinning. My problem is the engine wont spin from the S1 control.

 

[Guyfang]

I would check both the input and output of the S1 switch to see if you have 24V (on the 803a output is terminal 7 and all even numbers are input).

If you're getting 24v on terminal 7 on the S1 I would Trace along where that power goes using the wiring diagram until you find where it's disappearing.

I would like to give you exact wires and terminals but I can't seem to find an 804b wiring diagram.

No signal from the MPU, no start. The MPU is not a crank sensor. It monitors the speed of the engine.

 

[Guyfang]

Here is a simply schematic. Are you familiar with schematics?

 

[expeditionnw]

No signal from the MPU, no start. The MPU is not a crank sensor. It monitors the speed of the engine.

i understand it wont start, my problem is it wont CRANK.

 

[Guyfang]

My fault. its 00:30.

 

[Guyfang]

Here are all the schematics.

 

[155mm]

sounds like a start relay, or s1 took a dump

 

[expeditionnw]

sounds like a start relay, or s1 took a dump

Thanks for the reply, It does sound like that is the case. However As I have said several times, I have tested them both several times and they are functioning as they should.

Unless you are referring to a starter solenoid other than the 8 pin relay found under the flip down control panel?

 

[Guyfang]

It can not be the K2. If the unit cranks with the S10, then the K2 and B1, (cranking motor are good. Look at the colored schematic. Find S1. Turn the S1 to start. You said you had 24 VDC when you tested this. So S1 should be good. If you have 24 VDC, then measure at CR4. Do you have voltage up to CR$? Do you have Voltage on the other side of CR4? If so, go to S14, (plastic relay in the control panel) and measure at pin 18 and then through the S14 to pin 19. Still got voltage? Then you need to look at K15 and then on to K2-X1

 

[expeditionnw]

It can not be the K2. If the unit cranks with the S10, then the K2 and B1, (cranking motor are good. Look at the colored schematic. Find S1. Turn the S1 to start. You said you had 24 VDC when you tested this. So S1 should be good. If you have 24 VDC, then measure at CR4. Do you have voltage up to CR$? Do you have Voltage on the other side of CR4? If so, go to S14, (plastic relay in the control panel) and measure at pin 18 and then through the S14 to pin 19. Still got voltage? Then you need to look at K15 and then on to K2-X1

THank you for your diagrams, and your help in general!

S14, are you referring to the board with the blue metal shell in this photo? I do have power thru the CR4 diode. however, pin 18 on the blue board has no current in any S1 position, but pin 19 has 22v in start position.