When the manual gear box 740gl 1988 cat. Did not start the other day replacing the fuel pump relay did not help this time. The car then started after a few hours of checking fuses, ignition leads,testing the control unit with a multi- meter etc. The car ran ok yesterday and this morning. Died this evening after 500 meters. I towed my wife home with our “new” 245 1984 gle auto. Any ideas of what to look for? Thanks for your help Justin.

Go to www.stepbystepvolvo.com for free diagnostic guide to 740 no-starts.

It's been my experience that the amp doesn't fail intermittantly but the Hall affect unit can. Check if your tach jumps a little when you crank the engine over. No jump probably the Hall affect unit.

Hi Justin,

Are you looking for some divine guidance?

You need to narrow down the problem-
fuel, spark, timing, compression....
no one can guess what's wrong without some diagnosis.

Opened the petrol pump relay and got the pump working, no start. Tried a spare spark plug on several ignition leads, the plug earthed to the exhaust manifold no spark in the dark. Next step please?

See if you get spark from the coil, check your distributor cap/rotor.
use the brick search feature for "No Spark"
There's a way to get your answers faster.

Bill

Hi Bill,
No spark from 740gl coil LH 2.4 1988b, replaced by another working coil and still no spark. Coil from 740gl tested in 245 gle and works. Distributor cap/ rotor 1 year old, checked. Tried 2nd hand ones. Distributor leads tested with ohm meter and ok.
Need to test the Hall switch and the Ignition control module next.
thanks justin

Now you're narrowing down the culprit...
Do you get Plus 12V at the blue wire to the coil?

You can check the diagnostic socket for Plus 12vdc at pin 4
and ground at pin 8
That will tell if the ignition sw or the power stage is suspect.

Hi Bill,
Yes I got 12V at the blue wire at the coil with the ignition on position 2, 12volts at both input terminals. The tach does not move while while cranking. Suspect the hall switch or ICU. Did a Hall switch test but no spark or fuel pump working. Tried to test the ignition control unit (ICU) but unsure of where socket B (yellow wire) and socket C (black wire) are. The three leads on my ICU connection at the distributor are black 1. Blue 2. Red 3.
Thanks Justin

Sounds like separate problems.
Is the cam turning when you crank the engine?
(look in the oil filler hole)
Check all your fuses and see if you pull any diagnostic codes.

Hi Bill,
Just no spark. Can smell fuel from the exhaust after cranking. If the ignition does not work the fuel system. will not continue to pump. The cam moves when I turn the engine. Could be the ignition control unit? I am going to have a look at it today. Perhaps buy one from the breakers yard. Thanks Justin

Hi Bill,
Working at last. Was at the pick and pay today. Bought an ICU, a radio suppression relay and an ignition amplifier. Changed them in that order and the car started first after the “new ignition amplifier”, on the fender by the air filter on the 740. Thanks for your help and the forum, Regards Justin

Thats great Justin.

I'd just use junkyard relays for temporary duty while you're waiting for a new one. Relays are junk after so many years and cycles.

Bill