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Unread 09-28-2013, 12:45 PM   #1
bligon64
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electric and mechanical fuel pump

Ive read in a few places on the internets about people who use their mechanical pump for everyday driving, but who also have an electrical pump in-case things get sticky and their mechanical pump can't send enough fuel. I was thinking of doing this to make my jeep more reliable, so if I decide to make it a crawler in the future I'll already have that done.

i have two questions about this

1) what are people's opinions about this?

2) How would i go about doing this? Would put the electric fuel pump in the gas tank, and then run the same line to the mechanical fuel pump, or would i have to somehow run two lines or something?

Thanks for the input/ help

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Unread 09-28-2013, 01:01 PM   #2
Spieg8
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If you currently are running a mechanical pump, I assume you have a carbureted motor. If you get an electronic pump, it will need to be of the low pressure variety. I'm not aware of any low pressure fuel pumps that go inside the gas tank (all I've seen in tank are high pressure pumps for fuel injected engines).

No idea how or why you would add an electric pump in line with a mechanical pump... I'm sure someone else will explain how that works.
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Unread 09-28-2013, 01:12 PM   #3
zbd74
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I run a stock mechanical & Holley red fuel pumps w/ my amc 401 (Holley 0778 carb). Just plumbed in-line, coming off of a RCI fuel cell, wired to a switch, seems to work fine for me
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Unread 09-28-2013, 02:51 PM   #4
bligon64
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zbd74, when you are driving do you run the electrical always, or only when the engine stutters?
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Unread 09-28-2013, 02:53 PM   #5
CSP
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An engine isn't going to stutter from a mechanical pump not keeping up. A mechanical pump is either going to work or it isn't.

OP I think you're chasing a problem that won't exist.
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Unread 09-28-2013, 09:46 PM   #6
zbd74
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Quote:
Originally Posted by bligon64 View Post
zbd74, when you are driving do you run the electrical always, or only when the engine stutters?
The only time I don't run it is when I forget to turn it on, it reminds me though when not on. I've been caught w/o it on on some climbs that cause a temporary panic on my part

The electric pump does cause the mechanical to starve for fuel, thus the shutdown when the electric is not on. But again mostly on a hill if I forget to turn it on, other wise on down hills or flats the mechanical works by it self no problem
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Unread 09-29-2013, 09:20 AM   #7
WindKnot
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^^^This was my experience as well.^^^

When I first got my Jeep that's how it was set up as well, even down to having to turn on the electric fuel pump. I figured out that it was best and safer to just eliminate the mechanical pump. (If you have a 258, a fuel pump cover plate for a big block Chevy works perfect.)

zbd74,

You might want to consider rewiring your fuel pump through an oil pressure switch. It's safer in the event you get into a wreck. Wired through the oil pressure switch, it won't run if the engine is stalled with the ignition on. It will run only when you have oil pressure. The switch does allow it to run while you're cranking the starter though so your engine can get fuel when starting. Other wise if you hit a tree or another car, unless you turn that pump off, it could be pumping gas into a fire. (Something to think about)

I set mine up like this:



Some will argue that the brass wasn't a good idea and that galvanized steel is more rugged, and that Teflon tape can be an insulator and ruin continuity for your ground. That may be true, but so far after some years it hasn't been a problem for me.

this can be done for less than $30.
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Unread 09-29-2013, 04:49 PM   #8
zbd74
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Quote:
Originally Posted by WindKnot View Post
^^^This was my experience as well.^^^

When I first got my Jeep that's how it was set up as well, even down to having to turn on the electric fuel pump. I figured out that it was best and safer to just eliminate the mechanical pump. (If you have a 258, a fuel pump cover plate for a big block Chevy works perfect.)

zbd74,

You might want to consider rewiring your fuel pump through an oil pressure switch. It's safer in the event you get into a wreck. Wired through the oil pressure switch, it won't run if the engine is stalled with the ignition on. It will run only when you have oil pressure. The switch does allow it to run while you're cranking the starter though so your engine can get fuel when starting. Other wise if you hit a tree or another car, unless you turn that pump off, it could be pumping gas into a fire. (Something to think about)

I set mine up like this:



Some will argue that the brass wasn't a good idea and that galvanized steel is more rugged, and that Teflon tape can be an insulator and ruin continuity for your ground. That may be true, but so far after some years it hasn't been a problem for me.

this can be done for less than $30.
Excellent feedback & suggestion, I'll look into your suggestion or figure something out...Thanks

A concern is there are some drops & climbs that are so steep that oil pressure actually drops off, I wonder how your configuration would be in those situations?
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Unread 09-29-2013, 04:53 PM   #9
bligon64
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Windknot, thanks for the info, looks like thats the next thing after i get my engine rebuilt.
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Unread 09-29-2013, 06:02 PM   #10
WindKnot
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Hasn't been a problem for me yet, and I off road frequently (Steep grades all the time, rock climbing, no)

All it needs to run is 5psi.

I'm not a genius, someone much smarter than me thought of it long before I did. NAPA sells a switch and Holley even markets one. The switches are also used for manifold heaters and idiot lights.

This may help: http://www.jeepforum.com/forum/f8/ho...l-pump-607282/
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Unread 09-30-2013, 01:38 AM   #11
BagusJeep
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Quote:
Originally Posted by bligon64 View Post
Ive read in a few places on the internets about people who use their mechanical pump for everyday driving, but who also have an electrical pump in-case things get sticky and their mechanical pump can't send enough fuel. I was thinking of doing this to make my jeep more reliable, so if I decide to make it a crawler in the future I'll already have that done.

i have two questions about this

1) what are people's opinions about this?

2) How would i go about doing this? Would put the electric fuel pump in the gas tank, and then run the same line to the mechanical fuel pump, or would i have to somehow run two lines or something?

Thanks for the input/ help
You have a standard 258, the mechanical pump will keep up with it.

I have both, on puthijeep electric and Bagusjeep mechanical. The mechanical wins as there are no electrics to give up.

The electric pump sits on the fender near the oil pressure sender and clicks away to itself. It feeds the Weber 38DGMS through a 3 way filter and tank return, which delivers high volume low pressure gas.

The electric pump could do with a spare, of the same model sitting alongside waiting for the connections to be swapped over.

My mechanical has a spare electric one on a bracket next to it, if the meachnical does fail I can swap over connections. Hasn't yet.




ntrodicng a low pressure fuel pump
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Unread 09-30-2013, 09:45 AM   #12
DougE
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Installing a low pressure electric fuel pump near the tank would pretty much eliminate the possibility of vapor lock.
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Unread 09-30-2013, 11:52 AM   #13
AFRd_CJ5
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Quote:
Originally Posted by bligon64 View Post
Ive read in a few places on the internets about people who use their mechanical pump for everyday driving, but who also have an electrical pump in-case things get sticky and their mechanical pump can't send enough fuel. I was thinking of doing this to make my jeep more reliable, so if I decide to make it a crawler in the future I'll already have that done.

i have two questions about this

1) what are people's opinions about this?

2) How would i go about doing this? Would put the electric fuel pump in the gas tank, and then run the same line to the mechanical fuel pump, or would i have to somehow run two lines or something?

Thanks for the input/ help
What were the reasons given for the mechanical pump not being able to "send enough fuel"?
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Unread 09-30-2013, 12:07 PM   #14
WindKnot
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For myself, I don't know. But I do know that the PO put a huge oversized Carter AFB on my 258 and it sucked gas down like I like my beer!

It would barely run with just the mechanical and it would simply starve if I accelerated. I never bothered to diagnose; I just got rid of the mechanical. Trying to second guess why the PO did what he did would be a second career for me. With this guy it could've been he was just too lazy to pull it, or he couldn't find or was too cheap to buy the right pump cover plate.

He definitely made my life interesting for a while, that's for sure.
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Unread 10-02-2013, 10:01 AM   #15
bligon64
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I don't remember offhand what the listed reasons I was thinking for like getting air into the line before the pump, so the pump stopped and stuff like that.
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