I pulled the old plugs off my M38A1

Deadguy · Post by **Deadguy** » Wed Aug 31, 2011 1:44 am

and they had a decently thick layer of carbon on them. Not damp (like when my CJ5 was leaking oil through the piston rings), but enough it was probably interfering with the spark. I replaced the ignition coil as well and.....my Jeep fired right up, and ran better than ever before. I'm hoping that was why my engine sometimes wouldn't start without quick starter fluid.
I think the carbon on the plugs is either the fuel mix running rich, or maybe the previous owner overused the throttle pull cord too much (he was in a much colder climate). Any opinions?

ApacheWillys · Post by **ApacheWillys** » Wed Aug 31, 2011 6:58 am

This happened to me once on my Ford Courier. I neglected a tune up, and hauled dirt bikes to Flagstaff during a snowstorm. Engine lost power and died. Removed plugs and cleaned them with gas (on the roadside) and closed the gap some. Ran great afterward. Yours probably just needed cleaning and gapping.

Post by **wesk** » Wed Aug 31, 2011 9:21 am

With todays 100,000 mile engine tuneups many folks loose sight of the required maintenance frequency on the older vehicles.

Clean and gap plugs and check points and timing every 3000 miles.

Plugs will pick up carbon no matter what or how you run. The quantity will vary based on use and engine condition. It has little effect on the spark until it is thick enough to bridge the gap then the plug will misfire. Engines operated for only short periods will often show the fuzzy layer of carbon but not because the engine is too rich rather because you didn't run the engine long enough to burn the plugs clean.

Plug gap will slowly open with use. The plug electrodes will shed material with use. This is why gapping periodically is necessary.

If compressions, fuel supply and cranking RPM are good and an engine still is hard to start then the next step is inspect the ignition system. Don't assume and throw hard earned money at it by shotgunning replacement of parts. Inspect the parts properly and replace if their condition dictates replacement. Wide plug gaps make starting difficult. Add a slow turning starter because the batteries are low from sitting for a month and the carb bowl is almost empty from sitting then the hard starting is expected.

These engines cannot be operated and maintained the way today's engines are. They need the TLC found in their original maintenance schedules and when they misbehave use a troubleshooting chart found in all the manuals and one item at a time verify the real cause of the problem and then fix it.

In piston engines the single routine maintenance item that offers the greatest increase in performance is cleaning and gapping plugs. If you insist on tossing money at engine problems then always start with the best investment for your buck. A new set of spark plugs.

Another little goodie often overlooked is proper torque for the spark plugs. The spark plug companies all list a recommended torque for their plugs and most engine manufacturers list a torque as well. This torque is not to just make sure the plugs don't fall out. It is also to make sure you don't alter the gap setting by overtorqueing the plug.

Deadguy · Post by **Deadguy** » Wed Aug 31, 2011 12:04 pm

I was looking in the manual, and I need an adapter for the lead plug in order to use the timing light on the waterproof engine setup. Do you know who sells this adapter? Wes?

pilotomutante · Post by **pilotomutante** » Wed Aug 31, 2011 12:53 pm

Try John Bizal at Midwest Military:

http://www.midwestmilitary.net/adpage3.html

Deadguy · Post by **Deadguy** » Wed Aug 31, 2011 4:45 pm

My truck is running a little better now, but i still had to play with the choke and throttle levers to get it to start today. When it finally does start, it revs really high, and I have to ease up on the throttle. The manual says to pull the choke all the way out, and the throttle 2/3rds, but that still doesn't always help. I'm getting a timing spark plug adapter, and a feeler gage to measure the points. Any other opinions?

Post by **wesk** » Thu Sep 01, 2011 11:12 pm

$40 or $50 dollars for a test adapter that also comes in a complete set of 5 different test adapters for $70 is not real sharp business dealing. The complete set comes with the other two distributor adapters, a generator cable to regulator cable adapter and a regulator to body harness adapter.

Sam-Helm · Post by **Sam-Helm** » Fri Sep 02, 2011 7:29 am

Wes,

Do you have the instructions for the kit you showed the picture of? I got one from e-Bay, and it appears to be complete, except that it had no paperwork with it. . . Thanks in advance for the help.

skyjeep50 · Post by **skyjeep50** » Fri Sep 02, 2011 7:47 am

The set doesn't come with instructions. There is a guide in the "Downloads" section of this website under "Testing 24 Volt Systems" - it has some good diagrams showing how to connect the adapters. But the instructions are for using a military engine analyzer with the adapters. Anyone have a guide how to set up more modern test equipment like a digital VOM using the adapter set?

Oldsalt · Post by **Oldsalt** » Fri Sep 02, 2011 9:34 am

If you look at those test instructions closely, you will see the first picture is a closeup of the test meter set showing the labels for the meter connections. All the connections on the right are for the volt meter. Different scales. The connections on the left are ammeter connections, different scales. A modern digital meter changes scales internally so only needs one connection. If you follow the drawings carefully you can figure it out. You may need to study it on your computer though, so you can zoom in on the drawings. The position of the little jumpers on the generator and regulator connections can be hard to see. The only connections I can't read in the drawings are the middle ones. Resistance maybe. You should be able to get through the generator tests though.

I bet someone around here has that meter set and can describe it better.

Post by **wesk** » Fri Sep 02, 2011 11:41 am

The test lead adapter kit has a set of instructions with it normally. The instructions are not for troubleshooting a vehicle. They are only for the basic application of the individual parts of the kit and how to insert them in your harness. I have a copy loaded on my TOOLS photo album. I also have a copy of one of the Army Low Voltage Test Set manuals loaded there as well. This manual also deals primarily with the test unit itself and it's functions and not much on applying the test unit to troubleshooting situations on the trucks. Also keep in mind that most of these test fitting have electrical connections that are exposed and will usually be hot while you are using them.

http://www.willysmjeeps.com/v2/modules. ... php&page=1

Sam-Helm · Post by **Sam-Helm** » Fri Sep 02, 2011 1:27 pm

Thanks, Wes! I may not need this yet, but the time is (hopefully) coming in the not too distant future.