I have a 86 ser3 with the type L jetronic Ecu my ignition is working relays bench checked and ok and flap on masair working voltage is to injectors all grounds are good and cleaned
Just no injection pulse.
My question is how often does an ecu fail or am I on the wrong trail? Has any one had a issue like this? Engine cranks fuel pressure is good just no pulse. Using node lights to check
thanks for your time

 

Those ECUs seldom fail....but 'seldom' isn't the same as 'never'.

Just to clarify and be certain of what you've said....

You are getting 12v supply voltage TO the injectors? This comes from the "main relay" via injector ballast.

The grounds you mention are the ground wires bundled together at the rear of the water rail? These are the grounds for the fuel injection system.

Cheers
DD

 

The voltage is at the injector plug and the ground at the water rail is checked and good. My next step was going to be taking the plug off the Ecu and checking for voltages and grounds from the plug
thanks

 

Don't forget that nothing will work if the pulse from the ignition isn't getting to the ECU, either due to a fault with the ignition system or a break in the wire.

 

Great point.

Look at the wires coming off the coil "-" post. One of them (white/black as I recall) runs aft along the water rail. This is the trigger wire for the fuel injection system

Cheers
DD

 

I have moved on to the ECU doing research I’ve found

http://www.seattlex19.org/data/figuide/

this is atype L jetronic system and I crossed the PIN numbers on the plug of the ECU with the wire schematic out of my jag service Manuel and they match up, just wanted to get thoughts on the direction that I’m headed
thanks

 

While the fundamentals of L-Jetronic remain the same no matter what the type of car, the details are different. Personally...just me...I think the Fiat-versus-Jaguar differences would just confuse the matter.

A lot of the ECU inputs and outputs concern altering injector pulse width to trim the fueling. Not that much is needed to fundamentally operate the injectors: power and ground to the ECU, signal from the ignition, signal from the AFM....and, I think, signal from the coolant temp sensor.

Which reminds me.....

Have you checked the coolant temp sensor wires and connector?

Just for the heck of it remove the CTS connector and jump the terminals with a paper clip. Any change?

Cheers
DD

 

Jumped the CTS plug disconnected with paper clip no pulse on node light while cranking. Checked pin 1 at ECU while cranking flashing light so ignition is sending signal to ECU; pin 5 ground good pin 16 and pin 17 ground good....... ECU is getting power and pulse from ignition and grounds are good. I can only deduct that the pulse generator in the ECU must be faulty. Seem like I’m thinking the right way?
thanks

 

What about AFM input/interface to ECU? Pins 7-8-9? I've never checked this; not sure exactly how to do it or what readings to expect. The AFM is, in essence, a big variable resistor so some sore of varied voltage, I suspect, but I don't know the range.

If that's Ok then I'd say the ECU is kapoot

Cheers
DD