No spark no fuel.

[Richard_TD]

I thought there might be some kind of sensor that wouldn't allow fuel supply or spark if the cam wasn't where it should be. I'm not entirely familiar with modern engine systems though.

Not all engines clash when the cam belt goes, though I'm not sure if yours is an interference engine or not. The tell-tale is if the engine turns over at a constant speed instead of the pulses you normally hear when you turn an engine over on the starter. As you say, it shouldn't be the belt after 3000 miles- though it's possible something has come adrift after the belt change.

It does sound like you need to get the codes read.

[Toplights]

My problem is i have use of a code reader but can only borrow it every other week,(when my lads off shift).

[shimon340]

hello

how did you confirm no spark and no fuel exactly?

regards

S

[Toplights]

Originally Posted by shimon340

hello

how did you confirm no spark and no fuel exactly?

regards

S

shimon340 thanks for the interest,Turned car over repeatedly,took out plugs staight away,dry as a bone,

Removed all plugs earthed them to bolts on the head and turned car over repeatedly no spark,(used an assistant to watch for spark).

[shimon340]

hi there

Thanks for the update.

I've currently got an 850 which starts ok from cold and then stalls once warmed up. It then refuses to restart. Investigation ongoing.

Does your car log any fault codes? Is your car OBD2 or do you have the red LED flashing fault code system? (OBD2 conector is inside car. Earlier system is an A and B plug front left under the bonnet near the ECU box). You can read the earlier codes without a laptop or code reader etc.

After a period of time standing, indeed the 850 series engines (pos 960s also but not heard of one doing this) do need to be cracked for some time to build adaquate pressure in the hydraulic tappet to open the valves fully.

Sticking valves was an issue with these engines for vehicle driving only short distances without fully warming up. Cause was varnishes forming on the valve stems making them sticky. Original solution was to replaced valve guides but that was later updated to a bulletin which in effect went for a thinner oil spec and a "Italian tune up" of the engine.

On the 940s, when the immobiliser/alarm is activated, the fuel pump is cut so the car cranks but doesnt start. Im not sure if the 940 system also stops spark. Indeed, given the age the 850 could be the same.

Have you checked if the fuel pump is running ok? Another common 850 fault (interestingly also on the 240,740,940 onwards as well) is intermittant lost connection to the fuel pump relay. Is supply to the fuel pump ok?

sorry to not have model specific info exact for your, but some Volvos, if the flywheel sensor signal is lost, the engine wont fuel or spark but allows cranking. However, 850s have cam and crank sensors so can run on just one if needed (will produce a fault code as well). On 850s though if the coolant sensor signal is lost, the car wont start at all. In some cases even, this connector can cause the car to stall in use as per some other cases here and on some American websites.

please keep us updated with your progress!

S

[Toplights]

shimon340,to be honest i first thought it was a valve or lifter problem as i stopped and started it 3 or four times in a very short distance eg 1/2 mile or so.now i am tending to think its Imobiliser related.
Car is very well maintained (by me).,has regular oil and filter changes 5,000 miles,Petrol is treated (Forte)at same time so Engine is clean and loose enough.

Just took Fuel Relay appart contacts open and clean,no other obvious faults with it. going to have a look at the Imobiliser portion of the ignition switch later.going to wobble the key in the Ignition switch at the same time.

[shimon340]

hi

good luck with it and tell us how it goes.

Just checked but your 241 miles from me otherwise Id come along to help!

S

[liuleichan]

Could be the cam position sensor, or perhaps the immobiliser thing around where the key goes in.

[Toplights]

Just checked,Cam Shaft turning, fuel pump relay(can feel it engaging)can also hear fuel pump start for about 3/4 secs, the Imobilizer thingy,took the plug out and replaced it two or three times to clean contacts, seems in order,waggled the key in the ignition barrel no start,battery now flat.

Just had a thought i wonder if the battery is turning the engine over to slow to make a spark (allthough it seems ok to me)is that possible or would it still produce a week spark? I have had the car 3 years now so i dont know how old the battery is. Can anyone tell me what the most powerfull battery is for my car? when i renew a battery i allways get the most powerfull one i can.

Will probably try ganging my battery with jump leads of my other car just to test the idea out.Job for tomorrow,had enough for today,you'r thoughts are welcome.

[liuleichan]

If you're not getting a spark, and ignition components are OK (coil, leads, plugs, dizzy cap, rotor arm) then cam position sensor, and immobiliser antenna would be my hunch.