Carb problems
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From: Sapulpa OK
Carb problems
My '52 F1 239 Flathead carb is very difficult to open the throttle. When I rebuilt the carb about a year ago it was easy and smooth. Now that it has had gasoline in it for a few weeks the accelerator pump is very tight when the throttle is first opened. After the first few degrees of movement it becomes easy.
I have the carb apart now and notice the pump plunger (# 9B544) does not follow the spring (9336) down. Even by hand the plunger is tight in its bore.
I'm thinking this synthetic material in the pump cup has swollen due to the gasoline. I would think the material would be compatible with todays fuels. This kit is a current kit, not something that has been sitting on a shelf for 60 years.
Anybody run up against this before? Are there leather cups available anymore?
Any help would be appreciated.
I have the carb apart now and notice the pump plunger (# 9B544) does not follow the spring (9336) down. Even by hand the plunger is tight in its bore.
I'm thinking this synthetic material in the pump cup has swollen due to the gasoline. I would think the material would be compatible with todays fuels. This kit is a current kit, not something that has been sitting on a shelf for 60 years.
Anybody run up against this before? Are there leather cups available anymore?
Any help would be appreciated.
Fleet Owner
Joined: Jul 2004
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From: NM
Is the cup blue or black rubber/plastic? I have a bunch of spares, blue, pink, and black. Yes, there are a few sources for leather cups but I don't know that it holds up as well as synthetics. Who made the kit?
For some reason some carbs seem to be downright sloppy fits to the cups, others are tight. All seem to be tapered slightly. I can't believe it's wear that makes them sloppy, but it doesn't seem to matter if they are a close fit. Are your passages out of the pump clear (not blocked)?
For some reason some carbs seem to be downright sloppy fits to the cups, others are tight. All seem to be tapered slightly. I can't believe it's wear that makes them sloppy, but it doesn't seem to matter if they are a close fit. Are your passages out of the pump clear (not blocked)?
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From: Sapulpa OK
Think I discovered the problem. When I put the carb together the first time I put the accelerator pump in the #3 hole. Being the longest stroke I lost the mechanical advantage afforded by the shorter strokes. I took the throttle body off again and set the pump arm in the #2hole and it works much smoother.
Soaking it in gas overnight made it a little tighter though.
Soaking it in gas overnight made it a little tighter though.
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Sanity check: Is the ball that's trapped under the spring free to move? Is the needle valve under the discharge nozzle working? These valves sticking could cause resistance once fuel is present. The ball could make up-stroke difficult and the needle could affect the downstroke. We are talking "Holley 94" style, right? The pump can be tested and valves checked on the bench or in the vehicle. Videos of how to check are on the net. Mike's carbs is a good source of info. and parts.
In my experience, fuel only helped lubricate the pump. Made it easier to move in the bore. If your diaphragm is swelling, ditch it for a known good. Maybe a fuel additive or you got some "extra" ethanol from the gas station (I was in the test equipment design business, trust me, it happens much more often than you might think).
In my experience, fuel only helped lubricate the pump. Made it easier to move in the bore. If your diaphragm is swelling, ditch it for a known good. Maybe a fuel additive or you got some "extra" ethanol from the gas station (I was in the test equipment design business, trust me, it happens much more often than you might think).
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