Occasional Starting Difficulty

[Clifford Pope]

Every time I think I have found the cause, it works for a few weeks and then the problem recurs.
So far I have:
Dismantled and checked both fuel pumps - they run fine
Checked all wiring and connectors
Cleaned fuses
Fitted new fuel pump relay
Fitted new fuel pressure regulator
Tried starting by bypassing the relay, jumping fuses 4 to 6
The engine has just started playing up again. Often it is very reluctant to start when cold, but will suddenly fire and then run perfectly. It will run, and start again from cold, for several days, and then suddenly refuse to start. It never falters or cuts out once started.
I am running out of further options to try. Is it worth replacing the temperature sensor? The crankshaft position sensor? The fuel pump, even though it runs and develops a good pressure? Or is it the electronic control unit itself? How do I test that, or do I just have to keep buying new bits until by chance it works?

I am seriously thinking of dumping a perfectly good engine and fitting a spare carburettor version with an old contact breaker ignition system, all for the sake of a niggling little fault that I cannot find.
Any more suggestions would be gratefully accepted.
Many thanks

Have a look at this post;
http://www.volvoadventures.com/forum...um=1&topic=183
Jim

[Peter Milnes]

Thanks for the invite Jim, Have registered and had good look. Nice site easy to understand and clearly presented. Would it be possible to add your site to ours? We have on-board access to Brickboard FAQs so far. If possible, even if only by link, let our webmaster Bob know and he may then include your site reference in links form or on drop-down menu.

All the best, Peter

Thanks Peter,
My site is already listed as a personal Volvo web site on the clubs Links page

[Clifford Pope]

Thanks Jim, but it's a different problem. It doesn't cut out when hot, or indeed ever faulter at all once running, and the Lamda/emmission values are spot on. There's no sensor in the distributor, just a flywheel sensor on the bellhousing
It's simply that sometimes it is very hard to start when cold. (not weather-related, can be warm, cold, damp, dry, heatwave)
It doesn't look like ignition, because when it does start there is no smell or spluttering to clear excess petrol, it fires and idles perfectly.
It feels as if something intermittently isn't sending a signal to the injectors during cranking. But they obviously work all right once running. I have just checked the fuel pressure - about 35psi during cranking, so clearly not pump, relay or regulator.

[Clifford Pope]

I have just had the whole system diagnosed by a specialist, and it turns out to be the Ignition Amplifier Module. (That is the innocuous looking flat black thing mounted just in front of the battery)
Apparently these commonly develop intermittant faults and are very susceptible to changes in temperature or humidity. (Why is it fitted at the front of the car then?!)
If they don't operate properly when cranking then the computer doesn't recognise that the engine is turning. He put in a secondhand one, and it has been perfect since. He advises always carrying a spare, and simply plugging it in if ever the engine doesn't start.

Interesting that in all my long pleas here and at Brickboard, there have been lots of suggestions but not a single person has suggested the Amplifier Module.
Thanks anyway everyone. I have found this thread as tedious as I expect everyone else has!