940 Intermittent non-starting / cutting out

[Bonzo]

I recently bought a 150K Mile, 940 LPT Estate as a potential replacement for my current 940 (refer to my recent listing about rear caliper sizes!!!!).

The car came with a weird intermittent starting fault. - I knew about it when I bought it, so please feel free to call be a silly sod!!!!

When the car is behaving itself, it starts on the button and runs well. - I have noticed a slight hesitancy/misfire? under hard acceleration, but otherwise it pulls well and idles nicely.

Sometimes it either cuts out (only happened when either going slow or when stationary up to now). - It refuses to restart unless it is left for at least a few minutes and then it restarts on the button and perfoms without fault.

It seems to do this completely randomly whether the engine is cold or has run for miles and is fully warmed up. - It did once refuse to start at all when cold on a very cold day, if that is an additional clue....

As this 940 is one of those with the OBD II diagnostic interface which will only work with a proper Volvo scanner, I haven't been able to do any electronic diagnostics at all.

I have replaced plugs, rotor arm and distributor cap and done the usual service-related things, but it still does it. - The only 'service' item I haven't changed is the inline fuel filter, but plan to do this soon.

Any suggestions? - I do have my other 940 (same engine same spec) which I could swap sensors etc from to get to the root of the problem, but can anyone suggest possible causes before I have to resort to this?

Because of the intermittency of the cutting out I don't want to use this car as my daily runner, as my other (157K Mile) 940 is the perfect 'jump in and drive' reliable workhorse, despite it starting to develop a smoking habit...

Hope someone can help.

Regards,

Steve

[940_Turbo]

There are three classics for this.

Fuel pump relay, re solder it

Ignition amplifier

Crank position sensor

[Oilydad]

Another quick check for the fuel pump relay (favourite for me too) is, next time the car stalls, take out the relay and give it a sharp tap on something solid. Replace it and if the car starts, that's probably your problem.

The contacts stick, and this tap frees them.

That's why you've got this symptom where the car will eventually start up again, because sometimes it can be 2 minutes, and sometimes it will take ages for them to free. The only cure for me is a new relay.

You are wise not taking the car out, because having a sudden engine failure with a 40 ton articulated lorry behind you is something that isn't to be recommended.

I know....it happened to us, and I still have nightmares about it!!

[Bonzo]

Thanks guys. - I had suspected an electrical fault, and did wonder about the ignition amplifier. - I will try the fuel relay first (easiest and cheapest to replace) and go from there.

Once again thanks for the advice. - All I need to do now is to work out about my rear calipers!!! (See my recent seperate thread for more details!!!)

Regards,

Steve

ps Typo about the mileage on my old faithful 940, it's done 257K Miles, not 157K miles as I stated. - Barely run in still!!!

[Diesel-do-nicely]

I have had this on 3 petrol 940's, it has been the air mass meter, the tubular thing on top of the airbox, and one of them it also had a iffy connection in the plug to it aswell.
Try swapping it, just change the lid over complete with the other one, then try both cars.

[ericbeaumont]

Bonzo,

I've had an intermittent non-start (but turning over) on my '93 945 (202,000 miles) for the whole of January, and en route to solving the problem the AA came out three times (1: diagnosed RS/injector relay, 2: no symptom when operative turned up but car started! 3: no feed from flywheel sensor multi-plug to fuseboard) and all their efforts were off the mark.

The local Volvo independent swapped the RSrelay, after which it ran well. When it refused again, I changed the fuel pump relay, checked the fuses and other relays, cleaned the distributor cap, rotor arm, leads (water in coil lead under cap caused two unrelated non-starts), battery and earths, and all multi plugs in sight. Later I swapped the ignition switch, cleaned and re-greased the ignition amp., checked other earths and connections; another time a new flywheel sensor was fitted.

None of these were unserviceable, most were A1, but were cleaned and the multi-plugs treated with Contralube electrical connector protector (Maplins).

Every helpful thread on any Volvo forum relating to the above was read, until I ran out of energy and solutions.

Some changes to the system resulted in the car starting and running for several days or even a week, and when it started it ran well. I tried to replicate the fault by wiggling every cable and connection I could find, without success.

Last week it didn't even want to turn over and was towed back to the Volvo independent, who traced it to a break in the feed between coil and ignition, and finally to the ignition control unit (a black Bosch box under the driver's dash panel to the left of the clutch pedal) which is apparently an unusual fault. Forty quid for a second-hand ICU and two hours labour and she's back to normal.

What I learned from the experience, and from reading about similar ones, is how frustrating and difficult such faults can be to track down, and how expensive it could become if new parts are thrown at the problem. The Volvo indi. I use is five minutes walk from me and so swapping relays and borrowing switches from the friendly parts department was easy; they also have a yard of second-hand parts.

Relays should click when they operate. The fuel pump can be heard under the floor when the ignition is turned to position two, and if you have an in-tank pump put your ear to the filler cap while someone turns the ignition to position two. Check earths, of which there are several around the car. Apparently, the failure of a minor electrical item such as a interior light can affect other more important parts of the system.

Your symptoms are different from mine, but will also drive you bonkers trying to resolve them, especially in this weather! My advice, if all else has been tried, is to get the electrical system tested.

Eric.

[Bonzo]

Eric

Thanks for the comprehensive response. - You have been through the mill!!!

Luckily my existing 940 has be ultra reliable (am I tempting fate by saying that?), and is still my daily driver, so the newer one with the starting problem I can use as and when until I get to the root of the problem.

I will try the cheap and simple avenues first, and then perhaps when I don't need 'old faithful' for work for a few days, start swapping parts and conduct some local test drives.

Their are two difficulties with intermittent faults as you well know. 1) They don't stay there long enough to get a definitive answer if you've cured it or not; 2) You lose all faith in the reliability of what is usually a get-in-and-drive ultra-reliable bomb-proof car!!

Best regards and thanks again for all who have submitted valuable responses,

Steve