rebuilding MEP802a fuel injectors??

[zarathustra]

I finally got the 802a fired up, or at least it was spinning..

I disconnected wire #6 to the voltage regulator in advance 'cause I figured it would need to crank a while, and I wanted to address getting the engine running and at this point I don't care if it generates any electricity at all.

I did the fuse mod as well, but the manual tells me that if Pin 6 is disconnected it won't generate any electricity.

Wouldn't start.

There seemed to be plenty of fuel going down the return-to-tank line, so I pulled the injectors. There was plenty of fuel on the input side, but the business end of the injector was dry as a bone.

So, it looks like they will come apart if I unscrew 'em. Anyone have any suggestions/tips on getting these things working again? Haven't taken them apart yet -- am I in for any surprises in disassembly?

Upon re-assembly are they just screwed back together to make them tight or is there some sort of adjustment?

Any suggestions would be appreciated...

z

 

[Knuckles]

Before you take them apart, I would try soaking them in marvel mystery oil and PB blaster. Then use a brass brush to gently brush the ends. Worked wonders on my 803a

 

[zarathustra]

I do some of my best thinking when I am asleep. About 3 this morning I came up with the thought that the injectors may not be bad, but that something upstream from them might be akilter. I recall that one of the attaching nuts on the aft cylinder line -- in the pump area(?) was disconnected, leaving the fuel line resting on the fitting.

So, even though there is some spring-like tension between the fuel line and fitting holding them together, I'd expect to see fuel coming out that fitting-to-fuel line joint; at least a little bit 'cause of the high pressure required by the injectors, and perhaps some back flow from a clogged injector, but there was none.

However there appeared to be fuel at the source end of the injector(s).


So, not saying that the injectors are bad/clogged, but perhaps the pressure there might not be enough to pop the injector......

There's a diesel shop not too far from home - I'll take the injectors to them for a pressure test.


Till Monday I'll soak them in MMO

 

[m-35tom]

the injection pumps are just gravity fed. if they don't pump there are very limited options of what is wrong.
1. the actual pump piston is stuck in the up position.
2. the fuel dump sleeve is rotated to 'no fuel' position.

fuel rate is set with shims under injector body, just don't mix them up, take the bottom of injector apart noting exact position of everything, clean with gum cutter or laquer thinner, lube with fuel and put back together.

 

[ETN550]

the injection pumps are just gravity fed. if they don't pump there are very limited options of what is wrong.
1. the actual pump piston is stuck in the up position.
2. the fuel dump sleeve is rotated to 'no fuel' position.

fuel rate is set with shims under injector body, just don't mix them up, take the bottom of injector apart noting exact position of everything, clean with gum cutter or laquer thinner, lube with fuel and put back together.

The shims set timing, and as you say must go back the way they came out and may be different on each cylinder. Fuel rate is controlled by rotating the pumps. The pumps should go back at the same angle of rotation as they came out. One pump must be left in at all times to keep the rack in location. If all the pumps are pulled there is a good chance the rack will move out of location and the front end of the motor will have to come apart to reset the rack position. Be sure to read the manuals. The fuel rate can be adjusted by reading the individual exhaust port temps and rotating the pump to raise or lower the temp so they become balanced. Otherwise, one cylinder pulls mare load than the other.

 

[zarathustra]

Without having taken out the fuel pumps or having even seen them removed, this sounds awfully tricky. Is this saying that when, for example, the #1 pump is removed that it is possible to re-install that pump so that the delivery rate is different from what it was before it was removed? I can't imagine that it would be possible to hold the pump rotationally in exactly the same position as when it was removed and at the same time check to see if it functions and free it up if it isn't functioning.

I must be missing something --- perhaps it will be self explanatory once I remove a pump.

I know fuel drains back into the tank 'cause I've heard it, but I also know that on the aft pump that the holding nut had been loosened by some Army tech, so that the fuel line was just resting on the pump output with whatever tension that the 'springy-ness' of the line provided. There was no fuel squirting out that junction, so I believe that no fuel was leaving the aft pump. There was fuel in the injectors on the input side, but I suppose it could be residual fuel from the last time the gen worked.

I can't speak for the forward pump since it is properly plumbed, but both injectors appeared to be dry and carboned up on the injection end. Odd, for an engine with 41 hours on the Hobbs, but this must have sat for a long time since the mfg date was 1998.

I appreciate any and all comments on this.

I'll also be taking the injectors to Blue Grass Diesel tomorrow to see if they can test them for me. I've had them soaking in Mineral Spirits all day... However I suspect that even if they check out good or can be made good, that I have problems in the pump end as well. But, from experience on troubleshooting I will re-install the known-good injectors, and tighten down that nut on the pump and try to start it before I tackle the pumps.

No point in creating a problem where there may not be one...

 

[m-35tom]

the fuel just needs to be in the inlet side of the pump, it does not need any pressure, it just needs to be there and if the plunger is moving and not worn out and the dump sleeve is working it should pump. a few if's but it is a real simple process.

when the plunger closes the supply port on it's up stroke, that is the timing part and is set with shims, then both pumps are syncronized by rotating the pump bodies so fuel delivery is the same.

the pumps can only be removed from the engine at or very near the no fuel position. this is when the fuel solenoid is off.

 

[m-35tom]

did some research, talked to some injector people and came up with this.

I took one pump apart not knowing if it ran or not. conclusion, it was put together correctly and was ok, but there is one mistake that can be made. The pump plunger can go in 180° rotationally out, so the dump groove never would dump fuel. (well it would dump fuel but only after it injected max fuel) This looks like the only thing you have to really pay attention to as this would result in a runaway. The plunger has a notch in the side that goes opposite of the pin on the part that rotates it. No fuel delivery it seems, often results from the fuel delivery valve sticking from sitting. Chances are you will not need to take the pump out of the engine if this is it.

WARNING DO NOT ROTATE THE ENGINE WHILE DOING THE NEXT STEP
If you have no fuel delivery, first remove the line to the injector and remove the top part of the pump. This is the fuel delivery valve, just a very high pressure check valve. There are 7 parts inside so be careful not to lose any! With that removed you can look down inside the pump and should see the plunger in the center with a notch just to the left of the fuel supply hose. That is to say that if the hose is your 12 o'clock then the notch is at 11 o'clock. This is with fuel shut off, move the shut off solenoid to the on position and the notch should rotate to 8 o'clock. If this is all good, turn on the electric fuel pump and fuel should flow out the top. Inspect the delivery valve to see if it could be stuck and reassymble. Now you can crank the engine to see if fuel comes out before replacing the pipe to the injector.

 

[zarathustra]

fuel delivery woes

Haven't got it apart yet, but the pin will not move in either direction. I just figured a way of getting that top fitting off, but haven't tried it yet.

Previously it would not budge using a vise, vise grip or plumbers wrench.

My next effort will be to put a short 1/4 inch bolt into that hole that is drilled part way through the housing and then put it back into a vise and use an ordinary wrench on the fitting....

I'm going to start with the top fitting and work my way downwards. I'm hoping that the spring doesn't present too much of a problem....

 

[m-35tom]

Your pump looks different than mine, but that pin rotates the plunger and it should move easily. If the fuel control sleeve with the pin rotates, there is no need to take the bottom apart, just unscrew the top delivery valve. Are you saying the pin at the bottom does not move (rotate) the lower part of the pump?? I hold the pump in my hand and hit it with a small impact to get the top off. Going back in, it does not need to be very tight as it has an o ring for sealing, just maybe 20 ft lbs. Putting some laquer thinner in the fuel hose port should free it up.
tom

 

[zarathustra]

Any trick to getting the spring and spring cap off? It almost looks like it needs a special tool.

I did get the top part off. The pin will not move, it won't budge

 

[m-35tom]

you will notice your spring is compressed, the cam has forced the plunger to go up and it is stuck there, hence it does not pump. removing the spring retainer will be almost impossible now. soak it in laquer thinner for a day then it may start to move. you can try to gently force it to turn and it should come free.

 

[zarathustra]

Well, I got the pump working(?) and installed. Putting the push rod back in was an interesting task. I wasn't sure which way it went together, but in the end I aligned the dot on the rod with the pin and, given the rotation and the up and down motion it appeared that it would pass fluid and not pass fluid based on the relative position of the rod rotation and up-down movement.

I didn't do the second pump 'cause when I loosened the fitting I had diesel come out and I figured that the fore pump was ok.

It didn't start. It didn't even act like it wanted to start.

Next stop is the fore pump checkout. However, I loosened the fitting at the top of the 'fixed' pump and cranked the engine. I expected diesel to squirt out of the fitting, but nothing... I loosened the nut on the fuel pump discharge and it squirted out diesel, so I know the main fuel pump is working.

So, I'll work on the fore pump, but even if I find it stuck I don't think that will fix the problem.

After I check out the fore pump I'll leave the input to it disconnected and try to start. I should see fuel there - if not then the fix should be easy, quick, and cheap. If I can ever get fuel to come out of those pumps I'll pull an injector and see if it sprays fuel.

I assume that the rack that drives the pins goes forward and aft, and that there are a couple of small 'pistons' that move the rod up -- the spring moves it down. Any experience(s) with trying to get the rack moving freely?

And I suppose I'm facing some sort of engine disassembly if the cam that moves the small 'pistons' up and down isn't working or I can't get the rack to move.

 

[m-35tom]

warning, the mark on the plunger goes opposite the pin that rotates it. (my pump is different than yours so it may be the other way??) the other way there will be no control over the fuel and it will always inject max. not good.
the rack should move quite freely as should the pin as it rotates the plunger. the plunger is the pump piston. it starts injecting when the top of it covers the hole near the top of the cylinder it is in. it stops pumping when the ramp slot comes over the same hole and dumps fuel from the top or pressure side. the plunger and spring sit in a lifter with a roller on the bottom which runs on a cam.

 

[zarathustra]

Well - Regarding the pump dot and pin ---My friend Chuck Ledtje always told me there was no such thing as a 50/50 chance...

 

[zarathustra]

Well, here is a big shout out to Tom, m35-tom for his explanation of how the fuel systems work (and don't work) in these units.


The problems it had were clogged injectors and two siezed up injector pumps. The injectors sure looked bad for a gen with only 41 hours on it.

As of 1600 today the 802a is up and running and making some AC.

Ran it for half an hour with no problems...

z