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Intermittent fault on 940 2.0 turbo 1992

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Old Aug 19th, 2019, 12:31   #21
Laird Scooby
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Quote:
Originally Posted by haymitch View Post
I recently replaced my RSR. It wasn't the cause of my problem but the relay from this eBay listing is working fine:

https://www.ebay.co.uk/itm/NEW-Volvo...2/283302819779
I couldn't find any of those when i looked for mine and if memory serves, even Volvo were listing as NLA, hence my comments above.
Obviously products come and go on the marketplace and although that ebay one is cheaper, it's still a lot to pay for a specific relay that only performs the same duty as a standard, easily available generic relay.

For about £6 or thereabouts plus P&P for the generic ones i linked to, i know what i'd rather do - it also means that any corrosion inside the 20+ year old terminals is addressed as they have to be cut off the original loom to fit the new terminals.

First though, we need to confirm the exact fault - everything is pointing to it being the RSR in this case but there's always the chance something has been overlooked and that could change things.
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Old Aug 19th, 2019, 18:58   #22
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Right got home from work early and tested radio suppression relay this is working fine and delivering 12V to the injectors when the ignition is switched on this made me think the issue is with the ground switched supply from the ecu. To prove this theory I bared a little of the wire to one injector and bridged a wire to the negative terminal of the battery, the car sprung into life and sounded the best it has for ages clearly this isnít a fix but itís progress any suggestions where to go next?
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Old Aug 19th, 2019, 19:19   #23
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I have NOT read the whole thread but on LH2.4 a dodgy ECT sensor does not prevent starting.
Two sensors can wreck starting : FPR and CPS.

All these TLAs (three letter abbreviations) are giving me a headache.

I might or might not go read the whole thread now ...
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Old Aug 19th, 2019, 19:27   #24
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Originally Posted by nigellazypostman View Post
... we noticed that the spark plugs were dry as a bone even after extensive cranking of the engine.

To see if it was fuel related we tried a squirt of easy start and the car sprung into life until the easy start was used up.
STOP farting about,
get a new FUEL PUMP RELAY from evilbay,
unscrew the bit above the fusebox-ashtray/below the radio, (small phillips)
remove that front panel,
replace your FPR which is on the left middle I think in the relay tray
SEE FAQ for exact placement.

I own a 1993 2.0 and had to do this exact job some years ago. Evilbay replacement cost £13.
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Old Aug 19th, 2019, 19:46   #25
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Quote:
Originally Posted by Dirty Rooster View Post
STOP farting about,
get a new FUEL PUMP RELAY from evilbay,
unscrew the bit above the fusebox-ashtray/below the radio, (small phillips)
remove that front panel,
replace your FPR which is on the left middle I think in the relay tray
SEE FAQ for exact placement.

I own a 1993 2.0 and had to do this exact job some years ago. Evilbay replacement cost £13.
He hasn't got a problem with fuel delivery, it's something on the injection side. A new fuel pump relay ISN't going to help at this stage!


Quote:
Originally Posted by nigellazypostman View Post
Right got home from work early and tested radio suppression relay this is working fine and delivering 12V to the injectors when the ignition is switched on this made me think the issue is with the ground switched supply from the ecu. To prove this theory I bared a little of the wire to one injector and bridged a wire to the negative terminal of the battery, the car sprung into life and sounded the best it has for ages clearly this isnít a fix but itís progress any suggestions where to go next?
Your ECU is mounted in the drivers footwell behind the kick panel. Check all the wiring between the injectors and the ECU, if all is well, disconnect the battery -ve and then remove the kickpanel trim and check the main plug is connected properly into the ECU. If not, refit it correctly, reconnect the battery and try again

If it is connected properly, unplug it and spray contact cleaner into the plug and socket area, connect and disconnect the plug several times giving it one final squirt of contact cleaner before final reconnection. If that doesn't work then it points to the ECU sadly.
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Old Aug 19th, 2019, 21:54   #26
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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
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Old Aug 19th, 2019, 22:48   #27
Laird Scooby
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Quote:
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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Old Aug 29th, 2019, 15:42   #28
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Just wanted to get back to you all and confirm that with your help we now have a running and reliable car

It turns out that rather than being a single problem there were actually multiple problems some of which look to have been caused by a previous "enthusiastic" owners maintenance. The root cause of the issue was an intermittent connection between the ecu and the negative supply to the injectors, however following all of the advice on this site I also found the main fuel pump pressure was not up to scratch so also replaced that.

The error messages found on the diagnostic were traced to yet another wiring fault which i have also now resolved.

Ultimately i do not think the car has run this well for years! I just have to finish setting up the throttle body and tick over (my timing light with RPM indicator is on loan to a friend) as it feels a little too low.

Once again I appreciate everyone's help and hope i can return the favour with some of my new found Volvo knowledge.
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Old Aug 29th, 2019, 18:58   #29
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What is it idling at now? Is the idle switch making when the throttle is released? What did you set your base idle at with the AICV defeated?

Ignition timing isn't adjustable by the way but i guess you're using the timing light purely as a tachometer?
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