I just want to ask this forum a question.

With basically the sensors sending signals to the computer that analyzes and adjust accordingly……

CAN YOU MAKE A MANUAL ADJUSTMENT TO THE ELECTRONIC DISTRIBUTOR AND CHANGE THE TIMING??

As always Thanks

Softball60/Paul

 

https://www.jaguarforums.com/forum/x...engines-66536/

 

The "Andy Bracket" is the best value in terms of bolt on power you can buy.

 

I am just curious. I am not looking to make any modifications although it sounds tempting.

In the old days you could influence how the car ran and started with small adjustMents to the distributor based on mfg.spec. For degree of setting…and every so often you would reset your timing because it would gO out……….but if I understand the way this electronic system works you don’t or shouldn’t do anything in the way of adjustments.

Last week with the help of this forum I was able to solve an issue of of a bad temperature sensor causing the engine to stall out or bog down.

Since the fix the car has been running SCARRY GOOD!!!!

the only issue (in my mind) is that it now starts within a fraction of a second with the ignition key being turned. I am wondering if I can adjust so that I can get back to the way it used to start….maybe one (1)crank before it fires.

Thanks

Softball60/Paul

 

No, you cannot make such an adjustment. But congratulations on a Forum First: "My Jaguar starts too well!" !

 

96 must be Inline 6 so Andy bracket is the way to go. Most modern cars are timed by a crank position sensor which is absolute and can never move during the service life of the engine, Most older engines with adjustable distributors run that distributor from a chain which may also be driving the cam shaft(s) so it will stretch considerable over time . Therefore it will require adjustment now and then to bring it back into spec. Hot Rodder's then and today would adjust these a few degrees past spec and enjoy a bit more power and throttle response. The ability to do this long term and successfully will requires a watchful ear for engine ping'ing and a tuned eye on the temp gauge.

 

Icsamerica,

are you saying that it is possible?

All I am trying to do is move it minisculy so it gives more of a normal start. I am going on 77 yrs. And I have never had a car start this quick!!!

DOES THIS ACTUALLY MEAN THAT ALL SYSTEMS (Sensors) ARE COMPLETELY IN SINK AND READY TO FIRE?

Thanks

Softball60/Paul

 

Not possible on your car. On an earlier one, yes. The sensor is monitoring the crankshaft, so that relationship is fixed.

 

I think you're good, Dont mess with it. Enjoy it for what it is. The 1996 is a great year for the XJS, and as long as you keep the PCM dry, you'll have a very reliable car with just basic maintenance.

 

Thanks for the input.

You win I will leave it alone…..And enjoy my currently faster than a speeding bullet start.

Thanks

Softball60/Paul

 

Paul,

In theory, you could have a 1996-built V12 XJS. But as we know, you have a 4 litre car (And I know where all the 1996-built V12 cars are!)

As others have mentioned, the ecu fuelling and ignition map is preset and, short of remapping the ecu, you can't easily change anything. EXCEPT the Andy bracket will fool the ecu into believing that the car is an earlier position of the crank and hence the standard ecu map settings start earlier in the combustion cycle giving the equivalent of applying extra degrees of advance. It is noticeable in its improvement.

As regards how well / fast the car starts, that's a function of a few major things:

- The Crank Sensor sending the appropriate signal of where it thinks the car is in it's crank position (hence the Andy bracket giving a false reading of where it thinks the crank is)
- The CTS (Coolant Temperature Sensor which ensures the fuelling is optimised for a given engine temperature
- The Engine Camshaft position sensor (sometimes referred to as the Cam sensor). As you can appreciate, the crank sensor sensor knows where No. Piston is, but it doesn't know if it's on the combustion or exhaust cycle. The Cam sensor knows the cam position, so sends a signal to the ecu to indicate when it sees the combustion cycle position of No 1 piston. .

The ecu starts firing sparks and fuel based on what the crank sensor says. But it's just guessing which is the correct combustion cycle until the cam sensor says it's seen the combustion cycle position (or the engine having started)

You might think that throwing sparks and fuel on every cycle would mean it starts quicker but it's not true. It potentially overfuels from firing fuel that can't be ignited properly and it can therefore churn for a while, The car will almost definitely start without the cam sensor at all, but it will take time until it eventually catches, the knock sensors operate, and then the ecu starts to settle down and fire at the right time.

So, in theory, your engine HAS to see the cam sensor to indicate the first combustion cycle position before the ecu really operates properly. So if the engine just happens to have last stopped just before the combustion cycle on No.1 Piston, then it will see the signal quicker on the next startup and the engine will start quicker. it may be that this is coincidentally part of what you've experienced. But of course the correct fuelling ratio is hugely critical as to how well the car starts and you'll undoubtedly be benefitting from that.

All in all, be grateful! An XJS that starts quickly is a good thing! Don't try and change that! But if you want an increase in performance, fit an Andy bracket.

Hope all that made sense!

Paul

 

PTJS1

Thanks for the response and last weeks efforts to walk me through the temp sensor. It solved the rich start condition w/soot out the tailpipe.

Thanks

Softball60/Paul