Engine 850: B5234T/2.3/20v/T5: Starting issue

[don0412]

if mine dont start i wait at least 30 secs before i try again any time ive tried immediatley after it wont go but short delay always does trick for me

[pookie]

FWIW the ECU does NOT trigger the coil. The ignition amplfier does this, has it been checked or substituted?

Pookie

[stuartvolvo]

Yeh Pookie, i thought that. From what i have found out the ecu does not really controll anything to do with the starting. It is more for the running of the car.
Where exactly is the ignition amplifier. Could you please describe it to me and where i would find it.
Thanks

[Sprintman]

Hi all,

just read the end of this thread, not all the 143 replies, but I thought I would relate a recent experience with a 2 litre 20 valve which may be of help. It seemed to start and run OK from cold but once it got hot after about 4 miles would cough and splutter, eventually stalling and would not restart until being left to cool for some time. Had it on the diagnostics, nothing found wrong so was very puzzled as to what the problem might be. Tried another coil but this didn't cure it. Eventually reasoned that if there was nothing wrong with any of the sensors then the cause must be something that is not sensed by the diagnostics, so tried a new distributor cap, rotor arm and plug leads, and lo and behold it runs perfectly! I wouldn't have thought these simple things would make that much difference but they obviously do, and so they're something worth trying if all else fails!

[DLM48]

Originally Posted by pookie

FWIW the ECU does NOT trigger the coil. The ignition amplfier does this, has it been checked or substituted?

Pookie

well the ECU must trigger the coil the amplifier is an integral part of the coil unit even if it is mounted externally

[DLM48]

Originally Posted by pookie

FWIW the ECU does NOT trigger the coil. The ignition amplfier does this, has it been checked or substituted?
Pookie

Originally Posted by stuartvolvo

Yeh Pookie, i thought that. From what i have found out the ecu does not really controll anything to do with the starting. It is more for the running of the car.
Where exactly is the ignition amplifier. Could you please describe it to me and where i would find it.
Thanks

the amplifier is that rectangular black block mounted below and attached to the coil

Stuart what you wrote re the ECU - well that cant be right Stuart - how else can the coil know when to send out a high voltage pulse to the distributor if the ECU does not control it - do explain that one to me - if you really think it is not the ECU that does that.

the engine supplies two rotational signals to the ECU one from the Camshaft the other from the Crankshaft - the ECU uses these signals to work out what the engine is doing rotational speed and rotational position wise - using both of these sensors it can work out exactly where the engine is on its cycle and how fast it is turning - when the ECU sees one cylinder getting close to TDC the ECU then signals to the coil VIA the amplifier (which as far as i am concerned is a part of the coil unit) to pulse once - that pulse goes to the center contact of the distributor - the distibuter then sends that high voltage pulse to the correct cylinder to fire the spark plug Stuart IF you really think the ECU has nothing to do with starting the engine - well take it out - how can you possibly think that Stuart this is basic stuff. Since you seem to understand/suggest the ECU has 'something' to do with the engine when it is running - you wrote "From what i have found out the ecu does not really controll anything to do with the starting. It is more for the running of the car." - Stuart i thought that starting was the first part of getting an engine to run - for sure and ABSOLUTELY the ECU 'times' and 'initiates' the spark whenever the engine is turning with the ignition switched on - it does this if the engine is only turning over slowly - while you try to start the car either on the starter with a push or a tow - or revving at 5,000 RPM - the ECU also suppresses this signal when you hit the rev limiter.................

OR the ECU would do this (initiate the properly times spark) on a car that was working 100% properly with these non starting cars the ECU takes a holiday intermittently and when it does that you dont get the HT/HV Pulses to start the engine - THIS IS THE PROBLEM

What we have all yet to discover is WHY the ECU takes a holiday - i am told but have not seen YET with my own eyes - i was 5000 miles away when my car was being investigated/repaired - it is the ECU being swamped with RFI/EMI interference from the starter motor to such an extent that the ECU cannot work out that the engine is turning or how fast or what position the engine is on its cycle - you need to get a scope hung on that engine and see what signals are there in REAL TIME - i did suggest you set up a temporary bypass of the ignition key/switch that would be my next 'thing to do' to eliminate any possible fault in the start switch and associated wiring. ONCE you have eliminated the ignition/start switch and all associated wiring you have nothing left in the car that could be causing this problem apart from the starter motor itself - and probably this EMI/RFI issue. Both the starter and battery were replaced on my car with new Volvo parts without making any difference.

[DLM48]

Originally Posted by Sprintman

Hi all,

just read the end of this thread, not all the 143 replies, but I thought I would relate a recent experience with a 2 litre 20 valve which may be of help. It seemed to start and run OK from cold but once it got hot after about 4 miles would cough and splutter, eventually stalling and would not restart until being left to cool for some time. Had it on the diagnostics, nothing found wrong so was very puzzled as to what the problem might be. Tried another coil but this didn't cure it. Eventually reasoned that if there was nothing wrong with any of the sensors then the cause must be something that is not sensed by the diagnostics, so tried a new distributor cap, rotor arm and plug leads, and lo and behold it runs perfectly! I wouldn't have thought these simple things would make that much difference but they obviously do, and so they're something worth trying if all else fails!

my car had all these replaced even though it was 100% obvious that there was no HT/HV spark from the coil - garages love to spend other peoples money - interesting fault and fix - and for sure worth a try - i think at this point in time almost anything is worth a try - if only to eliminate these item from our minds as 'possible' causes - however how do you equate these items being faulty - the car not starting on the starter motor - yet starting easily with a push?

[stuartvolvo]

Hi David, i see you point with the ecu. I also know that the ignition switch is fine as i have already put a new one on. There are several areas which i am going to have a look in next.

1. The cranking circuit i.e. from the ignition switch onwards.
2. Check ecu connections, at bottom of ecu.
3. Imobaliser circuit.

What i dont quite understand david, is what would create/cause this electrical interferance. I have been trying to locate a scope to check for interferance, but i am not having any luck. My dad who would probably be able to lay his hands on one has been away on holiday for a while, although he will be back home tomorrow, so i will try and see if he can get a loan of one from somewhere.
I have also tried to and moved the wiring loom that runs along the front cross member further away from the engine to see if it cuts dont on any interferance if there was any.
Do you know exactly where the imobaliser usit is at all, as i would like to have a look at that, although i dont know if the imobaliser would stop the engine from cranking or just stop it from sparking.
Anyway, im away for the rest of the day and ill let you know of any updates either tonight or tomorrow.

Regards
Stuart

[ShadeTek]

Stuart, remember your car was fixed by my friend before you owned it yourself. He had to repair the ECU chip upgrade which was poorly soldered in. It is possible that some of the track was damaged and may be causing a problem again. An ECU swap-out is a very good suggestion to narrow down the cause of this problem.

[DLM48]

Originally Posted by stuartvolvo

Hi David, i see you point with the ecu. I also know that the ignition switch is fine as i have already put a new one on. There are several areas which i am going to have a look in next.

1. The cranking circuit i.e. from the ignition switch onwards.
2. Check ecu connections, at bottom of ecu.
3. Imobaliser circuit.

What i dont quite understand david, is what would create/cause this electrical interferance. I have been trying to locate a scope to check for interferance, but i am not having any luck. My dad who would probably be able to lay his hands on one has been away on holiday for a while, although he will be back home tomorrow, so i will try and see if he can get a loan of one from somewhere.
I have also tried to and moved the wiring loom that runs along the front cross member further away from the engine to see if it cuts dont on any interferance if there was any.
Do you know exactly where the imobaliser usit is at all, as i would like to have a look at that, although i dont know if the imobaliser would stop the engine from cranking or just stop it from sparking.
Anyway, im away for the rest of the day and ill let you know of any updates either tonight or tomorrow.

Regards
Stuart

Originally Posted by ShadeTek

Stuart, remember your car was fixed by my friend before you owned it yourself. He had to repair the ECU chip upgrade which was poorly soldered in. It is possible that some of the track was damaged and may be causing a problem again. An ECU swap-out is a very good suggestion to narrow down the cause of this problem.

Stuart you are welcome to try the ECU out of my 2.5 20V 855 i also have a few spare good ones somewhere as well as a few coils and crank and cam shaft sensors in a bag somewhere i am free all of this weekend apart from the F1 GP qualy and race times and well i am just round the corner so could come round any day or evening moving that harness is 'something that is recommended' to help fix this problem did you manage to get any adhesive backed copper tape?

i truly have no ideas as to why the starter is throwing out EMI/RFI interference - well i do really as that is fairly standard with any electrical motor - what i dont understand is that why this is causing a problem 'now' with 850's (and it seems to be only 850's) once these cars get older and why the car reacts in a non consistant way sometimes starting and sometimes not starting - as i said i have not seen this real time myself as i was in the USA while my car was being fixed - it was in the garage for almost 18 months the cost was horrendous - they did of course go OTT replacing everything with new Volvo parts and even though doing that did not fix the problem - somehow i was left with the bill for new (not needed parts) and even though the bill that i agreed to pay was only about 5% of the true cost - it was way in excess of the book value of the car.

Even after all of this work about 18 months later the car had the last laugh dumping all its oil out when i was dashing/thrashing up the M74 and causing masive terminal damage to the engine i am still really really interested in solving this one - finding out the REAL cause of why these cars dont and wont start on the starter.

I note you have replaced the ignition switch - i would still ask you to try the temporary start circuit bypassing all the cars wiring and going straight from the hot terminal of the battery to the solenoid on the starter motor - that i suggested quite a few posts ago - that to me is your next move and one very easy to set up and try - please try that for me and let me know the outcome.