I posted this first on an old thread but thought it should be on a new thread. I followed the flow charts presented by Grant Francis on a 2017 thread, awesome info by the way.
1976 (late build) XJS V-12 (pre HE). Car sat for 19 years in a unheated storage shed.
The engine will run on carb spray indicating the ignition system is working as it should.
The fuel pump will turn on for a second or so when the key is turned to the on position, but not while the engine is being cranked over or right after releasing the key from the start position.
I've confirmed fuel pressure and delivery are fine. ( running off a separate clean tank and lines flushed)
The car is still fitted with three wire, reed style, trigger board. I ran tests on the board per Grant's post and it is working as it should.
I removed the throttle switch and confirmed it operates as it should. Also adjusted the throttle stop setting with a .030 feeler gauge.
I have battery voltage and earth at the injector amplifier mounted on top of the radiator support.
I have a few questions.
When the voltage is measured at both terminals of the injector connector, is the connector unhooked from the injector?
With the key on and the connector off of the injector I have 2 volts to both terminals of the connector.
The information I have learned the voltage should be 12 volts ( or battery voltage) at both terminals?
Even though the trigger board checks okay, can it still cause an issue with the "tach" signal input to the ECU?
Thank you,Tom H

 

Tom,

Never needed to do that voltage test, so no answer, BUT, battery Volts makes sense to me.

The fuel pump working on the timer is also good, but, after that 2 second squirt, is there fuel in the rail. Easiest way is the rail supply hose off, in a jar, and great care. Should be a good solid powerful squirt. The pump will deliver a lot of fuel in a big hurry.

Now, memory, HAHAHA, the ECU gets the pulse for spark activity from the Ballast Block, and that is 30+ years ago diagnosis, and that car had the Opus removed a week later for a Crane system, and I never touched it again.

Try this, Ignition ON, open the throttle capstan SLOWLY, you should hear "click, click, click,......," of the last 6 Injectors fired, as the internal wiper crosses the segments in the TPS. Should be 9? clicks of the Injectors as you get to WOT.

 

Hi, I have attached a couple of photos of the workshop manual which should go towards answering your first 2 questions. The trigger board , in my experience, either works or it doesn’t and as long as its switching between the 2 groups of injectors it should not stop the car from firing up.
The injectors on these models are very prone to sticking or getting blocked , sometimes they can be coaxed back to life by pulsing a direct feed, (9 v battery ideal) and you will hear them clicking, if not they are easily removed compared to the later 5.3 cars, and that would be my first check. Good luck


Injector test 1

Injector test2

 

Simon is on the money.

Just because they "click" DOES NOT mean they are passing the Bang Juice. I have woken many up with that 9V battery and a small hammer, and as you power the Injector, give a sharp tap, NOT stupid "belt the crap out of it", just tap, tap, tap. They will wake up. I have never had a failure yet.

Also found this, attached, might help a tad.

 

Thank you. I traced the low voltage (2volts) to the main relay. I cleaned the contact in the relay and tightened up the connectors. I now have battery voltage at the injectors. I also have pulse at the injectors and the fuel pump will run while cranking. Next is to pull the injectors and clean the,19+ years of sitting, crud out of them.

 

Scd, your information was awesome. I have the injectors out and will be cleaning them. Thanks for help.

 

There is a lot of information on the early fuel injection system here: https://jetronic.org/en/

 

Dleit53,

Thank you. After unsticking all 12 injectors and cleaning them, I was able to get the car started. Thanks to all who helped me on this. Tom H