Car won't start

(Neil Bennett. Patron) #21

I would suspect the battery if the no load voltage is 11.08v at least try charging it to anominal 12v or jump start from a running car, since if when cranking the battery volts drop below approx 10v the electronics can and do screw up!

(Big Michael) #22

Hi guys!
Here is my report. :slight_smile:
Pin 1 is the only connector that has any power.
When I tried to jump 3 to 5, I discovered my battery was indeed low. It would barely turn the engine over. It’s on the charger now. I probably left the key on for a while, because the battery was quite strong when the problem arose. Memory is not my strong suit these days. :slight_smile:
If there is no power to 3 or 5, as I have determined, is there any point to jumping them?
Another question. Is the starter motor circuit a part of this exercise? If so, would I not have to turn the starter over while testing to see if I had power to the appropriate pin.?
As you can see, I heartily embrace the notion that there are no dumb questions. :slight_smile:
Best regards!

(Eric Capron) #23

Here is a picture of the relay showing the pinout. The numbers are easier to see in the photo than they are in real life and I observe that they are not the same as the ones in the photo of the socket.

Now, here’s an interesting thing. The 1999 MY wiring diagram in JTIS and my paper version of the 2000MY diagram both show the fuel pump relay as relay 6, as in Rob’s snip above. The 2001MY diagram is also used for 2002MY and here the wiring has changed and the relay for the fuel pump is relay 7. By 2002.5 the wiring has changed yet again and the relay concerned is now relay 15. You can easily tell if you have this version because the Rear Power Distribution Fusebox has curved sides.
So, obviously it’s important to know which one you have. As your car is 2002, if the RPDF isn’t curved, from the diagrams it appears that you should investigate relay 7, not 6.
Again from the diagrams, whichever version you have, pin 3 should have a standing 12 volts and pin 1 receives power when the ignition switch is in positions II or III ie run or start.
I hope this moves your investigation forward.

(Big Michael) #24

Hi Eric!
Thanks again to all of you for all the trouble you are going to in
order to help me.
My computer can’t connect to the link you provided, Eric. However, I
think you gave me enough info anyway to proceed. I have the
rectangular RPDF, so I will focus on relay #7.
Once more into the breach!
Quoting Eric Capron via Jag-lovers Forums

(Big Michael) #25

Hi Eric!
I responded to your email without going to JagLovers first. Now that I see your picture of the relay on JagLovers, I can report that pin #3 is, as we say over here, “hot”. It has power whether the key is on or not. #1 has power only when the key is turned on. Relay #6 is the same as #7, so I switched the two, but the car would still not start. It seems highly unlikely that relay #6 is defective also, so I think we can conclude that relay #7 is “good” as well. Does that leave us with the fuel pump as the likely culprit?

(Rob Reilly) #26

Here is a corrected picture, thanks to Eric whose relay has markings, mine doesn’t.

(Eric Capron) #27


Yes it could be the fuel pump but there are other things as well. The relay does not drive the fuel pump directly. The pump is a variable speed one and its speed is electronically controlled by information from various modules and sensors. The drive actually comes from the Rear Electronic Control Module which hides away behind the trim on the right hand side of the trunk. Here is the relevant bit of the circuit.

There is a good description of the fuel system in the S Type Technical Guide which is too large a file to upload. I’ve put it in my Dropbox. Here’s a link. The fuel system description starts on page 38.

Hope this helps a bit in tracking down the problem.

(Big Michael) #28

Hi Eric!
Thank you for the wiring diagram. I am not up to speed on what wire color the initials stand for, but I will look it up.
The drawing, to my untrained eye, seems to show only two wires connecting directly to the fuel pump. I have four wires connecting to the fuel pump. A black and a red one and a smaller red with black stripe, as well as a smaller wire that appears to be yellow or white.
I just opened the wiring connector at the pump and checked for power at the pump. When connecting the female connectors of the two smaller wires with my multi meter, I show 10.47 volts, whether the ignition is on or not. When connecting the two larger wires with my multi meter, I show no power with the ignition on or off, or with the starter engaged.
The location of the female connectors in the end of the harness that is now disconnected from the fuel pump is as follows. As a frame of reference, the side of the connector housing that has the clip that holds the connector together shall be the RIGHT SIDE. The opposite side shall be the LEFT SIDE and the other two sides shall be TOP and BOTTOM. The female connectors for the two smaller (thinner) wires are in the top right and bottom right corners. I cannot tell which wire goes to which corner. The two larger (thicker) wires go the the top left and bottom left corners. Again, I cannot tell which of the two goes to which corner. I connected the black probe of my multi meter to the bottom right female connector and my red probe to the top right to get the 10.47 voltage reading.
I never heard the pump operate when the ignition was just on or when activating the starter.
I hope I have acually provided some useful information and not just muddied the waters. :slight_smile:

(Eric Capron) #29


Fortunately for me, I have not had any need to work on the fuel system of my car so this is all from the various information provided by Jaguar. First, here is the key to the wiring colour codes.
The car has two fuel level senders, one in each side of the saddle. On the side that has the pump (RHS) there is a combined connector so I guess that’s why you find four wires. The two wires for the pump should be in braiding and are Green/Orange & Black/Red. The other two wires (I suspect the thinner ones) are for the level sender and they should be White/Red & Brown/Red on one side and White/Blue & Brown/Blue on the other.
I think the voltage you’re measuring is probably for the level sender. The fuel pump is not driven with 12 volt DC supply but by a pulse width modulated signal. This is a signal that switches between +V and -V rapidly and the system control varies the duty cycle to control the pump speed.
If you look at the Control & Operation Section of the description of the fuel system in the TG you’ll see that the fuel demand comes from the Power Train Control Module and the various sensors that are connected to it. The signal is sent via the data network to the RECM which in turn supplies the power to the pump. Even though it’s PWM signal I would have thought you should be able to see some volts between the G/O wire and ground with the ignition on. If you find volts there, it does indicate the pump has failed but if not you are getting into an area of fault finding where you need more than a multimeter. I would definitely recommend getting the car scanned to see if there are any fault codes that might pinpoint the problem.


(Big Michael) #30

Hi Eric!
Thank you for the color codes!
I am embarrassed to report that all my research yesterday was done with the #7 relay resting serenely on top of some papers on my computer desk. I had removed it for some worthy purpose and failed to reinstall it. I finally noticed it as I was preparing to make this reply.
Things make a lot more sense with the relay in place. :slight_smile: The two thin wires still show 10+ volts, whether the ignition is on or not. However, now the two thick wires show 11+ volts with the ignition on and nothing with the ignition off.
Time for a new fuel pump, I presume?

(Eric Capron) #31

It’s got to be a strong possibility if you have supply volts and the pump doesn’t run. I hope that they are not too expensive. There maybe cheaper alternatives to a genuine Jaguar one. Worth investigating before you splash the cash.


(Big Michael) #32

Hi Eric!
If you order the whole assembly they can run as high as $500.00!
However, the pump itself, without all the hardware, is anywhere from $12.00 to $80.00. Guess which way I went. :slight_smile: If you google 2002 Jaguar S-Type fuel pump replacement, you will find a You Tube video showing how to replace the pump only.
The pump is available through Rock Auto and Ebay. Ebay is cheaper, with a wider selection.
Again,I can’t thank you enough for your help!

(Eric Capron) #33

We’re all waiting for the dénouement as you drive it away!


(Big Michael) #34

Hi Eric!

The denouement has come to pass!
New fuel pump installed and she purrs like a kitten.
Many thanks to all of you who took the time to help me!