After I diagnosed and solved the no crank issue with the help of those in this forum i am now on to the next phase which is to start our Jaguar. So I've read a lot of posts and will continue to as I have found very valuable information here. This morning I followed Don B's post "Poor Battery Charging: Bulkhead Power Stud & Other Electrical Maintenance" and cleaned up all the ground connections. Stepping back a few days i started with the fuel pumps. Some threads mentioned that i should be able to hear the pumps come on with ignition in the ON position. I did not hear anything. Seat is removed and both covers are off the pump access holes. Next I checked the voltage on pins 2 and 4 of both main and secondary fuel pumps and have voltage of 11.97 volts. The battery is new though it has sat on the shelf with a trickle charger for about a year. I suspect something with the battery as I have put a charger on and get 14.5 volts and once disconnected it slowly drains to 12.2 volts. One strange thing about the fuel pumps. Even with the key removed from the ignition i'm still getting voltage to the fuel pumps. One test i did early on when i installed the battery is a voltage test between the positive battery post and lug and there was a small volage displayed. In my experience this usually means a short. Is this whats causing voltage at the fuel pumps with no key in ignition?

 

You got a lot of odd stuff going on there.

So for your voltage supply @ Ign. off, AI tells me, what I expected:Q: Jaguar S-Type, 2000, V8: Does the fuel get battery voltage with ignition OFF?

• Fuel pump: Normally NO, it should not have continuous battery voltage with the ignition OFF.
  • With ignition ON, the PCM activates the fuel pump relay for a short priming period.
  • While cranking/running, the relay stays energized.
  • With ignition OFF, the pump should shut down.

And YES, you should hear the fuel pump, when you turn the ign. key to ON.

If you would not have presented me with those oddities, I would have suggested this :

I know that the fuel filter for the 2005 S-Type is behind the front left wheel arch liner.
I do not know, where is is for S-Type 2000, but if AI is correct, then it is there:On the Jaguar S-Type, the fuel filter is mounted under the car, roughly:

• on the driver’s side (right-hand side on Australian cars),
• near the area below the front/rear seat transition,
• attached to the chassis rail underneath a protective cover/bracket.

Here is what it generally looks like and where to find it:






The system is under pressure — depressurize before disconnecting lines.

So, if you want to know, if your fuel pump works, one way would be to remove the fuel line from behind the fuel filter. Put a tub underneath and turn the key to ign. on, which someone else keeps an eye on that open ended fuel filter to see, if the fuel comes out. If not, next step would be the same with the fuel filter removed - 'cause it could well be blocked. And swapping that filter, would be a good idea anyway.

BUT BACK TO YOUR VOLTAGE ISSUE AT IGN. OFF:
I asked AI, and got a good answer - but note that I would not expect a "hum" in your case with IGN. already off, as I am expecting your fuel pump to be long dead:what could be the fault reason, if the fuel gets battery voltage with ignition OFF?On the Jaguar S-Type, if the fuel pump still receives full battery voltage with the ignition OFF, that is abnormal and usually points to one of these faults:

1. Fuel pump relay stuck closed
   • Most common cause.
   • The relay contacts weld together internally, so power continues flowing permanently to the pump.
2. Shorted relay control circuit
   • Wiring fault causing the relay coil to remain energized.
   • Possible chafed wire or water intrusion in fuse/relay box.
3. Faulty PCM (engine ECU)
   • Rare, but possible.
   • PCM may incorrectly keep grounding the relay control line.
4. Incorrect aftermarket wiring / alarm / immobilizer modification
   • Previous owner or installer may have bypassed relay logic.
   • Very common on older Jaguars with aftermarket security systems.
5. Water or corrosion in fuse box / relay module
   • The S-Type can suffer moisture intrusion issues.
   • Corrosion can bridge contacts and keep circuits alive.
6. Backfeeding from another circuit
   • Incorrect wiring repair can feed voltage backward into the fuel pump circuit.

A quick diagnostic method:

• Locate the fuel pump relay.
• Pull the relay out:
  • If pump voltage disappears → relay or relay control issue.
  • If voltage remains → wiring short or bypass.

On the 2000 S-Type V8, the relay is usually in the under-bonnet fuse/relay box.

Symptoms often associated with this fault:

• fuel pump continues humming after key removal,
• battery drain overnight,
• rich running or fuel smell,
• intermittent no-start,
• relay getting hot.

One important detail:
If you only measured voltage with a multimeter, some Jaguar circuits can show “ghost voltage” through electronics. A proper test is:

• measure with a test lamp or
• verify whether the pump actually runs continuously.

That distinction matters a lot.

 

Just to confirm, this car has not been started for some time, right? In your other thread, you mentioned having replaced the engine and transmission. In that case, troubleshooting will need to a bit different than if dealing with a car working okay until a new problem appeared out of the blue.

On a related note, why was the engine replaced? Was there a mechanical failure, such as loss of compression, a broken timing chain, etc.? Or was it running fine but suddenly wouldn't start for no apparent reason? Forgive all the questions, just trying to make sure the existing problem didn't predate the replacement engine.

What is the PATS indicator doing? Previously it was telling you the security system was not happy with that particular key, inhibiting the starter. After switching keys, the starter now works but the engine still won't start. IIRC, there are 2 stages of PATS responses. In more extreme cases, the starter will be inhibited, which you experienced. In other cases, only the fuel pump and injectors are inhibited. I think the logic is to let a thief crank and crank the starter fruitlessly, until he either kills the battery or panics and flees.


If you ever find the second fuel pump, be sure to let us know.

Only the supercharged models (2003+) had two electric pumps. All other models only had a single electric pump on the right side. The left side does have a venturi pump (non-electric) that moves fuel to the electric pump on the right.

You're gonna want to look carefully at the wiring diagrams here:

JagRepair.com - Jaguar Repair Information Resource


See figure 3.3 for the fuel pump. Note how power to the pump is via pins 1 and 3. Pins 2 and 4 where you measured voltage? That is for the fuel quantity senders, one on each side. See figure 07.1. Not sure why you're seeing voltage there, but that may be as simple as a digital meter being too sensitive.

Back to troubleshooting. You should be able to hear the pump run briefly when you first turn the key to run. No need to go to start yet. Since you can't hear the pump, check relay R6 in the trunk (fig 03.3). Have a helper turn the key to run and then off. You should feel the relay click. That will let us know if the command is being sent for the pump to run.

 

Thank you Peter, I'll look at the relay first. All good suggestions.

 

OK will report back with results

I'm heading out to tackle the beast!

 

Yes listen to Karl! Many years of experience right there!
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Karl has been very helpful! Appreciate the patience of the seasoned forum experts!

Cheers

 

Something important to check before removing the fuel pump:

Is the PATS indicator happy? Jaguar used a switched ground system on many circuits. Even though you've confirmed a proper voltage supply to the pump, the ground side of the circuit is controlled by the Rear Electronic Control Module (RECM). It's not just a simple on/off, but a Pulse Width Modulation (PWM) signal. That's a rapid cycling of power to vary the pump speed to maintain the desired output pressure. But if PATS is not happy, it will inhibit the RECM from completing the pump circuit.

These pumps are prone to failure after a period of inactivity. So your pump could certainly be kaput. But definitely rule out a PATS issue first.

If you do change the pump, be VERY careful with the miserable fittings where the fuel lines attach. See my sob story here:

https://www.jaguarforums.com/forum/s...essure-265522/


Not sure if this applies to the early models, but your tank may have these mystery clamps installed. Removal is not intuitive:

https://www.jaguarforums.com/forum/s...l-band-221643/

 

What I hear between the lines is that that Jag hadn't been driven for a while.
While I think that your fuel pump may be long gone to the "Happy Hunting Grounds" (or did you ever hear a hum of it?), and I think that its tiny moving parts, which "pump" the fuel, are seized in place due to gluey old petrol, you should possibly consider draining the fuel tank (if the fuel is indeed old), before installing a new pump. That can be done by disconnecting the fuel line from before the fuel filter and connecting a transfer pump there instead to pump out the tank.
Because if your fuel is old and sticky, your new fuel pump will last for about 5 minutes before seizing again... I had exactly that experience on my Fairlane, which runs on LPG, which is why the fuel got old.