Changed over to the 2bbl Weber carb with a Holley pressure regulator on my 88 4.2L YJ and it runs great. Still have the stock mechanical pump. However, the longer it's parked the longer the crank time is before it will start. I have been told it's likely the fuel is draining all the way back to the tank, resulting in the long crank time along with rapid pedal pumping before it finally starts. Also, it was suggested to me to add an electric fuel pump. Any ideas, suggestions or solutions??????????
Hard Starting With Weber Carb
- Thread starter smripper
- Start date
Watching.
My 88 4.2 does the same thing. I recently did the "nutter bypass", added a Mr. Gasket fuel pressure regulator.
My "Weber" carb is clearly a chinesium knockoff though.
My next attempt at a fix will be adding an inline check valve.
Guy at O'Reilly just told me to check the position of the fuel filter.
I just replaced mine about 3 weeks ago and didn't even pay attention to it's orientation, but apparently having the smaller return line lower than the feed line can allow it to syphon the fuel from the bowl back to the tank. I just went out and repositioned mine... will let it sit an test start up this evening.
before/after
I just replaced mine about 3 weeks ago and didn't even pay attention to it's orientation, but apparently having the smaller return line lower than the feed line can allow it to syphon the fuel from the bowl back to the tank. I just went out and repositioned mine... will let it sit an test start up this evening.
before/after
Gilaguy23
YJ Addict
I'll throw this out not being familiar with those particular Webers. Chevy Quadrajets are notorious for draning the bowls out after sitting a bit from a leaky welsh plug on the bottom of the bowls. Rebuilders epoxy them up and problem solved. Wondered if the webers have a flaw like this too. On a positive note cranking it a bunch to get it fired up it eliminated "dry starts". By the time its fired up oil is already pumping thru the engine.
Welp... just discovered my problem.
Noticed some fuel leaking onto the manifold, traced it down to the accelerator pump on the carb. Removed the diaphragm to discover 3 little pinholes.
Noticed some fuel leaking onto the manifold, traced it down to the accelerator pump on the carb. Removed the diaphragm to discover 3 little pinholes.
That will do it.
Been in many of that style Weber, and that's usually the fail point, that or the throttle shafts.
It's not like that failure is a weakness, they're good little carburetors when they're right.
They just get old, and the really old ones don't like ethanol.
Whenever I bought a rebuild kit, it was primarily for that diaphragm.
Been in many of that style Weber, and that's usually the fail point, that or the throttle shafts.
It's not like that failure is a weakness, they're good little carburetors when they're right.
They just get old, and the really old ones don't like ethanol.
Whenever I bought a rebuild kit, it was primarily for that diaphragm.
Found this interesting fix on another auto forum.
Carb diaphragms are extremely expensive, about $60 each, as they are only sold integral with the slide. But they can be repaired easily and quickly.
Symptom.
With all else verified to be correctly set, one or more cylinders do not respond correctly to the throttle, and it is impossible to synchronize the carbs.
Test
Remove the airboxes, this will allow you to see the carb intake and reach the slide. There is a small crescent shaped opening at the top of the carb intake, this is the inlet to the chamber below the diaphragm. With the enrichener knob ("choke") fully in on the later models, or the "choke" lever in the off position on the earlier models, do the following. Raise the slide fully with your fingers, and then cover the crescent shape hole with the thumb of your other hand. Release the slide, keeping the crescent shaped hole sealed with your thumb. If the diaphragm is OK, the slide will not descend until you remove your thumb and let the air escape. If the diaphragm has a pinhole, it will creep down. If the diaphragm has a tear, it will snap shut. The reason the enrichener circuit or "choke" must be off, is because the enrichener circuit opens a port to draw additional air from the chamber under the diaphragm, thus opening this chamber to atmosphere and allowing the slides to snap shut whether you have your thumb over the crescent shaped opening or not. Note; if the slide only creeps down, it is not essential it be repaired. A small single pinhole will not materially affect the operation of the carbs. But an ounce of prevention is worth a pound of cure; repair now will keep it from later tearing.
Repair Procedure
(1) A your NAPA store buy part # 765-2527 "Plasti Dip" spray-on heavy duty flexible rubber coating, which comes in a spray can and also in a ordinary can for brush application. Under $10. The part number given is for the spray in black, that's what I bought. Hereinafter called PD
(2) Remove the carburetors, remove the tops, and withdraw the diaphragm and slides. You might as well check them both while you have them out. But do not mix up the parts between the two carbs.
(3) Clean the diaphragms with denatured alcohol.
(4) Hold against the light to locate any pinholes or tears.
(5) Spray a small portion of the PD onto a piece of shiny coated cardboard to form a puddle. Using a Q-tip take wet PD from the puddle, and lay it over any pinholes, over any small tear, and also paint it under the outside seating lip over all the tiny little holes which may be able to be seen against the light. Put these repairs on the underside of the diaphragm only, so pressure holds them against the diaphragm, rather on the top where vacuum would work to pull them off.
(6)Then give only the underside of the diaphragm one THIN coat of spray, including over the seating lip. Too enthusiastic spraying of the diaphragm will make it too stiff. This layer will bond with the repairs, adhere to the diaphragm, and prevent the repairs be drawn through the tear by vacuum. Immediately wipe off any spray that went onto the slide body or the plastic clamping disc with a cotton ball wetted with rubbing alcohol. No masking tape, it will cause ragged edges on the PD coat.
(7)Let it dry/cure for the recommended 4 hours.
(8) Assemble it into the carbs.
(9) Test again as described above.
Repairing a tear in the carb diaphragms
Carb diaphragms are extremely expensive, about $60 each, as they are only sold integral with the slide. But they can be repaired easily and quickly.
Symptom.
With all else verified to be correctly set, one or more cylinders do not respond correctly to the throttle, and it is impossible to synchronize the carbs.
Test
Remove the airboxes, this will allow you to see the carb intake and reach the slide. There is a small crescent shaped opening at the top of the carb intake, this is the inlet to the chamber below the diaphragm. With the enrichener knob ("choke") fully in on the later models, or the "choke" lever in the off position on the earlier models, do the following. Raise the slide fully with your fingers, and then cover the crescent shape hole with the thumb of your other hand. Release the slide, keeping the crescent shaped hole sealed with your thumb. If the diaphragm is OK, the slide will not descend until you remove your thumb and let the air escape. If the diaphragm has a pinhole, it will creep down. If the diaphragm has a tear, it will snap shut. The reason the enrichener circuit or "choke" must be off, is because the enrichener circuit opens a port to draw additional air from the chamber under the diaphragm, thus opening this chamber to atmosphere and allowing the slides to snap shut whether you have your thumb over the crescent shaped opening or not. Note; if the slide only creeps down, it is not essential it be repaired. A small single pinhole will not materially affect the operation of the carbs. But an ounce of prevention is worth a pound of cure; repair now will keep it from later tearing.
Repair Procedure
(1) A your NAPA store buy part # 765-2527 "Plasti Dip" spray-on heavy duty flexible rubber coating, which comes in a spray can and also in a ordinary can for brush application. Under $10. The part number given is for the spray in black, that's what I bought. Hereinafter called PD
(2) Remove the carburetors, remove the tops, and withdraw the diaphragm and slides. You might as well check them both while you have them out. But do not mix up the parts between the two carbs.
(3) Clean the diaphragms with denatured alcohol.
(4) Hold against the light to locate any pinholes or tears.
(5) Spray a small portion of the PD onto a piece of shiny coated cardboard to form a puddle. Using a Q-tip take wet PD from the puddle, and lay it over any pinholes, over any small tear, and also paint it under the outside seating lip over all the tiny little holes which may be able to be seen against the light. Put these repairs on the underside of the diaphragm only, so pressure holds them against the diaphragm, rather on the top where vacuum would work to pull them off.
(6)Then give only the underside of the diaphragm one THIN coat of spray, including over the seating lip. Too enthusiastic spraying of the diaphragm will make it too stiff. This layer will bond with the repairs, adhere to the diaphragm, and prevent the repairs be drawn through the tear by vacuum. Immediately wipe off any spray that went onto the slide body or the plastic clamping disc with a cotton ball wetted with rubbing alcohol. No masking tape, it will cause ragged edges on the PD coat.
(7)Let it dry/cure for the recommended 4 hours.
(8) Assemble it into the carbs.
(9) Test again as described above.
Ouch!
The last carb kit I bought cost me about $25, I guess it's been a while!
That is an interesting fix though, If only Plasti-Dip was available 30 years ago...
Please let us know how it works out.
Not that I have a carb anymore, but as an old mechanic, I'm always looking for new tricks (or old ones for that matter).
The last carb kit I bought cost me about $25, I guess it's been a while!
That is an interesting fix though, If only Plasti-Dip was available 30 years ago...
Please let us know how it works out.
Not that I have a carb anymore, but as an old mechanic, I'm always looking for new tricks (or old ones for that matter).
Gilaguy23
YJ Addict
That bit of info applies to motorcycle carbs of the "CV" style or constant velocity. Those diaphragms are literally thinner than paper and sit up on top of the carb under a plastic or tin cover and are not exposed or submerged in fuel like a accelerator pump diaphragm is. I really cannot see any possible way one could repair an acc pump and have it last any length of time. For a test I could see one silicone up the pinholes,let it dry overnight,reassemble and see if the silicone makes it thru the night for the next days start up. I think your gonna have to bite the bullet and buy a carb kit.
Get off the mechanical pump......If you don't know the age of it, Or you're running that 15% ethanol blend, The diaphragm could be stretched out of shape and not maintain the tension it once did.....Get a Holley 12-170 100GPH and regulate down to the Weber requirement with a regulator set up on either the inner fender or firewall.......
Dumb question: How would you recommend plugging the port on the block once the mech pump is removed? Or just leave it in place?