Ruby, needs help

Karens xj6 , started, but oh shes running real rough.I have a brown with a white stripe wire unconnected ,that comes from the wiring harness that runs along the intake. then there is another loose end ,a green wire that I am unsure as to where it goes. I am a bit discouraged

Don’t take it to be accurate.

Bullet connector? That goes to the coil via another wire and pulses the injectors. It is very important, the engine will not run without it.

You better look closely, Mark - brown/white is not a ‘valid’ combination. As David’s excerpt will show; brown denotes a permanently powered wire - while white denotes a wire powered with ign ‘on’ or in ‘crank’.

A relevant combination is black/white; black for direct ground - and black/white combination denotes a wire powered with ign ‘on’ and grounded through something. Which is indeed relevant for ignition and injection. The coil ‘+’ should have 2 white; one from ign key, the other to the ign amplifier. Coil ‘-’ should have 2 white/black; one to the ign amp - the other to the ECU via a bullet connector along the manifold, as David says. And a white/slate blue to the tacho…

However, while coil misconnections will interfere with engine running - but with any of the white or white/black disconnected; the engine will not run at all. So while disconnected wires is always a concern to be rectified - other causes for rough running should not be disregarded…

Have you done any work on the car prior to the symptoms appearing…?

Green wires power sundry auxiliaries - like electric radiator fans, or headlamp wipers. Which you may not have - and is left unconnected? The best way is to find out what items do not work…:slight_smile:

xj6 85 Sov Europe (UK/NZ)


does the problem tend to go away or exacerbate with engine temp? What is “real rough”? Does the car idle on its own or does it need “help”? Which elements did you touch? Very simple, but easy to disturb: check the HT wires - firing order correct and well-seated on the plugs?

As for the wires you might think of a white/brown wire instead - other similar combos?

Good luck

75 XJ6L 4.2 auto (UK spec)

David, thank you very much, you may have given me the reason why I am having troubles. The brown wire with a white stripe does have an inline bullet connector. You mentioned the wire in question, via another wire,goes to the coil. would you email me what side of the coil? +,or -.
And via what wire? Or do I just send the brown wire with a white stripe directly to the coil? Thank you, Mark

Page 53, top left - I assume it’s positive - the bullet connector attaches to the next wire that might be connected to the coil and dangling around?
There’s a video on YouTube, XJ6 Difficulties starting, that shows that wire. Frank’s description should be helpful. Please answer Jochen’s questions (you’re probably at it right now), as that one wire should kill the engine and it won’t run long without it.
I sometimes use it to stop the engine.

I forgot to mention that the brown wire with a white stripe is 12 volts with the key in the run position

First,thank you for helping me. David Jauch from jaguar lovers forum sent a reply to my topic ,and stated that the brown with a white stripe wire has a bullet connector, and goes to the coil to make the injectors pulse. So I am a little confused. The brown with a white stripe does have a bullet connector ,and is 12 volts with the key in the run position. Mark

Mark, maybe it is to the negative wire. I can have a look on my car tomorrow if you wish.

Thing is, there is only one wire with a bullet connector that runs at the cam cover and is part of the injection wiring loom. And that is the signal wire that informs the ECU in the trunk about the engine speed so it can fire the injectors accordingly. If it has 12V you might have tested the side that comes from the coil? Is it a male or a female bullet?

thank you for your help, I must look more close when I get home tomorrow, for the 3 day weekend from work
thanks again Mark

The wire from coil ‘-’ to ECU has indeed a bullet connector, Mark, but that wire is white/black. Carefully check the color - then find the other black/white wire connector and connect the two together…

However, with that ECU wire disconnected, the injectors do not work - so a running engine must then get fuel from somewhere else. Which it should not - and such fueling will certainly give rough running…

But connecting up loose wire ends is certainly a first step…then we’ll see…

xj6 85 Sov Europe (UK/NZ)

thank you for your help to me with Ruby,I will check wires in a few minutes today, the fiirst of 2021, Mark

Testing the coolant temp circuit as mentioned will go some way in verifying if this works properly, Mark. In which case the fault is elsewhere, possibly a fueling/mixture anomaly requiring ‘full cold’ fueling for the engine to run. Ie, plugging in the CTS directs the ECU to go to intended fueling - and something is not up to spec…

The ECU receives air mass information from the AFM, flap position - but if the flap position does not give the correct info; the ECU is in blissful ignorance of it. And fuel delivery/mixture is plain wrong. Also; fuel delivery is totally dependent on fuel rail pressure - wrong fuel pressure is not an ECU input - the ECU is programmed to assume correct fuel pressure. Which vary according to manifold pressure to maintain a ‘constant’ pressure difference between rail and manifold. Which of course simplify the ECU’s computations…

xj6 85 Sov Europe (UK/NZ)

Oops, Michael - correct answer but to a different issue; it was actually for Mark’s mysterious symptoms …:slight_smile:

xj6 85 Sov Europe (UK/NZ)

sure enough, I read it wrong, the white/with a black stripe has the bullet connector,and does go to the coil.The brown/with white stripe comes from the first screw in sensor on the coolant rail closest to the firewall/bulkhead.Out of a two male flat tab connection from this sensor on the coolant rail,this brown/white wire is joined together with another white wire.I need to find out where the other end of the brown/white 12 volt wire goes.
Get this one, I try to start the car, and it tries but wont run. I put the car in drive ,key turned to start,I hear the fuel pump run,so I stop turning the key,I pull out the relay on the bulkhead where the fuelpump wire is attached.I try to start the engine,and it runs! for quite awhile,then shuts down,seems surely running out of fuel .
It seems the fuel is flooding the engine with the relay plugged in. I am not sure what is going on . Boy am I in deep
Thanks very much Frank,and all for helping me. Mark

Check your fuel pressure. Report what happens when. A cheap 0-50 psi gauge should do, plus a length of hose from the cold start (7th) injector.

With the relay out the pump won’t run anymore and after a few seconds it stops. If it runs this long the injectors can be assumed fine.

I don’t have any experience with the rearmost sensor because my car has no emissions items and the rearmost hole is a blank.

The rearmost sensor on the water rail should be the water temp, Mark - but that wire is supposed to be green/blue and go to the dash gauge…?? I can’t find any brown/white anywhere on the diagrams - and it is an anomalous combination…

With the fuel relay removed, the bump will not run (of course) - but the engine may still run for ‘some time’ with fuel already pumped into the rail.

That the engine won’t start with the fuel rail in place is a bit odd - but may have some other cause…try again?

The fuel pressure regulator may have failed, causing excessive fuel pressure - which may flood the engine. As an initial test; disconnect the vacuum hose from the pressure regulator and run the pump. If fuel leak out from the vacuum spigot; the pressure regulator has failed - replace regulator…

If no leaking and the problem, no start with relay in place, persists you need to run a fuel pressure test. However, there might be more to ‘no start’ than meets the eye…

xj6 85 Sov Europe (UK/NZ)

thank you very much for replying to my post,I have the brown 2 vacuum connections switch out of the fuel rail to check for any problems in it .
the pressure regulator vacuum line come from this switch,right? maybe it needs replacing. I will put a picture of the water rail with the many sensors
incuding the one with the brown/white wire coming out of it which is closest to the bulkhead. I checked all thru the Haynes manuel I have ,and I see no picture location, or what on earth it is called, but in the center of this sensor it shows elmwood 3000 thanks again,I wonder if Im ever going to get everything right!!
patience will travel, I will keep pluggin. Mark

It won’t do anything for you, bypass it for the time being. It increases fuel pressure when hot (then it clicks). It’s brittle, and you can remove it without fuel coming out, there is no connection.
But you won’t because it works. Bypass it for elimination .