Yeah, I think the warm restart problem is more common on these cars.
Not mine.
Cold start if they have been dormant for 3 or 4 weeks or more - yes.
Just goes to show…
Well, what does it show ?
Same here, mine restarts in an instant when warm.
When cold just sitting overnight, takes about 4 cranks, and will cough a bit as it tries to catch, and run rough for the first 10 seconds.
Have you tried the trick of turning the key from off to on, wait until the pump stops, then back off and back on to run the pump another couple of seconds, four or five times before you turn the key to the start position? Does it make any difference at all to the starting difficulty when cold?
yeah, i’ve tried that, no difference. I thought it cold be fuel pressure too.
i think i’m just slowly bringing my old engine that sat many years, and poorly running by PO (failed two smog checks before it sat for 7 years), out of hibernation. It’s been running better and better when warmed up over the last year, and the old musty/fuel smell inside is gone. Perhaps it will eventually run better when cold. I’m about to switch to Mobil1 synthetic, which I know you said will slowly help clean the internals.
oh, another thing i noticed, the first 6 months after taking her for a drive, I noticed as she cooled off in the garage, it smelled like a wet dog. Now when she cools off in the garage, it smells like a clean car.
OK, you forced me to break out the Haynes and look over the wiring diagram in Fig. 13.10. When the starter relay is energized, it sends power to the starter solenoid, to pin 26 on the EFI ECU, and to the Thermotime Switch. If the Thermotime Switch is closed, that sends power to the Cold Start Relay, which in turn fires the Cold Start Injectors – which are history. So basically the entire scheme involving the Thermotime Switch and Cold Start Relay is moot.
That leaves that pesky connection to pin 26 of the ECU. Presumably that’s not there just for looks. Presumably it tells the ECU to do something useful when the starter is engaged, like get off its duff and start the engine. If it doesn’t get that memo, presumably the engine would eventually start anyway just on its normal run circuit – but it might take a few turns of the crank.
So, as I understand it, this circuit from starter relay to ECU not working would likely result in the symptoms being observed?
IF this is the problem – and at this point it’s all theoretical – there could be one of two problems here. First is that the physical wire from the starter relay to pin 26 is broken somewhere. I’d suggest looking at the starter relay itself. Wires in that vicinity tend to get fupped for some reason.
The second possible issue would be within the ECU itself. A circuit is dead or whatnot. I have no idea how to help there. Time to call Roger Bywater, if he’s still answering his phone.
There was some story that much can be accomplished by simply replacing electrolytic capacitors in the ECU, as those things don’t age well. I recently had a pleasant experience with a Channel Master DVR (nowhere near as old as an XJ-S ECU!) that was misbehaving. Opened it up and found there were dozens of those capacitors in there, but exactly one had the telltale domed top of a capacitor failure. Oddly enough, there was a photo online of the same PCB with the same domed capacitor. I replaced that one cap and the thing works perfectly once again.
I tried this, didn’t work out so good. Lots of leakage from an old engine that isn’t really designed for a lightweight oil like this. Also, expensive on the wallet. If you think it is necessary then I would use a flushing oil, or an oil conditioner to clean the system before an oil change, then switch to a good quality semi-synthetic of the right weight.
Thanks, I was wondering about that too. I can always switch back if it’s an issue.
In the last 14 months since I got the car running, I’ve done three oil/filter changes with conventional oil, I’ve used Rislone, and am now using 2 qts/10 of Marvel Mystery Oil.
I’ve so far noticed any little drips at back of engine are gone now, or to an absolute minimum, so something’s working. We’ll see what happens when I add the Mobil 1! 
I’ve bought 10/40, so it’s not too off from 20/50. And I’m in a not so hot climate (Seattle, WA) And car has 51,000 miles with excellent compression. 
Kirby, you got me thinking about the starter relay. Took mine off, and the center tab where the brown wire + power connects to was slightly loose from it’s rivet. I could wiggle it a bit back and forth just a wee bit.
So I put a dob of solder on top of the rivet so it firmly connected it to the tab, which made it no longer wiggle. Solid connection between rivet and tab.
Waiting until today to turn her over when cold, started up almost instantly!
For me, front wheelson a ramp causes trhe engine bay to be at the best level for my sore old back and shoulders…
Car