I have a 1995 3.2 LWB Sovereign and it lost all power on me three times the other day.

I'd picked up the car from a garage, having had the exhaust downpipe welded up, with a pretty empty tank (needle on E, light on). I've never let it get that low before. I filled it up to the top as soon as I could, adding 67 litres. I then drove for about 25 minutes down an A road (so ~50mph) just fine. I then turned onto a dual carriageway, travelling at about 70 mph, when I noticed it started to slow down. There didn't seem to be a loud noise, it didn't sound rough - it was exactly like I had lifted off the throttle pedal. There were no lights on the dashboard that I recall. Pressing the pedal had no effect - the revs didn't change, it continued to slow at the same rate. I pulled over and slowed to a stop. I didn't turn the ignition off and the car idled happily in D and both idled and revved OK in N and P. I set off again, warily, and 10 minutes later, it did it again. This time, I didn't pull over and kept my foot on the throttle (perhaps pressing harder than I would to maintain my speed). After a few seconds of the speed slowly falling, there was a big 'thump' through the drivetrain and the car suddenly sped up. This sequence of events happened again a short while later, to I pulled into a nearby car park and called my recovery company.

They checked the fault codes and just found P1621, which they didn't have any further details on. They checked the current on the fuel pump and at idle it was 5.3A rising to 6.0A after a few minutes. With an escort behind me for safety, I drove the vehicle back through the middle of town (I wanted to avoid being stuck on a major road) and along local roads until I got home and it was fine all the way, even with some periods of sustained ~60mph and a few 30 - 60 mph full throttle runs.

My biggest problem is I don't think my wife will ever want to go anywhere in it again, having wasted four hours of our weekend getting recovered and doing the journey all over again in her car (we were on our way somewhere important and far away). My second biggest problem is, I'm not sure where to start with the diagnosis. My best guess is running the tank low has shifted some dirt which blocked the fuel lines temporarily but managed to clear itself. Either that or the fuel pump died and came back to life. It probably hasn't had a fuel filter change in a while, so maybe that's worth doing just to be safe.

Suggestions welcome!

 

I would more suspect an electrical issue.

I think I've heard of that code and a similar power loss being caused by the crank sensor breaking down when hot. You could try testing it but they're cheap enough to just swap out (if you don't buy from dealer). Also, if it hasn't been changed it's good preventative maintenance as they are a common failure point.

Another possibility is a coil breaking down when hot and arcing causing some kind of electrical surge.

That's my suggestions!

 

i would change the fuel filter as preventative maintenance even if the car seems fine now, and as an added bonus tell the wife thats what the problem was and now it's fixed. And considering the low fuel level it very possibly could have been some junk in the tank so maybe run some fuel system cleaner through it as well

 

Saw this in the thread titles as I was scrolling down to my usual destination in the XK8 section and it brought back memories.

I had an X300 3.2 Sport for four years and 65K miles. It also had this mysterious power loss a number of times during which the revs would fall off to idle and no throttle movement had any effect. Very worrying and potentially dangerous.

The possible causes were discussed on another forum. Two other owners had similar incidents and the common factor there was it affected the 3.2 only. This may have been co-incidence but no 4.0 owners at the time reported the problem. We all eliminated fuel supply problems and focussed on electronics.

The code P1621 was, if I remember correctly 'ECM engine immobilisation circuit malfunction' but do check this as it was a few years back and a number of Jaguars ago for me.

The only temporary resolution was to stop, switch off, remove the key and then restart.

One of the other's affected was a German electronics engineer who did some analysis and sent me an eMail or some notes at the time. I can have a hunt for this in backup CD's if you don't get any more up-to-date knowledge from current owners.

Regards,
Graham

 

I tried to drive the car back to my house tonight with a view to getting it through it's MOT re-test in the morning before the 10 day re-test period expired.

First it sat idling for a few minutes as I discussed with my mother's partner whether the exhaust was still blowing. A quick feel under the car confirmed, yes, it's still got a small leak. The garage who fixes the exhaust will be getting a stern letter in the morning.

Anyway, I set off and managed to drive about 100 yards up the lane and out on to the main road when it died again. This time I was accelerating up hill, but I'd only got to about 10mph. The battery light came on, I felt the car slow down, I noticed the battery needle was well below the mid-point and then it stalled. I recall the first time I tried to restart it it wouldn't crank, so I removed the key, double checked I'd put it back in Park (there's a lot of bleeping if you don't do that), waited five seconds and tried again. This time it fired up fine, so I reversed it the 100 yards or so back from whence it came.

I recall when we I had it serviced, one of the coils had a hairline fracture. Given I saw the battery light on this time, before the car stalled, I think that's probably the first candidate for replacement. I remember the coil, as it had white marker pen on it, like it had come from a breakers.

Given that, I probably know the answer to the next question, but is it worth getting a second hand coil off ebay for £12, or paying £60 for a new one?

Cheers,

JP

 

JP,

I can see you're connected to this thread now and, given it's after 11:00 at night and you're hoping to go for an MoT in the morning , are probably looking for some quick answers!

A very slight blow on the exhaust might get you a pass with an 'advisory' but anything worse will have to be fixed before it will pass.

Is the battery on its last legs or does it just need charging after all the starting attempts recently?

You think you've a faulty coil - do you have a misfire on one cylinder?

 

The MOT's a no go as the car is parked up 20 miles away. The battery was declared a 'fail' on a battery tester, but it's started the car OK every time so far. I don't think it has a misfire, but then I've owned nothing but compression ignition for the last decade and I've never had a six before, so what would I know. I would describe the idle as a little bit rough though.

Thinking about it a bit more, I do recall seeing the battery needle wave around a bit in the past. It would dip below the mid point for a few moments and then return to the 3/4 mark. The car has had a *lot* of starts lately, what with the service and the MOT. Maybe the battery was covering up some electrical fault and it's now just had enough.

 

If the battery is borderline, it can throw up all sorts of 'apparent' faults. This is definitely one to get sorted first. An exhaust blow is going to throw the engine mapping so that's the next thing.

The six is quite smooth on tickover and it should be obvious of you've a coil or plug off. eBay is probably not the best source for replacement coils if you do need one but there's no need to go for new. There's several specialist Jaguar breakers in the UK to source a good used one with a certainty of replacement if it's faulty.

 

I ordered a new crank sensor and coil next day (£120 the pair, shipped) and fitted them today. The old crank sensor wasn't half filthy. I also got covered in oil when I removed the cable bracket as the bolts seemed to also be holding on some kind of cover.

Coil #2 was the worst cracked on, so I replaced that. Coil #5 has a hairline crack underneath the black sticker, so that'll need doing soon.

Result - it's much better! Snappier starting. Much smoother idle. No cut-outs on the brief test drive. As it's too late for a free re-test and it was already on the ramp, I figured I might as well move on to the front bumper and then trailer it to the body shop for the welding work. More on that in another thread.

 

It broke down again, just as I went to leave the MOT station with my pass. Cranked, started, ran OK, dropped to 500 rpm and then died several times. It's locked up in the MOT garage now but I bet when I go back to it having had it sit for a couple of days it will be fine. It only seems to be when it's got warmed up it causes trouble.

Next stop, we'll check the voltage across the pump to check for bad wiring/relays and look to change the pump. How exactly does it come out?