Hi all,
Half a year ago, I found a 39000 miles XJS year `1988 in a abandoned in a storage for $3000, with no rust, beautiful paint and great internal leather. I took it to a local garage that works on jaguars. The elderly mechanic worked on it for half a year and finally it got on the road. It worked for a few days, although it did make a minor knocking sound when idling. One would not hear it going faster than 30 mi.

Then it started holding back a bit and a few times it backfired. Afther 15 minutes the engine stopped while slowing down at a crossing. I got it running again with the ignition. As I continued driving it got worse, halting more often backfiring increasingly more often. I just barely made it home. This morning I hoped I could get it to the garage when cold, but it did not do more than 400 yards and then it would not even start anymore.

So far I spent $9000 on getting it fixed, with many hoses replaced, new fuelpump, tank drained twice, all liquids flushed and replaced, sparks new, battery new, brakes new, new sets summer (daiton rims) + winter tires (regular rims), exhaust repaired, bottom rust treated, engine all shiningly polished. In short, the car looks fabulous. Only a "minor" problem, the engine does now run...........

 

Congrats on the new car. I’m confident you’ll get it running soon. Look at Grant’s post on how to troubleshoot a car that doesn’t run. It’s a sticky post. Check if you have ignition first, take the coil lead out, use a spare spark plug and ground it and check if you get a spark at the coil. Proceed to the spark plugs. I recommend doing the ignition test with the fuel relay removed so that you don’t flood your car. I assume you have a lucas distributor. You should get a fat, blue spark.
Next, proceed to check the condition of your throttle position sensor. With the ignition on, connect a digital voltmeter to 2 leads and ensure you’re in the 0.32-0.40 volt range. Turn the pedestal and see if the voltage rises linearly to about 4.5+ volts.
by removing the fuel relay crank the engine to ensure it is not flooded with fuel. Take a few spark plugs out, one at a time, check if they are wet or white. Report back what you find.
Take the distributor cap off, use a short wrench, and rotate the crankshaft clockwise till it aligns with the TDC. The rotor should point to cylinder 1B.
Then, take a look at the reluctor/ star wheel and the sensor, the wheels should be super close to the sensor. Proceed to take the rotor out and align the pickup to the star wheel only if the gap appears too big. There’s a youtube video on this, search for xjs no start on youtube.
If this fails, (very unlikely related to the issue you have mentioned) do a continuity test by running a long 16 foot cable from pin 18 of the ecu after disconnecting the ecu plug to the white coaxial cable that goes to the ignition amplifier on bank-B. It is a white cable with a bullet connector. Ensure that you strip the black heatproof insulation if the white wire appears cracked. It is like a skinny TV cable, the outer sheath grounds to a back cable that runs alongside the coaxial cable.
we can proceed to fuelling issues after you have confirmed that ignition and timing are prefect.

 

Thanks so much. I forwarded the info to my mecanic so he can try it out

 

IMPORTANT:

"Take the distributor cap off, use a short wrench, and rotate the crankshaft clockwise till it aligns with the TDC. The rotor should point to cylinder 1B."

With respect I think this is a touch ambiguous. At TDC on the firing stroke the rotor should point to the HT lead socket whose HT lead goes to cylinder A1, and the distributor cap should have a small 1 cast into it to identify that position. In this photo that place is ringed in red and the small 1 is just visible bewteen the socket and the ventilation tube outlet spigot.

 

Great, Thanks, I forwarded it to my mecanic. Lets give him some time to work on it with these instruction. He is waiting for some parts to arrive as well.

 

I forgot to mention, check connection to the Coolant Temperature Sensor as well. If it's disconnected, the car won't start.

 

Thanks all for all the great advice. It turned out that the culprit was a failing fuelpump. After it was replaced, the car started right up and no more backfiring. I started driving with 94 octane and Gumout 510013 High Mileage Fuel Injector Cleaner, after which an annoying knocking sound totally disappeared in the course of about 150 miles.

 

Thanks for all the great advice. It has taken some 10 months to get my Jag running great. What a fantastic ride!

After I had taken the car out of the lousy care of the garage that still had not restored my car properly, my neighbour took it upon him to rescue my car. He ended up replacing the injectors, the ballow and a whole lot more. Now the car runs fabulously. The cruise control works too! I find the latter very important, opposite from advice elsewhere on the forum, I want to drive my 35+ years old car gently and avoid shifting back as much as possible. Driving with my cruise control on, on country roads (I live in the country side) prevents that from happening most of the time.