Thousand Dollar Supercar Posted January 29 Author Share Posted January 29 8 hours ago, MikeR said: Just wanted to congratulate you on a great project and useful stuff you are sharing. Love the laconic style too (bought a 1992 XJS 4.0 recently, so consuming all I can ! r's mike (Sydney) Welcome to the forum. There can be some weird humour here because many of us know each other from the real world - 20 years of sporadic club events. If you're likely to be doing much of your own maintenance on your Jag, you'll have picked up that I've found Kirby Palm's "Experience In A Book: Help For The Jaguar XJ-S Owner" (a.k.a. The Barry Bible) to be useful. It's a free PDF you can download online. @dmulally sent me a 1992 XJS electrical system PDF too. Be careful treating my build thread as 'useful stuff'.. I'm a dodgy and not-very-enthusiastic amateur, this is my first Jag and I've been finding things out the hard way. This thread is just a diary for entertainment purposes and should not be considered mechanical advice. No doubt someone well versed in these cars would have a hit list of proactive replacements they would immediately perform on an under-maintained, high mileage XJS, and they wouldn't get stranded out of town, stumped by known issues etc the way I have been. FYI we run a system on oldschool.co.nz where only the car owner posts in their build thread. This prevents discussions cluttering the threads. Each car has a corresponding discussion thread, and the discussion thread for my Jag is here: 2 Quote Link to comment Share on other sites More sharing options...
dmulally Posted March 4 Share Posted March 4 Good move on the rear subframe mounts. I always get nervous about mine. When I put the 340s on the hoist I have a wood post jig/stand that I wedge under the rear suspension as I'm worried something will fall out. I'm not sure if it's even possible for it to fall out but it always bothered me just hanging there off the rubber mounts. 1 Quote Link to comment Share on other sites More sharing options...
h4nd Posted March 8 Share Posted March 8 Nicely done, wedging some torque into the impellor old chap. Nice bit of fettling, that. Gosh I say, I don't mean to be impertinent, but the commutator did rather catch my eye. I had a chat to my man Goggle, and he offered this: I just cant help but a nagging feeling that the someone might have scarpered with a bit of your spinny thing. but well, it's running fine, so I'm probably just imagining it. So sorry to have troubled you, old bean! Quote Link to comment Share on other sites More sharing options...
Thousand Dollar Supercar Posted March 8 Author Share Posted March 8 13 hours ago, h4nd said: the commutator did rather catch my eye. I had a chat to my man Goggle, and he offered this: I just cant help but a nagging feeling that the someone might have scarpered with a bit of your spinny thing. but well, it's running fine, so I'm probably just imagining it. So sorry to have troubled you, old bean! Hmmm… I did notice the commutator was worn but I didn’t notice that bit. I’ll have a look at higher-res photos when I get back from Nats. 1 Quote Link to comment Share on other sites More sharing options...
thegreatestben Posted May 5 Share Posted May 5 You don't think it's electrical supply to the pump being iffy? Over supply of voltage can cause excessive wear to the commutator. Quote Link to comment Share on other sites More sharing options...
Thousand Dollar Supercar Posted May 5 Author Share Posted May 5 27 minutes ago, thegreatestben said: You don't think it's electrical supply to the pump being iffy? Over supply of voltage can cause excessive wear to the commutator. The pump gets a continuous supply of whatever voltage the alternator's putting out (square #35 in the diagram below connects to the battery). The supply is switched via a relay controlled by the ECU, therefore supply would be either on or off (not variable). Even if the alternator drive belt decided to slip at high rpm, the pump would receive a minimum of the battery voltage minus some losses. If the supply is 'iffy' as in too low, it must be magically reducing (but not switching off) through unknown means, and only at high rpm I've previously measured the voltage at the pump terminals to be around 13V at idle. If the supply is iffy as in too high, I don't think I'd have a fuel starvation / rev limiter effect at full power Although I don't think I'd find anything, I could connect a meter to the pump's terminals, set it to min/max logging mode, and then go and do some pulls. I really doubt that's the problem though. I believe that my XJ-S has an open-loop fuel injection system with no oxygen sensor. It probably makes assumptions about the fuel pressure and fires the injectors based on the airflow meter or throttle position or something. This would mean that it has no clue that anything's going wrong. It couldn't make any adjustment in response to low fuel pressure / lean mixtures, let alone log some kind of fault code once the injectors reach 100% duty cycle. It would just idle poorly and shrug, suddenly lose power at full noise and shrug... Quote Link to comment Share on other sites More sharing options...
Nominal Posted May 5 Share Posted May 5 Can you bodge a fuel pressure gauge onto the fuel rail, before the regulator? (don't use non-pressure-rated hose DAMHIIKT) Quote Link to comment Share on other sites More sharing options...
Thousand Dollar Supercar Posted May 5 Author Share Posted May 5 2 hours ago, Nominal said: Can you bodge a fuel pressure gauge onto the fuel rail, before the regulator? Maybe if I possessed one. I could buy one and insert it here with the appropriate tee piece, but the normal-looking Jaguar fuel fittings probably have some horrible thread pitch. Quote Link to comment Share on other sites More sharing options...
keltik Posted May 5 Share Posted May 5 Crappy idle and suspicious fuel delivery issues... Have you had the injectors cleaned and flow checked? Especially likely in old cars with rusty fuel tanks that have probably eaten a lot of stale fuel. And impossible to figure out if you don't have an o2 sensor measuring fuel trims 2 Quote Link to comment Share on other sites More sharing options...
Kiwibirdman Posted May 6 Share Posted May 6 I would start off with that new fuel filter, you may have sucked in a bunch of crap from the tank. If that is OK fuel pressure would be the place to look. The connection to the vacuum source is to help regulate pressure correctly when the vacuum is high. 1 Quote Link to comment Share on other sites More sharing options...
VitesseEFI Posted May 6 Share Posted May 6 On 05/05/2024 at 18:34, keltik said: Crappy idle and suspicious fuel delivery issues... Have you had the injectors cleaned and flow checked? Especially likely in old cars with rusty fuel tanks that have probably eaten a lot of stale fuel. And impossible to figure out if you don't have an o2 sensor measuring fuel trims This!! Injectors!! Quote Link to comment Share on other sites More sharing options...
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