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Engine ‘start’ is one thing, Lee - but what about the running when started?
Pushing in the AFM flap increases the amount of fuel delivered by the ECU - that’s all…
Frank
xj6 85 Sov Europe (UK/NZ)
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OK Folks, I’m sure all of you will be glad to hear that my '87 is now starting okay unless the problem re-occurs. What did I find? Nothing! After giving up and letting the auto cool down to temperatures in the 20’s, I tried to start yesterday morning and it fired off! Didn’t think it would. So why? Well I suspect that with all the checking done, disconnecting plugs to the starting ignitor etc, perhaps corrected a bad connection. That’s the only thing I can come up with. Question is, what really controls the fuel/air mixture(AFM flap) when a cold start? Took it to the grocery store last night and noticed that the left two instrument panel gauges were essentially unlit. A completely different subject, but wonder how in the devil would one ever be able to replace the instrument panel lights??? They don’t last forever!
Lee
It happens.
[cold start circuit] + ECU (air temperature, water rail temperature, air volume = opening of the air flap by air rushing through) changing injector pulse length (+ Auxiliary air valve adding air that has already been measured and will have the ECU add more fuel together with that extra air so the idle is higher, not affecting mixture)
Twist the large instruments to the outside of the car, pull out warning light cluster, reach through for the small instruments and don’t lose the thumb nuts and so on… the heated rear window lamp could be different.
To pull the two offenders out, you only need to pull the left large instrument. The rest by undoing the ski slope or panel. Quite obvious if you look at them, pull out the window lock switch and the upper two a bit.
Or as in carburated USA cars. Auto or hand Choke and fast idle cam or hand throttle…
From atop? Remove the crash pad and access the back side of the fascia.
Via the speedo or tack openings? Twist and push?
I may need to do that.
Carl
Try a piece of tape to get a better grip. They can be stubborn, but it’s a counter-clockwise bayonet for you. I had a hard time with one…
You, sir, are a master of understatement! They can be an absolute devil to get out if they have been in there a long time.
David
True - but getting the dash top out means disconnecting the battery (important this time) and fiddling around with the cabin temperature sensor duct besides removing the cheek panels and the bolts from below, besides getting it back on correctly with the defrost foam pads, so it is about the same work twisting it out. They can be an absolute devil. I had others come out nicely, though!
Either way not an easy task it appears. I may just forget about that and use a flashlight if need be. Will attempt to get the large left one out by twisting but if it does not want to come out, I will not press the issue.
Lee
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Good on you, Lee - what is cold and hot idle…?
For the record; the xk engine is a strictly ‘feet off’ starter - if at any time during cranking you move the gas pedal the engine may not start. Another side; if the engine initially won’t start, for whatever reason; prolonged cranking will eventually flood the engine - and just waiting around for a (long) time will clear it. And the engine may then behave normally…
So it may, as you say, be a one-off - only to be pursued profitably if the problem recurs…
Frank
xj6 85 Sov Europe (UK/NZ)
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Your message is interesting Frank. Yesterday I went out to start and it spun & spun and not one fire. I thought still have the problem. But then I thought I would step on the accelerator pedal one time to see if that made any difference. It did!! With that short one push on the throttle, it fired off. So I may still have a problem if you say kicking the accelerator pedal is not a normal procedure to get the auto to start. Anything you would like to add would be appreciated. Is the engine being flooded or not enough fuel?? No way to tell.
Wondering what just one short push & release of the gas pedal does to make it start? Weird.
Lee
I don’t see what a push and release would activate to get a start?
OTH, contrry to norml start, holding the throttle open might clear an over fuel and get a start.
But, just wait a while will also do that!!!,
On balance, I suspect the push and release was a mere coincidence. The issue is intermittant and still present…
Fired mine up yesterday. Almost immediate fire…
Carl
A very perplexing problem. Don’t know why I get these always weird, far out problems.
Lee
Well this morning, same thing, would not start. So I again kicked the throttle once and tried again. This time I got some fire but it would not take off. Then after that no start. So back to the drawing board.
Lee
I had a theory that when mine did it it was too lean to ignite, but then after some cranking it flooded. Or so. Now it starts great. Anyways, as I said, it happens.
Next time you have a no start episode pull a couple spark plugs. Are they wet with gas?
Cheers
DD
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Firstly, Lee; pushing the throttle without the engine turning has absolutely no effect on anything but throttle linkages. If pushing the throttle while cranking has an effect it is to allow more air into the manifold - ie your idle set-up, throttle gap/idle screw/AAV, does not allow enough air into the engine.
Operating the throttle to compensate for wrong set-up is extremely tricky. The xk engine is very particular; it wants it just so - and getting air flow right using the pedal is dumb luck. If you get it wrong the engine will baulk and/or refuse to start - and further cranking just aggravates the situation. The reason for this is obscure, its likely overfuelled due to ECU confusion. Flooring the pedal while cranking, as Carl mentioned, is a factory suggested remedial action for one-off nonstarts.
You need to go back to check basic idle settings!
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Disconnect air duct at the throttle body. Clean out any gunk i the throttle body and set throttle gap to 0.002" - dust, if needed by setting the (tiny) throttle stop screw. Ensure(!) that the throttle cable moves freely, and with a slight slack in the throttle cable - to ensure that the butterfly responds consistently. (It won’t hurt to check the air ducts from leaks - including tight clamps)…
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Remove top hose on the AAV and verify that the slide is about half open when cold. If not; try ‘massaging’ slide movement with a small screw and open it when hot.driver. The slide is spring loaded, by a bimetallic strip, to close the slide when the engine is hot and open when cold - to allow extra air with the engine cold. Recheck function when the engine is hot. The AAV can of course be checked out of the car, but for cold start problems a visual slide inspection is adequate…
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With the engine hot; set idle to 800 - 900 rpms, which of course requires a running engine…
This done; try starting - ‘feet off’. If these setting are correct; the engine gets the appropriate air for a cold start - if it still refuses to start, the problem is elsewhere. To be pursued…
Frank
xj6 85 Sov Europe (UK/NZ)
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1 Like
Thanks for the info Frank. I will have to get my training legs again on this vehicle. Each auto has their own peculiarities and the Jag has it’s own book almost. Yes it appears that the vehicle is not getting enough air, since when I hold the air flapper open it will start.
Lee
The air flapper regulates the fuel volume. The throttle regulates air. You’re on the wrong path.
That does not surprise me. I am totally confused!!
Lee