M151 running rich

1959 - 1978, M151, M151A1, M151A2, Technical questions and discussions, regarding anything related to the M151.
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ldj1002
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M151 running rich

Post by ldj1002 » Tue Oct 25, 2022 6:08 am

My M151a2 all of a sudden started running rich, I assumed the needle wasn't seating. Took carb off it was clean, blew it out good anyway. Checked it by blowing and sucking at fuel inlet and all good, needle is seating. Put back on and still run rich. I even blocked fuel line and just before carb ran out of fuel engine run good so that tells me really is running rich. Any ideas appreciated.


Blake
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Re: M151 running rich

Post by Blake » Tue Oct 25, 2022 7:17 am

Check the diaphragm in the bottom of the carburetor.

ldj1002
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Re: M151 running rich

Post by ldj1002 » Tue Oct 25, 2022 8:10 am

What will I look for, a hole or split. I rebuilt this carb a few months ago and it should be good but the kit could be many years old. If it is bad how could I rig it to stop it from funning rich as a temporary fix? I think that acts as accelerator pump. I would rather run with hesitation than running too rich.

markrdje
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Re: M151 running rich

Post by markrdje » Tue Oct 25, 2022 8:23 am

Does the float float in a reservoir in of gas?No gas in it?
change user name to mark

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muttguru
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Re: M151 running rich

Post by muttguru » Tue Oct 25, 2022 9:31 am

ldj1002 wrote:
Tue Oct 25, 2022 8:10 am
What will I look for, a hole or split.
Idj,
Here's one that I fixed five years ago. you can clearly see the split.
Ken
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Rickf
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Re: M151 running rich

Post by Rickf » Tue Oct 25, 2022 10:14 am

If the diaphragm is cracked there is nothing you can do, it is pulling gas through the diaphragm and into the main circuit through the vacuum port that actuates the accelerator pump. PM me your address and I will send you a diaphragm I have taken out of carbs I have rebuilt that were still good.
What will do these is is people adding gasoline additives like gas "dryer" to their gas which already has alcohol in it so now the alcohol content is well above the 10-15% maximum the factory rubber can handle. Or, You can get a bad load of gas with far too much alcohol in it. I got 60 gallons of gas in my RV which turned out to have 23% alcohol in it! I can tell you that a carbureted 454 big block does not run well on that!
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
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svramselaar
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Re: M151 running rich

Post by svramselaar » Wed Oct 26, 2022 3:09 am

hi

if you don t have a diagram make so cald blind gasket
take the spring out and make a gasket from rubber or material witch can hold petrol
if you do this you have only no acseration pump
i have done this with a Rolls Royce engine from Austin champ

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
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ldj1002
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Re: M151 running rich

Post by ldj1002 » Wed Oct 26, 2022 3:18 pm

I took the diaphragm out and it had a little knot smaller that a pin head and right opposite was a little bitty oblong spot. looked like a defect. I couldn't see any light through the spot and didn't think it was a leak. It must have been leaking there because I made a gasket from a piece of bicycle tube and it idles smooth now but has a bad dead spot. Thanks to Rick I have a diaphragm coming.


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