Some Dumb Questions
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Joined: Apr 2011
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Some Dumb Questions I swapped a 5.3 into my 03 wrangler. I got it to start today after a wiring gremlin in the harness that i bought from a company specializing in the jeep swap. It will crank and run for say twenty seconds or so and then cuts out. It sounds like it is running out of fuel.
I have the jeep fuel tank and pump. I know it doesn't make quite enough pressure, but i was wondering if the pressure should be ample enough for it to at least run at idle.
I don't have the front o2 sensors hooked up yet. The motor should still run without these hooked up? just rough?
I think what happens is when the key cycles on the jeep pump is told by jeep computer to pump fuel for the standard amount of time. I turn over engine cranks and runs, but the gmc computer is not telling the jeep fuel pump to keep pumping so it runs till it drains the rails and no gas equals no fun.
I am going to buy a fuel pressure gauge in the morning and test rail pressure and see what is going on with it, but my best guess is the wire going to the jeep pump from the chevy harness must not be on the right wire or is not sending the proper signal for the jeep pump to keep sending fuel.
Recap:
1. Jeep PSI to low to run 5.3 at idle
2. Front O2 sensors air fuel mixture won't let it stay running
3. Jeep/5.3 wiring not communicating to keep fuel flowing.
I am hopeful that it is 2 or 3 but figured i would ask some experts. If you want to hear it run search matthewsavery on you tube and there is a video of it running today
I have the jeep fuel tank and pump. I know it doesn't make quite enough pressure, but i was wondering if the pressure should be ample enough for it to at least run at idle.
I don't have the front o2 sensors hooked up yet. The motor should still run without these hooked up? just rough?
I think what happens is when the key cycles on the jeep pump is told by jeep computer to pump fuel for the standard amount of time. I turn over engine cranks and runs, but the gmc computer is not telling the jeep fuel pump to keep pumping so it runs till it drains the rails and no gas equals no fun.
I am going to buy a fuel pressure gauge in the morning and test rail pressure and see what is going on with it, but my best guess is the wire going to the jeep pump from the chevy harness must not be on the right wire or is not sending the proper signal for the jeep pump to keep sending fuel.
Recap:
1. Jeep PSI to low to run 5.3 at idle
2. Front O2 sensors air fuel mixture won't let it stay running
3. Jeep/5.3 wiring not communicating to keep fuel flowing.
I am hopeful that it is 2 or 3 but figured i would ask some experts. If you want to hear it run search matthewsavery on you tube and there is a video of it running today
Stock Fuel Pump It is not your vats if that was the case it would only run for 2-3 seconds at max, what is the Jeeps stock fuel pump rated at? You need 58-62 p.s.i. Of fuel pressure for it to run, you need to see what that Jeep pump is rated at and you are on the right path by checking your fuel pressure with a gauge.
Thread Starter
Registered User
Joined: Apr 2011
Posts: 4
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Jeep does not have that much pressure but some fellow keepers have made swap with no issues. I was hopin could get it to run and make sure everything is shifting properly. I ordered special kit to modify jeep pump so pressure would be right. At the moment though I think I am losing all fuel pressure. I will test in morning it sure is a c$&( tease when it runs for twenty seconds
