Cranks will not start

Hi:

Since you sometimes get power, then I will assume it isn't a fuse. There is an ASD relay (auto shut down) which can shut off the pump and a fuel pump relay. Both are located under the hood in the power distribution box. I attached a pic below showing their locations (Pic1). I would start by checking these circuits and relays. Here are the directions for testing.
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2001 Jeep Truck Cherokee 4WD LHD L6-4.0L VIN S
ASD and Fuel Pump Relays Test
Vehicle Powertrain Management Fuel Delivery and Air Induction Fuel Pump Fuel Pump Relay Testing and Inspection Component Tests and General Diagnostics ASD and Fuel Pump Relays Test
ASD AND FUEL PUMP RELAYS TEST
Fig.1 ASD And Fuel Pump Relay Terminals - Type 1

Pic 2

Fig.2 ASD And Fuel Pump Relay Terminals - Type 2

Pic 3

The following description of operation and tests apply only to the Automatic Shutdown (ASD) and fuel pump relays. The terminals on the bottom of each relay are numbered. Two different types of relays may be used, (Fig. 1) or (Fig. 2).
- Terminal number 30 is connected to battery voltage. For both the ASD and fuel pump relays, terminal 30 is connected to battery voltage at all times.
- The PCM grounds the coil side of the relay through terminal number 85.
- Terminal number 86 supplies voltage to the coil side of the relay.
- When the PCM de-energizes the ASD and fuel pump relays, terminal number 87A connects to terminal 30. This is the OFF position. In the OFF position, voltage is not supplied to the rest of the circuit. Terminal 87A is the center terminal on the relay.
- When the PCM energizes the ASD and fuel pump relays, terminal 87 connects to terminal 30. This is the ON position. Terminal 87 supplies voltage to the rest of the circuit.

The following procedure applies to the ASD and fuel pump relays.
1. Remove relay from connector before testing.
2. With the relay removed from the vehicle, use an ohmmeter to check the resistance between terminals 85 and 86. The resistance should be 75 ohms ± 5 ohms.
3. Connect the ohmmeter between terminals 30 and 87A. The ohmmeter should show continuity between terminals 30 and 87A.
4. Connect the ohmmeter between terminals 87 and 30. The ohmmeter should not show continuity at this time.
5. Connect one end of a jumper wire (16 gauge or smaller) to relay terminal 85. Connect the other end of the jumper wire to the ground side of a 12 volt power source.
6. Connect one end of another jumper wire (16 gauge or smaller) to the power side of the 12 volt power source. Do not attach the other end of the jumper wire to the relay at this time.

WARNING: DO NOT ALLOW OHMMETER TO CONTACT TERMINALS 85 OR 86 DURING THIS TEST. DAMAGE TO OHMMETER MAY RESULT.

7. Attach the other end of the jumper wire to relay terminal 86. This activates the relay. The ohmmeter should now show continuity between relay terminals 87 and 30. The ohmmeter should not show continuity between relay terminals 87A and 30.
8. Disconnect jumper wires.
9. Replace the relay if it did not pass the continuity and resistance tests. If the relay passed the tests, it operates properly. Check the remainder of the ASD and fuel pump relay circuits. Refer to Wiring Diagrams.

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Let me know what you find.

If it starts starting fluid, then it has spark. The ASD shuts down the fuel pump. Are you sure it isn't an issue with the immobilizer?

Hi,

At the pump, the wires go to these things:

Dark green/white To fuel pump relay

Dark blue/light green To PCM (low fuel light)

Brown/yellow To camshaft position sensor, O2 sensors, VSS, battery temp
sensor, cruise control

Black To Ground.

I cut a portion of the wiring schematic for you to see. If there is something specific you need, let me know. There are several pages associated with this.

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I'm glad to hear it's running. Please keep in mind, the vehicle has an automatic shut down system that turns power off to the pump in the event of a roll over or accident. That will not happen if you have it powered direct.

Let me know if the wiring helps.

Hi,

I attached a picture of the connector for the pump. It is a 6 pin connector but only 4 are used. I noticed that you have a new connector with different colors. The pic shows what each pin does. Since the wires are different colors, confirm that the pins are in the correct locations. Pins 1, 3, 4, and 6 are the only ones used.

I would need to determine which color wires on the new plug go to which pin. Look at the pic I attached above, determine the new colors going to the pins, and that should identify which new color should get power and which shouldn't.

Also, please understand that by running a toggle switch, you remove an important safety feature and that is fuel shut off in the event of an accident. Also, it is easy to forget to turn things off.

Hi,

Compare it to the old one and then to the schematic I attached above. I don't want to take a chance and give wrong information causing a short.

Let me know how things work out.

Honestly, without being there I can't answer that. Have you tried to compare it to the old plug?

Please understand, my schematics don't offer the wiring gauge. However, the dark green / white wire runs to the relay, so it should be powered. As far as the level sensor, it is most likely the lower power supply you mentioned. The best thing I can suggest is to follow the original layout I gave indicating what each wire does then look at the pin designation and wire those wires to the new plug based on what the pin out shows.

As far as just running power direct, I don't recommend it, but the dark blue /. Light green wire goes to the PCM, so I wouldn't recommend powering that wire. Based on what I am seeing on the schematic, if you supply power to the dark green / white (relay) wire and then ground the black wire, the pump should run.

Please understand, not being there makes me somewhat concerned making these recommendations. I don't want anything to catch fire, melt down, and mostly have you get hurt. I am here to help, I just don't want to have something go wrong for you.

As far as the inline fuse blowing, how many amp fuse are you using? Is the wiring that supplies power to the fuel pump heavy enough to handle the load of the pump? Is the toggle you have capable of the amperage that it will be supplying?

Let me know.

Joe