MEP 804A Won't Start

[hawk-aggie]

Full transparency - I haven’t all 319 pages of threads about generators on SS. I, also, haven’t scoured the TMs - yet. (Probably could have during my surgery recovery, but my mind was on other things.)

With that said, our museum has an MEP804A that cranks, but won't start (never has in the 2 years we've owned it).

Battery voltage - 24.88v
Switch on - .013v to fuel actuator
Switch to start - 21.16v to fuel actuator
I connected battery power directly to fuel actuator to check operation, and I heard a click. When I did that same test on another same model gen set, I thought I remember hearing more of a “thunk”.

Fuel tank is more than 1/2 full
Has new starter - cranks well
Wanted to run on a short squirt of ether
Have fuel to bleeder valve on 1st fuel filter
Have fuel to the inlet side bleeder of the injector pump
Have fuel to the outlet side bleeder of the injector pump
Cracked open a couple of fittings on the lines on top of the injector pump that go to the injectors - no fuel came out.
Applied direct power to the fuel actuator with those same fittings open, pumped the primer pump - no fuel came out.

I thinking one of two things:
1. The injector pump needs reworking, or
2. The fuel actuator is not functioning fully.

Any help will be appreciated.

 

[Guyfang]

I thinking one of two things:
1. The injector pump needs reworking, or
2. The fuel actuator is not functioning fully.

Do not jump to conclusions. You are not an positive person!! Could be very simple.

I would pull the MPU out, inspect it, clean it, reinstall it and TEST it. IAW the -24 TM

Have you downloaded the TM's. Because when I say MPU, S1, K2, IAW the TM, and so on, its kinda hard for us to be on the right sheet of music.

Has the set the Quad Mod?

 

[hawk-aggie]

I thinking one of two things:
1. The injector pump needs reworking, or
2. The fuel actuator is not functioning fully.

Do not jump to conclusions. You are not an positive person!! Could be very simple.

I would pull the MPU out, inspect it, clean it, reinstall it and TEST it. IAW the -24 TM

Have you downloaded the TM's. Because when I say MPU, S1, K2, IAW the TM, and so on, its kinda hard for us to be on the right sheet of music.

Has the set the Quad Mod?

I’m not being negative. Just a little frustrated I suppose. I have all the TMs and have adjusted the MPU on other units. I’ve been working on this one on and off for over a year, so I don’t remember if I checked the MPU output. I don’t know what the Quad Mod is. I will check the MPU next week - if the weather permits. Thanks.

 

[hawk-aggie]

I have the attached info, as well as the process for removing, installing, and adjusting the MPU. What is the original source of the attached? If it's in a TM or other available document, please advise. I'd like to have any info that comes before and after.

 

[Guyfang]

I worked as an FMT, Field Maintenance Tech., here in Germany for the Army. This info was given to me by the Senior Master Tech, for CECOM.

 

[hawk-aggie]

So far, only had a chance to check MPU. It had some debris on it, but no damage. I think it wasn't adjusted correctly before I removed it. When I reinstalled it and adjusted it, my meter was reading 2.8-3.0VAC. Still didn't start. I still think it's a fuel flow issue, but will conduct further electrical tests in a day or so.

I still don't know what the Quad Mod is. Please advise. Thanks

 

[kloppk]

I still don't know what the Quad Mod is. Please advise. Thanks

It's the addition of a fuse holder and fuse next to the A1 AC Voltage Regulator. It's a fuse to protect the static exciter from being damaged should the AC Voltage Regulator fail.
It's detailed in TB 11-6115-741-24 section 5.4

 

[hawk-aggie]

It's the addition of a fuse holder and fuse next to the A1 AC Voltage Regulator. It's a fuse to protect the static exciter from being damaged should the AC Voltage Regulator fail.
It's detailed in TB 11-6115-741-24 section 5.4
View attachment 925094

View attachment 925095

Yep, this gen set has that mod. I know, because I had to borrow the fuse for another gen set, then I ordered more fuses.

 

[hawk-aggie]

Diagnosis data:

Using Guyfang's A5 GCU diagnostic sequence....

MAG Pickup
Wire 147C to A-5/17 = .794K ohms
Wire 147C to A-5/17 = 2.8VAC

Fluctuations
A-5/9 + and A-5/10 - = 19.6VDC
Wire 153A to wire 192B = stationary around 6.74K ohms (no movement at all throughout entire range of Voltage Adjust Rheostat)
Points A-5/6 to A-5/8 = 4.57K ohms

A5. Adjustment
Points A-5/4 to A-5/3 = 21.26VDC
Points A-5/4 to A-5/1 = 19.85VDC
Points A-5/4 to A-5/19 = 19.83VDC
Points A-5/4 to A-5/18 = 19.82VDC
Fuel actuator lead when starting = 21.6VDC

Checked presence of fuel up through output side bleeder on fuel injection pump. Removed large cap shown in photo. It is bone dry inside. Should it be, or should it be wet with fuel? Observed small rod inside the cavity while attempting start up. It barely moved.

Generator cranks but will not start. Going to remove fuel actuator to see what it might do on the bench after some cleaning.

 

[Guyfang]

Have you ever seen this generator start and run?

Yes it should be wet.

 

[hawk-aggie]

Have you ever seen this generator start and run?

Yes it should be wet.

Answer to your question is no.

 

[Guyfang]

You wrote: I wrote:


Full transparency - I haven’t all 319 pages of threads about generators on SS. I, also, haven’t scoured the TMs - yet. (Probably could have during my surgery recovery, but my mind was on other things.)

With that said, our museum has an MEP804A that cranks, but won't start (never has in the 2 years we've owned it).

Battery voltage - 24.88v
Switch on - .013v to fuel actuator (A6)
Switch to start - 21.16v to fuel actuator (You measured this at P10?)
I connected battery power directly to fuel actuator to check operation, and I heard a click. When I did that same test on another same model gen set, I thought I remember hearing more of a “thunk”. (Look at the screws holding the A6 on the end of the IP. Do they look like someone has had it off? If someone has had it off, and not hooked it back up right, it wont start. And its easy to not hook it up right. )

Fuel tank is more than 1/2 full
Has new starter - cranks well
Wanted to run on a short squirt of ether
Have fuel to bleeder valve on 1st fuel filter (With the hand Pump? Or just turning it over?)
Have fuel to the inlet side bleeder of the injector pump (With the hand Pump? Or just turning it over?)
Have fuel to the outlet side bleeder of the injector pump (With the hand Pump? Or just turning it over?)
Cracked open a couple of fittings on the lines on top of the injector pump that go to the injectors - no fuel came out.
Applied direct power to the fuel actuator with those same fittings open, pumped the primer pump - no fuel came out.

 

[hawk-aggie]

You wrote: I wrote: Reply:


Full transparency - I haven’t all 319 pages of threads about generators on SS. I, also, haven’t scoured the TMs - yet. (Probably could have during my surgery recovery, but my mind was on other things.)

With that said, our museum has an MEP804A that cranks, but won't start (never has in the 2 years we've owned it).

Battery voltage - 24.88v
Switch on - .013v to fuel actuator (A6). Directly on the connector to the fuel actuator
Switch to start - 21.16v to fuel actuator (You measured this at P10?). Directly on the connector to the fuel actuator
I connected battery power directly to fuel actuator to check operation, and I heard a click. When I did that same test on another same model gen set, I thought I remember hearing more of a “thunk”. (Look at the screws holding the A6 on the end of the IP. Do they look like someone has had it off? If someone has had it off, and not hooked it back up right, it wont start. And it's easy to not hook it up right. )

Fuel tank is more than 1/2 full
Has new starter - cranks well
Wanted to run on a short squirt of ether
Have fuel to bleeder valve on 1st fuel filter (With the hand Pump? Or just turning it over?). Both
Have fuel to the inlet side bleeder of the injector pump (With the hand Pump? Or just turning it over?). Both
Have fuel to the outlet side bleeder of the injector pump (With the hand Pump? Or just turning it over?) Both
Cracked open a couple of fittings on the lines on top of the injector pump that go to the injectors - no fuel came out.
Applied direct power to the fuel actuator with those same fittings open, pumped the primer pump - no fuel came out.

MAG Pickup
Wire 147C to A-5/17 = .794K ohms
Wire 147C to A-5/17 = 2.8VAC

Fluctuations
A-5/9 + and A-5/10 - = 19.6VDC
Wire 153A to wire 192B = stationary around 6.74K ohms (no movement at all throughout entire range of Voltage Adjust Rheostat)
Points A-5/6 to A-5/8 = 4.57K ohms

A5. Adjustment
Points A-5/4 to A-5/3 = 21.26VDC
Points A-5/4 to A-5/1 = 19.85VDC
Points A-5/4 to A-5/19 = 19.83VDC
Points A-5/4 to A-5/18 = 19.82VDC
Fuel actuator lead when starting = 21.6VDC

 

[jamawieb]

The most common problem I have found with the 804a is the main fuel line coming from the tank to the mechanical pump on the motor. That particular hose degrades and will let air seep into the line not letting the system prime. It does not seep fuel so its hard to find. You can take the line off and cover one end with your finger and take compressed air to blow in the other side. Usually you will see the leftover fuel weep out the line. It causes the no start issue.

 

[Guyfang]

Yes, this is the biggest problem after the MPU, for this set.

 

[hawk-aggie]

I connected battery power directly to fuel actuator to check operation, and I heard a click. When I did that same test on another same model gen set, I thought I remember hearing more of a “thunk”. (Look at the screws holding the A6 on the end of the IP. Do they look like someone has had it off? If someone has had it off, and not hooked it back up right, it wont start. And its easy to not hook it up right. )

The attachment screws on the fuel actuator/governor do not appear to have been messed with. Will get back to diagnosing in a day or so - hopefully. It's hot! Will try to find an appropriate resistor for testing the A6.

 

[jamawieb]

How many hours is on the unit? It sounds like the plungers are stuck. I had one with low hours stick. You have to take the top of the pump apart. Just take the hard lines off and then take the holders loose under the hard lines, then you will see the plungers. They should move up and down when the motor rotates over. If they dont take car cleaner a d spray then lightly tap with a brass punch. After they are moving put it back together. I say this because direct voltage of 24v to the actuator will open it to run. And if your not seeing fuel it sounds like the plungers