4A084 engine info?

[cbvet]

Trying to get the engine running in my M51 Shelter trailer.
Cranks fine, but no spark.

Questions:
1. There is a single white wire going to the magneto. Is that wire supposed to be hot when the engine switch is on, as in a distributor system? Or does that wire go to ground when the engine switch is off, killing the engine?

2. Wiring diagram shows wires A thru J coming from AC alternator. The "alternator" behind the rope-start pulley only has 2 wires coming from it. Is diagram referring to the 3-phase generator driven by the engine?

I realize there could be a points/condenser problem, but I'm looking for simpler fixes.

I just want to see if it will run, then I'll start checking out the other components.

Appreciate any help.

 

[Carl_in_NH]

1: Mags typically get their connection grounded to kill the spark

2: The two-wire alternator is the one used to charge the starting battery; the alternator with A-J connections is, I suspect, the main AC alternator.

To see if you get spark, disconnect the wire from the stud on the mag and you should have spark. Let us know if that works.

 

[Recovry4x4]

If it's been sitting for some time, the points on the mag are probably funky. You can point file them and get spark but once you start filing them, the seem to require it on a regular basis. You have to remove the mag IIRC to swap this stuff. I had help with one of mine and the guy hand spun the mag afterwards and it was quite obvious it had spark.

 

[cranetruck]

Eric, when you say "no spark", do you mean that it actually doesn't have a spark or just isn't starting?
Mine has developed a starting problem, but a couple of squirts of starting fluid gets it going. I suspect that the fuel pump isn't doing its job at low cranking rpm, because it runs beautifully once started. Measured the fuel pressure at the pump output and got an erratic 1.5 to 2.5 psi during cranking. Didn't leave the pressure gauge in when running, but the pressure should be about 4 psi according to one reference, while running.
Could use a carb rebuild kit too, I have cleaned it, but would be nice to have replacement gaskets and seals...(Saturn was out of stock last time I checked).
Let's know how it goes.

 

[liftman]

The white wire to the mag grounds out the mag to shut the engine off from the stop switch.

Wires I & J in the plug appear to feed the DC exciter in the generator, according the the drawing.

Wire D appears to be the exciter wire to the DC (battery) regulator which would control DC output to the battery form the engine alternator.

As everyone has said, remove the wire fronm the mag and crank to see if you get spark. If not, it probably is a points/condenser issue.

Hope this helps.

 

[jbk]

if you have no fire to the plug. pull the mag, mark its position although i have had to put a light on mine to time it correctly. when you get it out use some contact cleaner on the pints and check the gap. then spin the mag if you can get it to fire then order new points and cond, i wouldnt pull the mag unless i put in new points. if you get no fire then you might have a bad coil. saturn surplus have the points you need. also check the resourse section for the engine manual i think you will need it.

 

[cbvet]

Thanks guys!
I had tried disconnecting the white wire from the mag, assuming it was the "shut off" ground. When I say no spark, I mean no spark at the plugs.
Looks like I'll have to pull the mag. Supposed to rain all weekend, so I'll probably work on it.
Are there any other sources for points, condenser, & other parts?

 

[liftman]

When I needed points for mine, I found that Saturn had the best pricing. Other suppliers had the parts, but they were about twice the price.

Also, with a no spark situation, be sure that the condenser is not shorted to the body of the mag, as this will also give you a no sprk condition.

 

[cranetruck]

What does the low oil pressure switch (to the left in the image below) act on?

 

[cbvet]

Beats me, Bjorn.
And why does it have an oil pressure transmitter, when it has no gauge?
And why would either of these connect to the AC generator?
How would a similar engine be set up to run something else? Like a pump or an ultralight?
We're missing something here.

 

[cranetruck]

Well, at least mine has an oil pressure gauge (as well as the oil pressure switch). You may want to check the resistance to case/ground. The NC should read zero ohms when the engine is not running and the NO infinity. Those are the terminal markings on the switch, if that wasn't clear.

 

[Recovry4x4]

Hmmm, IIRC there is a magneto somewhere on my workbench in the garage from my days with them. I shoulda given that to Bjorn.

 

[cranetruck]

Thanks Kenny, the generator runs good, just that little problem starting it and that is a new development, like I said, probably the fuel pump.

Below are two pages from the troubleshooting procedure as per TM.

 

[liftman]

The oil pressure switch on the left is the low oil shutdown for the generator. When cranking with the starter, a relay in the panel prevents spark until it sees pressure. It does this by grounding the mag thru the shut off wire on the mag.

If starting the generator with the pull start, the switch should be put into emergency to keep the pressure switch from preventing spark so the engine will start with the rope. It does this by keeping the relay from energizing.

However, if the grounding wire is removed from the coil to check spark from the mag and the starter is used to crank the engine, the circuit is left open by virtue of having the ground wire off the magneto.

I had forgotten about this safety circuit before, but if the magneto ground wire is removed the whole safety circuit is temporarily disabled anyway.

 

[cranetruck]

Thanks, much appreciated!

 

[cranetruck]

Looked over the wiring diagram this morning and what is stated above about the oil pressure switch is not entirely correct.
The relay, which is controlled by the oil pressure switch is energized via a diode during cranking at which time the oil pressure switch action is bypassed. If there is no oil pressure after start, then the oil pressure switch will shut down the engine, but only after it has started.

 

[cbvet]

Well, I ended up working all weekend, so didn't have a chance to work on this thing.

The control panel on the shelter trailer is a lot different than that of an engine/generator-only unit.

As i said, it has an oil pressure sending unit, but no gauge. There is no "emergency" switch as liftman mentioned.

I am not looking forward to pulling the magneto. The left side intake components will have to come off to get it out. And with the engine in the trailer surrounded by all the heating, A/C, inflation, & air filtering components, it's mighty tough on my back trying to work on it.

I really need to simplify the whole thing by taking out all the unwanted parts. I may even just remove the engine & try to get it running.

Thanks for all the help & ideas so far!
I'll report when I can get back to it.

 

[callbt]

Hello,
Anyone here have experience pulling the gear cover off the front of a 4A084? My governor decided to lock up and shear the roll pin that drives the plastic gear on the governor. Trying to decide how far I should open the engine up to find metal pieces? From the looks of the governor guts, it's mostly aluminum bits. All my gears are un-harmed, but figured the oil flow sent bits down the gear train.
do I just let the heavy parts sit in the oil pan, flush out what I can while letting the filter catch the rest or start pulling this engine apart (only 124 hrs on this MEP-018a).

Thanks,
Brian yes I need to post some pictures of this issue.

 

[liftman]

Pretty simple to do. Remove the mag and the governor, as they are attached to the cover. Remove damper in front of engine. Alternator stator will stay on the cover if I remember correctly. About 10 bolts hold the cover on, be careful as they are different lengths. Then the cover comes right off.

I put the cover back on with the old gasket and just added a thin film of silicone for a sealing surface where the gasket separated at removal.

 

[callbt]

Hello,
Thank you for the advice, I'll number the bolts prior to removal- do you recall how hard it was to remove the dampener? Curious if I need to round up a large puller to get the damper off. How much torque is used to put the nut back on and how to keep the engine from turning in the process?

Brian