Getting no where with this. I am going thru these posts (and any others on this forum..) - it has to be something (probably simple). So far I am not impressed with how difficult diagnostics are with this car. On other car three things are needed - rotation, spark, and fuel. If any of the three were not happening thru simple tests - it was only two or three parts to make any of them work - and bypassing something like a bypassing the switch by jumping a solenoid or setting a gas can on the roof of the car for an alternate fuel source would get you pretty far in proving where the problem is. From the gambit of suggestions ( from much more experienced people than I regarding this car ) - they are all over the map!

Sorry - just venting. I own and restore older cars. I have never not been able to get one to run in more than two days, ever! ( unless there was something critically wrong with the car ( which I can normally learn in a few hours of tinkering )).

What am I missing?? Am I explaining the problem wrong?? Please help! I need it!

 

The ignition and FI for a 12 in those days were at the limit so it could be a number of issues. Combined with a total lack of onboard diagnostics it is tedious work, but very rewarding when you get it right so don't despair. However as the spark seems OK (and idling forever means it should be good to go for picking up speed) I would go into fuel. Pressure is good. As Doug clarified you do have an idle switch, only it is part of the TPS. I would check if the engine dies the moment it opens as you move the throttle. Also the pulse duration going to the injectors. Buy a cheap (but not the cheapest) USB scope for your laptop and connect to a couple of injectors. Ebay ID 140855451405 would be OK, USD 70,- You should look for considerable and immediate lengthening of the pulse duration upon accellerating, dropping a bit back again as you settle at a higher rpm. Post back when you have checked.

 

I have never been great at grasping things that I cannot see but only measure... It looks like I may have to dive into new tools ( oh darn). Will also have to build a couple in line test lines - male on one side and female on the other and a contact spot to measure from. I cannot figure a way to get a probe on one of the injector signal wires without compromising it. Is it possible that the spark plug wires are in the right order - just starting one position clockwise or counterclockwise (or should I say anti clockwise )? I really do no want to pull number 1 plug to find TDOC compression stroke... I would not think this would idle, but I have to ask.

Looks like that osscope comes from china 4 weeks to deliver... Anyone ever rent these out?

 

Just for the heck of it make sure the vacuum line to the ECU (in the trunk) is attached at both ends.

This a a stretch because, if it is disconnected, I don't think the symptom matches the problem....but it's a free and easy thing to check.

At the engine end it attaches to a nipple on the balance tube at the rear of the engine

Cheers
DD

 

Hmm, a vacuum run ECU.. I guess that is what draws the Lucas smoke that I keep reading about... Will check around lunchtime. Want to check all vacuum signals - anywhere have a report on what they should be at each location (and where those locations are? I do not recognize have the sensors and switches on this engine (making guesses, but not for certain (yet)).

M.

 

No problem with that vacuum line Doug. Pulled off both ends and pulled vacuum on it - held. Then pulled the plug and vacuum dropped instantly. Keep any other suggestions coming - it will be a mo before the oscilloscope gets here :-(

 

Just a couple of random thoughts while you wait for the 'scope to arrive:

What happens if you try to start the engine with the Engine to ECU vacuum line disconnected from the ECU?

Have you removed the ECU and cleaned up all the pins on the ECU and all the sockets on that enormous plug that connects the loom to the ECU?

Courage, it will run - eventually!

Greg

 

I will try to see if either makes a difference (pull the vac line, pull the ECU (and clean fastidiously while off), then put back together....

I know these things do run.... This video inspires me:

M.

 

Greg, no apparent change. Still starts. Idle is lack luster. Absolutely no ability to get off idle without te car wanting to just die. Will pull the ECU plug and clean it with contact cleaner and a brush and put dielectric grease on the connectors. This car would be so much more fun to drive if I could drive it....

M.

 

This is a long shot, but those are the exact symptoms I had when when my crankshaft position sensor went out on my BMW. Just a thought, I am sure someone more familiar with the inner workings and failures of the XJS can shed more light on it

 

There is no CPS on an '86 V12.

Another thought. Have you tried looking at the shielded cable that runs from the Lucas Ignition box on the B bank inlet manifold top? This is the cable that runs backwards and goes to the ECU eventually; The cable is shielded with a tube of steel netting, and if this earths to the actual wire inside it can cause all sorts of havoc. The shielding is probably not even needed, so it might be an idea to have a look at this and replace what you can see with a new bit of wire.

Assuming that does nothing (!) make a complete list of evrything you have tried so far and post it, please, so we can all think again.

Greg

 

From the top...
1) new NGK spark plugs gapped to .025 (per under the hood)
2) cleaned both ends of spark plug wire (glass bead) and dielectric grease
3) cleaned dist. cap and rotor
4) verified firing order 1a-6b-5a-2b-3a-4b-6a-1b-2a-5b-4a-3b
5) replaced fuel pump and flushed line
6) replaced fuel filter flushed line again
7) sent fuel injectors and rail off to be sonic cleaned and new hoses and o-ring seals
8) reinstalled injector rail
9) installed fuel pressure gauge on rail.
10) verified fuel pressure 36 lbs
11) re verified spark order and spark to all cylendars with inline spark checker.
12) verified each injector was getting power with noid light
13) checked vacuum line to ECU (unplug engine side - draw vacuum - no leak - pull ecu line and vacuum drops immediately)
14) reconnect vacuum lines.
15) check all vacuum line ends and that they were not clogged or have leak in the middle (by plugging end - drawing vacuum - release).
16) disconnect and clean ECU plug (both sides) applied dielectric grease to pins
17) bought oscilloscope (came in with wrong USB cable - waiting on response).
18) fresh fuel (does have ethenol - but all gas here does now. Fuel was gotten at the same time as fillup on another car - no prob w/ that car)
added stable and injector cleaner to fuel before putting in tank.
19) pulled fuel line again and checked a sample in clear jar (sample from fuel rail)
20) Checked for any wires that were loose, or rubbing anything
21) checked throttle tower voltage - smooth between "at rest" was .30v at full throttle it was 4.62.
22) butterflies checked on both sides - cleaned well - no slop in any ends.
23) verified gap on butterflies (cannot remember but seem to remember .002?)


Symptom was: car would idle pretty smooth (maybe about 500rpm) but as soon as any throttle was introduced, car would want to die immediately. If I back off the added throttle it would resume running.

Now after rechecking ALL that, I just tried to start it and it will not start! I do see the speedometer go up and the miles flying by - but I am in park and my wheels are not moving!

Anyone have any suggestions (or verifications on what I have already done?).

M.

 

'On other car three things are needed - rotation, spark, and fuel'.
I think that you will find that you also need air; have you checked that the filters aren't choked?
Steve

 

While waiting for the scope cable: Have an assistant spraying start gas into one intake while spraying into the other intake yourself and at the same time giving it a bit of twist at the throttle capstan. If it picks up a bit you have verified that it does not get more fuel as it should.

 

Which Mustang DD? Don't currently need a TPS, but might one day and I enjoy playing with stuff like that.

 

Steve, I am really scratching my head. I am familiar with the three needs, (I pulled the filters and it made no difference).

I have rotation (not 100% sure if timing is correct, but PO said it ran great when the fuel pump went out), I have spark. white/blue good arc. I have fuel pressure, and noid light indicates I am getting some signal. and air seems to be able (going to borrow a boroscope and send down the intake.

What are the possibilities of having something plugging the exhaust? Pipe looks a bit sooty (like running rich before) - but do not want to pull the thing apart unless this is a realistic possibility.

Thoughts?

 

Per, will try the starter fluid test this weekend.

One strange thing - the speedometer needle is jumping all over the place and the odometer is spinning when I go to start the car...

 

That is weird! It is as if it thinks that you are actually driving.
I can't recall if it is a manual or auto box.
If it's a manual it could be the clutch dragging or partially seized although that would just stall it at tickover......
If it is an auto then presumably you are in park or neutral when trying to start. Is it possible that the gear selector is not setting correctly?
Are the wheels going round if it is jacked up in Park or neutral?
It is possible that there is a transmission fault that is stopping the whole thing from turning when you try and load it up.
You seem to have tried everything else engine wise so maybe a change of direction is called for.
Steve

 

Farily common, not Jag-specific, and usually an indicator of a voltage drop/lack of voltage. Not sure if it would be related to your primary issue but it might be a good clue.

Perhaps already asked and answered but what kind of voltage are you getting to the coil "+" post?

Cheers
DD

 

There are four important components that have not been changed/looked at:

1. the ignition amplifier on the top of the B bank, together with its associated wiring conections
2. The box on the RHS inner fender to which the injector harness connects (forgotten the name, "power resistor" maybe?)
3. The distributor internal mechanism and function (as in working just at tickover and not working at higher revs).
4. ECU itself

Now I do not know how the correct functioning of these things can be checked, but they can be, if necessary by substitution, and I suggest this is the next area to diagnose, using minds and advice more competent than mine (not hard!).


Greg