Hello
I am a JLR master tech and can not figure this one out. I was wondering if there are any other Jag techs on this Forum?
Basically, I have a 2000 s type V6 in my shop. Steering column lock works and PATS light is on solid for 3 seconds when ignition is turned on. Engine cranks, I have injector pulse but no fuel pressure. No fault codes in ECM or RECM. Vehicle has new genuine fuel pump and I have tried a different RECM. According to Topix, the fuel pump should run for one sec when ignition is turned on to prime the system which is not happening. Data logger in IDS shows ECM is demanding 70% of fuel from RECM. I have checked all power supplies and earth to RECM, ECM and GEM. I have checked signal wires from ECM to RECM (fuel delivery demand) and security signal to GEM for continuity, all OK. Inertia switch is OK, fuel pump relay and diode are OK. I am running out of ideas.
Any help is appreciated

 

Have you checked power/ground at the pump connector? I see no mention of that. Ideally you could backprobe the connector. If not feasible, you could disconnect the plug and check that way. However, if testing with the circuit unloaded like that, the results can be misleading so be careful. Basically, you can have a marginal power supply with just enough oomph to show good voltage at a voltmeter so it looks good, but not enough power to actually run the pump when the circuit is loaded.



Please describe how you tested the relay. Not trying to bust your butt, just want to make sure we're not overlooking something.

I would suggest beginning with a click test of the fuel pump relay. Place your favorite finger on relay #6 in the trunk. Have a helper cycle the key on and off a few times. You should feel the relay click with each cycle. If so, that tells us the relay control circuit is good, and the internal electromagnet coil is being energized. This does NOT confirm power for the pump is actually being sent out, merely that the control side is good.

If the click test passes, take a good look at the prongs on the relay. Any signs of discoloration? If the contacts within the relay are arcing, you'll typically see heat damage on the prongs. In severe cases, the heat can also damage the corresponding sockets in the fuse panel.

If good so far, try swapping with a known-good relay from another position. I would suggest the fog lamp relay (#7) from the front power distribution box under the hood. Those lights typically see minimal use. Make sure the lights work and there's a good donor.

One last thought:

So far all of your troubleshooting is on the electrical side of things. We've had a few instances of a mechanical fault, with a line coming loose inside the tank. The pump was running as normal, but all flow was dumping back into the tank, causing zero pressure at the injector rail but no other clues. The first step to check this is remove the rear seat bottom cushion, and the rubber cover across the opening in the sheet metal. Turn off the radio and HVAC to make it as quiet as possible in the cabin. Turn on the key, and if the pump is actually running (but not making pressure for reasons unknown), you will be able to hear it run briefly as it tries to prime the lines.

 

Absolutely. I have done the click test of the relay and I swapped it with one from another, running s type. Also, power supply to the RECM from the relay is OK.

What you mention with the supply to the pump is correct. I have power to the pump with the pump connector disconnected but as soon as I put load on (even a 12V bulb), the RECM cuts power. So I checked power supplies to RECM again, hoping to see one of the supplies to drop under load but all OK. I have a power probe that I used to power the pump. It runs and builds up pressure straight away if powered up directly. I also checked the fuel pressure sensor on the rail, thinking the ECM wants to see an increase in pressure before running the pump. All good.

 

Could this power cut actually be the timer for priming the injector rail? Maybe you're not seeing a response to a fault. Perhaps it is simply normal operation that could be misinterpreted as a problem.

Do you still have another car handy for comparison? (You mentioned robbing a relay) Just thinking out loud. Wondering if it's normal to see voltage available (with virtually no amperage behind it) in a PWM-controlled circuit, before the pump is commanded to run.

The pump runs when power is jumpered directly. Can you get an amperage reading on it? Maybe the new pump is defective and drawing too much current, so the RECM shuts it down quickly.

What original symptoms brought the car into your shop?

 

This s type is actually a Traga car. Targa is an Australian version of Tarmac Rally which is held all over the country. Pretty cool to see an old Jag getting flogged and compete with the big boys...
The customer took it out of his garage to move some cars around. The engine stalled and never started again.
I was also wondering why I have permanent power with the pump disconnected when Topix clearly states the RECM runs the pump for 1 sec.
I replaced the fuel pump because it was still the original pump and beeing a Targa car it will make it more reliable. It does not matter if the old pump is connected or just a 21W bulb. The RECM shuts power down.
I don't have another car handy at the moment but as soon as one comes in I'm going to take some measurements
I will take some Amp readings and let you know

Thanks heeps

 

Re: the history. Seems these pumps are notorious for seizing after periods of inactivity. Pulling it out of storage and then failing shortly afterwards certainly fits the pattern.

When you jumpered power to the pump, was this done at the plug on the pump module? What if you disconnected the plug at RECM and applied power from there as a test? Kind of a long shot, in case of damaged wiring between the RECM and pump. A quick test from there would rule out this remote possibility.

Sorry none of us have a quick fix for you. Might be a painfully slow process of elimination.

 

I have done both actually to rule out the harness from the RECM to the pump.
I currently have the fuel lines disconnected at the top of the pump to monitor fuel delivery when powering the pump with an external power supply and to check if the internal fuel pipe inside the tank is OK.
I will re connect tomorrow to see if it makes a difference as there is currently no fuel delivery to the rail pressure sensor . I have a feeling the ECM wants to see a change in rail pressure for fuel demand

Thanks heeps for working with me on this one...

 

I'm not aware of this, but it wouldn't be the first time I didn't know something. For example, have you ever investigated where babies come from? The answer was an eye opener, let me tell you. I've since moved on to researching how they get in there. You're not going to believe what I've found so far!

For the fuel rail pressure sensor, could you somehow trick it into seeing pressure? If you have a spare, you could connect it to the vehicle harness and apply low pressure compressed air. If no spare, remove the sensor, plug the rail so fuel doesn't spray out, and apply compressed air. Or simulate pressure electronically with appropriate resistors in place of the sensor.

 

Have you considered the CKP sensor? I forgot all about one important safety function. See post #2 in this thread:

https://www.jaguarforums.com/forum/s...e-base-271383/



Years ago, I had a similar problem (crank, no start with no fuel pressure) on a Lincoln of the same era. The CKP sensor had failed but since it was a no start problem, not specifically an emissions problem, no OBD codes were generated.

I think the logic is if a fuel line were to break and dump all pressure, the crankshaft would stop turning. For safety, the pump is then quickly turned off assuming a major leak.