Car stops =/

[Damian.Gardner]

Hi there, took my v12 xjs out today and it just started cutting out =/ Mostly at junctions but sometimes at speed. One time it would'nt start for about 60 seconds. Im wondering if this is a possible fuel filter problem or may be an electrical fault. Im not sure how to test for these. Any Ideas?

The engine would turn over but not start for a while, then it kicked in.

Thanks

Damian

[Damian.Gardner]

Its funny how being stranded in the middle of no were can help you solve a problem. Seems that the power lines for the fuel pump had come loose. When I eventualy stoped looking at the engine for wire faults I found it.

[leodistiger]

Hi Damian

Sounds like a problem I had just recently - although when mine cut out it would take longer before I could get it to start. In the end I have had to replace the Idle Speed Control Valve / Auxiliary Air Valve

Have you had yours checked?

Nick

[Damian.Gardner]

As stated in the post above it was the fuel pump wires that come from the
battery that came loose. But thanks for your response.

Damian

[Mark_B]

Hey there's a lot of readings of this thread showing (158) for the number of postings, does this mean these cars stop a lot?

While I'm here, I might as well hijack the thread now the original issue is closed and say I did have the 'engine stopping' thing a few years ago, it only did it coming up to a stop at road jucnction or traffic lights, never while driving like Damian's.

Why my engine stopped was because of a blocked-with-gunge butterfly throttle valve. Common fault with many cars. When foot is off accell pedal, throttle valve completely closes up, no air gap, shuts the air completely off. The Idle Speed Control (on the jag) is supposed to maintain an even tickover speed, but doesn't function at all when rpm below 500, so there's no 'pullup' effect and engine stalls. I'd found while car slowing down to a stop that if I declutched quite late, the engine rpm was prevented dropping below 500 and the ISC duly pulled up the revs and prevented the stall (by opening air valve as required), a useful tip to try if suspecting this problem.

When the throttle buttterfly cleaned out of gunge the Base Idle Speed became restored (just above 500 rpm), which is within ISC capture range. Of course if there's a different engine problem that's causing BIS to drop, you'll get the same 'stop' symptoms.

The fault can be hidden/compensated for by turning up the throttle stop screw to widen the throttle gap, (the one that's supposed to be set with feeler gauges according to manual).

Note that adjusting the allen key air screw in the ISC will make no difference to the BIS rpm, a common misconception!, all that does is set the maximum opening of the ISC air valve (the max amount of pullup).

[dhdove]

Mark B
Sorry old chap, don't understand your banter........
Regards
DH Dove

[Mark_B]

It's OK I don't blame you, thanks for pointing it out, I guess it doesn't help me confusing the topic: 'car stops' with: 'engine stops' and then hijacking the thread with it!

What I should'd said is base idle speed (BIS) can go screwy and the 'engine stops', infuriating though not as bad as 'car stops', as the former is usually while stationary, the latter could be in the fast lane- not to be sniffed at.

Though while I'm here bantering again, the idle speed control on these cars is quite often misunderstood. Way people get by with the ISC is to follow instructions religiously but blind faith doesn't help you when something is missed out at the starting point or not 'normal' which is where having knowledge is handy. I've seen someone wind the hex screw right out the air valve and couldn't understand why the idle speed kept dropping back to normal each time he stopped turning it. The idea of my hijack posting was an excuse to share my knowledge, when I'm old and senile I might read it

[dhdove]

Mark
No worries, what I meant was that the technical bits lost me about half-way through your post - my prob, not yours. Share away, I'll try and keep up in future
Best Wishes
DH Dove