Just purchased a beautiful XJ-6 with 48,000 original miles. It was parked in a a yard for a couple of months as the PO said "one day it just wouldn't start." I traced the "no start" condition to a bad fuel pump and was able to drive it away BUT... Each cold start requires two or three 10-15 second cranking periods before it fires up. Once it starts, subsequent "warm starts" are relatively instantaneous. Reviewing a past service record, this has been going on since long before the fuel pump failed, so not a new issue for this car. I am wondering if anyone is familiar with the symptoms of a failing fuel pressure regulator as it seems like there might not be good pressure to the rail.

Perhaps related, perhaps not...the voltage gauge reads zero after starting and ever-so-slowly climbs up to around 10 volts after 20 minutes or so of driving. After an hour it is up to the 13 volt mark. The battery has never seemed low and measures 13.1 volts at the terminals when running.

On a final note, I had the car just two days when someone tried to break into at night. Unable to get in, they keyed the perfect 34 year old paint job Still just a beautiful example but it makes me sick that people do such things. As always, I think everyone for their time and ideas. Keith

 

If the cold start components fail then starting is dependent on the main injectors which will eventually start the car after some churning. See here: -
Fuel injection and the Jaguar XJ6 4.2 Series 3 / AJ6 Engineering
The cold start system is totally independent of the main injection system. It is controlled via something called a Thermotime Switch, there is no link at all to the normal fuel injection system. However from your description, there may be something else amiss. Read the AJ6 article very carefully. It is a superb description of the whole L-Jetronic system, one of the first EFI systems. It is totally analogue, there is no fuel map, firmware or software, or anything modern.

 

First guess is cold start injector, or maybe the switch that controls it, i think it's called thermotine switch, its on coolant manifold, someone will be along shortly to give you instructions on testing it, i think its to jump the switch but cannot remember exactly, so dont go jumpering anything till you hear from someone else...

 

Or... someone will be responding same time as i was...

 

yes like Darren said, check the cold start injector, remove it and have someone crank the engine and see if a squirt of gasoline comes out. Same principle as adding Ether to a carburator to start.

second option, prime the fuel system before trying to start engine.

1) move the shifter to D or to 1,
2) turn ignition switch all the way to START and hold it there for 4 to 5 seconds while you listen to the fuel pump humming or "charging". Then turn switch to OFF.
3) repeat this 3 or 4 times,
4) then move the shifter to P and crank it.

It should start inmediately. Mine does.

 

This link details how to check the cold start circuit:
Cold Start Circuit Checklist, Jaguar XJ6 Series III

 

When I took the voltage at the cold start injector (engine cold), I only measured 6 volts; not the battery voltage I was expecting. I swapped out the Thermotime switch because I happened to have a spare and it fires right up now. So, if you measure low voltage at the injector, a bad thermotime switch can be the issue.

 

Glad you managed to finally sort it out.