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post #1 of (permalink) Old 12-13-2000, 06:33 PM Thread Starter
 
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wiring electric fuel pump

I had an electric fuel pump just lying around so I decided to try to hook it up in my 78 CJ-5 with a 258 6cyl engine and carter YF 1BBL carb. The reason I tried this is that when I park my Jeep for more than a day the fuel all drains back down the line and it is a pain to start back up again, and I had the pump so why not try it out. My question is where or how to wire this up. I found a couple of circuits that are 12 volts when the key is in the run position, but they don't have power when you crank it. I can't find any circuits that have both 12 volts in the run and crank position. This is a pretty spartan Jeep, so there aren't any extra electrical accesories on it's fuse block. I thought of wiring the hot lead directly to the battery and putting a HD switch to turn on the fuel pump, but I'd rather find a better way to do this. I set the fuel pressure on the pump at 8psi is this right? Also I'd like to keep the old mechanical fuel pump in place in case the electric fails. Can I do this, or does the mechanical pump use the fuel it pumps as a coolant/lubricant etc? Anyone run an electric pump in their CJ before or am I better off leaving well enough alone? I plan on swapping in a MC 2100 later this winter and I believe CJJeepercreeper said he ran his at like 2.5 psi off road is that correct for that carb? Thanks for any help!!

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post #2 of (permalink) Old 12-13-2000, 09:29 PM
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Re: wiring electric fuel pump

Try supplying the 12volts for the pump from the 12 volt circuit that feeds the oil pressure switch, it's hot in both start and run igniton modes.

8 psi is excessive...put it down to 2.5 to 3.0 psi and run the excess back to the tank.

Remove the mechanical fuel pump, shaft and bearing, bag it and throw it in your parts box. It's only a couple of bolts to remove and reinstall. Bear in mind that the diaghram will dry out... and it could pinhole or crack. A year from now it may not be good anylonger.... I'd not bet on it.

Happy Holidays and Safe Jeepin'

Larry
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post #3 of (permalink) Old 12-14-2000, 06:52 AM
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Re: wiring electric fuel pump

You need to run power to it through an oil pressure switch. This to ensure that the pump will not keep running if the engine stalls. The pump could force seat off in carb and fill engine with raw gas. Then also run power to pump from the key switch for starting only. Once engine starts this source will stop and pump will run from power through oil p. switch. Unscrew oil pressure sender on rear right side of engine. Buy some 1/8" pipe fittings(like a "T" and a couple of elbows and nipples) in either brass or iron to add another switch with a low p. limit. Of course you could just put a momentary switch on dash that you would have to hold while starting engine. My Jeep has the same problem, and it sits on an angle helping fuel to drain back. I just pump the gas pedal frantically and keep cranking.

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post #4 of (permalink) Old 12-14-2000, 12:56 PM
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Re: wiring electric fuel pump

[img]/wwwthreads_images/icons/tongue.gif[/img] I'm with Jimmy Z on this one. There is nothing like being in a crash, the engine is dead, but you can hear the pockety-pockety-pockety of the fuel pump as it sends gas up to the damaged engine to build a nice big fire to toast you. We had a case here locally, where a VW bus coughed up a fuel hose in the drive-thru at McDonalds, the engine quit, but the key was left on. The fuel pump proceeded to dump gas on the hot engine and they had some unexpected flame broiled burgers. When you wire this in, you will need a relay, or else the oil pressure circuit will keeep the starter running. If your Jeep drains back, isn't that a fuel pump check valve problem?[img]/wwwthreads_images/icons/crazy.gif[/img]

CJDave
Quadra-Tracs modified While-U-Wait by the crack moonguy[img]/wwwthreads_images/icons/wink.gif[/img] Quadra-Trac Team.[img]/wwwthreads_images/icons/tongue.gif[/img][img]/wwwthreads_images/icons/smile.gif[/img]
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