A little background. Got the car from my father in law in non running condition. 4.2L

Things he replaced:
New fuel pump, lines, tank solenoid.
New key tumbler/ignition
New Plugs, wires, cap, rotor
Has a spare ecu with it.

Car cranks fine
has 36psi fuel pressure.
Has spark (verified by pulling a plug)
Plugs smell like gas and were wet.
I have not put a noid light on the injectors but seems like they are firing.
Plug wire order is correct
Will start if you spray starter fluid in intake tube but dies immediately.

I was thinking coolant temp sensor?

Any other ideas?

 

Mmmmm.

It has spark, you verified that, and it runs with a snort of ether.

It may not have injection pulse.

The plugs wet is confusing, coz if that wet was fuel it should fire the same as ether has it doing.

I am nit sure where the 6cyl gets its injection pulse signal from????, The V12's are that shielded wire, but you dont have that wire.

I reckon Doug will come past soon and spot the issue straight up. He is the man with S3 cars.

 

The ecu gets its pulse from the negative post of the coil. There is a connector half way along the water rail loom from memory that branches the ecu and tacho off. Mine was crusty and had fallen to pieces at one point and wasn't firing the injectors off. If you put the blade of a large flat screw driver on an injector and your ear on the butt then with someone cranking the engine over you can generally hear a clear 'click' from the injector.

Old petrol can be a real issue. Apparently in Australia we are importing allot of our petrol from Asia now and it lasts nowhere near as long as it use to. I went to start my motorbike not so long ago after sitting for 6 months and it just refused to start. Drained the fuel and put fresh stuff in and it went first kick. Likewise my neighbor had issues with 6 moth old fuel in his Packard, had to drain every last bit out and clean the carby to get it going. Having to use aerostart would suggest fuel issues, although it could also be a lack of compression as aerostart is probably more volatile then petrol and easier to ignite, hence needing less compression. At work we often come across old xk motors with almost no compression, sometimes a shot of oil down the bores will bring them to life enough to get them started. After that some come good and some just smoke their head off.

Coolant temp sensor should not be an issue as you can remove the plug and it will run, same deal with the airflow meter, although you will have a huge cloud of smoke.

If it appears to have spark and injector pulse then ide check the compression next. While you have the plugs out it wont hurt to put a shoot of clean motor oil down the plug holes anyway as often when cranking and cranking the rings will stick up and you will loose compression anyway.

Hope this provides some source of direction,

Regards,
Jay

 

I respectfully disagree with Jay on the coolant temp sensor.

The engine won't run (or shouldn't) run with it disconnected, and a running engine will die instantly if you unplug it. Some say a disconnected sensor stops injector pulse; others say it fattens the fueling so much that the engine dies. I'm in the former camp, not the latter.

Anyhow.....

Pull the connector and jump the terminals inside with a paper clip. This tricks the ECU into thinking the engine is fully warmed up and commands the injectors accordingly. If the engine now starts then you're on the right track.

Naturally you'll check the condition of the terminals while you're there.

Cheers
DD

 

You got me there Doug, I mixed it up. I had mine jumped for a long time till I put a new thermostat in, not disconnected. I suppose I should have a bit better think about things before I press post.

Regards,
Jay

 

Ok,
I tried the coolant temp sensor since the new one came in and no go.

Pulled the fuel rails off and tried starting it again, injectors are not firing.

Was gonna go through the Haynes manual tonight, any thoughts?

I tried both computers, neither will start it.

Has correct 36psi at the rails, but injectors wont fire.

 

Isnt that the coolant temp sensor that's halfway down the water rail?

 

Have a read of this: -
Fuel injection and the Jaguar XJ6 4.2 Series 3 / AJ6 Engineering

Trouble shooting is on Page 6

 

awesome thanks!

 

anyone have a good description of where the injector power resistor pack is located?

 

On a Ser III 4.2 the resistor pack is on the right side inner fender, well forward, down low. Roughly at the same level as the power steering pump. It's silver....about the size of a pack of cigarettes.

You'll see two brown/slate wires....among a slew others. These two brown/slate wires should show 12v positive with the key "on". This voltage comes from the "main relay" on the firewall.

Post back if you are not getting 12v at the resistor

Cheers
DD

 

Also, you'll see a slew of ground wires under a bolt head at the rear of the water rail. These are the fuel injection grounds. Make sure none of the wires have broken off and that the connection is clean and tight.

Cheers
DD

 

Awesome doug thank you. I will be checking this today.

 

I did not have 12v at the resistor.
Checked the 3 relays on the wall and one had 12v constant but it never switched over to feed the resistor.
Jumpered the relay and got 12v at the resistor.
Went and got a new relay and tried it with no luck. Car still wont start.

Gona try and replace the other 2 relays (although at least one has to be good as its the fuel pump relay)

Pretty lost at this point. Gonna plug a noid light in now and see if I get power to the injectors.

But all injectors ohmd out good

 

Careful !

The red "relay" isn't a relay, it's a diode pack. Don't replace it with a relay.



Cheers
DD

 

Ir was originally not plugged into the red plug. I put it in the red plug. Is that correct or did I screw it up? Just made sense that the red "relay" (diode) plugs into the red plug, and the brown relays plug into the 2 black plugs.

Thanks again for all the help.

I found new info to trace power to find the problem since its been narrowed to injectors not firing

 

Diode check out. As does fuel pump relay.
The starter relay also checks out.

No 12v to the brown/slate wire going to the afm.

2nd relay on wall has 12v constant but does not transfer voltage to the afm. Its a brand new relay. So I assume it doesnt transfer due to another wire? I need to do a vo tunuity test to assure the brown slate at the afm does actually go that relay.

But that appears to be the problem. No 12v to the afm

 

Maybe this will help:


MAIN RELAY
terminal 86 white wire 12v with key "on"
terminal 85 black wire ground
terminal 30 brown wire 12v constant
terminal 87 brown/slate 12v with key "on"

As you now the brown/slate wire eventually branches off to power up the injector ballast, ECU, and AFM

The white wire comes from terminal 4 of the red diode pack. It is fed by another white wire on terminal 1 of the diode pack. Do you have 12v on both these white wires with the key "on"?


Cheers
DD

 

Thats basically what the writeup I found said.

Yes I have 12v at the white wires.
On that same relay terminal 87 brown/slate I do not get 12v with the key on.

 

At this point im gonna run some looped wires from what I kjow has 12v constant and key on to the relay that has the issue to see if I can get it to start. I would assume this will work