fuel pump pressure test - 1985 AMC150 - how? - JeepForum.com

 
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post #1 of 11 Old 04-06-2013, 10:00 AM Thread Starter
VanHermanator
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fuel pump pressure test - 1985 AMC150 - how?

I suspect my fuel pump may be bad. I've got a pressure testing gauge. Is there a test port on a stock setup for 1985 with Carter YFA and AMC150? It seems like I'll need to install a temporary t-fitting because I can't find it. Thanks - Mark.

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post #2 of 11 Old 04-06-2013, 04:15 PM
Caish
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just use a piece of rubber hose and unhook the line from the carb.
Slip on the rubber line on the end of the fuel line and crank it over
and see what your pressure is.
Could also just put the end of the hose in a coke bottle and
crank it over and watch how much its flowing.
Pretty simple check.

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post #3 of 11 Old 04-06-2013, 05:06 PM Thread Starter
VanHermanator
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Thanks. I've confirmed the pump is working, but suspect it's not pumping enough pressure as it 'cuts out' upon full throttle. Before I start in on the electrical system, this is my last fuel system test. I thought that it had to be running to test for adequate pressure?
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post #4 of 11 Old 04-06-2013, 05:27 PM
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Fuel filter good? A plugged filter will start to starve an engine under load.. full throttle, going up hill...etc. Mechanical fuel filters generally work or they don't.

'80 CJ5 w/AMC360, T176, D44 w/Detroit 4.56, RE 4" YJ lift and 35s..



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post #5 of 11 Old 04-06-2013, 05:35 PM Thread Starter
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I expect so. I swapped it out too, and made sure that the outlet line back to tank was on top. It idles fine, but upon full throttle it chokes and will die unless I let up. Checked for vacuum leaks and can't find any. I just had the carb professionally rebuilt so I expect it's good. At this point all I can think of before changing distributor, coil is confirming that the fuel pump is good. I would have figured it to be a yes/no thing too, but some of the forums talk about bad ones from the store. As I also recently replaced mine I figured I'd rule that out too.
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post #6 of 11 Old 04-06-2013, 05:47 PM
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What caused you to have the carb rebuilt? Was it doing the same thing before the carb was rebuilt.. or did it start after the rebuilt carb was reinstalled?

'80 CJ5 w/AMC360, T176, D44 w/Detroit 4.56, RE 4" YJ lift and 35s..



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post #7 of 11 Old 04-06-2013, 05:55 PM
Caish
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how much pressure did you have?
Carbs generally only need 5 to 7 psi, and your good.
If its starving for fuel at higher RPMs you could have a weak
spring in the fuel pump and its actually floating on the cam,
much like a valve float, but to be honest I've never seen it
happen....

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post #8 of 11 Old 04-06-2013, 06:49 PM Thread Starter
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Just bought the Jeep last year and it had not run for a couple of years, so after draining the fuel, replacing the fuel pump and filter, it still wouldn't start up, other than briefly when I sprayed carb-start down the throat. She fired up straight away after the rebuild which made me pretty happy. It's only got 140,000 kms on it btw. Pretty nice find! Anyways, now I just can't give it a good amount of gas without bogging down and sputtering. Not sure what else to check other than starting into the electrical. The fuel pump test seemed pretty easy until I couldn't find a test port. Am I destined to look into the electrical system now? Thanks for your replies.
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post #9 of 11 Old 04-06-2013, 06:59 PM
Caish
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Sounds like the accelerator pump is not moving enough fuel from what you just described.
Try opening the throttle very slowly so the venturis have time to react to increase in flow.
If you can do this, and it is smooth, now look in the carb and see if you have two streams
of gas squirting when you open the throttle by hand.
If not you have an accelerator pump issue in the carb.

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post #10 of 11 Old 04-06-2013, 07:14 PM
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I had a brand spanking new Fram fuel filter that wouldn't let me get over about 1,200 RPM one time. Dropped in a NAPA Gold filter, and it ran fine.
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post #11 of 11 Old 04-22-2013, 06:36 PM Thread Starter
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I finally got back to this. I can definitely get the revs up with slow, steady throttle. It's when I punch it that it wants to stall. Does that mean the accelerator pump is OK? I can see the fuel mist in the chamber when I floor it when not running. I'm wondering if I shouldn't just go ahead and replace my distributor to rule that out?
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