I bought an xis 1984 a few months ago and had it all flushed and cleaned. I got it started today and it ran for about 30 minutes just fine. I noticed none of the guages were working tho, but the car ran fine. Idled just great. 30 minutes in, the engine started acting up, like it was losing fuel. I shut it off and waited about five minutes. Its started up just fine and then started acting up again. I shut it off and now it won't start at all. It will crank, but no started. I hear the fuel pump cycle when I turn the key on without starting. What could be the likely suspect here? It has been starting fine, but now this. Last week it started and ran just fine and did the same thing. I waited a night and it wouldn't start the next day even. Trickled charged the battery and today got it to start and run for 30 minutes. No unusual smoke, ran smooth, even with throttling it....any help would be amazing. Thanks!!

 

The "could be list" is pretty long.

I like to begin with the free-n-easy things so I'd run a jumper wire from the orange wire of the fuel pump relay to a good ground. Grounding this wire allows the pump ro run whenever the key is "on" rather than when commanded by the ECU.

The circuit of the ECU which normally grouds the fuel pump relay is a bit notorious for giving problems.

Give it a whirl and post back.

The fuel pump relay is in the trunk behind a small trim panel above and to the right of the battery....sorta next to the trunk lid hinge.

Cheers
DD

 

Friends..thanks so much for all of the welcomes. I'm so glad I found this site. I first tried staring the car this morning...to no avail...its about 34 degrees out and the engine turned just fine. I tried jumpering the relay orange for the pump relay and as expected, the pump ran without fail and stayed on....but still no start. Could it be that my coolant temp sensor is shot? Odd that the engine quit when warm. I'll go around and check all my connections too...thanks to you all!

 

The V12 is a Beauty and there is nothing like it, Welcome to the forum XJ' and I look forward to you having some Good Fortune!
Keep us up to date, I am sure many other Cat Lovers will join me in saying they wish they "HAD A CAT LIKE YOURS"!
FORTUNE FAVOURS THE BRAVE, WHEN SHE'S UP AND RUNNING, YOU'LL BE SO PROUD!
Enjoy your Dream!
Stu

 

The coolant sensor could be going flaky, they do that.

Unplug it, and bridge the terminals in the plug, a paper clip will do, and do not let it short on the surroundings. that will trick the ECU temp circuit. it might be difficult to start cold, but it will eliminate the sensor. A sensor is only about $15, common Bosch unit used on many cars.

The infamous ignition module inside the amp bolted to the LH inlet manifold is also a known flaky item with heat, and sometimes comes good when cooled, sometimes not. I use an Echlin brand TP45, made in USA, and never had issues.

As Doug said, the list is looooooong indeed. Those 2 have been reasonably common back in my V12 days.

 

I was just in RI a few weeks ago, wish I'd known as I would have stopped by to help! (Cranston area)

 

After checking all of the above, if you still have the problem, check the pick-up screen in the surge tank. Have a similar issue as you with my 85 and thanks to the advice of Grant, I checked for sediment in the surge tank and took the pick-up screen to find it clogged. I have the old style version which is extremely fine mesh, too fine, and prone to clogging and leading to a fuel starvation issue. Worth checking out.
Hope that helps
Bill

 

Make sure the water temperature sensor is plugged in and making good contact. I doubt that is your problem, but you never know! Mine will attempt to start but won't actually run if the plug is not making contact, and the engine will stop if the connection loses contact. On my '87 it's a white connector at the front left side of the engine, somewhat hidden by the air box.

Good luck!

John

 

Hi to everyone that send me advice. Is the pick-up screen at the bottom of the fule guage sencor? I took the ecu apart and reset the mixture screw and the cae fired up but it seems to be stuck on 2000 revs. I haven't had chance to have a proper look at it at the moment, could that be the tick over valve that is stuck open and not closing? I haven't tried reving it yet, but will try and get it up and running in the next few days. Thanks

 

Hold on...with the V12 engine and a history of cold starts but difficult or NO warm starts, the very first culprit is the GM module in the ignition amplifier (mounted on top of the manifold)...this behaviour is typical. The module is easy to replace (but it must be a genuine GM or Delco module not an aftermarket brand). These fail so frequently on the V12 that having a spare unit is a good idea. The next culprit: the coil itself (although this 1984 car should have the two coil arrangement), next: the wire for the distributor pick-up (but this will result in consistent no-starts); this is a soft pink wire found in front of the distributor in the engine V. Next, but rarely, the distributor pick-up itself - I had this fail once. It could also be, as has been mentioned, a failing coolant temperature sensor but these normally fail by making the ECU over-fuel the engine. Finally but not likely in this case, a faulty main relay (which powers the fuel pump relay).

 

My 86 xjs wont start either. It has spark at the plugs and fuel to the rail. I don't think the injectors aopening because the plugs are dry

 

A new thread might get more answers as this one is getting older.

If you have what you say, then the signal down that DUMB shielded wire to the ECU from the ign amp is your problem.

A more common failure than modules, coils, etc etc.

There would be PAGES of info on this in the archives, but if you cannot find them, ask, or PM me and I will detail it for you, NOT rocket science by any means.

 

Jaguar66, my apologies, you appear NEW, so first up WELCOME to the real world of motoring.

Let me know if you get stuck, I have a Word doco somewhere on the laptop detailing that wire and its many, many mysteries.

 

Thanks Grant, I am new to the site and I don't know how to find my way around yet. Any help would be very appreciated. Jerry

 

If you don't have anything to test fuel pressure with I would clean out that pickup screen and change the fuel filter. Does the fuel pump still kick on after the car cuts out?

 

You may want to check the state of the distributor cap and rotor. I found that a distributor with the center button (coil center feed post on the cap) failing will display the same conditions that you are describing. Need to get a new cap and rotor which is a good idea anyway if it has not been changed for a while.

 

Hi Grant, How do I identify which wire goes from the amp to the ECU Which pin number on the ECu would it be? Thanks, Jerry

 

Thanks for the reply. I have good spark at the plugs so I thinl that side is OK. I have fuel pressure to the rail as I cracked the supply fitting and it shot 2 feet. I dont think the injectors are opening. After I started this process it started and ran until warm when I turned it off. Tried to re start and it wouldn't. The next day it started again and ran for a few minites then quit. I am waiting for new relays now because the fuel pump wont come on when I turn the key.

 

That shielded wire goes to PIN #18 of the ECU. By that I mean the DUMB thin wire in the centre. The shielding is earthed at the ECU only, nothing to do with any pin.

It is easily found coming out of the rear of the ign amp, and is a "thick "looking" wire in a black covering. Inside that black covering is the coax cable.

It is notorious for breaking down anywhere between the amp and the far RH side of the engine bay.

The ECU units do fail at times, but that is quite rare in the big scheme of things. The early HE cars have a 6CU unit, and the later cars are 16CU. The change point is around '86?????. The 6CU were a problem with the fuel pump control circuit that I know of, and maybe the EFI circuit as well. However that coax wire is waaaaaay up there as a PITA.

 

I agree with Grant about that sheilded wire, however mine was white not black (83)so there may be some variations on colors?