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Old Aug 19th, 2019, 23:48   #27
Laird Scooby
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Last Online: Today 16:15
Join Date: May 2012
Location: Lakenheath
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Originally Posted by nigellazypostman View Post
Cheers once again Dave I agree with you I am confident that the fuel injection relay and the radio suppression relay are sound as the injectors have power and the fuel pumps run, Luckily had a spare ECU in stock so tried this on the car and it has made no difference the car still wont start unless i bridge negative onto the grey injector wiring.

Out of curiosity there are two ECU's in the footwell the silver one that is low down under the bonnet release and a black Bosch one higher up. I only had a spare silver one in stock so have not been able to substitute this one

That aside all of this is pointing to a wiring fault and the only option appears to pin each wire out one at a time. I have managed to find a Volvo service manual with all the test details for the 2.4 lh jetronic its for the non turbo engine but i am hoping it will lead me to the cause, I intend to start with the ECU earths and take it from there.

Its going to be later in the week now though as unfortunately I have to travel.

At least i know now that if the injectors see negative the car will run so thats progress and rules out a heap of other components
The other black ECU is for the EZK unit that controls the sparks - it also feeds an rpm signal to the fuel ECU but as the fuel pumps are running, i'd say the fuel ECU is getting this signal.

Would be worth checking all plugs are secure on the black one though and also checking fuses 1, 11 and 12, in fact renew them with new fuses!

Given the cost of a fuse against a lot of head scratching it's worth it! I had a weird one back in April, the offside sidelights went out during the MoT thanks to an old, dirty/corroded fuse. Renewed it the next morning and sidelights returned. The fuse itself was intact and didn't look that dirty but still caused a failure.

While you're in the fusebox changing those fuses, push down on all the others and the the relays, just to make sure they haven't vibrated loose, had that happen before!
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Cheers
Dave

Next Door to Top-Gun with a Honda CR-V & S Type Jag Volvo gone but not forgotten........
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