Zenith carburetor, it never ends :(

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Grasshopper
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Re: Zenith carburetor, it never ends :(

Unread post by Grasshopper » June 20th, 2017, 3:54 am

I think my A2 came with a spare carb, so if I can find it I think I'll take that to a carburetor specialist (a rarity here in the UK). Seems they have quite a waiting list! That way hopefully over next Winter when I do the exhaust manifold gaskets (and all that may entail!) I can also install the rebuilt carb. They've done a couple for me (International Harvester M55 and Dodge WC51 ) and they worked perfectly straight off. No point in me trying to get the machine running well as the blows the manifold has will not be conducive to good running.

I also have a NOS distributor installed that sits at a different angle to the one that was removed, so I think I'll build a good one from the 2 as where it currently sits it fouls the oil filter in order to achieve the correct timing. I've had to install a slightly smaller oil filter to achieve correct timing. I recall helping Mike install it years ago - initially we just swapped like-for-like, and she wouldn't start, then he remembered something about a batch of distributors built incorrectly, moved it and away she went. Anyway, enjoying my MUTT for now, even if only going shopping locally. First proper MV show outing for her (in my ownership) in a couple of weekends time.

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Re: Zenith carburetor, it never ends :(

Unread post by PPanagakos » June 20th, 2017, 10:07 am

Grasshopper, Billy Brooks is in Florida. I can see from the posts here that he draws some comments. I paid about $290 with shipping from New Mexico. All Billy asked me when I sent my carb was what altitude I'm at. Here in Albuquerque we are about 5000 ft. When the carb came back from him I could tell it was cleaned to the point of looking brand new. I also notice that the accelerator gasket was black instead of the usual red and looked like a thicker material. There are many here who know how to work on these carbs and they would say do it yourself. I'm not one of them. I've worked on many Jeeps, but this carb works on vacuum, no accelator pump. I know everything has to be right for it to run correctly. I did all that and had the same problem you describe. I gave up and sent it to Brooks. Have not had carb problems since. All I meant to say was if all else fails and you can't stand it anymore, $300 bucks was worth it to me. I spent way more than that on seat cushions. This carburetor drove me nuts.

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Re: Zenith carburetor, it never ends :(

Unread post by rickf » June 20th, 2017, 10:30 am

m3a1 wrote:I think you are thinking of me. I actually did that with my A2 after swapping in the Brooks Rebuild that had originally hung on the Alley Cat. He told me to make the angle cuts saying that the fuel wouldn't flow through in sufficient quantity. It was actually quite an easy modification.

http://www.g838.org/viewtopic.php?f=27&t=10252&start=30

Cheers,
TJ
TJ, That will do absolutely nothing! All that is doing is letting gas up into the area above the threads which is a blank area and goes nowhere!! The gas flow comes into the bottom of the chamber and exits the bottom of the chamber, all below that threaded area.
PPanagakos wrote:Grasshopper, Billy Brooks is in Florida. I can see from the posts here that he draws some comments. I paid about $290 with shipping from New Mexico. All Billy asked me when I sent my carb was what altitude I'm at. Here in Albuquerque we are about 5000 ft. When the carb came back from him I could tell it was cleaned to the point of looking brand new. I also notice that the accelerator gasket was black instead of the usual red and looked like a thicker material. There are many here who know how to work on these carbs and they would say do it yourself. I'm not one of them. I've worked on many Jeeps, but this carb works on vacuum, no accelator pump. I know everything has to be right for it to run correctly. I did all that and had the same problem you describe. I gave up and sent it to Brooks. Have not had carb problems since. All I meant to say was if all else fails and you can't stand it anymore, $300 bucks was worth it to me. I spent way more than that on seat cushions. This carburetor drove me nuts.
Sir, There IS an accelerator pump in these carburetors. All carburetors work on vacuum. And the color of the accelerator pump diaphragm will change as the supplier feels fit to do so. I get black ones and I get red ones. My last order was half and half. They are all the same thickness. And they are coming straight from Zenith.
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: Zenith carburetor, it never ends :(

Unread post by m3a1 » June 20th, 2017, 12:15 pm

Yeah, Rick that's what you said last time. :lol: but in my case (and in my defense) I was dealing with Brooks because he was the guy who built the carb and I was loath to muck up someone else's good work, which we all know is a no-no.

But for the brand new members who may be following this thread, Rick knows his stuff and has more been-there-done-thats than most of us. Heck, I'm a noob here as well.

Getting back to where this thread all began, I'm surprised that Rick hasn't started where he usually starts - mentioning the all important issue of the engine's valves being properly adjusted. Everything else really depends upon that (except my noisy brake lever). You're slipping, Rick! :lol:

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Re: Zenith carburetor, it never ends :(

Unread post by PPanagakos » June 20th, 2017, 1:24 pm

I know all carburators work on vacuum. I mean these don't have the kind of accelerator pumps the Willy's MB, M38 and M38A1's had. A downdraft carb with an accelerator pump with the spring plunger deal. Clearly many of us have problems with these carbs or you would not keep seeing posts with the same problems.

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Re: Zenith carburetor, it never ends :(

Unread post by Haas » June 20th, 2017, 1:35 pm

PPanagakos wrote:I know all carburators work on vacuum. I mean these don't have the kind of accelerator pumps the Willy's MB, M38 and M38A1's had. A downdraft carb with an accelerator pump with the spring plunger deal. Clearly many of us have problems with these carbs or you would not keep seeing posts with the same problems.
M38s and M38A1s are all vacuum operated as well, no mechanical accelerator pumps and metering rods like an MB.
1942 Willys MB "slat grille"
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1953 M38A1
1952 M38A1
1951? M38
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1953 M37
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Re: Zenith carburetor, it never ends :(

Unread post by Horst » June 20th, 2017, 2:24 pm

rickf wrote:Horst, While we are talking about Zeniths, a while ago didn't you say you could not use the inlet fitting with the filter in it in a late 13660 carburetor? The one that screws in from the top that has the bypass on the later carbs. I just did some testing while rebuilding some carbs an swapped them back and forth between each other with no problems. There is no difference on the inside of the fitting other than the late model has no filter and it does have a small hole for vapor return. Apparently this is one of his mods, he grinds a spiral cut in the thread for some unknown reason. All that will do is allow gas into the unused chamber above the threads, it goes nowhere from there. I would like to see one in person.
no, that was a little different. You can use late carburetors on early jeeps, so a 13660 A or B will just work fine with an A1, but not the other way. An A1 carb, don't have the number ready, will not work with the fuel return set-up of an A2. Reason being the location of the internal openings. Remember the A1 set-up has the internal fuel filter at the same location the A2 has the return fitting. Screwing in the return fitting into an A1 carb will simply block those entirely and there will be no fuel flow.

upper picture: A1 carb, lower picture, later model, fuel hole way down compared to the old carb
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1972 USMC M151A2 w/ROPS (ex Barstow) and M416
1962 M201 and trailer
1966 GTO,1982 E350 Skoolie, 1987 SJ413, 1987 911
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Re: Zenith carburetor, it never ends :(

Unread post by rickf » June 20th, 2017, 6:46 pm

Thats the picture I was looking for. I looked at one of my 13841 carbs and it has the same flow as the 13660. I will have to check out a 12848. It would make sense since the other way the gas would not flow through the filter. Either way the carbs are getting plenty of gas as long as the pump is good and the float drop is set correctly. We are not talking big block Chevy fuel consumption here.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: Zenith carburetor, it never ends :(

Unread post by Mulerider » July 5th, 2017, 10:44 am

Thought I would jump in to say that I am having same issues with my Carb. It idles good but has a flat spot or hesitation when accelerating fast. I found that by pulling choke out slightly it would run better and eliminate the flat spot. Have a local mechanic working on it with me, he made adjustments to timing and we have choke very slightly closed and it is running pretty good.
Another issue is when I cut motor off it will send two squirts of gas in the carb( after engine stops turning) enough that it will run out. What would cause that and do you think it is a problem?
(FYI I have a mechanical fuel pump on the engine)

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Re: Zenith carburetor, it never ends :(

Unread post by Mulerider » July 5th, 2017, 10:44 am

Thought I would jump in to say that I am having same issues with my Carb. It idles good but has a flat spot or hesitation when accelerating fast. I found that by pulling choke out slightly it would run better and eliminate the flat spot. Have a local mechanic working on it with me, he made adjustments to timing and we have choke very slightly closed and it is running pretty good.
Another issue is when I cut motor off it will send two squirts of gas in the carb( after engine stops turning) enough that it will run out. What would cause that and do you think it is a problem?
(FYI I have a mechanical fuel pump on the engine)

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Re: Zenith carburetor, it never ends :(

Unread post by rickf » July 5th, 2017, 11:17 am

The squirts on shutdown are a result of the vacuum operated accelerator pump, As the vacuum dies off it shoots a shot of gas into the engine. Are you test driving this with the air cleaner hose off? If so then that is your problem with the flat spot a fast acceleration. that is an acceleration pump issue but if that hose if off it will screw up everything. Timing has to be set right on the line and valves have to be set perfect, if that is all done then set the idle mixture a little on the rich side and the flat spot will be gone. With the choke all the way in.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: Zenith carburetor, it never ends :(

Unread post by Mulerider » July 5th, 2017, 12:20 pm

Thanks Rick
No I had hose off just while making adjustments put it on while driving.
Guess I need to check the valve settings, I assume I can find them in manual.. Never thought abt valves affecting flat spot.
We set the timing by listening to engine. Do I need to use a timing light?

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Re: Zenith carburetor, it never ends :(

Unread post by Horst » July 7th, 2017, 3:21 am

Mulerider wrote: We set the timing by listening to engine. Do I need to use a timing light?
Yes!
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1972 USMC M151A2 w/ROPS (ex Barstow) and M416
1962 M201 and trailer
1966 GTO,1982 E350 Skoolie, 1987 SJ413, 1987 911
Gone: 2xM35A2c, Unimog 404S, Hanomag AL28, DKW Munga

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Re: Zenith carburetor, it never ends :(

Unread post by rickf » July 7th, 2017, 11:04 am

Yes on the timing light, my guess is that the timing right now is probably around 10 degrees. It needs to be 6 which is right on the timing mark. Valves are set at .015 hot. And you do not say what vehicle you have but if you have an A1 with points then set the points BEFORE setting the timing because point setting changes timing. The carburetor is the very last thing you set.
1964 M151A1
1984 M1008
1967 M416
04/1952 M100
12/1952 M100- Departed
AN/TSQ-114A Trailblazer- Gone

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Re: Zenith carburetor, it never ends :(

Unread post by m75 » July 9th, 2017, 12:18 pm

Isn't all of the same advice in RIck's sticky note at the lead of the forum topic page??
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