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Tom M

Jeep carburettor problems

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Can anyone give me some advice on a Jeep fuelling problem? I decided to rebuild my '44 Willys MB carb this week, as I suspected fuel starvation; I took the Jeep out a few weeks ago in the really cold weather and it kept cutting out at idle, but would start again with some throttle and choke, eventually I got home and it stalled and wouldn't start again. I got it to start a few weeks later, but it would only run with the choke and would cut out really easily when the throttle was opened.

I have just rebuilt the carb using a kit I had from Dallas Autos, and put it back on the engine, but it was difficult to start and still won't run without choke, even when warm . If I open the throttle it dies straight away. It sounds like a fuel blockage, but I don't know where to start. Does anyone have any ideas on the likes culprit? I don't want to have to strip the carb down completely all over again if I don't have to, as I don't have a lot of time. I am trying to get the Jeep ready for an event on Salisbury plain this weekend and it is refusing to cooperate!

 

Any advice greatly appreciated.

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Are you running on a Carter or a Solex carb,?

Only running on choke could indicate an over lean mixture caused by an air leak (running on choke will give you an over rich mixture to compensate for the leak).  As you say you had this problem before you rebuilt the carb start by checking for air leaks around the inlet manifold to block mating face. 

Get the engine running after a fashion and spray a little WD40 around the inlet manifold joints and the carb to manifold joint, you are looking for a momentary increase in engine speed to indicate the leak or better still attach a vacuum  gauge to a point below the throttle plate you should be reading between 17 and 20 inches of Hg at around 800 to 1000 RPM fairly steady.

Pete

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Thank you Pete, I hadn't considered it that it might be something after the carb. I will check the manifold tonight. I've checked the pump, and fuel filter and all seems ok.

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Posted (edited)

Just another thought If your running vacuum windscreen wipers check all the connections are sound,  the take off for them is below the throttle plate on the inlet manifold. 

If you have a problem there it produces a direct air leak into the manifold giving a weak mixture and dropping the inlet manifold depression particularly when you open the throttle plate suddenly on acceleration. 

The net result of this is two fold obviously a very weak  mixture but also the loss of vacuum in the choke tube (result of air getting in below the throttle plate) will give issue with the fast running circuit as  naturally aspirated engines rely on the correct vacuum to generate air flow to draw fuel (controlled by air flow via the throttle plate) to operate the fuel circuits correctly.   

In short air leak into the system as a whole = :banghead: 

 

Pete

Edited by Pete Ashby
added a bit more by way of explination

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This sounds like it may be a worn butterfly valve axis in the body. I had my body rebored and bushed by Scoutpilot in the USA. Simple way to see is to spray an accelerent next to the axis pin and see if the revs pick up. Lighter fluid works.

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Extract from a thread on the Carter. This is the problem I think you have. The poster is the guy who fixed mine for me. The housing came back bushed to spec and a nice new park finish as original (not painted).

 

: Carburetor question

Post Mon Oct 06, 2014 4:39 am

Considering this latest info, your problem may not necessarily be the plate. Instead, check the throttle shaft for wear. If it mic's out at less than .310", it probably needs to be replaced. Check the area of the shaft that passes through the body. If you can, mic the passages themselves. Greater than .3125" suggests you may need bushings. These shafts/housings wear into an egg shape and allow a vacuum leak which necessitates choke usage to maintain an idle. A quick check is to spray, in short bursts, starting fluid at these points while the motor is at its best warm idle. A change in RPM will tell you of the leak.

scoutoh6@outlook.com

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For it to stall when you open the throttle  means you have a problem in your high speed circuit. The rebuild kits going around are not the best,  the plunger stuck in mine. Also if you changed the meter rod etc you have to adjust it (not easy).

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Thanks for all the advice guys. After going through through the manual and rebuild instructions again, I realised that (as Phil.c says) I hadn't set the meter rod correctly. I had just refitted it without setting it at all - one of the down sides of working on ones Jeep until the early hours of the morning for three nights in a row!

After setting it correctly it started on the button and ran perfectly. I have just spent a weekend on Salisbury Plain and it didn't break down! It was difficult to start, but I am guessing this is probably down to me not getting the choke settings correct, and either flooding or running the battery down from frequent starting.

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