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Old 11-10-2008, 04:12 PM   #1
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fuel pump problem in jeep wrangler to chevy engine conversion

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I am doing a 350 engine swap in a 89 jeep wrangler with a 700r4 tranny and a 231C chevy transfer case,edelbrock carb. and Mr. Gasket regulator with a return line. In earlier posts it was said to just use a regulator to regulate the fuel from the existing pump. The problem i am having is when i turn key on the fuel pump it will energize for 3 seconds and motor will start normally but motor will stop running after it runs the gas out of fuel bowl. I know the fuel pump is not pumping after motor starts because i am using a see thru filter. Any ideas with problem? The original motor was a 2.5 tbi and i am using a edelbrock carb. on chevy 350.

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Old 11-10-2008, 06:42 PM   #2
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I had the same problem. Your computer still thinks your running a 2.5L with injection so its priming the fuel system. That's where your 3 seconds is coming from. But the computer is no longer getting a signal from the engine that tells it that its running so it never energizes the fuel pump relay. That's where your problem is. It's a very simple fix and there are 2 ways to do it. First would be to run a new wire that's hot while the ignition is on to the fuel pump. Or you can do what I did and remove the fuel pump relay and run a jumper wire using to crimp connectors and a really short piece of wire.

Here is a pic of what mine looks like.


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Old 11-11-2008, 06:22 AM   #3
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Thanks for all of the help you gave me. This is a great site. Thanks again.
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Old 11-11-2008, 10:28 AM   #4
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One thing to remember doing that with a jumper, you crash and a fuel line ruptures gas pumps out at around 45 PSI until the key is turned off. I would suggest something like a switch that uses oil pressure to close the switch, that way once you start the engine you get oil pressure, and fuel, engine dies you loose oil pressure and the fuel stops.
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Old 11-11-2008, 12:23 PM   #5
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What kind of switch are you talking about and how would you hook something like that up?
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Old 11-11-2008, 02:38 PM   #6
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He is talking about a Hobbs switch. You'll want a normally open one. You will want to put a tee inline with your oil pressure gauge and hook it up there.
Here is one on ebay.
NEW HOBBS PRESSURE SWITCH 4 PSI NORMALLY OPEN - eBay (item 180305885345 end time Nov-18-08 09:27:33 PST)

Thanks Lancem I forgot to mention that.
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Old 11-11-2008, 02:40 PM   #7
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I did a quick look at Mcmaster.com, the cheapest switch they had there that would do the job was like $22, part # 3460K41. An easier and probably cheaper way to do it would be to use relay and a regular oil pressure sensor that a car uses to turn on an idiot light. You would need a single or double pole, double throw relay, and the sensor. Wire the relay power from switched 12V to the sensor, the sensor will be ground at zero oil pressure. So with the key on and engine not running the relay will be engaged OK? Now wire the fuel pump through the relay so that when the key is on, engine is running, the relay will be disengaged because the sensor is no longer grounded and those contacts will be running the pump. Wish I could draw a picture it would be a hell of a lot easier to explain! Anyway with the relay turned on there would be no fuel pump(no oil pressure), relay turned off the fuel pump would be on (you have oil pressure), oh and you would have to Tee in the sensor with your normal oil pressure sending unit.

Probably clear as mud right??
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Old 11-11-2008, 02:41 PM   #8
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Quote:
Originally Posted by coyote_94yj View Post
He is talking about a Hobbs switch. You'll want a normally open one. You will want to put a tee inline with your oil pressure gauge and hook it up there.
Here is one on ebay.
NEW HOBBS PRESSURE SWITCH 4 PSI NORMALLY OPEN - eBay (item 180305885345 end time Nov-18-08 09:27:33 PST)

Thanks Lancem I forgot to mention that.
That's it! thanks that makes things easier!

Lance
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Old 11-11-2008, 02:44 PM   #9
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No prob. I'm here to help.

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