'86 XJ6 VDP extremely rough running and cutting out

Quart of Pepto Bismol in L tank may have helped. Still running smoothly. Planning colonoscopy L pipe tomorrow. Seriously, could fouled spark cause raw fuel and resulting smoke? Would I have noticed sound, performance change? Just a thought…Alan

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Smoke colours tend to define what’s a being burnt, white either coolant or brake fluid, blue is oil, black is over fuelling.
Keep an eye on the brake fluid level if it drops over the next drives with no obvious leaks then its probably time to look at the booster.

…Fluid levels, brake or coolant, must be watched over a fairly long time to detect any anomalies, Alan - there is no quick way…

No repeats; no problem - but if there is a repeat; it would do to record the circumstance, not just observe the symptom…

Frank
xj6 85 Sov Europe (UK/NZ)

Words of wisdom, Frank. Thanks… And I’ll keep a closer eye on color, Robin. An intermittent problem is always the worst kind to diagnose, human or Jag. I’ve topped off brake and coolant levels.
I also picked up a set of spark plugs (Champion Copper Plus N12YC) yesterday and I’ll replace them later this week. I gave each of old plugs a healthy squirt of Kroil to hopefully make job easier.

Plugs 1 - 5 came out easily, but # 6 broke and left piece of plug in boot. In trying to remove it, I pretty much chewed up the boot. New plug harness on the way from Moss. I’ve numbered connections on distributer cap and they match the 15-36-24 firing order. Question…should I match these in same positions or can I simply follow 15-36-24 sequence starting in any location on dist. cap?
Alan…101

You must keep them in the same locations so that when the distributor fires on say socket 6 cylinder 6 ends up with spark!
The spark must happen just before the mixture is fully compressed and not during the exhaust stroke or when the piston is at the bottom etc…

Put some antiseize on the plug threads and be careful as the aluminium threads are delicate.

In case you forgot where the wires were it’s no big deal, everything can be figured out.

[quote=“Alan_Munson, post:286, topic:436930, full:true”]
Plugs 1 - 5 came out easily, but # 6 broke and left piece of plug in boot. In trying to remove it, I pretty much chewed up the boot. New plug harness on the way from Moss. I’ve numbered connections on distributer cap and they match the 15-36-24 firing order. Question…should I match these in same positions or

can I simply follow 15-36-24 sequence starting in any location on dist. cap?

Goodness gracious no(!), Alan…

The spark follows the rotor to the plug lead it is pointing to - and must point to the cylinder ready to fire. As David says; if the engine ran OK before; replace the plug leads on the dist lid as was - if(!) you are sure…

From scratch; you set the engine to TDC with the #6 on the compression stroke. The #6 lead must be placed in the position on the lid the rotor points to. Then place the rest of the leads counterclockwise on the lid in the firing sequence. 6-2-4-1-5-3 - the #6 is used for easier access…

Frank
xj6 85 Sov Europe (UK/NZ)

Not to worry. I’ve taken several pics and some sketches of existing connections, so I’ll replace “as is”. It was just a thought…Alan

![Original plug labels-fotor-20231127131942|581x500, 50%](upload://vBvOrEbObnXfJfyuXcXzNsPbW78.jpeg

Based on this information and “tug-tracing” each wire, I think I will be able to pull this off. Please check my work. I’ve confirmed #4…Alan 101

Yes…er…well, Alan…

Seems good to me - and if the engine runs OK; it is! Your 'ignition sequence is then 4-1-5-3-6-2…:slight_smile:

Frank
xj6 85 Sov Europe (UK/NZ)

Mission accomplished…runs fine :slightly_smiling_face:

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Good to hear, perseverance pays off.


Wondering about pros/cons of replacing current generic coil with PerTronix Flamethrower II. And if I do, should I retain ballast?

If the engine runs as it should ‘as is’, Alan, there is no point - a fancy name is no guarantee…:slight_smile:

You can compare primary and secondary resistances on the two coils - it reflects, to some extent, current and performance. The CE system works OK with a with a wide variety of coils - but may not be too happy/lasting with high coil currents…

Frank
xj6 85 Sov Europe (UK/NZ)

I wouldn’t change it either. When the original fails it’s a good spare - ballast is needed for 6v coils, not for 12v.
The way it works is the 6v coil is overdriven at 12v during cranking, afterwards it is supplied with 6v from the ballast. With the electronic ignition it doesn’t make as much sense as it did with points systems.
That being said my 1969 did not come with the fancy ballast system and I never had starting issues because of it.

OK…I’ll leave things be and have a spare. Turning my attention to fan control. Works on high and defrost but not on low or auto. I’ve snooped through the topic but not sure where to start…

Start at the relay bank and the fan resistor, Alan…

The fans are operated by microswitches via the resistor unit and relay bank - the latter has 4 relays within a single unit. The relays connect main power (50A fuse) to fans. Two microswitches on the function control activates the ‘Hi’ and ‘Lo’ relays; in ‘Hi’ the relay connects power directly to the fan motors. In ‘Lo’ the relay connects the motors via a resistor - which lowers fan speed…

In ‘Auto’; two other relays are operated by two microswitches at the servo, ‘auto high’ and ‘auto low’ - both originally via the resistor unit with different resistances for different fan speeds. The position of the servo, as set by the AC amplifier, dictates which relay is activated.

As fans always runs whenever the function control is out of ‘off’ something is amiss - then it gets complicated - you may have two faults. One or more relays or microswitches may have failed - or resistors.

You really need the wiring diagram as connections are rather complicated - but as neither fan speed operates in ‘Auto’; check if the 15A AC fuse is OK.

Start with locating the relay bank, behind ‘left’ consol side cover - ‘main’ power is brown/white. AC amplifier (‘right’ above the relay bank) power is green/slate.

Then we’ll see…

Frank
xj6 85 Sov Europe (UK/NZ)

Thanks Frank. I’ll try to remove L side panel and go from there. Where is 15 A a/c fuse? It’s not listed in L main fuse box…Alan


Yikes! How do I begin?

There appears to be an inline fuse on the right. Can I evaluate status of relays without removing relay module (part # C.46179 ?).