Just been doing some work on the old girl. Replaced rocker cover gasket. Now turns over ok but wont start. Any ideas? Leads are numbered one to six one at the front six at the back replaced in same order. Hmmmm

 

it was running fine. have had the cam cover off for a week or two while i found time to get it back on. where is the intertia switch? Turns over no worries but no kick nothing

 

how to u make sur ethe imobiliser id not working ? if its fitted im not sure. 91 xj40 sovereign. alarm comes on occasionaly turn it off with remote. As a sidelight get a high pressure escaping from fuel tank when i open the fuel cap.

 

Spark at 3 and 6, no fuel on plugs.

 

where is the fuel relay located on a dec 91 xj40?

 

Mick,

Maybe won't be your answer but if there's a bad connection or a problem with the oxygen sensor heater relay (on the firewall, near the back of the cam cover) the fuel supply gets shut off and the car won't start.

Larry

 

Dumbo may have bumped it ? lol we shall see thanks for the tip. Into research now even located what I think is the fuel relay a yellow one staring you in the face when you take off the trim underneath the glove box. Damned tight litte *******s those electrical connections im am stuffed if i know how to get them apart

 

Hi mickvic,

According to the Haynes manual, which you can download free from this forum, the fuel pump relay on a '90-'92 is yellow, mounted near the brake pedal housing on a LHD car, so on your car it probably would be under the glove box.

On our '93, the inertia switch is in the outer corner of the driver's (left) footwell, behind the carpet. It's a black plastic box with a button on top that pops up when it is triggered. To reactivate, you just push the button down.

Cheers,

Don

 

Thanks Don, the intertia switch just shows a very faint line of red so not tripped (wont go down) the yellow relay is one of a number.

 

Lawrence cant see a relay , I do see a spade connector for the wire running down to the oxygen sensor (i presume) going into the exhaust. Cleaned up the spade connector. Larger brown connector passenger lh side of rear cam cover wire coming out the bottom looks to heading for the starter motor, white line coming out the top. Havent done anything with that what would that one be for?

By relay I look for a small square box of some sort and cant see one.

Have not tried her tonight battery is on charge and have cleaned up all earths in the engine bay. Positive cable from battery to starter has its black insulation either flaking away or eaten away lol. Have a new one off ebay may as well put that on

Don and lawrence once ive done that ill try and start her if no go I presume examine the starter relay is next and test fuel pressure. Would that be the way you would go?

 

Sorry Mick, I was just looking through Haynes and the relay I was referring to doesn't appear in the diagram of relay locations for the 90-92 MY cars - seems the oxygen sensor heater relay was only used on the 93-94 cars.

Larry

 

Not a worry. Its damned cold here at the moment and a struggle to get out and work at night as the car is not in the garage. I seem to be having consistent bad luck with cars at the moment a small bmw which I bought for my daughter lights go on but no starter and it was starting fine, was about to get it off to the mechanic. Now the jag, fixed nearly everything about to get it off for a roadworthy check and now she wont start. Have a rover did same thing turns over wont start, spark no fuel. Happened a while ago now. No idea with that one. Bit of a black hole here. Bermuda triangle. What steps would you suggest next with the jag?

 

Hi Mick,

If that yellow relay is one of a group, if there's another yellow relay, try swapping their positions to see if things improve. Off the top of my head I can't recall what the other relays are - Haynes should tell you if you consult the correct '90-'92 diagram.

A very common cause of cranking but no start is low battery voltage. If the battery voltage sags much below 11V while cranking, the ECM will not trigger the ignition to fire. If you have a fast-reacting voltmeter you can measure the voltage while cranking.

Another known problem is the ignition switch itself. The last time I needed one replacements were still available:

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Please keep us informed.

Don

 

I have spark at the plugs don. Charged battery up, turns over nice and fast, no start. Cracked nuts at either end of fuel rail, no pressure at all barely a dribble of fuel.

 

Hi mickvic,

Okay, sounds like fuel pump relay, fuel pump, or the fuel pump electrical circuit. The following procedure, courtesy of Bryan N at the Jag-Lovers forum, works for the '93/'94 cars. Your '91 may have some differences, but it will give you the idea of how to rule out possibilities until you find the root cause:

1) With ignition OFF
2) Remove fuel pump relay (black base, right rear corner
trunk above BFM)
3) Do you get 12 volts at pin 30 (Brown/yellow) of the fuel
pump relay base from fuse C6 in right fuse box?
4) If yes, jump pin 30 (Brown/yellow) and pin 87 (Blue/red)
in fuel pump relay base - does the pump run continuously?
5) If pump does not run, fault is in the wiring / connector
between fuel pump relay and pump
6) If pump runs, suspect fuel pump relay is defective.
7) Replace / re-fit fuel pump relay
8) Remove oxy sensor heater relay (yellow base on firewall)
9) Do you get 12 volts at pin 30 (Brown/pink) of the oxy
sensor heater relay base from fuse C4 in right fuse box?
10) If yes, jump pin 30 (Brown/pink) and pin 87
(Blue/purple) in oxy sensor heater relay base - does the
pump run continuously?
11) If pump runs, suspect oxy sensor heater relay is defective
12) Replace / refit oxy sensor heater relay
13) Remove EMS main relay (black base on firewall)
14) Do you get 12 volts at pin 30 (Brown/yellow) of the EMS
main relay base from fuse C1 in the left fuse box?
15) If yes, jump pin 30 (Brown/yellow) and pin 87
(White/brown) in EMS main relay base
16) Try this both with the ignition ON and the ignition OFF
17) Do you hear the fuel pump give its half-second priming
burst? [You can repeat this many times and you (or an
assistant listening at the open filler neck) should hear the
half-second 'whirr' of the pump every time you jump pins
30 and 87 of the EMS Main relay base]
18) If yes, suspect the EMS main relay OR the EMS ECU is
defective (the latter, very unlikely but possible)
19) Turn ignition OFF
20) Replace / re-fit EMS main relay
21) Remove Ignition 'ON' relay (on a '94 it should be in a
white base on the firewall but on a '93 it may be buried
under the dash behind the radio)
22) Do you have battery voltage at pin 30 (Brown) of the
Ignition 'ON' relay base?
23) If yes, temporarily jump pin 30 (Brown) and pin 87
(White/pink) in the Ignition 'ON' relay base
24) Do you hear the half-second priming burst from the pump
each time you jump those pins in the Ignition 'ON' relay base?
25) If yes, suspect the Ignition 'ON' relay is defective or
fuse A5 (fuse A3 on ‘94 models) in the left side fuse box -
but if either is defective, you will get NO dash lights when
you turn on the ignition.
26) If when you jump pins 30 and 87 of the Ignition ‘ON’
relay base you do get dash lights but you do not hear the
half-second priming burst from the fuel pump suspect the EMS
Main relay.


Please keep us informed.



Cheers,


Don

 

Well Ive found the pump is in the tank...and ive got the wrong fuel filter. Was hoping the pump was external...

 

Hi mickvic,

Sorry your ordeal continues. Removing the fuel tank to replace the pump is really not as hard as it sounds. On your '91, there may even be a rubber hose that connects the fuel filler neck to the tank so you can disconnect that without having to disconnect the fuel filler assembly from the inner fender (on our '93 the fuel filler neck is welded directly to the tank, so the entire fuel filler latching mechanism had to be disconnected).

The trickiest part of the entire job is disconnecting the two fuel lines that attach to the bottom of the tank. You have to reach around the rear suspension and differential to access the wire clips that secure the lines to the tank fittings. Each wire clip has a small "loop" that you grab with long needle-nose pliers or a long flat screwdriver and force sideways, away from the hose and fitting. I like the needle-nose pliers best because they can help you prevent the clips from flying into some inaccessible part of the rear suspension when they come free.

This isn't one of my better phototutorials because I was in a hurry and working out-of-state, but hopefully these photos will be helpful:

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Cheers,

Don

 

Done how do you do this: 3) Do you get 12 volts at pin 30 (Brown/yellow) of the fuel
pump relay base from fuse C6 in right fuse box?

does that mean run a wire from the fuel pump relay to fuse six in the rh fuse box?

And: 4) If yes, jump pin 30 (Brown/yellow) and pin 87 (Blue/red)
in fuel pump relay base - does the pump run continuously?

what do you mean by "jump pin" 30 to pin 87?

 

Till Don gets here, I think what he is saying is

3) measure the voltage at pin 30 with a multimeter

4) use a piece of scrap wire to connect those pins (by-pass the relay)

cheers

Larry

 

Hi mickvic,

Larry is right, as usual!

By the way, I think I mentioned that Bryan N's diagnostic procedure was written for the '93/'94 cars and may not always agree with your '91 wiring. You may have to rely on research and/or intuition if your wire colors don't agree on certain steps.

I hope to hear soon that you've isolated the problem.

Cheers,

Don