Hi all,

I have an '85 XJS v12 with approx 58k miles on it. I have owned the car for about 8 months and it has been running great....until this week. We have been running the car all winter in North Dakota with no problems at all.

Anyway, I was out of town and the car sat in the garage for a month without being started. When I got back I had to jump start it but it started up just fine. It was running like a champ...until I closed the trunk. I let the trunk latch then i pushed on it to make sure it was closed causing the rear end shocks to engage a small bit..nothing unusual, and the engine just stopped. Not sure if this was a coincidence or what, but it stopped at the exact time i rocked the rear end of the car by pushing down on the trunk.

So, now it wont start. It will crank with no problem. While its cranking though it makes kind of a sputtering or popping sound and will eventually sound like its going to start (the initial woosh sound when the engine starts up) but then nothing happens. Fuel coming out of the fuel filter is clean. No loose connections I can see anywhere in the trunk. Haven't checked the plug wires themselves but all the connections seem good.

Any suggestions are appreciated.

Thanks in advance.

 

Always go back to where you were.

The rocking of the car whilst catching the boot lock MAY have tripped the enertia switch, I know its a long shot, but it does happen. Some have reported that thing tripping by slamming the door.

It is on the "A" pillar, and on our RHD cars it is on the RH side. Simply lift the button and push it back down to reset it.

Firstly, switch ON teh ignition, DO YOU HEAR THE FUEL PUMP WHIRRING. If so, it aint that switch.

Nothing comes to mind that closing the boot lid, softly or firmly, that would do that, but I will keep thinking.

 

Not the switch. I reset it as you suggested and got the same result. I do hear a definite whirr or hiss of the fuel pump for a few seconds when I switch on the ignition, so I don't think its the pump. I'll try to post a recording of the sound it's making when I crank it soon.

 

the injector relay is also in the boot, its next to the main relay , and must make contact on both outputs for the pump and the injectors to run, it might just be a duff relay


BB

 

Fuel pump works great, but not sure about the injector.

Here is a .wav file of what the car sounds like when I attempt to start it. You can hear the pops and sputters, as well as the engine trying to start.

Thanks again for the help.

 

i may not have explained myself correctly i the last post

the injectors and the pump come off two separate spade connectors from the same relay , the relay internals can break in such a way that the pump supply remains but the injector supply fails,

so, if the pump runs, and the car cranks, it can only be fuel , as in either pressure or injector, but the pump runs so has to be injector related, prove the power to the injectors , and work from there

BB

 

Still working at this. I have verified fuel pressure and flow and i have a nice blue arc on the main distributor wire. I pulled the main relay and checked the voltages on the terminals with the following results:

Using black (85) as ground
Brown (30) - 12v
White (86) - 12v when key is turned
Pink/Black line (87) - 0v

Should I be seeing 12v on the 87s with the relay unplugged or is that where the voltage is sent when the relay is switched on (closed)?

 

things that could be disrupted in the boot/trunk by a slam are the relays above the ECU and the ECU itself.

 

Yep i been checking all of that stuff. That's why i wanted to know if i was getting the correct voltages on the main relay.

 

#87 is generally the supply TO the item being relayed.

Have a look at the MAIN battery +ve cable, and you will see a plastic cover about 6" down from the battery. Inside that cover are 2 LARGE spade terminals. These are the battery supply to the 2 relays in question, and they do have female moments from time to time, and lose contact with the battery cable connector. Unplug them and CAREFUILLY replug them, ensuring the spade actually slides over its mate, and not down the side. Down the side is soooooo simply to do, and I have done it.

When ign is ON, the main relay goes active, and that "powers up" the ECU and the fuel pump relay, so I do reckon all is OK, but checking at this stage is all we can do.

Another thoght.

Have the ign ON, and the bonnet OPEN, now move the gas pedal quickly to full throttle, you should hear the injectors "click" as they fire once, and squirt fuel into the engine. Now go for start, and it will/should run for a second on that "squirted" fuel.

If you got NO click, then the ECU is having a moment.

The EFI resistor pack, on the panel in the engine bay behind the RH headlamp is a prime suspect for no injector pulsing. Greg in France did a write up on that recently.

The infamous "shielded wire" from the ign amp to the ECU is a classic failure item for no running apart from the squirted fuel.

The list goes on, and I am moving away from the simple shutting of the boot, coz I reckon that may just be unrelated, dunno.

 

Checked the spade connectors on the +V cable. Unplugged them and replugged them, then checked continuity between each male connector and the end of the cable that attaches to the battery. No problems there. I did find out these cables are the supply voltage to terminal #30 on both the main relay and fuel pump relay, however, not terminal 87 as was suggested. Looking at the diagram it would appear that the 12v on terminal 30 is actually what turns on the relay, so I guess not getting a voltage on terminal 87 with the ignition off makes sense now, so at least that's something.

There is definitely no clicking coming from the fuel injectors, and the engine does not fire or run for any length of time after doing the test with the gas pedal as you suggested.

I have not checked into the EFI resistor pack yet.

So now I am wondering if there is a way to test the ECU to see if its functioning properly. Also, would it be a wise/worthwile test to try spraying some starting fluid into the intake?

 

Check and clean the resistor pack plug with contact cleaner first. This is a favourite for no injector clicks. There is a write up about it up there.

Greg

 

Greg has suggestd the way I would go.

Save the spray for better things. You got NO injector activity, that is why it is not running as designed. The spray will only re-confirm what you already know, it does run, just not forever.

Unplug the large multi pin plug at the ECU, look inside that plug, sometimes there is a Green growth inside. Clean this with Lemon Juice, and spray with contact cleaner to dry off.

When you plug those original relays in the boot back into their sockets, TAKE CARE that the 87 wires dont push out of the sockets, thus not making any contact with the relay spades, so whatever that relay is operating will NOT operate. This I have found MANY times over the years. 10 seconds later the beast is ALIVE.

 

I have had this issue on several XJS Jaguars that have been sat for a while, the fuel seems to vapor lock or something crawls in the tank vent tube and blocks the vent.
I have a quick check/fix open the fuel filler cap so the tank is vented to atmosphere turn the ignition to on but do not start the car the fuel pump will run for a few seconds do this several time to pressurize the fuel system then start the car. Another tell tale sign is if you have been cranking the engine and it still will not start try opening the fuel filler cap if air rushes in then the vent is blocked, hope this helps

 

So i tried this. When I opened the filler cap fuel actually came out in addition to the sound of air escaping. No engine fire after i let the pump run a few times with the cap off, replaced it, and turned the key.

This leads me to what is probably a stupid question -- where do I find the tank vent tube to check if it is blocked?

 

Are you saying that the car still refused to start with the cap open? If so, then this is not the cause of the no start.

The fuel breather system is quite complex, I think it might be best to get the car going before diverting off on tank breather problems, which at worst can involve tank out work. Why not take 10 mins and clean up the resistor plug and socket, and if that does no good, you have to find out why the injectors are not clicking, as that will solve your problem. Courage, the cause will be found!

Greg

 

no injector activity can be narrowed down quite a bit

its either no feed to the injectors, which are live all the time , and switch through the power resistor mentioned above , and is good practice to clean and keep clean

or the ecu isn't sending the signal to fire the injectors

a simple power test will prove power to the injector, the supply comes from the relay next to the 'main ' relay in the boot over the battery , it should have a red stripe on the relay top to indicate its importance ,

then if you have power at the injectors, clean the power resistor ,

finally I would reseat the plugs into the ecu , this has to be done in a specific way , as it seems its seated but isn't ,

BB

 

XJS vent tube is up in the right hand corner of the trunk kind of coiled back on its self above the rear wheel arch.
No starts you have to determine if its electrical/spark or fuel related otherwise you chase your tale around, spray starting fluid into one of the tubes joining the two plenum chambers and try starting the engine if the car attempts to run then its fuel related if not its electrical

 

Reading the reply's I was getting confused "fuel injection relay" on a 1985 XJS its called the main relay it does supply 12v to the injectors the ECU switch's them to ground in groups of three through the resistor pack, but again ignition or fuel issue?

 

Haven't had a chance to get out and work on this for the past few days. Hopefully will have an update by the weekend. Really appreciate all the help so far! If nothing else I am learning a lot about how to tackle this beast.