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Old 01-13-2014, 10:33 AM   #1
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Strange Fuel Issues with my YJ

Greetings All!!! In 2000 I did a engine swap on my 90 YJ to a 350 V8. We removed the in tank pump and installed a Holley Mechanical Pump. It drove fine for many years and then it started to starve when I went hill climbing (Not really steep but a incline). I then changed to a Summit Mechanical Pump and it gave the same problems... I then bought a Summit Electric Pump and that only lasted 6 months (We forgot to install the return so that could have cause it to fail). I then installed a Holley Red with return and it drove good for about three months and then started to starve. Even on the flat it would starve.... I bought a cheapo pump and it ran good for about three days and started to same issues.. I notice that when this happens, the pump gets hot and if i let it rest for 5-10mins, it will start and drive, but it usually starves shortly again. I have had times when i drive it no problem for months and then it starts.. We have pulled the tank X3 to see if anything was blocking the pick up but it was nice and clean. We then removed every inch of the gas line and checked for a broken or soft hoses... NOTHING was found... The jeep has most of it original fuel line and it was in very good condition for a 1990. I don't know what else to do.... HELP!!!

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Old 01-13-2014, 10:51 AM   #2
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Mine is in the shop for the very same reason right now. It heats up and then it acts as if it's starving and I had to pull over to let it cool off. My fuel pump is whining constantly and so I suspect it might be in the throes of death. They are doing a pressure test on the system for me right now. All my wires are new, plugs are new, rotor and cap are new, and I ran a can of SeaFoam through it just for grins and giggles but it's still doing it. If anyone can find the problem, it's my mechanic, Ed!! If he can't fix it, it ain't broke. He will be calling me shortly with an update and I'll let you know what he tells me.

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Old 01-13-2014, 12:14 PM   #3
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Thx Michael_Larson!!
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Old 01-13-2014, 12:48 PM   #4
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When you did the in-tank conversion did the new pick up have a filter sock on it ? They will act as a pre-filter and get clogged over time, it may be worth checking...
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Old 01-13-2014, 06:48 PM   #5
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Got word from my mechanic an hour or so ago. He tested the fuel pressure and found the following:

Cold system: 15 psi
Warm system: 8 psi
Hot system: 3 psi and falling

When my Jeep gets hot, it sputters and is useless as if starved for fuel. The fuel pump is bad and I also have a leaking heater core so he's replacing that too. He had to basically splice in a line to test to pressure from the sounds of it. I should have it back tomorrow though and then I'll do some more testing.
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Old 01-13-2014, 09:34 PM   #6
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Peety... I don't have a filter in the tank but I have one before the pump and another before the Carb. They both are new...
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Old 01-13-2014, 09:36 PM   #7
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Originally Posted by Michael_Larsen View Post
Got word from my mechanic an hour or so ago. He tested the fuel pressure and found the following:

Cold system: 15 psi
Warm system: 8 psi
Hot system: 3 psi and falling

When my Jeep gets hot, it sputters and is useless as if starved for fuel. The fuel pump is bad and I also have a leaking heater core so he's replacing that too. He had to basically splice in a line to test to pressure from the sounds of it. I should have it back tomorrow though and then I'll do some more testing.
Don't think it's my fuel pump.. I've changed 4 and they all fail after different times.. I also have a Holley pressure regulator and pressure gauge.
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Old 01-14-2014, 09:36 AM   #8
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Don't think it's my fuel pump.. I've changed 4 and they all fail after different times.. I also have a Holley pressure regulator and pressure gauge.
When running i usually have it set a 8psi. it will maintain this until the pump sucks dry or ????
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Old 01-14-2014, 10:40 AM   #9
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Is the Regulator the same one that's been on there the entire time, I'm too lazy to go re-read the OP...
If it is, check your pressures in front of the regulator first...
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Old 01-14-2014, 11:33 AM   #10
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Is the Regulator the same one that's been on there the entire time, I'm too lazy to go re-read the OP...
If it is, check your pressures in front of the regulator first...
I just put on a new regulator this week... Haven't driven it yet tho.. But my second fuel filter is just before the regulator.. If the regulator was blocked, wouldn't the filter still be full of fuel?
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Old 01-14-2014, 11:47 AM   #11
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if when you put a new pump on it,it works good for a few weeks or whatever then starts acting up again,that sounds like the pump is going bad..I have had good luck with the holley red pumps.I hear that the carter pump is a good pump too..the holley is set at 7 pounds and I think the carter is set at 6..neither of these pumps will require a regulator.I have seen regulators cause problems so if you remove it,that is one less thing to go wrong
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Old 01-14-2014, 12:23 PM   #12
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if when you put a new pump on it,it works good for a few weeks or whatever then starts acting up again,that sounds like the pump is going bad..I have had good luck with the holley red pumps.I hear that the carter pump is a good pump too..the holley is set at 7 pounds and I think the carter is set at 6..neither of these pumps will require a regulator.I have seen regulators cause problems so if you remove it,that is one less thing to go wrong

I've gone thru 4 pumps,,, Two Mechanical and Two Electric... The last electric is fine but it sucks dry when it gets hot... It "Seems" as if something is blocking the flow... Only problem is, I can't find out what.. All the pumps can't be faulty. Agree?
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Old 01-14-2014, 12:37 PM   #13
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I've gone thru 4 pumps,,, Two Mechanical and Two Electric... The last electric is fine but it sucks dry when it gets hot... It "Seems" as if something is blocking the flow... Only problem is, I can't find out what.. All the pumps can't be faulty. Agree?
you wouldn't think so.However if when you change the fuel pump,it works properly then that sort of tells you that the pump was bad..perhaps a restriction prior to the pump is causing them to work themselves to death..also,most if not all electric pumps are designed to push fuel rather than pull it..they need to be mounted very near the tank and the inlet to the pump should be a little lower than the bottom of the tank..replacing the pump with a good quality pump like I mentioned earlier,mounted like indicated,with all new lines and filters,without a regulator would no doubt solve the problem
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Old 01-14-2014, 12:58 PM   #14
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Are you sure that the line from the pump to the tank isn't getting collapsed? I've seen fuel lines that appear to be good on the outside but develop a "flap" on the inside that chokes off the fuel. Fuel line is cheap, I would suggest replacing the fuel line to your pump from the tank. if nothing else... just to eliminate it.
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Old 01-14-2014, 03:11 PM   #15
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Are you sure that the line from the pump to the tank isn't getting collapsed? I've seen fuel lines that appear to be good on the outside but develop a "flap" on the inside that chokes off the fuel. Fuel line is cheap, I would suggest replacing the fuel line to your pump from the tank. if nothing else... just to eliminate it.
Thx Gents.... I am in the process of changing the rubber fuel lines. Even though I have taken down the entire fuel line, separated each piece and have blown in them and have found nothing .. I will keep you posted...
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Old 01-14-2014, 03:15 PM   #16
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you wouldn't think so.However if when you change the fuel pump,it works properly then that sort of tells you that the pump was bad..perhaps a restriction prior to the pump is causing them to work themselves to death..also,most if not all electric pumps are designed to push fuel rather than pull it..they need to be mounted very near the tank and the inlet to the pump should be a little lower than the bottom of the tank..replacing the pump with a good quality pump like I mentioned earlier,mounted like indicated,with all new lines and filters,without a regulator would no doubt solve the problem
Harley, I'm using a Holley Red and the pump is located where the original fuel filter from the tank was located. I plan on changing ALL the rubber lines and see what happens from there... Do you think having the regulator can cause it? I have it set at 8psi... It's just really strange tho...
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Old 01-14-2014, 03:28 PM   #17
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are you sure that the line from the pump to the tank isn't getting collapsed? I've seen fuel lines that appear to be good on the outside but develop a "flap" on the inside that chokes off the fuel. Fuel line is cheap, i would suggest replacing the fuel line to your pump from the tank. If nothing else... Just to eliminate it.
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Old 01-14-2014, 03:29 PM   #18
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What blend of fuel is in common use there, E85 and MTBE will demolish a fuel system not desighed for it.
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Old 01-14-2014, 04:35 PM   #19
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Quote:
Originally Posted by JeepJamaica View Post
Harley, I'm using a Holley Red and the pump is located where the original fuel filter from the tank was located. I plan on changing ALL the rubber lines and see what happens from there... Do you think having the regulator can cause it? I have it set at 8psi... It's just really strange tho...
the holley red pump is preset at 7 pounds so you don't even need the regulator..someone,I think it was peety mentioned something about fuel..A few months back I swapped all my vehicles over to non ethanol..they all are running better,have a little more power and are getting more than enough better gas mileage to make up for the difference in price
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Old 01-14-2014, 07:47 PM   #20
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What blend of fuel is in common use there, E85 and MTBE will demolish a fuel system not desighed for it.
We use E10 here... Thought about that and I always add a additive to my fuel.
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Old 01-14-2014, 08:04 PM   #21
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Harley, I'm using a Holley Red and the pump is located where the original fuel filter from the tank was located. I plan on changing ALL the rubber lines and see what happens from there... Do you think having the regulator can cause it? I have it set at 8psi... It's just really strange tho...
not sure of your filter heigth but make sure that the inlet to your pump is a little lower than the bottom of your tank

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