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Unread 04-26-2004, 11:35 AM   #1
TampaXJ
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Stock fuel psi for electric fuel pump???

Decided the crappy mechanical pump has to go...but to get an electrical i need to know what the stock fuel psi is for the I6 on an 82cj7. Looked on the stock carb and cant seem to find a psi # anywhere.

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Unread 04-28-2004, 10:56 AM   #2
CJp2401
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I just switched my Mechanical to electric. I was told that the stock PSI on a Carter was 4-5psi. Of course, I was told this at the AutoMoan, so take that for what it's worth (however I think it is correct).
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Unread 04-28-2004, 12:02 PM   #3
MR.CJ-7
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4-5 could be correct. I was told 7 for my 304 with MC2100 carb. I was thinking about an electric, but decided I didn't really need one.
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Unread 04-28-2004, 12:14 PM   #4
CJp2401
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I would have kept the mechanical one, however it failed. When I went to replace it, I found the cam arm was worn so bad that it would not lift the pump mechanism anymore and deliver fuel. I was kind of forced into the electric one, unless I wanted to replace the cam (which I didn't).
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Unread 04-29-2004, 12:12 PM   #5
MR.CJ-7
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Ahh, bad deal for you.

I found some decent pumps through summit.com that were in the correct pressure range for me. It might be worth a look for you.
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Unread 03-09-2010, 02:07 PM   #6
dkronour
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Not to steal your thread but i just towed my cj home. Its got a weber carb and is on its third electric fuel pump. I didnt cap of the old fuel pump so im trying to figure out if i need to go back to mechanical or figure out a different electric setup as I am NOT replacing another electric pump. Any help would be appreciated.
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Unread 03-09-2010, 02:46 PM   #7
texasimport
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Quote:
Originally Posted by dkronour View Post
Not to steal your thread but i just towed my cj home. Its got a weber carb and is on its third electric fuel pump. I didnt cap of the old fuel pump so im trying to figure out if i need to go back to mechanical or figure out a different electric setup as I am NOT replacing another electric pump. Any help would be appreciated.
The first thing that I ask is are you running your fuel pump to include a return line?
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Unread 03-10-2010, 11:53 AM   #8
dkronour
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No return line. And the pump is in the engine bay, not near the tank.
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Unread 03-10-2010, 12:21 PM   #9
Mike Romain
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I think the stock mechanical pump is the better one for the system. It is an on demand kind of pump that puts out more as the rpm go up.

The electric pumps need a return line or they can cavetate and burn up, the mechanical pumps use a return line to prevent vaporlock, they don't need it. On a hot shutdown the return line off the top of the gas filter lets any gases created blow back to the tank so the gas line can't vaporlock.

Electric pumps also can fry from just running out of gas and the Jeep gas tank doesn't have the reservoir that electric tanks have to prevent it running dry on corners.
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Unread 03-10-2010, 12:28 PM   #10
dkronour
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So buy a mechanical? My only question is why would someone have switched to electrical? Im worried if i go back to mechanical i will slowly find out why someone switched it.
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Unread 03-10-2010, 09:05 PM   #11
AlbuqHenry86cj7
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Not to hijack but since it was mentioned, the fuel filter with the bypass line. What keeps all the fuel from going down the return line. Is there some kind of pressure regulator or something in there? It was said the return line should be on top, but on mine the the carb sits higher than the whole filter so eventually the carb line gets higher than the return anyway. What am I missing? I havnt had starvation problem but was just wondering how the system works- Thanks Henry
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Unread 03-11-2010, 06:00 AM   #12
Mike Romain
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Quote:
Originally Posted by dkronour View Post
So buy a mechanical? My only question is why would someone have switched to electrical? Im worried if i go back to mechanical i will slowly find out why someone switched it.
Some folks think newer is better? Later ones use electric so??? Besides the tank issues, there are the electrical issues of needing an emergency cut off so when the engine stops, the pump stops in case of an accident or stall.

The 1981 mechanical pump that is on mine right now still works perfectly.

They can wear out though....
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89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 03-11-2010, 06:05 AM   #13
Mike Romain
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Quote:
Originally Posted by AlbuqHenry86cj7 View Post
Not to hijack but since it was mentioned, the fuel filter with the bypass line. What keeps all the fuel from going down the return line. Is there some kind of pressure regulator or something in there? It was said the return line should be on top, but on mine the the carb sits higher than the whole filter so eventually the carb line gets higher than the return anyway. What am I missing? I havnt had starvation problem but was just wondering how the system works- Thanks Henry
Yes, the return line has a metered hole in it so it holds backpressure to the center outlet.

Your filter really should sit just slightly higher than the inlet to the carb, that is why they have that U shaped piece of gas line coming out of the carb, to set the filter at the right height.

Basically on a hot shutdown, the vapors produced get blown back to the tank off the top of the filter so the gas line doesn't get vaporlocked. This is what the return line is for on a carb'ed engine.

If you have issues with it, it will cause 'long' starts when cold and sitting. The gas can siphon back to the tank vaporlocking the gas lines if the return line isn't higher than the center line, not sure what happens when it is lower than the carb.
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89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
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Unread 03-17-2010, 12:20 PM   #14
dkronour
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Okay i found out i towed home for no reason as jeep ran fine last night. Leading me to believe once it gets hot it vaporlocks??? My instinct is to not replace another electric pump and somehow get a return line setup. So what do i need? Do i just buy a fuel filter with an extra outlet and run that back to tank with rubber hose? do i need anything else?
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Unread 03-17-2010, 12:40 PM   #15
Mike Romain
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Quote:
Originally Posted by dkronour View Post
Okay i found out i towed home for no reason as jeep ran fine last night. Leading me to believe once it gets hot it vaporlocks??? My instinct is to not replace another electric pump and somehow get a return line setup. So what do i need? Do i just buy a fuel filter with an extra outlet and run that back to tank with rubber hose? do i need anything else?
With no return line on it, the pump can cavitate which can allow it to over spin and overheat and die. This will also happen if you take a corner with a low gas level in the tank. FI tanks are built with a baffle area in them that gets filled up from the return line to prevent this. There is a reason all FI systems with electric pumps have a return line eh.

Stock your jeep has a steel return line and a dual outlet filter to prevent vaporlock on a hot shutdown. The filter needs to be sitting level with the center outlet to the carb and the top outlet to the return line. This way any vapors produced on a hot shutdown get blown off the top of the filter back to the tank.

You need to find out what is left of the stock lines. The gas tank has a vent line that leads to a charcoal canister also. If you have this blocked or the canister not hooked up, then the gas tank will get a vapor lock on 'it' starving the engine for gas to the point of plain running out of gas. This can/will also burn up an electric pump. It won't kill a mechanical pump, but you will still run out of gas.
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86/00 CJ7 Laredo, 33x9.5 BFG AT's, 'glass nose to tail in '00, 'New' frame,wires and plumbing in '09. Carter BBD Carbed 4.0 HO in '10.
89 YJ Renegade. BBD Carbed 4.0 HO. Locked front and rear with 33x9.5 BFG AT's
Some Canadian Bush Jeep Runs and Build Photos: http://mikeromainjeeptrips.shutterfly.com (10 new albums added Sept 16/10)
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