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Discussion Starter #1
Ok so this past week my 2000 4.0 died on me just in front of my house. Got it pulled up in the driveway and changed out the crankshaft position sensor. Still nothing. Got to testing voltages and come to find out my fuel pump relay(RL12) and RL10 are not being activated. I am getting 12 volts from the hot side but when I go to test the other side of the relay coil i get 5 volts coming from the BECM. Any ideas as to why they would not be coming on? Any help would be appreciated.
 

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Discussion Starter #3
I checked just about everything there is to check. When i jumper the wires for the fuel pump at the fuse box it comes on but like i said the relay is not getting the correct voltage to activate.
 

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dbjones said:
I checked just about everything there is to check. When i jumper the wires for the fuel pump at the fuse box it comes on but like i said the relay is not getting the correct voltage to activate.
Another thought,the fuel pump relay is controlled by the Engine ECM.If Relay 19 is u/s then the ECM will not function correctly and will not switch on the fuel pump.The ECM could of course have failed. :think:
 

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Discussion Starter #5
Relay 19 is getting the correct voltage and in turn switching on. I have also read that the crankshaft position sensor has a big deal to do with starting. I replaced it but is it possible the one that i replaced the bad one with was in itself bad? What should the resistance on the sensor be? Also the throttle position sensor and the MAF sensor. How can i test those?
 

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Does the engine turn over but not start?.
If so it can be a faulty crankshaft sensor.
When you first turn the ignition to Pos2 ,do you hear the fuel pump run for a short time and then stop.

The maf and Tps will not stop from starting,just wont run well at all.
 

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Discussion Starter #7
No the fuel pump does not run unless I hard wire it. (bypass the relay) What are the signals it need to receive before it will signal the fuel pump to start>
 

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John W said:
Does the engine turn over but not start?.
If so it can be a faulty crankshaft sensor.
When you first turn the ignition to Pos2 ,do you hear the fuel pump run for a short time and then stop.

The maf and Tps will not stop from starting,just wont run well at all.
So if the fuel pump runs when the ignition is on Pos2 briefly and there's no fuel pressure at the fuel rail, does that mean "Faulty Crankshaft Sensor"? I replaced my fuel pump over the weekend (swapped tanks with a known working used pump) and worked fine for a day, then started it this morning after driving for 20+ minutes and it died again! No pressure at the fuel rail but I hear the pump turn on. I filled the tank 3/4's full and put in some a gas additive, I’m wondering if I should change my fuel filter. Any advice would be much appreciated.
 

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bonnychoo said:
Surely the fuel pump will not run if the engine's not turning over - safety feature.

No the pump will run when the key is turned to pos2 for a short while as the system is pressurized.This is controlled by the ECM(engine) and will shut off after a period determined by the ECM. :thumb:
 

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So what does it mean when the Pump does turn on but doesn’t pressurize the system and the car won’t start?
 

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4dot6 said:
So what does it mean when the Pump does turn on but doesn’t pressurize the system and the car won’t start?
If the fuel pump is running but not providing pressure at the rail then either the pump has failed or your fuel filter needs replacement.
 

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Discussion Starter #13
The fuel pump does not turn on unless i hardwire it. it is getting incorrect voltage from the ECU. i am going to have to towed to the dealer to have testbook run on it to figure out the problem. unless somebody in the Knoxville, TN area has test software.
 

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4dot6 said:
So what does it mean when the Pump does turn on but doesn’t pressurize the system and the car won’t start?
Could it be a faulty Fuel Pressure Regulator? but not sure what the symptoms are if it fails.

Cheers
 

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Discussion Starter #15
Just heard from the dealer and they said the BeCM is not commuincating with the Engine control Unit. Still waiting to here why. :(
 

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Discussion Starter #16
Finally heard why. Coolant leak shorted out part of the BeCM. Help i now need a computer. :pray:
 

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dbjones said:
Finally heard why. Coolant leak shorted out part of the BeCM. Help i now need a computer. :pray:
You had that much coolant under your right front seat :?:
 

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Discussion Starter #18
Yeah it was parked on a hill and when they came to tow it about a half a gallon came out from under it. Where can i get a good replacement computer?
 
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