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Unread 07-19-2008, 04:15 PM   #1
NHwheelin
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Swapping a mechanical fule pump for an electric??

I am running a 304 with a mechanical fuel pump. I heard that I can bypass this with an electric one and gain some off road performance. I was wondering if this were true? If so then what psi would I look for on the fuel pump. I ask this because something real starnge happened today while I was out. I was doing some light wheeling when it stalled. I couldnt get it started for the life of me. I wasnt getting fuel to the carb. I took the fuel pump off, hooked up the feed line and pumped it by hand till fuel was squirting out. After reinstalling the fuel pump and lines I tried to start my Jeep again and it wouldnt start. I pulled the fuel filter off and there was nothing coming through the lines. So I pulled the fuel pump off yet again pumped it by hand, reconnected all the lines, and this time I tried syphoning the gas through the fuel filter. I heard a gurgling sound in the fuel pump. I turned the jeep over a few times and it fired right up. Go figure. I have a MC 2100 for a carb also. I dont want to go through this again .

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Unread 07-19-2008, 04:44 PM   #2
BESRK
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You won't notice any appreciable gain in performance between a mechanical pump and an electrical pump offroad. Sounds to me like the vehicle might have been low on fuel. When you started getting off camber, it starved the fuel pick up in the gas tank and the engine died. It would've done the same thing with an electric pump. I try to make sure I top off the tank before I go wheeling to avoid fuel starvation issues.

Now, if the mechanical pump is going bad, you may want to replace it. Also might do the "once over" on all your fuel lines to make sure everything is in order.
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Unread 07-19-2008, 08:23 PM   #3
jfwireless
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I switched to an electric fuel pump to eliminate all the hard starts after not running the jeep for a few days, really hepled when I did that. As for a performance improvement, no it will not happen.

Jim
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Unread 07-20-2008, 07:22 AM   #4
JeepHammer
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I'm going with BESRK on this one...
Sounds logical, and what I was thinking when I was reading the OP.

You might change the filter too, and keep in mind there is a strainer sock on the fuel pump that if it comes off, you will suck air in the tank sooner than you normally would.

Mechanical pumps are more reliable than electric pumps, and so better for off roading.
No wiring, no relays or switches, no problems if the alternator quits working...

I use a small electrical pump for fuel transfer from one tank to another, from gas can to tank, or tank to can, and I have fittings to use in the event that my mechanical pump quits...
But I wouldn't switch over to an electric pump for normal wheeling...
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Unread 07-20-2008, 09:12 AM   #5
CJ Chet
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I have an electric pump on my 258/Weber 38/38, and I agree with no performance increase. But, it sure does start easier, and the idle is smooth as a babies bottom with a more precise and constant fuel pressure. I also installed mine in such a way that I can re-install the mechanical pump in about ten minutes, using the same fuel lines. It's mounted to the fuel pump block-off plate.
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Unread 07-20-2008, 11:45 AM   #6
jfwireless
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Mechanical pumps are more reliable than electric pumps, and so better for off roading.
No wiring, no relays or switches, no problems if the alternator quits working

JH, this is one item I might not agree with you on. In the initial first six years (bought the cj new in 76) I had to replace my mechanical pump three times, after changing over to the electric pump, it ran for over 20 years no problem and ran that way until I converted to TBI. Sold that pump after removing it, that was a good investment. The install didn't need a relay, it just ran off accessary power with no issues, of course I did fuse it for safety. I saved a few starters with that electric fuel pump and really enjoyed the quick starts.

Jim
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Unread 07-20-2008, 06:16 PM   #7
NHwheelin
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i plan on keeping the mechanical pump but i am tired of killing the battery trying to get this thing fired up. im not sure if i have a problem with the carb or what. i was told that since the electric pump is a constant flow that when going off camber i wouldnt stall out as much. i guess it sounded logical. i plan on upgrading my ignition and doing the team rush as soon as i recover from the tranny and axle shaft swap.
so if i were to put an electric pump in how much psi would i need it to pump? like 4-6psi?
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Unread 07-20-2008, 06:59 PM   #8
jksull
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Quote:
Originally Posted by CJ Chet View Post
I have an electric pump on my 258/Weber 38/38, and I agree with no performance increase. But, it sure does start easier, and
It seems alot of people have and are having trouble starting with weber carbs. Including me. I change to a Holly and it can set for a week and one pump it lites. and continues to run. The weber would start and die, once the bowl was ful it would run fine. Something with the way they are made?
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Unread 07-20-2008, 07:27 PM   #9
JeepHammer
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Quote:
Originally Posted by jfwireless View Post
JH, this is one item I might not agree with you on. In the initial first six years (bought the cj new in 76) I had to replace my mechanical pump three times,...
WOW! Sounds like you had bad luck with pumps!
I usually get the 'Premium' brand of pump and I'm usually OK for 10 years or so...

Quote:
...after changing over to the electric pump, it ran for over 20 years no problem and ran that way until I converted to TBI. Sold that pump after removing it, that was a good investment.
You sold a 20 year old electric pump?
Didn't you feel bad about selling someone a 20 year old pump?

Quote:
The install didn't need a relay, it just ran off accessary power with no issues, of course I did fuse it for safety.
"Safety" would have been a 'Roll Over' switch, an 'Engine Kill' switch to shut the pump off if the engine stopped running, and all that is MUCH easier achieved if you use a Relay.

I sure don't want one pumping fuel if the vehicle is up-side-down or I'm wrecked and the engine has stopped running but I haven't been able to shut the key off!

Quote:
I saved a few starters with that electric fuel pump and really enjoyed the quick starts.
I could use that myself.
After mine sets a week or so, I need to crank on it for 15 or 20 seconds to get it started...

With my electric fuel pump running parallel to the mechanical pump, I can just flip the switch to prime the carb, but I normally forget the first time after it's been sitting a while,
And after that, it starts really easy and I don't need it...

With dual batteries, I'm probably not being that hard on the starter, but I'm sure the engine could use some oil pressure sooner and less dry cranking, even if it is only once in a while!

I still think the mechanical is more trust worthy in an off road situation, but like I said, I have an electric as a back-up and transfer pump.... Just in case!
Outside the tank electric pumps are just too cheap and easy to find not to have one for a back up!
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Unread 07-20-2008, 07:51 PM   #10
jfwireless
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Well I agree a roll over switch on any electric fuel pump is a must. But the Ford Pinto had a roll over switch, the only problem with the Ford Pinto is they just caught on fire without rolling over.

I did sell the electric pump, but not for very much, so I do not feel very bad, I told them it was twenty years old, dam, I wish I was only twenty years old. that just somehow does not seen so old now, JH, I bet you agree on that one.

But my main point was the electric pump was just very reliable, but having both pumps in a true wheeler like you have is a must and a great idea.

I am going to a very nice U-Pull-It yard over in West Palm Beach (cheap too) soon to get a Ford roll over switch for my new 1990 YJ TBI tank I am installing in my CJ. The YJ tank has the pan in the bottom to keep from air locking the internal pump, and the return line fits into a grommet and returns the fuel beneath the pan, very nice. The YJ 87-91 TBI internal pump can deliver 40 GPH at 15 lbs of fuel pressure, the 89-90 Chevy 1500 truck 350 internal TBI pump delivers 35 GPH at 11 pounds of pressure, so I am impressed with the TBI YJ internal pump being so robust for a 2.5L engine. Replaced the return line with a 5/16 inch line, the main fuel line is now 3/8 inch. So hopefully that will solve my fuel regulation pressure issues.

I know many do not like the internal fuel pumps, but there is just something about that external pump being mounted just a foot or so away from the exhaust system that bothers me. Hopefully my internal pump will be as reliable as my external low pressure pump was.

Jim
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Unread 01-04-2010, 04:25 AM   #11
jolly_rogger
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what make model and year of car comes with a good low presure electric pump that would be easy to score form a self service auto wrecker ? will i need a fuel pressure reg ? Im running a amc 304 v8 with a motorcraft 2100
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Unread 01-04-2010, 04:52 AM   #12
mmerlina
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I have a standard mechanical fuel pump and an mc2100. It was almost 0 degrees here for the past couple days and my jeep starts right up every time..

My system is, open the driver's door, reach in with my hand and pump the pedal about 4 times. Turn the key, usually 1-2 cranks and it's running. I have a manual choke also and normally I don't even need to use it. Then I walk away and let it warm up.

I've never done anything special to fuel lines or my ignition.. so I'm not sure why I have such an easy time starting mine when others are fighting it.. but I just figured this might help you see that you can get an easy start from a mechanical pump also..

Good luck.
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