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Discussion Starter · #1 ·
I have a 2006 Jeep Commander with the 5.7L Hemi. A few weeks ago we parked the vehicle at the store, and upon returning the engine turned but did not fire. About 30 minutes into checking and playing around, the engine suddenly started. A few weeks later same thing happened. We tried several things that seemed to solve the issue at times, but now we are stuck with an engine that does not fire. It very much looks that the engine is being restricted from getting fuel.

So, we found the following: the red/pink wire that is being controlled from the FP relay con 87 receives 12v, as long as we don't connect the fuel pump to the connector. As soon as we connect the pump, zero voltage. Running a straight wire from the battery to the pump will engage the pump (we only touched it). The wiring to the pump has four wires: two for the pump and two for the sender. The two black wires were told to be ground, but I don't know where they actually go to.

I am out of answers of what it could be, so if anyone could tell me why this is happening, it would be great, as I need this vehicle on the road.
 

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1966 Crown Coupe, 2016 200 S AWD, 1962 Lark Daytona V8.
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Any fault codes? You might want to trace the circuit to find the problem. Good connections and ground is important:
 

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Discussion Starter · #3 ·
Any fault codes? You might want to trace the circuit to find the problem. Good connections and ground is important:
Thanks for sending. No trouble codes were found. Spraying fuel directly in the TB will make the vehicle run. So basically something prevents it from priming. I starting to wonder if the computer has issues.
 

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. . . Spraying fuel directly in the TB will make the vehicle run. So basically something prevents it from priming. I starting to wonder if the computer has issues. . . .
Good job. Your test eliminated spark and timing as a cause of the no-start. Try this test. You need the area around the vehicle to be as quiet as possible. Turn off radio, climate control blower, fasten seat belt. Turn ignition key switch to the ON / RUN position but do NOT turn to START position. You should hear the electric fuel pump run for 1 - 2 seconds and then stop. If you do NOT hear the pump run then you need to check fuse that powers the fuel pump. Check the fuel pump relay in the power distribution center. Check wiring to the pump at the tank.

If you hear the electric fuel pump run for 1 - 2 seconds, you know the PCM (powertrain control module) can control the fuel pump and control to the pump is electrically sound (fuses, wiring, relay, etc). Turn the ignition key switch to the START position for 5 seconds and then release to the ON / RUN position. Do you hear the pump continue to run 1 - 2 seconds and then stop. If NO then the PCM is not receiving a proper signal from the crankshaft position center. The PCM must receive a pulsing signal that indicates the crankshaft is rotating before it will energize the fuel pump circuit. Check crankshaft position sensor and wiring between this sensor and the PCM.
 

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You could be reading voltages incorrectly.
I don’t have a wiring diagram of the fuel pump system, but 12 volts unplugged and 0 when plugged in would be completely normal depending on which circuit you’re testing and where you’re testing it.

If you’re actually on the 12 volt feed to the pump (from the relay) it should not, though.
If you’re on the correct circuit then the voltage is dropping because of high resistant somewhere. I would suspect the relay if in fact the system uses an actual relay (most modern injection systems use variable rate voltage via a control module, but I’ll bet your jeep does not.).

If you have an actual relay, replace it. Sounds like the contacts are probably severely worn/damaged.
 

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Discussion Starter · #6 ·
Thanks for all the input and ideas! I decided to replace the crankshaft sensor, and upon checking resistance with a meter, I got a different reading on the old sensor than with the new one. I do know that the adding 12V directly on the pump will engage the pump, so the pump itself is not dead (it is a brand new pump). By now I tried to start it, but I am afraid that all the trying has put the battery almost to rest.

As for the relays, I did swap relays around to see if any of them were bad, but no luck there. Experience has told me that just listening does not always mean it is right :)

One thing I am curious about; I think I have a leaking water pump seal, as coolant keeps disappearing and drips in a variety of places from below the pump. I am wondering if coolant has damaged something. This Jeep has had numerous coolant leaks and issues, which is disappointing for an engine that well known.
 

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. . . I decided to replace the crankshaft sensor, and upon checking resistance with a meter, I got a different reading on the old sensor than with the new one. . . .
The crankshaft position sensor uses the Hall effect so measuring resistance of the circuit does not necessarily prove that it is working or not working. Did you run the test proposed on my post #4, June 26, 2019? You HAVE TO KNOW if the PCM can control and energize the electric fuel pump.

. . . I do know that the adding 12V directly on the pump will engage the pump, so the pump itself is not dead (it is a brand new pump). . . . .
Yes, you can get the fuel pump to run but does the system have adequate pressure? You can rent a fuel pump pressure tester and attach it to the fuel rail and determine if there is suitable pressure.

. . .One thing I am curious about; I think I have a leaking water pump seal, as coolant keeps disappearing and drips in a variety of places from below the pump. I am wondering if coolant has damaged something. This Jeep has had numerous coolant leaks and issues, which is disappointing for an engine that well known. . . .
Look for any sensors in the vicinity of the water pump and below. Typically a small leak will not cause electrical damage but an inspection is always warranted.
 

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Discussion Starter · #8 ·
Did you run the test proposed on my post #4, June 26, 2019? You HAVE TO KNOW if the PCM can control and energize the electric fuel pump.
AllanC, from what I know so far, I turn the key to on, both relays from FP and ASD will click on and off after 2 seconds, power to the pump will come on during that time. However, no sound from the pump at all.

Yes, you can get the fuel pump to run but does the system have adequate pressure? You can rent a fuel pump pressure tester and attach it to the fuel rail and determine if there is suitable pressure.
I have been looking to see where I can connect a gauge to the fuel rail, as these vehicles do not have a valve anymore
 

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A . . . I turn the key to on, both relays from FP and ASD will click on and off after 2 seconds, power to the pump will come on during that time. However, no sound from the pump at all. . . .
That would indicate that no electrical power is passing through the load side of the controlling relays. That would indicate corroded or burned contacts on the load side relay circuit. But if you exchanged relays that would tend to prove there is no problem with the load side circuit at the relays.

You will have to check the load side wiring from the fuel pump relay to the fuel pump in the rear at the tank. Are you getting 12 volt power at the pump with the fuel pump relay energized?

I believe there is a fuel rail pressure test port but it may not be easily visible. Scroll to post at 03-13-2013, 11:02 PM and view attached images.

2004 5.7 Hemi Fuel Pump Pressure Test Port Location - DodgeForum.com (at https://dodgeforum.com/forum/3rd-gen-ram-tech/350877-2004-5-7-hemi-fuel-pump-pressure-test-port-location.html )
 

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You can also have great fuel pressure in the lines and rails, but if the injectors aren't squirting, you will still have no fuel to the cylinders.
 

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Discussion Starter · #11 ·
I checked again, and at least the fuse for the injectors is ok. I was wondering if someone could tell me if the red/orange wire that sits on the FP relay #87 goes directly to the pump, or through the PCM. Reason I ask is that when I put 12V on that wire from the relay connector, nothing happens. I would think that if the wire goes to the pump, ir should come on, unless the ground is interrupted.
 

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See the wiring diagram in post # 2. An Or/Rd wire goes to the IPM, a Zener goes to ground (maybe to prevent electrical spikes or noise). Power to the pump may be switched inside the IPM to allow current out to the pump on the Tn/Rd wire when appropriate? Do you have power on the Tn/Rd wire when the Or/Rd is hot?
 

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Discussion Starter · #13 ·
That I will have to check. I think there have been times that I didn't have power on the Tn/Rd, but I need to confirm. IPM; is that a fancy word for the fuse and relay box, or an actual module? I have learned a lot as I work on my cars, just not in school :)
 

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IPM; is that a fancy word for the fuse and relay box, or an actual module?
IPM - Integrated Power Module. In 2006 it became the TIPM - Total Integrated Power Module and is actual module in the engine bay. It is solid state and also has most, if not all, the fuses and relays.
 

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. . . So, we found the following: the red/pink wire that is being controlled from the FP relay con 87 receives 12v, as long as we don't connect the fuel pump to the connector. As soon as we connect the pump, zero voltage. . . . . . . .The wiring to the pump has four wires: two for the pump and two for the sender. The two black wires were told to be ground, but I don't know where they actually go to. . . .
See attached images which show the fuel pump relay wiring and wiring to the fuel pump module. The black wires at the fuel pump module are the ground for the pump motor and the return ground to the instrument cluster for the fuel gauge sending unit.

. . . .Running a straight wire from the battery to the pump will engage the pump (we only touched it). . . .
Where exactly are you connecting direct battery voltage to the fuel pump wiring and causing the pump to run??? Use the diagrams as a reference.

Is fuse #24 good?

Text Diagram Technical drawing Plan Floor plan
Text Diagram Line Plan Technical drawing
[/QUOTE][/QUOTE]
 

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Discussion Starter · #16 ·
Going to work on it now. Am I correct that the Zener is located within the wire in the PDC? I noticed that there is a shrink tube over the wire below the fuses. The diagram looks straight forward, with exception of where the actual locations of the ground wires are, but that always a challenge :)
 

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Discussion Starter · #17 ·
Update on this issue: I took the diagram and started from the beginning to test again. I took a wire and connected it on the constant 12v where normally the FP relay is, and the pump ran. Next step was to connect the constant 12v with the #87 of the FP relay location, and fuel pump ran. Out of nowhere the FP ran without touching anything else. Result: Jeep started right up.

So, I still have no concrete answers as to what actually is the problem, other than a wire directly under the relay. Not sure that ever happens. I did did bend the relay connectors a tiny bit to ensure a snug connection, but without a concrete finding I do not feel comfortable enough to send teh Jeep out
 

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Fuel pumps and associated electrical problems can be intermittent. This can be a frustrating and inconvenient problem. :(
If it does act up again, you want it to be under safe conditions and be ready to diagnose before the issue goes away again.
 

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U . . . I took a wire and connected it on the constant 12v where normally the FP relay is, and the pump ran. Next step was to connect the constant 12v with the #87 of the FP relay location, and fuel pump ran. Out of nowhere the FP ran without touching anything else. Result: Jeep started right up. . . .
Did you insert the fuel pump relay and now the engine will start and run? If YES then maybe the OR / RD female connector that mounts in the fuse box / TIPM has gotten dislodged. Inserting the spade connector of the relay pushes it away from its correct position and prevents good, solid electrical contact. That would cause a power interruption to the electric fuel pump.
 
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