Requesting for troubleshooting assistance

I am trying to solve the failure of '73 Volvo 1800ES D-Jetronic system.
Background: engine was running, a little rough, and then suddenly stopped running.
PROBLEM: Now cannot restart the engine - will not fire at all.

ANALYSIS RESULTS: None of the injectors are opening on start cranking.

Have tested resistance of MAP - Ohms in range; Temp sensors - ohms in range; Injector resistance - 2.5 ohms on all 4; distributor trigger - OPEN/CLOSE on rotation; throttle switch clean and changing throttle position does not affect non-starting; all tests at ECU end of cable so cable continuity verified.
Checked power supply and ground to ECU OK - 12+ V and ground present
Fuel pressure fine, pre-pressure before crank OK.
Have tried a spare, functioning ECU but still no injector opening.

As we say, I am tearing my hair trying to solve this.

Can someone on the forum provide some suggestions for diagnosing the problem?

Thank you,

Julius.

Hi Julius,
Welcome to the forum.
You have tested all the things I would test first, too.

Did you test the electric function of the trigger points or just the opening?

Some oil or grease might lead to disfunction.

Is there an electrical signal at the injectors? You can test this with a multimeter or with a led connected to the wire.

Norbert

Hi Julius,

also from me a welcome to this forum with your nice Volvo. I am sure Jörg will be delighted to read this.

Looking at what you have done, I have 2 questions:

1. Did you measure all these values at the ECU connector? This is necessary to eliminate possible wiring harness failures.
2. What about grounding of all injectors. Usually you have one common ground where all injectors are connected.

You could also measure the voltage on injectors connector while cranking. Best with oscilloscope, but also a multimeter should show an average value of around 1 V. The good news is that you have a constant failure. They are much easier to find than failures coming and going.

Hi Julius,
one more idea from me: The ECU needs the start signal or it won't inject at low rpm.
There will be a separate cable connection towards the D-Jet-harness.

You can use this to verify the connections: www.jetronic.org/de/forum/jetronic/19-me...nts-by-car-model#158

Regards
Norbert

Sorry have been away for a few months.
Want to thank you Volker and Norbert for troubleshooting suggestions which were very helpful..

Problem turned out to be poor ground connection for injectors as well as an ignition (coil) connection problem. Car is purring like a kitten now.

Julius.

Hi Julius,

thanks for your feedback. And be careful: Even purring kittens have sharp claws