Engine Hesitation

1959 - 1978, M151, M151A1, M151A2, Technical questions and discussions, regarding anything related to the M151.
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rdh778
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Engine Hesitation

Post by rdh778 » Wed Sep 22, 2021 7:23 am

Why does my Mutt have a small hesitation when I press down on the accelerator? Is there an adjustment to eliminate it? Do I need to rebuild the carb?
Thanks,
Bob


Rickf
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Re: Engine Hesitation

Post by Rickf » Wed Sep 22, 2021 8:38 am

You indicated in your last post that you got this carb from Brooks? I suggest you get in touch with him. If the timing, valves, points if you have them are all set correctly then it is a carb issue. Float setting or pump issue.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Fil Bonica
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Re: Engine Hesitation

Post by Fil Bonica » Wed Sep 22, 2021 11:01 am

As Rick said,
Look at the balance of the engine first,.
Failing that, then talk to Brooks about the carb.

Fil Bonica

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ARmedinaMUTT
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Re: Engine Hesitation

Post by ARmedinaMUTT » Thu Nov 04, 2021 7:50 am

The original poster is my dad (he's not familiar using forums & hasn't checked for responses). We're both new to the Military vehicle/ MUTT world & learning as we go. Anyway, I Just wanted to thank u guys for your input & advice. I told him to check timing before cleaning carb, & he said the timing is good. So we're gonna clean carb & replace gaskets.
But b4 we buy a gasket kit, will any m151 series carb gasket kit work? Or do we need a specific gasket kit for a Zenith 12848?
Again, thanks so much for your help & patience!
Semper Fidelis.
When a strong man, fully armed, guards his own home, his possessions are safe.
- Luke 11:21

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ARmedinaMUTT
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Re: Engine Hesitation

Post by ARmedinaMUTT » Thu Nov 04, 2021 7:56 am

Also. I forgot to mention that he has a '67 M151a1 MUTT that he bought in GA. The Zenith 12848 carb is what was already in the truck when he bought it. Not sure why he mentioned Brooks in his previous post. But he didn't get it from Brooks. It's either the original carb, or one the prior owner put in. Thanks again guys!
When a strong man, fully armed, guards his own home, his possessions are safe.
- Luke 11:21

Rickf
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Re: Engine Hesitation

Post by Rickf » Thu Nov 04, 2021 9:57 am

The 12848 is the right carb for that year so it is probably the original carb. Go to NORFAR and get their K2167 kit and that will do the job for you. But I will tell you that these carbs have to be very clean, passages and all, and the settings are critical. And do NOT lose the idle mixture tube from the bowl! It will possibly fall out when you take off the bowl. There is a very, VERY small gasket on that tube that will be in the kit. Watch for it in the bag, it will usually cling to the side of the bag as you dump the stuff out. Leave the tiny gasket in the bag until you are ready to put the jet in. Float setting is 9/32" and float drop is 3/8". Also be aware that there are seals for the throttle shaft and choke shaft. The throttle shaft seals are not bad but the choke shaft seal and spacer plus the housing are a real treat to get in without destroying the housing.
I have done over a hundred of these carbs and I can tell you that with cleaning and inspection and reassembly it takes me almost a day to do one.
To put that in perspective, A Rochester Quadrajet has 200 plus pieces and I can do one of them in 4 1/2 hours. These carbs are very finicky but when done right they run quite well. I have only ever had one return and that was one a guy ran on a vehicle he raced, underwater for the most part. They do not run well on water!
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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W. Winget
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Re: Engine Hesitation

Post by W. Winget » Thu Nov 04, 2021 11:12 am

Rick you forgot to mention that it usually ran best with the choke about an 1/8th of an inch out...as the choke plate is usually set incorrectly by the mechanic.
Now you can adjust this to be correct, eliminating play in the cable and getting it where it runs well, but that's the 1st thing I would try, it's easy to see if it DOES work just in driving down the street.
V/R W Winget
Looking for 1918 Standard B 'Liberty' truck parts

Rickf
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Re: Engine Hesitation

Post by Rickf » Thu Nov 04, 2021 5:17 pm

IF the carburetor is set up correctly there is NO extra choke needed. Not one of my rebuilds has needed extra choke. And I set the choke to be wide open on any that I put on a vehicle and I tell people who buy my rebuilds to do the same. If it stumbles just back out the idle mixture screw a quarter turn and that will usually fix the problem.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

bharr45
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Re: Engine Hesitation

Post by bharr45 » Fri Nov 05, 2021 4:52 am

Rick,What do you charge to rebuild one? Thanks in advance.

Rickf
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Re: Engine Hesitation

Post by Rickf » Fri Nov 05, 2021 5:35 am

Pm sent on price
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Firebird147809
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Re: Engine Hesitation

Post by Firebird147809 » Tue Jan 25, 2022 6:18 pm

Hi so I’m having trouble with my engine staying running we have checked all the gauges put fuel has oil not sure if sensor is bad
Any advice?

Rickf
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Re: Engine Hesitation

Post by Rickf » Wed Jan 26, 2022 5:21 am

Take the plug off of the oil pressure safety switch and put a jumper between the #77 and #77A wires. This will cause the fuel pump to run anytime the ignition switch is in the on position. See if the pump runs with the switch on. If it does then check for fuel at the carb. If it does not run then check for power at the connector on the tank, also run a separate ground from the tank preferably directly to the batteries. These had a big problem with the tank ground since all it does is clamps in and that is not exactly a good electrical connection. If it turns out to be a bad ground you can add one from the pump ground connector to a hidden spot under the seat on the body somewhere. If there is no power to the wire at the pump you will need to check the connector under the dash and also the #77 circuit breaker behind the dashboard to the left of the gauge panel.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Rickf
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Re: Engine Hesitation

Post by Rickf » Wed Jan 26, 2022 5:25 am

Firebird147809 wrote:
Tue Jan 25, 2022 6:18 pm
Hi so I’m having trouble with my engine staying running we have checked all the gauges put fuel has oil not sure if sensor is bad
Any advice?
posted to wrong person, OOP's
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

Rickf
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Re: Engine Hesitation

Post by Rickf » Wed Jan 26, 2022 5:27 am

Rickf wrote:
Fri Nov 05, 2021 5:35 am
Pm sent on price
Did not receive pm, it may not have gone through because you are a new member. I sent you an e-mail through the site here. Hopefully it works.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

hambone
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Re: Engine Hesitation

Post by hambone » Wed Jan 26, 2022 7:35 am

Firebird147809 wrote:
Tue Jan 25, 2022 6:18 pm
Hi so I’m having trouble with my engine staying running we have checked all the gauges put fuel has oil not sure if sensor is bad
Any advice?
What are the symptoms? does it die immediately or slowly die? is it missing or backfiring? could be fuel or fire.


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