I just recently got an '89 Jaguar XJS, it's in fairly good condition considering I got it for $900 but it turns over and won't start. It has spark and fuel and I tried squirting a little gas into the intake but was only rewarded with it backfiring through the manafold. I know now that this is probably realated to the timing, but I'm not sure where to start or what to look for. Any ideas would be greatly apreciated.

 

Do you have the Lucas or Marrelli ignition system?

 

Well, from what I found, it has a Marrelli ECU under the dash and a Lucas system in the trunk...

 

Sounds like a Marrelli car. You have both front and rear crank position sensors. Check those out first.

 

yep, both crank sensors work (or should at least), I replaced the one on the front of the engine and the one on the fly wheel is fairly new as well, but if they are the problem, does the car give out trouble codes? I'm also wondering, is the 5.3 v12 an interferance engine?

 

No trouble codes. It is not an interferance engine.

 

Hah, good news! I found that the timing problem was becasue the previous owner had totally wired the spark plug leads wrong, so I finally got some response out of the engine. It took a while to actually get the v12 to start on its own, probably because of the last remains of old gas, and belched a lot of white smoke and ran very poorly. Only problem is that now when I turn it over it doesn't even give a pop. I'll add some injector cleaner and better gas or something to see if that will help, but any ideas are appreciated.

Yay!

 

Glad to see you got it running, but be more descriptive of the symptoms that the car has when trying to start it! This way we can better help you...but at least you got it running!

 

Been away for a little while for the winter, have done a little work on the XJS, nothing major yet. I totally agree with you Glebshein, when I drained the gas it was so murky I couldn't see through it when I put it in a pint jar! The car also came with a new fuel filter so I threw that on as well.

UPDATES:
Replaced all sparkplugs, bank A #1 seems to be a little bunged up so I will be taking a thread chaser to it in the near future. I also pulled A #1 fuel injector and it gave a positive on the fuel delivery. Engine will pop and give evidence that it is getting some fuel, but still no start. I have narrowed the possibilities down to: 1. Problem in the dizzy 2. problem with the injector harness (it is in fairly poor condition) 3. Problem with the ECU (ugh!). Those are at least the most obvious reasons and I'm 80% certain it has to do with wiring of some sort.

I've also been reading "Experience in a Book" by Kirby Palm, so I hope to find some explanations/work-arounds there as well. Also, a teacher of mine used some sort of black rubber fuel line in between the dizzy and plug leads, and by touching a screw driver to the tubing was able to check if there was spark (it would arch across from the unshielded tubing which had enough conductivity for a car to run on!). Only I don't remember what sort of tubing he used...any ideas?

 

any luck with either of you? I'm having a no-start condition as well- 85 xjs he. Car turns over but wont start. Good gas, changed fuel filter- need to check fuel pressure and spark still.

 

Fuel and spark are the next step. You're on the right track.

 

No spark- At this point I'm out of my league due to having zero experience working on jags. I've taken some pictures- there is what appears to be a cap or resistor in front of the radiator and directly behind the grill- what is that? I ohmed out all the wires to the coil and the thing behind the grill...all seems well. There is also a "lucas ignition amp" that could be a player in this no-start scenario, mounted to the upper intake plenum on the drivers side. Is it just a guessing game from here as to which part crapped out, or can I test these various pieces with a multimeter? Also, is there a security system or something that would keep the ignition from firing? What do you guys recommend I do next? Please see pics at the link- thanks in advance

http://picasaweb.google.com/shannonlee425/Jag_ignition

 

Hi all- I just found that there is 12v at both coils- but no spark- does that mean one of the coils is bad? If I were to take the coils out and check ohms, what should they read? one of the coils does not have a plug wire going to it- should it? thanks

 

Check for continuity between the two wires on the plug for the distributor pickup. I don't know what the resistance spec is, but the wires break and go open circuit. I have seen several where mice have chewed those wires too, the insulation is a soft rubber that they find particularly delectible.

If the pickupshows continuity, you likely have a bad amplifier. I wouldn't call it common, but it happens.

 

jagtechohio- I pulled the vacuum thingy that I assume is the cruise control to get a better look at the dizzy- lo and behold- a RODENT HAD CHEWED THRU THE TWO PICKUP WIRES! I wanted to thank you and if you're ever in Florida I owe you a beer! The car is running, but it runs like garbage- it seems as tho its not firing on all cylinders, and I have to keep a little pressure on the pedal to keep it running, but not too much pressure or it dies. What should I do next? I have some new plugs and plugs wires to put on, but I don't think thats the problem. thanks again!

 

Pretty funny, isn't it? On occasion they chew the plug wires too, but they must not be as robust in flavor. Have yourself some fun changing the plugs and wires before you start chasing your tail. If you have a compression gauge, check it for dropped valve seats when the plugs are out. You have to unbolt the compressor and loosen the belt to get to the two front plugs, any other way is a waste of time. Similarly, you're better off removing the throttle pedestal to get at all the back 6. If you look at your engine and that information doesn't make sense to you, bring the car to a Jaguar mechanic. Good luck with the beast.

 

Changed plugs and wires- removed compressor and throttle pedestal as suggested...that was not fun! The 100-pound compressor was sitting on top of plug 1A causing a nice flat, chafed wire, and I suspect that it was shorting to ground- in any case, it runs much better now, but I couldnt drive it very long because the temp gauge wouldn't register any heat.

The coolant is a very nice clear shade of neon green so I suspect that its newer or newly flushed, but I'm going to flush it anyways.I read somewhere that there is a timing retard for the first 15 minutes? Can I disconnect that? Also, if I just replace the existing sending unit with an aftermarket piece and gauge, will that affect the ECU? Are there two water temp readings/units in the motor? Can I replace either one with the aftermarket gauge?Thanks very much-

 

Nice to hear you're making progress, glad ifI helped. The temp sender for the gauge is behind the right (passenger's) side thermostat housing: it has no interaction with the fuel injection system. Key on, disconnect and ground the wire that goes to the sensor, and the gauge should go straight to max. Sometimes the needles stick, and a knock on the plexiglass instrument panel cover will do the trick. The gauges are a bit tempermental, sometimes the terminal screws do not make good contact with the printed circuit, but the senders do not normally fail.

The ignition timing vacuum advance is disabled for the first 45 seconds after startup, this is to expedite the catalytic converter warm-up time. The normal sequence is that the supplemental air valve, in the RH air cleaner housing (electrical solenoid), is open for the first 45 seconds toassist withfast idle speed...maybe a 300 RPM boost. At the same time, there is a vacuum valve at the back of the RH intake that is closed, inhibiting vacuum advance. The 45 sec. times out and the timer closes the sup. air valve and allows vac. advance. You'll hear the fluctuation in idle speed when this occurs.

The timers almost never fail; the supplementary air valves occasionally fail; the vacuum advances often fail; and the worst part is that the centrifugal advanve mechanism inside the distributor siezes and plays all sorts of havoc with the timing. People will tell you this has a marked effect on engine temperature, which is an exageration. Usually the advance is stuck in the full retarded position, so idle quality will be unaffected but the loss of acceleration is very noticable if you are accustomed to driving an XJS.

Your approach is right on target, make sure you are not running the engine hot before you go any further. A mechanical gauge can be installed to more accurately measure the coolant temp in place of the electrical sender, but it's easier just to fix the stock setup. Coolant temp input for the fuel injection ECU is from a separate sensor behind the left thermostat housing on your car. If that sensor or circuit goes open circuit, you lose injector pulse and the engine stalls. Keep up the good work, this stuff isn't easy.