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Old 06-06-2012, 09:31 PM   #1
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Vapor lock?

I have an 87 YJ with a motorcraft 2150 carb. (1.08 venturi) Before I replaced the carb I was having trouble with what seemed like it was vapor locking. I swapped to the motorcraft and still had the same issue. It runs great until the outside temperature is around 90 degrees and the engine is hot, so to me it seems that it is a vapor lock issue. A buddy of mine told me to plug off the fuel return coming off the fuel filter. I did this and it runs fine but real rich. Changed the jets in the carb and still running rich. Did the TFI ignition uprade also. Once again it runs better, butt still rich. The ford that the carb came from had no type of return, but could this be my problem? Should I hook the return back up and just insulate the fuel lines?

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Old 06-06-2012, 09:34 PM   #2
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Get an electric fuel pump and a pressure regulator. Save lots of time

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Old 06-07-2012, 11:15 AM   #3
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I had the same problem when i did the nutter bypass on mine and switched carbs.

2 choices on eliminating the vapor lock problem.

1. re-route the fuel lines, take the top one around the back of the motor next to the firewall, and the bottom one around the front of the motor next to the radiator.

2. encase the supply line from the pump(top line) with a rubber hose. This is what i did.
Took a 5/8 heater hose and cut a length of it to fitfrom fitting to fitting. that should do it for the vapor lock problem.
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Old 06-07-2012, 02:43 PM   #4
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Originally Posted by 0III0forlife View Post
I had the same problem when i did the nutter bypass on mine and switched carbs.

2 choices on eliminating the vapor lock problem.

1. re-route the fuel lines, take the top one around the back of the motor next to the firewall, and the bottom one around the front of the motor next to the radiator.

2. encase the supply line from the pump(top line) with a rubber hose. This is what i did.
Took a 5/8 heater hose and cut a length of it to fitfrom fitting to fitting. that should do it for the vapor lock problem.
Thanks, I'll give it a shot.
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Old 07-17-2012, 06:47 AM   #5
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Get an electric fuel pump and a pressure regulator. Save lots of time
Where is the best place to install the pump? And forgive my ignorance but the ones I have looked at seem to be set at around 6lbs and say no need for a regulator. Also for my edification, how does this work with the mechanical pump? Does it just keep the pressure constant with out over working the mechanical. Thanks for your help.
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Old 07-17-2012, 10:23 AM   #6
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Where is the best place to install the pump? And forgive my ignorance but the ones I have looked at seem to be set at around 6lbs and say no need for a regulator. Also for my edification, how does this work with the mechanical pump? Does it just keep the pressure constant with out over working the mechanical. Thanks for your help.
The easiest fix is to first try and insulate the fuel line like was said. Then, possibly re-route it if you have to. You probably won't have to. It takes a bit of work to bypass the mechanical pump. Why go that route if it's not a problem.
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Old 07-17-2012, 10:36 AM   #7
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The easiest fix is to first try and insulate the fuel line like was said. Then, possibly re-route it if you have to. You probably won't have to. It takes a bit of work to bypass the mechanical pump. Why go that route if it's not a problem.
I have insulated the fuel line from the mechanical pump to the carb. My issue is that when the temps outside get above 90 degrees and I run her for a while then shut her down she doesn't want to start and there is no fuel in the clear filter. When she cools down fuel comes back into the filter and she will restart normally.
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Old 07-17-2012, 10:56 AM   #8
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that sounds to me like the o-rings in your pump are bad and letting the gas seep past them when its off. basically losing your prime.

the other problem that you have is your carb. it should have enough fuel in the bowl to get it to start long enough for the fuel pump to catch back up.

i had tons of trouble with the MC2150. never stayed in tune. wouldnt hold a constant vaccuum. i switched to a Holley 390cfm, and so far havent had any trouble with it. my mechanical pump keeps up to it just fine.
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Old 07-17-2012, 11:12 AM   #9
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that sounds to me like the o-rings in your pump are bad and letting the gas seep past them when its off. basically losing your prime.

the other problem that you have is your carb. it should have enough fuel in the bowl to get it to start long enough for the fuel pump to catch back up.

i had tons of trouble with the MC2150. never stayed in tune. wouldnt hold a constant vaccuum. i switched to a Holley 390cfm, and so far havent had any trouble with it. my mechanical pump keeps up to it just fine.
Ok this issue only happens on hot days. Would it still be the o-rings on the pump. Not arguing just asking. I have no idea how old the mechanical pump is. The carb did fine during the Winter. Never had any issues. It is an Edelbrock 1406. She acts like she is trying to fire but just dies. And once It cools off the fuel comes back....
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Old 07-17-2012, 01:23 PM   #10
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Might be clogging the in-tank pick up too, once the the tank gets warm enough to loosen up accumulated sludge.
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Old 07-17-2012, 02:23 PM   #11
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Charcoal Canister

Ok, I took a couple minutes and traced the vent line from the tank to the Charcoal canister. It is the only one attached. Should the others be blocked off?
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Old 07-17-2012, 02:55 PM   #12
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Charcoal Canister

Ok, I took a couple minutes and traced the vent line from the tank to the Charcoal canister. It is the only one attached. Should the others be blocked off?

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