M151A2 Won’t Start

1959 - 1978, M151, M151A1, M151A2, Technical questions and discussions, regarding anything related to the M151.
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Libertyforge
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M151A2 Won’t Start

Post by Libertyforge » Sun May 21, 2023 12:22 pm

Howdy all, I’m new to G503. My 1979 M151A2 arrived on Friday 19 May from Levittown PA. I got up early Saturday morning, yesterday, and put 5 gallons of 87 Octane Ethanol Free gas it, took it for a 15 mile round trip test drive. It did great except for turning off when I came to a coasting stop with the clutch pushed in. I bumped the Zenith 13660A idle screw 1/8th - 1/4 of a turn to give it a little more gas and it seemed to help, no more turning off when I came to a stop. I’m at 5300 Feet in elevation in Prescott AZ, Levittown Pa is pretty much at sea level, 36 feet. When I got home I parked it in the garage and had to run an errand with my wife. I came back about 5 hours later and jumped in to take it over to a buddies house to show it off. It started with a longer crank this time, but it started. I put it in reverse and it stalled/died. Now it only cranks and won’t turn over. The fuel is new, batteries are new and fully charged, started seems to crank strong, all 4 wires from the distributor to the block are getting spark, fuel is getting to the inline fuel filter which connects to the carb. I’m wondering if I need to adjust the air/fuel mixture in the Zenith carb, but can’t find it. Before I do that I’m going to change out the fuel filter. Any idea/suggestions would be greatly appreciated.

Thanks

Gene Hodges
USMC MSgt Retired
Prescott AZ.
Gene Hodges
USMC 1983-2004
Prescott AZ


svramselaar
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Re: M151A2 Won’t Start

Post by svramselaar » Mon May 22, 2023 2:42 am

hi

if it cracks normal speed and you have a nice spark 3/8 inch it must be the feul

it is posseble the filter at the barb is stuck or the floatneedle is stuck

try to start the engine with a litle brake clean at the intake if it runs

wen starting tap at the float chamber to loose the needle

let us know george
1976 ? M 151 A2 AMG MUTT lost in acsedent
1978 M 416 A1 ( parkhurst ) trailer
1970 m151 A2 FORD BUDD tub
1957 Volvo sugga radio truck
M 274 mule HOME MADE MULE

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Re: M151A2 Won’t Start

Post by 199th MP » Mon May 22, 2023 3:19 am

Libertyforge wrote:
Sun May 21, 2023 12:22 pm
Howdy all, I’m new to G503. My 1979 M151A2 arrived on Friday 19 May from Levittown PA. I got up early Saturday morning, yesterday, and put 5 gallons of 87 Octane Ethanol Free gas it, took it for a 15 mile round trip test drive. It did great except for turning off when I came to a coasting stop with the clutch pushed in. I bumped the Zenith 13660A idle screw 1/8th - 1/4 of a turn to give it a little more gas and it seemed to help, no more turning off when I came to a stop. I’m at 5300 Feet in elevation in Prescott AZ, Levittown Pa is pretty much at sea level, 36 feet. When I got home I parked it in the garage and had to run an errand with my wife. I came back about 5 hours later and jumped in to take it over to a buddies house to show it off. It started with a longer crank this time, but it started. I put it in reverse and it stalled/died. Now it only cranks and won’t turn over. The fuel is new, batteries are new and fully charged, started seems to crank strong, all 4 wires from the distributor to the block are getting spark, fuel is getting to the inline fuel filter which connects to the carb. I’m wondering if I need to adjust the air/fuel mixture in the Zenith carb, but can’t find it. Before I do that I’m going to change out the fuel filter. Any idea/suggestions would be greatly appreciated.

Thanks

Gene Hodges
USMC MSgt Retired
Prescott AZ.
send a note to rick faunce, who is on this page. there is no one who knows these carbs better. another good source for info is ken whowell, the muttguru. between those two, you can figure out almost anything.

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Re: M151A2 Won’t Start

Post by Rickf » Mon May 22, 2023 6:13 am

Levittown is only right across the river from me. If it came from a company I have a good idea where it came from.
sea level to 5300 ft should make it run just a bit rich which on an A2 is an advantage and would not cause starting issues. Since you got it started the first time when you got it then you are familiar with how to start the M-151. Pumping the gas pedal does nothing, you have to use the choke. But if you want to try the idle mixture that is a valid check. Looking from the drivers side fender at the carb you want to look at the flange where it mounts to the manifold, just to the right of the mounting bolt on top you will see a plug on the outer side of the flange, under that plug is the idle mixture adjustment. This tells me that your carb has most likely never been apart and will be set on the lean side. If you do run ethanol gas in it then it will run VERY lean. And just so you know, even though your gas is advertised as ethanol free I will bet my next pension check that if you tested it you would find at least 5% ethanol. So what you need to do is very carefully drill a small hole in that plug just big enough to thread in the tip of a sheetrock screw or the tip of an ice pick and start the screw or pick and lever that plug out. When you drill be sure to only just go through the plug and stop or you will bugger up the screw under it. The idle mixture screw will be a small flat head screwdriver head but I have seen a very few that are allen head so look closely in there. Once you get access to it set the mixture for best idle then go a quarter turn out and this should be what you need.

Something else to look for is to take the air cleaner hose off the carb abd while cranking it look for gas spurting in and when you stop cranking there should be a good shot of gas that runs out of the mouth of the carb. If you do not get this then the accelerator pump is not working. I may be the diaphragm or it may be an issue with not getting gas in the carb.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Libertyforge
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Re: M151A2 Won’t Start

Post by Libertyforge » Mon May 22, 2023 7:00 am

Sir, thank you so much for the help. Update. I had to travel to Virginia for work this week, I will be back home on Friday afternoon, 26th.
-Before I left a buddy and I also took out the brass screw at the bottom of the Zenith Carb, it was about 2.5 inches long/pin. We expected fuel to drain out, it did not. So I'm wondering if fuel is getting in the carb or if the float is stuck in the carb?
-While I was traveling yesterday my buddy also replaced the small inline fuel filter and tried to start it. No joy, just cranks, but still won't try to turn over.
-On the idle mixture screw, from your detailed description, I believe I know where it's at and that it is uncovered. "Looking from the drivers side fender at the carb you want to look at the flange where it mounts to the manifold, just to the right of the mounting bolt on top you will see a plug on the outer side of the flange, under that plug is the idle mixture adjustment." I can see the small embedded mixture adjustment screw and it is not plugged. We will try that. But before we do, we will follow your recommendation on the accelerator pump.
-Thanks again for your help Sir. We will get this. For the 15 miles that it worked, I was back in 1984 as a PFC loving life.

More to follow.

Gene.
Gene Hodges
USMC 1983-2004
Prescott AZ

svramselaar
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Re: M151A2 Won’t Start

Post by svramselaar » Mon May 22, 2023 12:37 pm

Hi
Rickf it can t be the idler screw
The engine was running
I think the float needle is stuck
So there is no feul at the camber

George
1976 ? M 151 A2 AMG MUTT lost in acsedent
1978 M 416 A1 ( parkhurst ) trailer
1970 m151 A2 FORD BUDD tub
1957 Volvo sugga radio truck
M 274 mule HOME MADE MULE

Rickf
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Re: M151A2 Won’t Start

Post by Rickf » Mon May 22, 2023 12:53 pm

Gene, you forgot to mention taking out the emulsion jet and getting no gas, that means you are getting no gas into the carb and George is right. The fact that you changed the filter and still no joy there is no reason to check the accelerator pump as you will find no gas there either. You are going to have to pull the carb off and take the bowl off and find out what the problem is with the needle and seat. Before you do that, on the left side of the carb, by the fuel inlet you will see a large bolt head. The A2 should have a return line from there to the tank. Take the line and bolt out and see if there is a filter under it. I have never seen an A2 with a filter there but the A1 had a filter there and I think the A2 was supposed to have one. The military mechanics like to "lose" them to prevent this issue since there was also an inline filter before the carb. If the filter is still there by some miracle take it out and toss it and put the cap and line back on and try that. If no go and you need to take the carb off let me know, there are a few things you need to watch for when taking it apart. (small parts that like to fall out and get lost).
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Libertyforge
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Re: M151A2 Won’t Start

Post by Libertyforge » Mon May 22, 2023 5:10 pm

-Rick and George, I think you are both spot on. The next clue. Today my buddy Shawn disconnected the large air filter inlet rubber hose. He said “it’s dry as a bone in there.”
-Rick, will check for the filter under that bolt, and please forgive me for failing to mention the emulsion jet. But, learning is occurring. :-)

Gene.
Gene Hodges
USMC 1983-2004
Prescott AZ

Libertyforge
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Re: M151A2 Won’t Start

Post by Libertyforge » Wed May 24, 2023 10:09 am

Update!!! Running!!! My buddy checked behind the large bolt, no extra filter. Then he took off the emulsion jet screw again, and put the long straw from a can of break cleaner up the hole and freed up the float. Put the emulsion screw back in and then he fired right up!! Didn’t have to drop the bowl. I thought that was a pretty cool trick. Thank you Rick and George for the help!

Gene Hodges
Prescott AZ.

Semper Fi!
Gene Hodges
USMC 1983-2004
Prescott AZ

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Re: M151A2 Won’t Start

Post by Rickf » Wed May 24, 2023 12:03 pm

Well, spraying up there will not get to the needle and seat but as long as it worked that is all that counts. Spraying in the other open spot would have shot right on the needle and seat. I am thinking that breaking that bold loose knocked whatever was holding it loose. Don't celebrate too much because whatever it was is still in there and the idle circuit in these is very sensitive to dirt.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Libertyforge
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Re: M151A2 Won’t Start

Post by Libertyforge » Fri Aug 04, 2023 10:37 am

Thanks Rick, I have a Carb rebuilt kit. I will take your advice and hunt for whatever is in there still. Gene
Gene Hodges
USMC 1983-2004
Prescott AZ

svramselaar
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Re: M151A2 Won’t Start

Post by svramselaar » Sun Aug 06, 2023 2:45 am

hi
i think the rubber tip at the float needle is solved a bid so it sticks
for years ago i had the same at every corner i made the engine stops and with a tap at the carb it was running agian
i had not a spare so i made one at the lathe from brass and after 20 years it still works
i drive at LPG now bud the petrol system still works so i can drive two fuels

george
1976 ? M 151 A2 AMG MUTT lost in acsedent
1978 M 416 A1 ( parkhurst ) trailer
1970 m151 A2 FORD BUDD tub
1957 Volvo sugga radio truck
M 274 mule HOME MADE MULE


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