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Old 01-19-2009, 04:22 PM   #1 (permalink)
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Angry AMC V8 Fuel Pump Problems at Angle

I put a 360 in my '85 CJ-7 about 10 years ago. For as long as I can remember, I've always had problems with the cheap ($25) stock mechanical fuel pumps.

Anytime I take it offroad, the darn thing wants to seize up and stop pumping. It seems to happen when I'm at fairly steep inclines the most but has also died during normally driving conditions more than any other part on the engine. I've even had new pumps not work right out of the box!

I've had luck with removing it, letting it cool and then reinstalling but it inevitably happens again. I've been stuck enough times now that I always carry a spare but I'm tired of the pump being my weak link.

Anyone else ever have this problem? Is there any kind of aftermarket mechanical pump worth trying? I was looking at the Edelbrock 1716 but it's pricey ($158 @ summit). How about electric options?

I'm pretty certain it's the pump but I'd be curious to hear any other theories. Thanks.
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Old 01-19-2009, 05:08 PM   #2 (permalink)
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I've been running a $40. Kragen electric for about three years now without any trouble. Their cheap enough that you can carry spares. Mount it on the frame back by the tank.
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Old 01-19-2009, 05:15 PM   #3 (permalink)
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are you sure it's not the carb?
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Old 01-19-2009, 05:15 PM   #4 (permalink)
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Have you plumbed a pressure gauge in the fuel line after the pump so you can see what psi you have? I had a similar problem with my 360 and could not diagnose it, I replaced all the usual suspects with no luck and the motor took a dump on me and ceased all worries.
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Old 01-19-2009, 05:34 PM   #5 (permalink)
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are you sure it's not the carb?
It has a fresh carb on this time around. I assume it's the pump because when I pull the outlet hose to check for fuel, nothing comes out when you crank it.

When I pop a new pump on, it always starts right up.
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Old 01-19-2009, 05:40 PM   #6 (permalink)
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I've been running a $40. Kragen electric for about three years now without any trouble. Their cheap enough that you can carry spares. Mount it on the frame back by the tank.
You don't happen to have a part number or a vehicle make for that pump, do you?
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Old 01-19-2009, 07:06 PM   #7 (permalink)
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Hard to believe it's the pump. Those things are pretty foolproof.
If ya really are losing pressure I look for a hole in the tank side of the fuel line letting the pump suck air (or there is that vapor lock thing). I guess the concentric on the cam could be wore/spinning and not "stroking" the pump but I've never even heard of that happening. In any case an electric pump near the tank should fix it.
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Old 01-19-2009, 07:41 PM   #8 (permalink)
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Hard to believe it's the pump. Those things are pretty foolproof.
If ya really are losing pressure I look for a hole in the tank side of the fuel line letting the pump suck air (or there is that vapor lock thing). I guess the concentric on the cam could be wore/spinning and not "stroking" the pump but I've never even heard of that happening. In any case an electric pump near the tank should fix it.
They've been fool proof for me on every vehicle but this one. It doesn't make sense to me either. I considered vapor lock but figured once I released the pressure in the line and reconnected, it should release any air pockets and start back up.

If there were a hole somewhere downline from the pump, it seems odd that it would work fine under normal driving conditions and then fail offroad (on inclines).

I wondered if somehow the cam lobe wasn't getting enough oil, causing the pump to overheat and cause some kind of temporary failure.

I think I'll try an electric for the hell of it.
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Old 01-19-2009, 07:57 PM   #9 (permalink)
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I guess the concentric on the cam could be wore/spinning and not "stroking" the pump but I've never even heard of that happening.
That's where my thinking was going. The one I pulled off the cam of my 401 was plastic
Cant imagine it not wearing out after a while.
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Old 01-19-2009, 10:02 PM   #10 (permalink)
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I just posted up on another thread about the same issue...
My 360 fuel pump acts the same way, but didnt start until i put the truck avenger 650 on it. My mechanical pump dosen't keep up with fuel consumption. Its completly emptying the bowls. I put a fuel gauge inline after the pump (brand new because the old pump was only moving 4-5 psi) and it is only pushing 4-5 psi. I've decided to just scrap that POS and go electric.

I would also be interested in the part number, or application that $40 kragen pump came from.
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Old 01-20-2009, 07:48 AM   #11 (permalink)
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That's where my thinking was going. The one I pulled off the cam of my 401 was plastic
Cant imagine it not wearing out after a while.
All the ones I've seen were steel but one had a deep groove worn in it, probably 1/16 ". There could be problems in the tank, filter sock plugged, hole in the pickup line, chunk of rust stuck in the pickup.
I had my tank down, checked all lines and blew them clear but that did nothing for me. For me it was when it was hot it just seemed to pump no fuel. I replaced the entire ignition system with a gm hei style distributor but no luck again.

Good luck!
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Old 01-20-2009, 07:48 AM   #12 (permalink)
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That's pretty strange. I would definitely look at the cam lobe. I've swapped in two of these motors, and I've never even bothered to LOOK at the fuel pump, much less replace one. Granted, I've always had a MC 2100 carb, not a big 4bbl.

On the incline you could be draining the bowl, and not pumping enough fuel through the lines. ie: on flat ground you aren't holding Wide Open Throttle long enough to drain the full bowls, whereas on an incline the bowls can't hold as much fuel as they are supposed to and they empty out faster under WOT conditions.
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Old 01-20-2009, 09:54 AM   #13 (permalink)
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I would also be interested in the part number, or application that $40 kragen pump came from.
I think the problems are a combination of vapor-lock and pump over-heating.

I just so happen to have an old electric pump sitting in my shop that I never used (still in the box w/ instructions).. I think it's about 12+ years old but I'm going to try it out.

After doing some reading online I think something like this should work. The one I have is made by a company called AG Amgauge. Part number is EP12S. It's identical to the Cube Facet / Purolator brand which is sold at most major retail parts stores (Napa, CarQuest, PepBoys, Checkers).

It's a multi-application, solid state electric pump that should work on most carb'd engines. According to Edelbrock, your pressure should never exceed 6.5 PSI. I'm thinking the 4-7 PSI version would be perfect. Here are some part numbers/prices that should work for most 6 & 8 cylinder applications:

High Performance ($115+/-)
Kit Part # FEP87SV or PRO87SV | Pump Part # 476087E (4-5.5 PSI / 32 GPH)

Cube Solid State ($45+/-)
Kit Part # FEP12SV or PRO12SV | Pump Part # 40106 ( 4-7 PSI / 32 GPH)

Posi-Flow ($45+/-)
Kit Part # FEP06SV or PRO06SV | Pump Part # 60106 (4-7 PSI / 32 GPM)

Last edited by sleeper-7; 01-29-2009 at 03:54 PM.
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Old 01-18-2010, 05:46 PM   #14 (permalink)
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Quote:
Originally Posted by sleeper-7 View Post
I put a 360 in my '85 CJ-7 about 10 years ago. For as long as I can remember, I've always had problems with the cheap ($25) stock mechanical fuel pumps.

Anytime I take it offroad, the darn thing wants to seize up and stop pumping. It seems to happen when I'm at fairly steep inclines the most but has also died during normally driving conditions more than any other part on the engine. I've even had new fuel pump not work right out of the box!

I've had luck with removing it, letting it cool and then reinstalling but it inevitably happens again. I've been stuck enough times now that I always carry a spare but I'm tired of the pump being my weak link.

Anyone else ever have this problem? Is there any kind of aftermarket mechanical pump worth trying? I was looking at the Edelbrock 1716 but it's pricey ($158 @ summit). How about electric options?

I'm pretty certain it's the pump but I'd be curious to hear any other theories. Thanks.
By the way, who knows where I could possibly get some nice & cheap stock mechanical fuel pumps.

Last edited by furblog; 01-19-2010 at 06:20 PM.
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Old 01-18-2010, 06:55 PM   #15 (permalink)
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I had this same think on my 401 I replaced the full pump ascentric and that did not fix the problem. So I put a block off on the motor and went with an electric pump and never looked back.

Just ask for a multi appication pump at kragen or napa for a carb.
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Old 01-19-2010, 09:49 AM   #16 (permalink)
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It has a fresh carb on this time around.
So what? Any carb can flood on a steep incline.

What carb is it? Many are pre-disposed to flooding when pointed uphill.
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Old 01-19-2010, 10:13 AM   #17 (permalink)
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I just posted up on another thread about the same issue...
My 360 fuel pump acts the same way, but didnt start until i put the truck avenger 650 on it. My mechanical pump dosen't keep up with fuel consumption. Its completly emptying the bowls. I put a fuel gauge inline after the pump (brand new because the old pump was only moving 4-5 psi) and it is only pushing 4-5 psi. I've decided to just scrap that POS and go electric.

I would also be interested in the part number, or application that $40 kragen pump came from.
If you are emptying you bowls, it's not a pressure problem but a volume problem. 4-5 psi is fine for a carb. You should do a pump volume test to see what your pump is moving.
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Old 01-19-2010, 03:32 PM   #18 (permalink)
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If you are emptying you bowls, it's not a pressure problem but a volume problem. 4-5 psi is fine for a carb. You should do a pump volume test to see what your pump is moving.
Travis..
X2 on this you need more gph. flow on the pump.
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Old 01-19-2010, 05:13 PM   #19 (permalink)
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Also, if your jeep ever sat for a long while during its life, check the pick-up tube in the tank for restriction. I had a Dodge truck that spent about 5 years sitting. The fuel had dried in the pick-up tube and restricted the flow. It would idle, but when I started driving it would run out of gas about 2 blocks away. It would idle all day if you let it. I pulled the pick-up and cleaned out with a wire. Problem solved, ran like a bat out of hell. You need to check your entire system when trying to diagnose an older vehicle.
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Old 01-19-2010, 07:42 PM   #20 (permalink)
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We had an identical problem with our '79 bronco. It had a 400 and would die randomly. We put a new mechanical pump on it and continued to have the same problem. We found out that the eccentric on the end of the cam gear was probably loose (can't remember if the 360 is bolt on or not). My husband ended up putting an electric fuel pump in line and eliminated the problem.

Of course it continued to die on steep inclines despite the carb having the offroad kit on it... ended up swapping it for our cherokee.
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