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Posted (edited)

So you're probably wondering why I haven't updated this thread in 1.5 years.

It's because the Jaguar bit me. :(

IMG_0668.JPG.392c65874c8729eb8c1cf0d107ce6f33.JPG IMG_0670.JPG.edf7622081516dd5540eac45aa8b669c.JPG

IMG_0666.JPG.f82e18f10bcdb00abca055414a96c655.JPG IMG_0671.JPG.08287943b2b210c0866d6cc3595d5c22.JPG

I was driving home in about November 2020 and the engine was up to temp, so I decided to go for an onramp pull. It wasn't raining, I had new rear tyres, not much power, and I was only flooring it in a straight line, so nothing would go wrong.:rolleyes:

Unfortunately the road was still a bit wet, the onramp was downhill and quite narrow. For a few seconds I was accelerating with full traction, still well short of the speed limit, then maybe the auto shifted gear or I hit some water or hit VTEC, and the rear stepped out to the right. I tried to catch it with the steering but I think I lifted completely off the throttle (I'm not experienced with RWD), and the car snapped back the other way. The back left corner of the car hit the concrete wall on the left side of the onramp, sending the car across into the barrier on the right. I hit that barrier squarely with the entire right side of the car. My side curtain airbags failed to deploy in the barrier impact, so my head whacked the driver's door window (cabin is pretty small). I managed to stop the car rebounding into anything else and I drove it home.

I could not sleep at all for the entire night. :pale:

I kept imagining the police were watching their highway cameras and they'd turn up at my door to arrest me for toxic masculinity. I was very annoyed at myself for crashing another classic car (even one with unfriendly handling).

Now what? I had no insurance, and the car might be uneconomical to repair privately, particularly if I'd done any mechanical damage when the RF and RR wheels hit the barrier. So I took it to get the wheel alignment checked, and apparently it was all fine. Jolly solid car / that's why it's so heavy.

I parked the car up and started looking for parts. For the longest time, nobody was wrecking an XJS except the absolute worst of TradeMe sellers. I'm talking guys so lazy that actually buying anything off them is like solving a puzzle.  I had been starting the Jag every few months and moving it back and forward, but still the tyres got square and the leather got mouldy and the car got dusty etc. :( I was tempted to abandon it and buy a more modern vehicle, but I eventually managed to get the bare minimum of B-grade parts to allow me to take the Jag to a panelbeater. I was worried that if I didn't get it back on the road in a somewhat timely manner, it would start to rust and degrade mechanically. The plan was to get it WOFable rather than presentable, so I could resume driving it.

(continued)

Edited by Thousand Dollar Supercar
fixing the images
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Posted

 

After running fine during Nats, the Jag has started doing its fuel-starvation-at-full-power thing again. :roll:

@h4nd had already pointed out that the commutator in my fuel pump had looked pretty worn. Here it is at 100% scale in the only photo which I hadn't already resized to low res:

fuelpumpcommutatorwear.jpg.4c6457926f4869e9f264204dfba78e17.jpg

Looks like it has done 36 years of service. I guess all that missing copper was caught by the old fuel filter and isn't still inside my fuel system somewhere..

I bought a new fuel pump, which is supposedly for the XJS though it's slightly smaller and has a different style of terminal:

newfuelpump.jpg.43c3f89f4ad217dce2eb51d0f665a9bf.jpg

Annoyingly, nothing changed! The problem is still present with the new fuel pump installed. This probably means that the old pump was never the cause in the first place, even before I performed the mod to stop its impeller housing spinning. :roll:

I'm still working under the assumption that the problem is caused by fuel starvation rather than by ignition, because surely if the coil was too weak to provide enough sparks at high rpm, there would be all kinds of backfires from the unburned fuel? My old Alfa would cut the spark to limit engine rpm, and when I hit that limiter too aggressively, it would just about blow the muffler apart.

I guess I could have a partial blockage anywhere between the pump and the injectors, or a problem with the fuel pressure regulator (which is controlled by manifold vacuum), or maybe the ECU is actually bringing in a rev limiter when it shouldn't.. I think I've noticed the rev counter spaz in the downward direction in response to the problem occurring, but generally you want to keep your eyes on the road when nearing redline, and you instinctively back off instantly if the engine starts doing strange stuff.

I still have the other issue of the engine not running smoothly at idle and low rpm - when you're under the bonnet you can detect an intermittent shaking of the motor like a partial misfire, up until the point where the rpms are high enough to mask it.

I don't know how to proceed with the diagnosis. Any ideas? Might have to take it to somebody who can actually measure stuff (exhaust CO, fuel pressure, injector duty cycle or whatever)?

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