M151A1 will not go to idle
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M151A1 will not go to idle
Two friends and I were working on resetting the proper timing using a timing light and a rpm/dwell meter. Jeep started right up
but maintained an idle at 1400 rpm and refused to idle down to 450-500. Using a brake cleaner to reveal any holes in vaccum system found none.
Shut off, removed/inspected Zenith carb which showed no symptoms. Looked in -39P for parts layout of distribuator for advance. Did not
find anything related to "advance".
Thoughts??
but maintained an idle at 1400 rpm and refused to idle down to 450-500. Using a brake cleaner to reveal any holes in vaccum system found none.
Shut off, removed/inspected Zenith carb which showed no symptoms. Looked in -39P for parts layout of distribuator for advance. Did not
find anything related to "advance".
Thoughts??
- Kurt Lesser
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Re: M151A1 will not go to idle
Timing advance in the 151 is all done with counterbalance weights under the breaker plate inside the distributor. If the vehicle has been sitting you might find either stuck weights or a broken spring.
Kurt Lesser
US Navy, 1969-1975
M996A1 Ambulance w/M101A3 Trailer
M274A2 Mule
M151A1 Mutt w/M416B1 Trailer
M890 Crew cab
US Navy, 1969-1975
M996A1 Ambulance w/M101A3 Trailer
M274A2 Mule
M151A1 Mutt w/M416B1 Trailer
M890 Crew cab
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Re: M151A1 will not go to idle
The timing advance could be the problem but I have never seen a m151 that you could not back the throttle down with the adjustment screw even with the advance stuck. You can adjust that idle down so far the plate is tight in the bore. Are the throttle shaft bushings worn out? Can you wiggle the throttle shaft up an down in the body? If so it is time for a replacement carb unless you have a mini lathe and some Teflon round stock to make bushings from.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: M151A1 will not go to idle
Thanks to Rickf and Kurt for your remarks. Having had two experienced mechanics stop by my M151A1 the other day they
found several vaccum leaks in the wiper motor lines which dropped the idle speed to a manageable level when clamped off. Both men then stated that either or both the intake and exhaust manifolds were leaking given the particular sound they made when running. So that will be followed up on
soon.
George in NH
found several vaccum leaks in the wiper motor lines which dropped the idle speed to a manageable level when clamped off. Both men then stated that either or both the intake and exhaust manifolds were leaking given the particular sound they made when running. So that will be followed up on
soon.
George in NH
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Re: M151A1 will not go to idle
Were those mechanics aware that the wipers are powered by a vacuum pump? The engine vacuum line feeds into the pump but this is not a fuel injected vehicle so a vacuum leak will not generally cause an idle increase. It will cause a lean idle and very rough idle. The fact that I am not there in person I cannot really offer much more but uncontrolled high idle speed due to unmetered incoming air is a fuel injected thing. Vacuum leaks on carbureted engines will cause rough idle and stalling, unless the idle mixture has been set very, very rich.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: M151A1 will not go to idle
George, take some WD40 or starter fluid and spray around the manifold surfaces.
See if you can find leaks.
The exhausts on older manifolds were sealed with
Hi temp grease.molydenumdisulfide
Later ones were sealed with gaskets.
The intakes were sealed with gaskets.
There is a gasket kit containing both sets.
They should allow you to fix things.
Good luck .
Fil Bonica
See if you can find leaks.
The exhausts on older manifolds were sealed with
Hi temp grease.molydenumdisulfide
Later ones were sealed with gaskets.
The intakes were sealed with gaskets.
There is a gasket kit containing both sets.
They should allow you to fix things.
Good luck .
Fil Bonica
- W. Winget
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Re: M151A1 will not go to idle
"removed/inspected Zenith carb which showed no symptoms"
No offense meant, but are you aware of 'where' the fuel mixture screw is on your Carb?
Sometimes they are covered by a small, inserted metal cap, (prevent tampering) which would need to be drilled through for removal to reach the normal screw.
It would be located on the mounting flange, and if you do not have this adjusted for the proper air/fuel mix, it is likely your issue.
Air leaks do not make the engine run faster, might make it run rougher, but it has to have both air AND more fuel to run faster.
V/R W. Winget
No offense meant, but are you aware of 'where' the fuel mixture screw is on your Carb?
Sometimes they are covered by a small, inserted metal cap, (prevent tampering) which would need to be drilled through for removal to reach the normal screw.
It would be located on the mounting flange, and if you do not have this adjusted for the proper air/fuel mix, it is likely your issue.
Air leaks do not make the engine run faster, might make it run rougher, but it has to have both air AND more fuel to run faster.
V/R W. Winget
Looking for 1918 Standard B 'Liberty' truck parts
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Re: M151A1 will not go to idle
Be sure you have the carburetor intake hose to the air cleaner hooked up when doing the manifold leak test so you do not get a false positive from cleaners going into the mouth of the carb. I see in the first post it mentions you used brake cleaner to finds leaks in the vacuum system but found none. So you may have already done this test. I think your expert mechanics are younger guys that work on fuel injected cars. A vacuum leak on an injected vehicle is unmetered air and will be picked up at the O2 sensor as a lean condition and the computer will add fuel to correct that which in turn will raise the engine speed. Carburetors have no O2 sensor and no computer. Just a plain old simple carburetor. All manual adjustment. If you can't get the idle down then something is holding the throttle plate open. OR, Someone has jammed the idle mixture screw in too tight and enlarged the metering hole in the carb body so that you cannot adjust the mixture down but even then you should still be able to adjust the throttle plate down to stall the engine. No air, no run. Check that your choke is adjusted correctly and that the choke rod to the throttle is releasing all the way.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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Re: M151A1 will not go to idle
Hi
Have sheckt the acselerator membranen for leaks
If this is leak the feul can get to the engine from the feul camber to the vacume side carb
George
Have sheckt the acselerator membranen for leaks
If this is leak the feul can get to the engine from the feul camber to the vacume side carb
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
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: M151A1 will not go to idle
But that would also just flood it out or cause it to run extremely rich, Not cause a high idle. Again, not fuel injected.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone
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- Posts: 50
- Joined: Thu Sep 15, 2005 3:41 pm
- Location: New Hampshire
Re: M151A1 will not go to idle
Many Thanks to all for your input!! More to be done!!
George in NH
George in NH
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