83 CJ-7 258 original Carter BBD Carb looses prime when left for long time.

John Godwin

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Jun 10, 2017
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I only drive my Renegade once a month. The first crank requires a lot of turning over for the mechanical fuel pump to deliver fuel to the Carb. After first start I have no trouble starting. I have tried pouring a tad bit of gas in carb and she fires up nicely. Any thoughts of how I could install an electric fuel pump to prime the system? My mechanical pump seems to work great after first start. My fly wheel doesn't have the best teeth any more so I don't want to spin those gears any more than I have to. She is not a daily driver. She is my Mountain Jeep. Thanks for any help. My thoughts were to install an electric pump between the mechanical pump and the Carb, but I am not sure if the elec - pump could pull fuel through a mechanical pump prior to starting to prime the carb. Then once started could the mechanical pump push fuel through the electric pump once I stopped powering the primer electric pump. Thanks again. John.
 
I dont know much about Jeep engines, but I imagine it's not very hard to find a block off plate to remove the mechanical fuel pump and convert to an electric pump and regulator.
 
I have thought about replacing the pump but I mostly want to add a primer. No fun opening the hood and air filter to pour gas in prior to each start. ;-) thanks for the great idea.
 
I would check choke to make sure it closes all the way.
 
Install check valve near the firewall.
 
Ron said:
Install check valve near the firewall.
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Ron. We're you thinking the fuel is slowly flowing back to the fuel tank? If that were the problem you probably have a good point. I was thinking the fuel was evaporating from the Carb side. Sorry if that was dumb thought. Ha ha. I am just trying to get my mind around this. Thanks
 
John Godwin said:
Ron. We're you thinking the fuel is slowly flowing back to the fuel tank? If that were the problem you probably have a good point. I was thinking the fuel was evaporating from the Carb side. Sorry if that was dumb thought. Ha ha. I am just trying to get my mind around this. Thanks
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I bet you are correct Ron. I am going to head to NAPA to get a check valve
 
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The fuel is most likely evaporating out of the bowls. The fuel inlet of the carb should be higher than the fuel level in the carb so it shouldn't be able to drain back, but it is open to atmosphere and likely to evaporate. Check valve will keep it from flowing out of the line, but no more.
 
NC-V said:
The fuel is most likely evaporating out of the bowls. The fuel inlet of the carb should be higher than the fuel level in the carb so it shouldn't be able to drain back, but it is open to atmosphere and likely to evaporate. Check valve will keep it from flowing out of the line, but no more.
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An electric fuel pump should solve this too though, right? Turn the key and let the pump prime the fuel system for a couple seconds before cranking the engine, etc.

I've heard of people putting an electric pump in parallel with the mechanical pump for priming reasons, but I just don't see any reason to keep the mechanical pump at that point, with the possible exception of having to plumb a single pump at the rear by the tank instead of using a priming pump as a crutch by installing in the engine bay.

As you can tell, I like electric pumps. :D
 
An electric pump should surely solve the problem. May just have to wait a short moment to let it fill the bowl of the carb after sitting a long period.

I too would eliminate the mechanical pump and install a QUALITY electric pump. I say that because most cheaper store bought electric pumps are not too reliable and if not mounted just right will burn up/fail the first time it runs dry.
 
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