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Old 03-29-2005, 03:37 PM
Sgt Rock's Avatar
Sgt Rock Sgt Rock is offline
Grease Monkey
Join Date: Feb 15, 2005
Location: British Columbia, Canada
Posts: 453

I just bought a Mr Gasket electric inline pump to provide a boost with my OEM mechanical pump.
The new one runs 4-7psi, Edelbrock advised me 6.5psi for my set up?
Can anyone give me any hints on the install(never done it before). How do I cut the gas line without blowing up the jeep?! Any other hints before I put my foot into it all would be appreciated.

Sgt Rock
'78 Chero S, sitting under a '90 YJ body. 401, TH400, BW1339 low option, d44 frt with trutrac, d44 rear with aussie lkr, 3.54 gears, 35" ProComp Xterrains, winch, hi lift, spring over conversion for total 8 inches lift. TFI conversion, MSD wires, MSD coil, MSD ign box. Bosch copper plugs at .50 gap. Holley Truck Avenger carb.
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Old 03-29-2005, 04:58 PM
Don S's Avatar
Don S Don S is offline
Gone,But not Forgotten.
Join Date: Feb 06, 2002
Location: Burleson TX
Posts: 5,613

Sgt Rock

... Tubing cutters are fairly safe and spark free. Start with the tank very low on fuel and lift the front as high as you safely can. I park on a hill with the front high and the passenger side and back low and block the tires so it can’t roll.

There are many advantages of using an electric fuel pump on vehicles equipped with carburetors.
Among these are;

... The carburetor float chamber can be primed ready for starting before the engine rotates.
The fuel delivery system can be checked without the engine running. After running out of gas the carburetor can be filled without running down the battery and overheating the starter.

The pump motors can be put on a hidden switch and used as a theft deterrent.
The pump will not leak gasoline into the crankcase.
Fuel can be removed from the tank by the pump.

... One might think that an electric fuel pump is just another electric fuel pump but there is a reason they don’t all look alike or cost as much to manufacture and purchase. Many fall short when it comes to dependability and lasting qualities.

... Putting pump types into categories might help us explain the attributes of each pump.
First lets look at causes a standard mechanical fuel pump to move the fuel. A rotating cam moves a plunger or lever that in turn moves a diaphragm. As the diaphragm moves it will reduce the volume in the liquid chamber and the fuel is forced out.
... There are two spring loaded one way valves in the chamber. One valve prevents the fuel from returning to the tank (input) and the output valve (on the carburetor side) prevents the fuel from returning to the chamber. If ether valve is not operating with a good seal the efficiency of the pump will be greatly reduced.

... A spring is used to pull the diaphragm back out of the liquid chamber and that draws the fuel from the tank. The spring also keeps the rod or lever on the cam. The cam, rod or levers and springs can wear out or break.

... Many models of mechanical fuel pumps can leak fuel into the engine if the diaphragm is ruptured. Adding an electric pump to feed a mechanical pump can shorten the life of the older diaphragms by causing a rupture. The addition of an electrical pump that is not running will slightly impede the flow of fuel to the mechanical pumps.

... There are two basic types of liquid chambers used in the design of electric fuel pumps. One is the similar the mechanical fuel pump described above and can be driven with an SCR, solenoid or electric motor. The other type of pump known as a gyrator is a rotating single cam wheel and driven by an electric motor. Gyrator pumps are used in fuel tanks of most modern vehicles.
Of the electric fuel pump models the gyrator pumps have the best long-term performance.
... The mounting of the electric fuel pumps should be done in accordance with the manufacture guidelines. Mounting them low out of harms way is recommended. In actual practice in the case of 4x4s mounting them in front of the tank can cause problems. As the truck ascends steep angles and requires more fuel for power the pump will be much higher than the fuel level in the tank and not operate at peak efficiencies. Mount the pumps as far as practical from heat sources. Using a filter between the tank and pump protects the pump but restricts the flow to the pump.
Use a rollover valve and switch for safety sake!

... You have two things to look for when selecting an electric or mechanical fuel pump. These are fuel pressure and flow rate such as gallons per minute or hour. Also one must consider the conveance of an electric over a mechanical plus the longevity of the pump and the price.

The requirements for some FSJs are here;

... A fuel pump for a six-cylinder engine should put out 4 to 5 psi and a fuel pump for an eight-cylinder engine should put out 5 to 6.5 psi. Both six and eight cylinder fuel pumps should pump one pint in 30 seconds at idle RPM. These are ‘specs’ for 1981 Jeeps per the AMC TSM.

... The rating of pressure and volume for a pump is at the out put of the pump.
The fuel pump also has to overcome pressure loss in the fuel lines due to friction. The stated pressure/volume at the output of the pump is not what the pressure/volume is as delivered at the carburetor except … A pressure at rest is equal on all sides i.e. fuel not flowing.

My ‘76 Wagoneer with a 401cid Bored .030 with an MC-4350 or its MC-4300 carburetor requires at least an $80.00 pump and prefers the Holley Red Top at over $120.00.

Have a good one and CUL.. Don S..
Sold our 1976 Wagoneer 406, MC4300, TH400, QT, TruTrac, 2" lift, 31x10.50s, duel Optimas,
It’s took us over 161 Colorado Mountain Passes, 3 Jeep Jamboree USAs & 2 Ouray Invasions from 1985 to 2010
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Old 03-30-2005, 12:23 AM
osceola osceola is offline
Master Mechanic
Join Date: Feb 12, 2004
Location: peoples republic of new york
Posts: 791

keep it as close to the tank as possible and below fuel level if you can.tubing cutter good idea .
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Old 03-30-2005, 01:29 AM
Max Power's Avatar
Max Power Max Power is offline
Master Mechanic
Join Date: Sep 25, 2001
Location: Illadelphia PA
Posts: 748

make sure you snip the correct hardline, theres identical looking brake lines running right along with it.

4-7 psi is fine, you don't need a regulator and you certainly don't need your mechanical pump at all, just get a block off plate, throw that POS mechanical pump away and never look back.

I also reccomend a clear plastic fuel filter before the stock 3 nipple one (yes you should keep that metal one and your return line too) so you can instantly rule out (or zero-in on) fuel supply problems.

3 years now on my same cheapy purolator E-pump. (altho I do carry a spare)


ps. theres a whole 'nother discussion regarding "oil pressure light cut-off switches" that I will not go into.

1980 Jeep Cherokee Laredo WT 360/727/208
1980 MBZ Euro 300D 4-speed manual - Oil Squeezer
1984 MBZ Euro 300D 5-speed manual - Oil Squeezer
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Old 03-30-2005, 10:40 AM
JeepsAndGuns's Avatar
JeepsAndGuns JeepsAndGuns is offline
AMC 4 OH! 1
Join Date: Jul 18, 2003
Location: Cullman, AL
Posts: 4,576

I have one on my cherokee. I put it right behind the tranny crossmember, mounted it to where I connect a short peice of hose to the metal line coming off the tank, then a clear plastic filter, another short peice of hose, then the inlet of the pump. I used a small hacksaw to cut the old metal line to the length I needed. Like they said, remove your old mecanical fuel pump. Use a blockoff plate for a big block chevy, I found one at the local parts place for a couple bucks. I put the clear filter before the pump so I can see if there is any gunk coming out of the tank, plus it keeps dirt out of your new pump. I can take pics of where and how I mounted it if you want.
79 Cherokee Chief 401/T18/D20, MPFI fuel injection, hydroboost, otherwise stock.
Future mods: Caddy 500/NV4500/NP205, HP D60 front D60 smooth botom rear, 5.13 gears, 35x12.50's on H1 beadlock wheels. Warn M12000 winch.
93 Wrangler 4.6 stroker/AX15/NP231,SYE,CV, OME 2.5 lift, front hub conversion/big brakes, 31X10.50's Warn M10000 winch.
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Old 03-30-2005, 12:33 PM
Capt murph Capt murph is offline
Grease Monkey
Join Date: Aug 30, 2004
Location: York, PA
Posts: 470

Oh my gosh Don S thanks for that good post. That's just what my J10 6 cylinder needs. I must yank on my starter for 7 seconds then pump the gas to get fuel flowing -after sitting 24+ hrs. I know it is not so good for the starter.
Great tips form other members too. Great forum.
'82 J-10 FSJ 258 4 speed
'02 Liberty
84 Mazda RX7 GSL-SE
Honda 150 scooter
bamboo raft
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