m151a2 starting issue

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Txjeeper81
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m151a2 starting issue

Unread post by Txjeeper81 » April 10th, 2017, 1:33 pm

Working to bring my friends M151a2 back to life it was a running mutt but sat for a few years and we all know what happens then. He took the mutt to a civilian mechanic with no luck so he has brought it to me.
Carb has been refreshed and I went through the normal check list to see if I could get it to fire. When I was checking spark I noticed it did not look right kind of like the spark was not hot enough. I decided to check the timing as it just would not start even on starting fluid I kept thinking I've got all the ingredients but it wont fire. so I put a timing light on it and boom it had so weak of a spark it would just barely light the timing light. So after sticking a 24v jumper cart to the mutt thinking I had a low batteries I noticed it did not change and neither did the speed in which the starter was turning the engine. I then took the distributor part and this is what I found.
Image
Image

Id say there's a little bit of moister corrosion in it. So after cleaning it as best I could and swapped the rotor cap and coil out of a running M151a2 motor I have I put it all back together and thought surly this will start now but still nothing. I double checked the fuel, the firing order of the park plug wire's, and check to make sure the rotor was pointing at the TDC of number 1 cylinder all checked out good. I tried it again and still nothing the engine would not fire not even on starter fluid.

All I can think of now is the starter is weak and will not turn the engine fast enough to start. I've got all the ingredients to start but what am I missing? I think the problem is lies in the distributor or the weak starter. What are y'alls thoughts any thing I should try?
CSM In the Texas State Guard
National United States Armed Forces Museum
1943 MB W/Trailer "Puddle Jumper II"
1968 m274A5 "Little S.N.A.F.U"
1976 M151a2 "Kermit"

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rickf
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Re: m151a2 starting issue

Unread post by rickf » April 10th, 2017, 7:23 pm

Pull that electronic module out and see if the potting material has melted out of it, if it has then you need a new one. Preferably NOT Prestolite again. Did you get a hot spark after cleaning things? What is the voltage on the batteries together and individually? You may have one battery going bad. These do not turn fast even when at their best. Check the voltage while cranking, if less than about 21-22 volts then the Prestolite ignition will not fire.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Txjeeper81
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Re: m151a2 starting issue

Unread post by Txjeeper81 » April 11th, 2017, 7:37 am

I did get a spark once I cleaned everything up but I still think that it is not a hot enough spark. The plotting material has not melted and I will try swapping out the module with a spare I have and do a battery voltage check as well on Thursday.

Is there something wrong with the prestolite modules?
CSM In the Texas State Guard
National United States Armed Forces Museum
1943 MB W/Trailer "Puddle Jumper II"
1968 m274A5 "Little S.N.A.F.U"
1976 M151a2 "Kermit"

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rickf
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Re: m151a2 starting issue

Unread post by rickf » April 11th, 2017, 8:01 am

The Prestolite modules have a problem with the potting material degrading and then the internal components short out. Keep in mind that even a NOS module is going to be 30-40 years old.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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m3a1
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Re: m151a2 starting issue

Unread post by m3a1 » April 11th, 2017, 2:24 pm

Basic automotive. Check those grounds and the condition of those major electrical cables. Clearly the environment that truck has been in has been hard on exposed metal.

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rickf
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Re: m151a2 starting issue

Unread post by rickf » April 11th, 2017, 5:14 pm

The corrosion inside the distributor is from the arcing of the rotor to the cap and the ozone not being removed from the distributor. This is normally done with the hoses that are attached on either side of the distributor. Are they hooked into the vacuum line correctly? A lot of people think those lines are for cooling, while they may do a very little bit of cooling the main purpose is to remove ozone.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

SturmTyger380
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Re: m151a2 starting issue

Unread post by SturmTyger380 » April 12th, 2017, 8:15 am

Check the inside cap for cracks or carbon trails too. Those will allow elec to leak. Alan
45' MB, ??' MBT, 47' CJ2A, 48' CJ2A,
51' M38 #1, 51' M38 #2, 51' M100,
52' M37, ??' M101A1 (1st Gulf War Vet),
53' M38A1, 53' M211, 65' M151A1, 67' M416,
MVPA #31724

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