Occasional Starting Difficulty

[Clifford Pope]

1993 Torslanda, LH Jetronic system.
About once in 100 cold starts the engine cranks but is very slow to fire. Usually it starts within half a second. I have sometimes suspected that the main fuel pump might have stuck, and a thump almost invariably causes the engine to spring into life. On the last occasion however that failed to work, but after pressing the tyre-valve on the injector rail to establish that there was petrol, there was a gush of petrol and then the engine started first turn.
After starting, whatever the difficulties, the engine runs perfectly. It returns an easy 32 mpg, and has just passed its MOT emissions with flying colours. I have cleaned the fuel pump fuses, established that the in-tank pump runs, checked the relay, and regularly clean out the Idle Air Valve and associated pipework and breathers. The Air Mass Meter is only 2 years old, and I have checked for air leaks in the ducting.
. The Lambda light goes out and stays out. I tried to check for diagnostic codes but cannot make it flash anything at all – it appears to be completely dead.

So now I am at a loss to know what to look for next. Any suggestions would be gratefully accepted.

With thanks,
Cliff Pope

What about the fuel regulator??? have you removed the vacuum hose to it? If it reeks of Juice then it's faulty, thus not allowing gas to the injectors....


P.S I have a spare one of these, if you need it, I bought it under the assurance that it would fit my car....and it doesn't x(

Regards
Dave M

[Clifford Pope]

Thanks Dave. I tried removing the vacuum pipe when it wouldn't start- no reek of petrol. I tried sucking it, and something seems to to be happening inside, presumably a diaphram moving. It didn't help. It was when I released the pressure with the tyre valve and then switched on again and let the pump re-pressurise that it started instantly. But it may just have been co-incidence. Maybe waiting a minute would have done the trick anyway.
That is what is so infuriating about very rare intermittent faults that cure themselves - there is never anything to test, so no conclusions can be drawn from any of the rather desperate twiddling one gives to pipes, connectors etc.
On the last dozen odd occasions since it failed to start, it has started absolutely 'on the button', within a split second of engaging the starter.
It always runs perfectly, and never hesitates in any situation, eg foot to the floor, pulling hard, picking up after overrun.

I know from previous occasions it will now be fine until I have almost forgotten about it, and then suddenly repeat.
It is livable-with but would be nice to identify the cause, especially if it indicates something on its way out.

Hi Cliff,

You mention how intermittent faults can be so infuriating. When I was in the trade I found the same thing in that I could rig up all the test equipment, connect it up to a vehicle and the test results would invariably prove inconclusive.

Personally, I think that some of the trouble started before the car got into the workshop as the customers would have to try and describe the fault to a receptionist (who might not have any technical experience).
This would then be de-ciphered and hurridly written down onto a job sheet for the technicians.

Oh the number of times I had to go and talk to the receptionist myself to get the full story.

[Clifford Pope]

Latest update:
The fault is getting slightly more frequent - ie about once a fortnight instead of once a month.
I have found a way of overcoming it if the engine fails to start - I jump fuses 4 to 6, and then it springs instantly to life.
The odd thing is as soon as it has fired I can remove the jump and the car runs perfectly for the next week.
So the fault seems to be in the circuitry that puts the relay into 'crank' mode as opposed to 'running'.
Can anyone enlighten me? Is something slowly failing, and what?
(Or I could just put a flick-switch on the dashboard to jump 4 to 6 when required, and live with it!)

Again I suspect the fuel pump relay, craked joints on the printed circuit board:
http://volvoadventures.com/howtodofuelpumprelay.html

[Clifford Pope]

Done that - new relay, checked connectors, sandpapered fuses, fuse holders, tried by-passing the relay just in case. Didn't make any difference. As I say, waggling the knock sensor connector made the biggest difference.
If there is anything left it seems it can only be in the control module or whatever it is called, and it's a bit pricey just to replace that on the offchance.
Thanks anyway

[Citizen.Agfa]

G'day. Been following this thread, you are now about where I was 18 mths ago. I'd had the same probs with my 2.3 inj. 745 and cutting a long story down to managable proportions, check the distributor.
Yeah, I know, there was no petrol coming out; well, my tame independent, Buzz, in Cwrtnewydd, West Wales, let me in on a little secret; the fuel relay is tripped by the distributor: no sparks=no fuel. This is, I believe, a safety measure, designed to stop fuel flowing in the event of an accident; I'm sure someone will correct me if I'm incorrect. Anyway, whacked on a second-hand 'strib, Bob's your mothers brother!
Nick Heneghan.

[Clifford Pope]

Thanks Nick.
But there are no LT wires to the distributor on mine (LH Jetronic 2.4). In fact there is nothing in the distributor, just an HT lead from the coil and then the 4 plug leads. ?
I had heard about this secret cut-out needed to trip the relay, but where does it come from? The coil, or somewhere else? Someone on Brickboard said the trick was to cut the wire to the control module and earth it, but the colour code didn't tally, so it was no help.
So far (touch wood) fixing the loose knock sensor wire seems to have done the trick, but I have been here before with false hopes.
I replaced the Fuel Pressure Regulator yesterday, as someone said they age and get erratic after 200,000 miles, so at 280,000 I gave it a go.
The car certainly runs better for it - just a little more zip when I put my foot down. But would that cause occasional poor starting?

I live in Newcastle Emlyn - Buzz sounds a good man to know - where is he?
Cheers,
Cliff

[Citizen.Agfa]

Do you remember Martin Whiteland (MVS)? Well, Buzz bought "Pensarn" from him a coupla years ago, and is now advertising in Cambrian Trader or Monthly Advertiser as Pensarn Volvos; he asked me(cos he's a V. busy man)not to put him on the non-franchised list, so I haven't; however, he didn't warn me off personal recc's!

Pensarn,
Cwrtnewydd,
Llanybydder.
Tel. 01570 434 459

Nick H.