Dropping cylinders?

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mutt and jeff
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Dropping cylinders?

Post by mutt and jeff » October 25th, 2020, 9:45 pm

Got an A1 and it runs "rough". Seems to bog down upon acceleration in neutral or in gear. Sometimes it runs through it and it will run smooth shortly and then seem to miss or bog down. Compression is 95 on all four cylinders at idle and goes up to about 145 or so on all four at acceleration. We played with carb and timing to no avail.
Diesel mechanic friend drove it and said cylinders are "dropping" and then coming back to fire. Sometimes one cylinder stops firing and sometimes two and sometimes all four are firing. Pulled plugs and they are dry and clean.
This is a new issue to me. My thinking is distributor or coil is weak.

Any of this make sense to you? And, if so, where would you suggest I start the investigation.

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Re: Dropping cylinders?

Post by Mark » October 26th, 2020, 12:53 am

Do you have a zenith carburetor on it?
mark


1968 m274A5
1960 m151
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Re: Dropping cylinders?

Post by rickf » October 26th, 2020, 7:42 am

It sounds like you have a vacuum leak but how are you checking compression while it is running? Compression is cylinder pressure measured dry and wet but can't be measured running. Have you checked around the intake manifold ports for a vacuum leak? very common on these engines.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: Dropping cylinders?

Post by svramselaar » October 26th, 2020, 8:41 am

hi

a1 has points check the gap
if they are to close the spark is not made at several time`s so it skips a cylinder
for Rickf i can check the compresion at running
my bosch electronic testbox (like a sun ) has a program to test it
wen the engine runs at idle he take the spark form a cylinder 1 till 4
he let me know the rev drop at the cylinders one of a time
so we testing the also the magneto`s from our allison V1710
we set it at 2000 rev 1 magneto off the revs mey drop till 1800 then the next one

george

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Re: Dropping cylinders?

Post by rickf » October 26th, 2020, 11:49 am

George, I am well aware of that test but that is a cylinder balance test, not a compression test. The balance test simply tells you if one cylinder is pulling the same as the others and will also show the vacuum leak on the offending cylinders but it will be moving around since a vacuum leak in the manifold will affect the A/F ratio of all the cylinders and cause misses in all cylinders. You can also check the draw on the starter and with a timing light or by removing spark plugs on other cylinders tell whether one cylinder has less resistance than the others but that test also will not give compression figures.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

mutt and jeff
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Re: Dropping cylinders?

Post by mutt and jeff » October 26th, 2020, 5:11 pm

OK, I'll check for vacuum leaks or leak. I do have some Bubba tapped off vacuum lines, but they appeared to me to go to a fuel pump that has been replaced by an electric one. The wiper motors are electric as well.

We put a cavuum gauge in each spark plug hole and hit the starter with the ignition off and that is how we get the 95 reading. With the gauge still in place, I start the engine and hit the gas a few pumps and that is when the gauge goes up to 145 on each cylinder. May or may not be the correct way to read, but I read all four the same way, so feel confident they are "balanced".

TO THE WORKSHOP!!!!

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Re: Dropping cylinders?

Post by m3a1 » October 26th, 2020, 5:32 pm

Hey fellas, before you go tearing into things, let's have a look down in that distributor housing and ensure that spark advance is moving freely and not clogged up with old potting material. If I remember correctly, you are using points ignition but that doesn't mean someone wasn't using electronic ignition earlier, experienced a meltdown and then went back to points....i.e. your distributor could be compromised. Your issue could also be as result of a rotor that is sloppy on the shaft. Both are easy checks all in one convenient location.
XdNFN1O.jpg
Reagan adopted a signature phrase - Trust, but verify. This applies especially to all things MUTT related.

Vacuum and spark/timing can have a huge effect on what's going on with your mill. It's not a high performance motor and it needs all the help it can get.



Cheers,
TJ

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Re: Dropping cylinders?

Post by mutt and jeff » November 16th, 2020, 10:50 am

I wanted to get back to this group with an update. I am always frustrated in reading old forum posts about the same issue I have having with my project, only to never see the issue resolved, or at least the OP never getting back to post what solved the issue. So here is where I am headed with this running issue. As of today, with hand holding from another forum member, I was told to look inside the distributor. Sure enough, both the coil and the EI module had pooped their pants and the entire inside casing of the distributor was filled with the heat sealing goop. Pulled all the parts out, cleaned up the casing and freeded up the spark advance counter weights and installed new EI and new coil. No spark this minute, but I haven't checked out why, I probably messed up the power wire going into the distributor by screwing it on and off severl times. We are headed down there this morning with the meter to determine what I did wrong.
But the thinking is that my spark advance being KIA may be my whole problem.

Fingers crossed. I'll report results ASAP.

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Re: Dropping cylinders?

Post by rickf » November 16th, 2020, 12:09 pm

Be aware that the oil in those coils is highly toxic! You do not under any circumstances want to get that stuff on you.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: Dropping cylinders?

Post by muttguru » November 16th, 2020, 4:55 pm

First things first. Is the power getting through to the coil?
1. Take to cap off the distributor and put it aside carefully.
2. Make sure the ignition switch is OFF.
3. Set your voltmeter to volts.... whatever the next highest volt range is shown. (for 24 volts use the 50-volt scale of the meter).
4.Touch the red probe to the wire that runs from the capacitor to the coil (+) terminal (at the terminal) and the black probe to a good ground.
5. Get an assistant to turn on the ignition but do not start the vehicle.
6. Do you get a 24-volt reading? Yes? power to coil is ok. No? - break in wiring....usually just at the point where the live wire goes into the Acorn-nut on the outside of the distributor. Repair the wiring.
7. If or when you get a reading of 24 volts at the coil but vehicle still will not start....check the new coil. If it's a chrome coil, it could be bad straight out of the box. Start saving up for a Mil-spec GI coil.
8. If you want to test the new coil (and you should)...go to this Youtube video dealing with the testing of foreign-made coils.... the link has already been posted earlier but here it is again....
https://www.youtube.com/watch?v=4pSG_X1 ... e=youtu.be

Ken
Kind regards....
Ken

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mutt and jeff
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Re: Dropping cylinders?

Post by mutt and jeff » November 19th, 2020, 6:26 pm

DOD Dead on driveway. Put in new chrome coil, new EI module and new rotor. Of course, no spark. 24v to the coil coming from dist. wire. Took out new coil nad put old coil back in, it worked a week ago. No spark. By no spark, no pop when we crank the starter and we pull no. 1 plug and lay on block and no spark seen at gap when coil is on and starter is cranking.

Suggestions?

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Re: Dropping cylinders?

Post by rickf » November 19th, 2020, 6:50 pm

Take wire off of the negative terminal of the coil and turn on the ignition switch, check for power at negative coil terminal. If yes then coil is good, if no coil is bad. Turn off switch. Hook wires back up and get an analog volt meter, has to be analog with the needle on it. Red wire on coil negative and black on good ground and turn on switch and try to start. Needle should swing back and forth as ignition module cycles the coil for firing. In no movement then module is bad. Verify with ohm meter that distributor body is grounded to block and also verify engine is grounded to chassis and batteries. If this is the same module that lost its potting material it has probably shorted out internally. That is what the potting material was there for since the components are so close together, just a little change in heat can make them move enough to short without the material to hold them.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

mutt and jeff
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Re: Dropping cylinders?

Post by mutt and jeff » November 19th, 2020, 11:45 pm

Brand new EI module, but we will walk through all these steps this weekend.
Thanks for the hand holding.

mutt and jeff
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Re: Dropping cylinders?

Post by mutt and jeff » November 22nd, 2020, 4:42 pm

Put original coil and original EI module back in and tested for spark. My son, (let's call him Curley) reports good spark. Still would not start and sounded like it wasn't getting spark. But Curlee (the one with burned fingers) reported good spark. So, hit it with some starting fluid and up she fired. Was able to adjust timeing, lean/rich and idle and and it starts and runs very smooth. Have not taken it out on the road yet, but I am confident this solution of cleaning up the spark advance weights and springs was my initial problem.

When my sone gets the numbness out of his fingers we'll go for a drive and see how it runs at 40 mph or so.

Thanks to all for the hand holding and to fellow forum member for the parts. I'm not touching anything until I have to again on the MUTT. I'm working on M416 and M762 trailers to complete the rig and then camo paint for the set of three.

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Re: Dropping cylinders?

Post by m3a1 » November 22nd, 2020, 4:58 pm

So, the new ignition and coil are as yet untested after the other changes you made?

You may want to consider conducting an experiment with that boiled out EI module. Electronic potting material is readily available on the internet. It really would be wonderful if you were able to restore that EI before it gives up the ghost. Not sure if anyone has done that yet.

Cheers,
TJ

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