No power to my fuel pump fuse?
 

got my multi meter out today and found out I don't have power to my fuel pump fuse... actually there are several of the fuses in that block that don't have power... disconnected and re-seated all the connectors.. still nothing...
HELP????

Some fuses are on the downstream side of a relay and only active when relay is. And i assume the ignition was on also :)

yes ignition was on... also there os only power to one of the poles on the relay... I checked others and there was only one pole without power...

i would suggest you get a wiring diag for your car so you can see the circuits and applications. lots of circuits are ground application and 1 hot, then a gnd signal from ecu and closes relay to complete a gnd circuit as is MOST new cars today even though yours is not very new anymore. most circuits are gnd circuits and triggered or pulsed grounds

Hi Glenn,
Check these fuses,
F3 5A, trunk fuse box, that is the ignition supply to the fuel pump relay in the same box, relay 4.

F7 20A, trunk fuse box, that is the fuse for the fuel pump from the output of the above relay contact.

In the high power protection module, also in the trunk, you should find 3 x 250A fuses. You are looking for the one with 2 output lines connected to it. Check this one also.

Also check the voltage with ignition on, at the input and output of the fuel pump relay.

Hope this helps,

ok.. no power to F3..
checked the high voltage block.. 12.30 all the way round
power to fuel pump relay 12.28 input... nothing on any other.

Ok, now check that your inertia switch has not tripped because that is what feeds the ignition positive relay in the trunk fuse box, which then feeds F3.

You should have ignition switched to position II while checking.

inertia switch is good... still no power

What you are seeing is normal steady state. The fuel pump (and relay) will not run continuously, just for a few seconds when the ignition turns on or if the engine is running. The relay is ground switched, as Brutal said. Have someone turn on the ignition while you are watching the voltage to the fuel pump...you should see the voltage briefly appear then drop out if the engine does not start.

Chances are you have a bad pump.

I have installed a new fuel pump.
the ignition relay in the trunk was out of place.. I am NOW getting power to f3.. 12.23v
again i had my wife cycle through the key positions and am only getting a couple mili-volts from to the f7 fuel pump fuse. I am getting 12.28 on two poles of the fuel pump relay

Brutal,
I found and downloaded a wiring diagram... looking at it now...

There will be 12v (to ground) on both Fuel Pump Relay COIL terminals until the ECM pulls one of the terminals to Ground, Energizing the Relay.

If you ALWAYS (with the key on) have 12v (to ground) on both Relay COIL Terminals, the ECM is Never Energizing the Fuel Pump.

These measurements are with the Relay Plugged in to the Socket.

The Relay COIL Terminals are the ones that are opposite and Parallel to each other.

The first link is for a voltage test I made to my 99xk8 and should help the second link is a wiring diagram for a 98xk8. Both should help.

Link JagRepair.com - Jaguar Repair Information Resource
Link http://www.jagrepair.com/images/Auto.../jagxk1998.pdf

Okay... with 3 and 5 jumped... I get fuel pump...
but no difference with the key. what else is on that circuit that I can check that may or may not be working? or are we looking at computer problems?

Try a relay swap (the brown ones are identical) if you have not already.

Assuming you still have the problem, you should check for wiring continuity to the ECM on the Pink/Brown wire.

If there is a fault on this ECM circuit to the relay, or the ECM itself, it should also set an OBDII fault code (P1230) and come back even if you reset the code.

Continuity between the pink/brown wire and what?
Also the car will NOT connect to my OBDII... it's the Innova 3100 I have read in the OBDII thread that it is known to work.

Just wondered whether your anti theft system has been activated recently.

Also, does the red light by the gear lever flash when you try to start?

Also.. while going through the stuff I got with the car... i have found two other ECMs I was told they changed out the ECM and reprogramed/flashed it so it looks like they felt it was a computer problem as well... BTW I have like many gotten the car in this condition with very little information attached.

no red light from the security system

Pin one of connector EM13 on the ECM and the fuel pump relay

It may be advisable to peak inside the ECM at the circuit board and look for physical evidence of dark brown stains around the capacitor cans and corrosion.
ECMs of this vintage frequently have leaking capacitors that can cause a bevy of unpredictable problems

Disconnect the battery first.

circuit board looks good..

maybe this is also where I say... I'm getting trans fault, failsafe, traction, stability, incorrect part, on the info center...

Not sure if that comes into play here or not..

Yes, that is an important clue.

Check all the fuses to the ECU and instrument cluster.

With no OBDII, I am starting suspect the internal High Speed network is down.

Do you have an oscilloscope by any chance? Without any history, and with no OBDII to go on, it is a guessing game unless you start looking at signals. The most likely suspects are the instrument cluster and ECU.

The instrument cluster computer is the hub of all communication in the car, and it has a habit of failing from jump starts with a dead or missing battery, so it is also a prime suspect.

No oscilloscope. The ECU has been changed.
And I also want to say thank you to everyone who is helping out, I would be LOST with out you guys!!

is there are visualy obvious clue to a short if I were to remove the cluster? I'm kind of thinking I may go ahead and get this one rebuilt.. the car does do some weird stuff... can't shift out of park (started after reconnectiong the battery) the rear windows go down by themselves. The battery goes dead in a couple days... and here's the kicker... it is impossible to connect the battery without sparking, so there is a dead short somewhere. I did install a battery cut off switch to minimize this. Without the car running I have to charge the battery often to minimize the sparking.

You can find used clusters for well under $100 on ebay. This could be the cheapest path. Based on my experience '97-'99 XK8 or XJ8 clusters will work, but the best odds are to get one from another '98, otherwise you should confirm SW version information which is often not available info from recyclers.

A problem in the cluster is still just an educated guess though..there could be other issues.

You can also have yours rebuild.

whiteXKR.. your educated guess is better than my un-educated guess :) and not too expensive. I don't doubt there are other problems but this is not going to break the bank and will eliminate a potential issue...

I have ordered a used instrument cluster. It'll take a few days to get here... the waiting begins.

I hope it at the very least restores OBDII operation, that will be a big plus for diagnosis. Disconnect the battery before unplugging the old one and plugging in the new one.

I hope so too..

Ok... I have installed the new/used instrument cluster and the OBD2 scanner still won't communicate with the car... what's next?

Also I can start a new thread if needed to keep problems seprate?

Thanks!
Glenn

hello i am have the exact same issues did you ever get this straightened out im dying to know the conclusion