The Stovebolt Site Forums The Shop Area Engine Shop Tired of dry carb!

Okay, it's a Rottenchester, I know. But my 55.1 3100 235 sits for a week or two sometimes, since I'm coming back from a hip replacement and I'm not driving much.

I remember reading some while back about installing a 6v electric pump with a push-button switch, so you could prime the carb electrically before starting and then run on the mechanical pump. Can't find where I read about it, but it can't be that hard to do.

I've just been reading that a low-pressure Airtex can be used in-line with the mechanical cuz it won't (much) interfere with the flow with the mechanical pump. Correct that if I'm wrong, please?

Also reading that pump pressure IS an issue, and that Airtex makes low pressure pumps. I can't find them. Anyone know a part number and source they'd recommend? Any other advice from the experienced would be appreciated.

We can talk carb replacement some other day...

Is the second one (4 psi) the better choice? Can I run it inline intermittently with my mechanical pump?

And then--am I correct that it should be inline BEFORE the mechanical pump? Hadn't thought about that one.

Thanks a heap, BTW...

I'm scratching my head over your issue. Is the fill fitting on the bottom of you bowl? Not familiar with the particular year/carb.

If not why is your gas draining or drying out within this short of time? Never heard of this.

Actually, from my conversations with owners of classics, it's the very rare old car that wil NOT dry out with a couple-three weeks of sitting. Discussed a lot on some forums. Mine's done it for all of the 20 years I've had it. Long sit = dry bowl.

Mine used to do it as well. 1950 3600 with a 54' 235. I went to the electric pump and have not had the issue since. Used to be if it sat a few days I had to prime the carb with live gas, always a risky way to go.

Ok. I've had some old rig sitters but never a problem where I had to crank excessively to get gas to start. Couple cranks, couple of accel pumps and start. Just feels like another issue to me, leaky carb, over vented, bad choke, bad accelerator pump???? Shouldn't be a hard start in 1-2 weeks, I would not like it either.

In any case if you go with the electric (before the mechanical), make sure the mechanical pump will allow flow through it's valve to carb regardless of arm diaphragm position.

Good luck, interesting idea.
Dave

Kermit,you might check THE CARBURETOR SHOP. They have good trouble shooting tips. I have the same problem with my 53 3100. Steve

mine has done that for 30 years, usually during the summer, I get about a week before I have to give it a little extra to start, during the winter, sometimes 2 weeks. Seems normal to me.

My rochester carb used to require priming (a little gas down the throat) after as little as 2 days. I replaced the Rochester with a YF-2100S Carter, and put on a new fuel pump. Now it may take a little pedal pumping and a few extra spins of the starter after a week, but NOTHING like what it used to require.

For what it's worth, I think the check valve in the pump was bad, and the gas in the line would drain back down to the tank. With a little evaporation from the bowl, it would take a lot of cranking (or a little gas down the throat) before she would fire.

I suggest you try replacing your existing fuel pump, and if that doesn't work, try replacing or rebuilding you carb.

Kurt

It's actually fairly common. If you think about the intimate contact between the intake and exhaust manifolds transferring heat to the carburetor as well as the natural flow of heat up around the carburetor it's not surprising that the bowl dries out when they sit for a while. A fair amount of it happens soon after shutting the vehicle off. That's why it's often difficult to hot start one of these old Chevys. Some of the gas boils out of the bowl and fills the intake runners with vapor. It's like trying to start a hot vehicle with the choke on. After a while you just get used to it. If my '38 sits for a couple of weeks the bowl is dry.

My Mono-jet carb (1970 Rochester) can set for three or four weeks and still fire off in just a few cranks and couple of pumps, not sure why a Model B would be any different. Sounds like a vent issue or casting issue. Fuel sure isn't going to siphon out the needle and seat clear back to the tank.

I would rebuild the carb before installing a electric pump. And if you use the electric pump, be sure to use a momentary push button only or wire in a safety switch to the oil pressure if using the pump full time. NEVER EVER use a on/off switch with out a safety backup, Never.

Joe,

If the float drops because the fuel in the bowl is low due to evaporation, the vacuum is broken and the fuel in the line can drain back to the tank if the check valve in the fuel pump is bad. It will not, as you say, siphon the fuel out of the bowl.

And I have checked my tank and the top of the tank is lower that the fuel pump. If your tank is behind the seat it may not drain back unless the tank level is low.
Kurt

My tank is behind the rear axle. If the float level drops enough to open the needle and seat, the remaining fuel still should start the engine. The accelerator pump may be weak causing the long crank, does if have any flat spots when driving?

Like I said above, rebuild kits are cheap for that model, so thats where I would start. I would also set the float to the high side of the spec sheet.

As for a test, remove the fuel line off the carb and replace it with a piece of hose coming from a fuel jug setting on the fender (about carb level). Get the engine running again to clear any air from the line and seal the fuel jug with a rag stuffed around the hose. Now let it set for the same amount of time as you have before and see how it starts.

Joe