Greetings,
I have a 91 ZX Volcane 1.9 i
It has backfired into the intake system and blown the plastic inlet manifold to pieces twice in only one month.
At £240 each these manifolds are not cheap and it is difficult to find them in the breakers.
I've ordered a new one but want to be sure that im also eliminating the cause.
One possibility is that a spark is jumping across from one lead to another igniting a cylinder while its on intake but I cant see any reason to suspect that as the leads are good quality and not very old.
Another possibility that has been suggested is that maybe I have a seeping injector and as a result fuel vapour is collecting in the manifold overnight but then I have to wonder what is igniting it ?
It only happens as I go to start the engine first thing in the morning.
Anyone who can offer any ideas as to what might cause this please reply with your ideas.
Also if anyone has heard of this before.
Paul.
ZX Vocane Plastic Intake Manifold Exploding
Moderator: RichardW
Hmmm....
Could well be wrong igniting - which is NOT solved by just replacing the HT cables.
Could well be the dizzy cap/rotor - being damp in cold mornings - even oil seepage from the cam out the dizzy - to the cap.
A seeping injector alone can not cause this problem - as the fuel has to be ignited at wrong timing.
Considering the hefty cost & hassle replacing the manifold - I'd definately try a new dizzy cap/rotor - even let a garage track down the problem. Could well be cheaper in the end.
Could well be wrong igniting - which is NOT solved by just replacing the HT cables.
Could well be the dizzy cap/rotor - being damp in cold mornings - even oil seepage from the cam out the dizzy - to the cap.
A seeping injector alone can not cause this problem - as the fuel has to be ignited at wrong timing.
Considering the hefty cost & hassle replacing the manifold - I'd definately try a new dizzy cap/rotor - even let a garage track down the problem. Could well be cheaper in the end.
It's solid state distributorless ignition so cant be distributor but definitely looks like something must be igniting it.
When it goes it's one hell of a bang and always the instant the key is turned.
I bought it from my sister, she had spent over £1000 in the last year in starting and running problems. My brother, before her, had spent hundreds in garage bills but it didn't do this untill recently.
One thing I dont know, that might provide some insight is, as its a wasted spark ignition system, do the cylinders all fire together or only 2 at a time ?
Usualy it starts and runs verry well. It's a verry pokey car usualy.
Paul.
When it goes it's one hell of a bang and always the instant the key is turned.
I bought it from my sister, she had spent over £1000 in the last year in starting and running problems. My brother, before her, had spent hundreds in garage bills but it didn't do this untill recently.
One thing I dont know, that might provide some insight is, as its a wasted spark ignition system, do the cylinders all fire together or only 2 at a time ?
Usualy it starts and runs verry well. It's a verry pokey car usualy.
Paul.
Ah well -
The combo ignition coil then = double wasted spark coil.
The wasted spark principle ignites 2 cylinders simultanously - one would be the cylinder at compression - the other would be the cylinder at exhaust - both cylinders near TDC when spark is arcing.
Next time these 2 cylinders are near TDC and gets a spark - they are both in opposite cycle.
At the same time the reamining 2 cylinders will be near BTC (bottom stroke) - one at end of working stroke - other at end of intake stroke.
If a seeping injector has left any fuel in a cylinder - then this fuel would intially burn at first start - either in a normal compression or in an exhaust -cycled cylinder.
That is if the spark STILL is considered to be timed correct.
If any fuel from injector seepage should be ignited to cause backfiring - then it must be ignited during the intake (vacuum) cycle - where an open path exist from the cylinder cavity to the intake manifold - due to an open inlet valve.
This would certainly happen if arcing occurs between the 2 wasted spark coils - either in the coil itself - or between HT cables.
But this would be kind of a persistent problem - as it takes quite a few sparks to change the coil working temperature or such - not a single shot.
Another problem could be the ECU itself having a problem controlling the initial spark at start.
This prevents any false sparking untill the ECU is fully reset - and knows where the flywheel is located in relation to the ignition sensor.
I don't think the ignition sensor itself could cause such problems - as it would then also be sort of a persistent problem - not just a single shot.
Wonder if an ignition sensor with too tight flywheel clearance - or sensor tip contaminated with metallic (magnetic) dust - in fact could fool the ECU initial ignition firing ?
*******
Came to think about it [8)]
The above reflections are based on my mind stuck in old carby/monopoint systems [;)]
As the Volcane has multipoint injection - then the only time a fuel mixture exists in the inlet cycle is when an injector has seeped for a while.
Once the engine has turned - this fuel is "cleaned" out - and fuel is then only injected during the compression stroke - no fuel would exist in the intake cycle where a path exists to the intake manifold.
Thus it is in fact possible you have a persistent problem with the combo coil - i.e. it's arcing internally between the 2 coil sets.
It's only seen at initial startup - when engine first moves and initially has seepage fuel left in a cylinder during intake - thus the engine backfires just once initially.
The fact that a multipoint injection engine could backfire puzzled me - as it's a known nuisance on older species that the injectors suffers from some seepage - but with no other consequences than smoking at start up - or in severe seepage cases - gives MOT emissions problems.
Backfiring would not be a common indication.
The coil can be tested quite easy - if disconnected totally from engine.
The LT side connector would have a 4pole connector with these pin connections :
1) coil set A CB input
2) coil set B CB input
3) radio interference suppression condenser - this pin connected internally on coil to pin 4 (may be an empty pin on your Volcane)
4) +12V feed from igntion key
NOTE : coil set A fires cyl 1&4 - coil set B fires cyl 2&3
NOTE : be SURE to identify HT cable locations BEFORE un-plugging from plugs - otherwise it may be cold sweat & cursing time [B)]
Unplug all 4 HT cables - insert 4 sparkplugs - old discarded ones are ok for free air testing. Make sure the plugs are resting on earthed surface.
Now connect a 12V feed on terminal 4 on coil.
Then connect a wire to one of the CB pins on coil - and slide the open end of the wire over earthed surface. This will give a series of sparking on the test plugs.
Important thing is to notice if all 4 plugs is sparking - as only 2 at a time should be sparking on each CB pin on the coil.
The combo ignition coil then = double wasted spark coil.
The wasted spark principle ignites 2 cylinders simultanously - one would be the cylinder at compression - the other would be the cylinder at exhaust - both cylinders near TDC when spark is arcing.
Next time these 2 cylinders are near TDC and gets a spark - they are both in opposite cycle.
At the same time the reamining 2 cylinders will be near BTC (bottom stroke) - one at end of working stroke - other at end of intake stroke.
If a seeping injector has left any fuel in a cylinder - then this fuel would intially burn at first start - either in a normal compression or in an exhaust -cycled cylinder.
That is if the spark STILL is considered to be timed correct.
If any fuel from injector seepage should be ignited to cause backfiring - then it must be ignited during the intake (vacuum) cycle - where an open path exist from the cylinder cavity to the intake manifold - due to an open inlet valve.
This would certainly happen if arcing occurs between the 2 wasted spark coils - either in the coil itself - or between HT cables.
But this would be kind of a persistent problem - as it takes quite a few sparks to change the coil working temperature or such - not a single shot.
Another problem could be the ECU itself having a problem controlling the initial spark at start.
This prevents any false sparking untill the ECU is fully reset - and knows where the flywheel is located in relation to the ignition sensor.
I don't think the ignition sensor itself could cause such problems - as it would then also be sort of a persistent problem - not just a single shot.
Wonder if an ignition sensor with too tight flywheel clearance - or sensor tip contaminated with metallic (magnetic) dust - in fact could fool the ECU initial ignition firing ?
*******
Came to think about it [8)]
The above reflections are based on my mind stuck in old carby/monopoint systems [;)]
As the Volcane has multipoint injection - then the only time a fuel mixture exists in the inlet cycle is when an injector has seeped for a while.
Once the engine has turned - this fuel is "cleaned" out - and fuel is then only injected during the compression stroke - no fuel would exist in the intake cycle where a path exists to the intake manifold.
Thus it is in fact possible you have a persistent problem with the combo coil - i.e. it's arcing internally between the 2 coil sets.
It's only seen at initial startup - when engine first moves and initially has seepage fuel left in a cylinder during intake - thus the engine backfires just once initially.
The fact that a multipoint injection engine could backfire puzzled me - as it's a known nuisance on older species that the injectors suffers from some seepage - but with no other consequences than smoking at start up - or in severe seepage cases - gives MOT emissions problems.
Backfiring would not be a common indication.
The coil can be tested quite easy - if disconnected totally from engine.
The LT side connector would have a 4pole connector with these pin connections :
1) coil set A CB input
2) coil set B CB input
3) radio interference suppression condenser - this pin connected internally on coil to pin 4 (may be an empty pin on your Volcane)
4) +12V feed from igntion key
NOTE : coil set A fires cyl 1&4 - coil set B fires cyl 2&3
NOTE : be SURE to identify HT cable locations BEFORE un-plugging from plugs - otherwise it may be cold sweat & cursing time [B)]
Unplug all 4 HT cables - insert 4 sparkplugs - old discarded ones are ok for free air testing. Make sure the plugs are resting on earthed surface.
Now connect a 12V feed on terminal 4 on coil.
Then connect a wire to one of the CB pins on coil - and slide the open end of the wire over earthed surface. This will give a series of sparking on the test plugs.
Important thing is to notice if all 4 plugs is sparking - as only 2 at a time should be sparking on each CB pin on the coil.
Thanks for the idea for testing the coil.
I'm interested by the mention of the ecu reset.
Usualy when starting the engine I turn the key to on and wait the aprox 3 seconds defore the oil level guage starts to register. I've noticed that the dash illuminations and guages all kick in together about 2 to 3 seconds after turning the ignition on.
Once the oil guage has registered I start the engine. It usualy starts after about 2 seconds of winding if its cold and instantly if its warm.
However both times that it has blown it's manifold apart I've just turned the key from cold and instantly started the engine without waiting for the guages to kick in.
Could it be that by not waiting that 2 seconds the ecu hasn't quite reset and is out of time ?
Paul.
I'm interested by the mention of the ecu reset.
Usualy when starting the engine I turn the key to on and wait the aprox 3 seconds defore the oil level guage starts to register. I've noticed that the dash illuminations and guages all kick in together about 2 to 3 seconds after turning the ignition on.
Once the oil guage has registered I start the engine. It usualy starts after about 2 seconds of winding if its cold and instantly if its warm.
However both times that it has blown it's manifold apart I've just turned the key from cold and instantly started the engine without waiting for the guages to kick in.
Could it be that by not waiting that 2 seconds the ecu hasn't quite reset and is out of time ?
Paul.
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RichardW
- Forum Treasurer
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Has it exploded as you cranked the engine or before?
There is clearly a fuel leak into the manifold that is making a flammable vapour, then when you power up the car something is causing it to explode (I understand this is not uncommon on cars converted to LPG, and which are started on LPG). Does it use the heated wire type of air flow sensor - this could well be enough to set off the mixture. I think you are going to have to look at the injectors and see if one is dribling.
There is clearly a fuel leak into the manifold that is making a flammable vapour, then when you power up the car something is causing it to explode (I understand this is not uncommon on cars converted to LPG, and which are started on LPG). Does it use the heated wire type of air flow sensor - this could well be enough to set off the mixture. I think you are going to have to look at the injectors and see if one is dribling.
-
philhoward
Search for any supplier of LPG kits and they do an "explosion flap" to be fitted to cars fitted with plastic manifolds to stop what you've got hapening!
Sounds like leaving it for the 2/3 seconds before turning the engine. Is it one of those systems which will pulse the pump for 2 seconds as soon as the ignition is turned on (to get the fuel rail to pressure); could this push fuel through a weak injector? I'd guess getting the injectors tested is a good starting point.
As for the firing on the induction stroke only, most injectors will run at something like a 60-70% duty cycle (i.e. they're open upto a maximum of 60% of all the time)..as the induction stroke is only about 25% of the time, the injector can be firing well before the induction stroke has started. Granted the 70% probably only occurs at full throttle at redline revs!
Sounds like leaving it for the 2/3 seconds before turning the engine. Is it one of those systems which will pulse the pump for 2 seconds as soon as the ignition is turned on (to get the fuel rail to pressure); could this push fuel through a weak injector? I'd guess getting the injectors tested is a good starting point.
As for the firing on the induction stroke only, most injectors will run at something like a 60-70% duty cycle (i.e. they're open upto a maximum of 60% of all the time)..as the induction stroke is only about 25% of the time, the injector can be firing well before the induction stroke has started. Granted the 70% probably only occurs at full throttle at redline revs!
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tomsheppard
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What a sad and expensive tale of woe. I feel for you. this could be due to a problem with injectors
Hot wire anemometers burn off their deposits by raising the wire temperature to red heat. on Saabs, this happens at switch off but if the design has changed or is different in Cits then this may be the source of ignition; does it happen just as the engine is cranked or as the ignition goes on?
Another possibility is that an intake valve is not closing properly and the compressed mixture is forced into the manifold. The spark does the rest. This is not very likely but it should be ruled out with a compression test. More likely is a spark happening at some time that it shouldn't. Most ecus will advance the ignition to start the engine using a temperature sensor to control enrichment. If the advance had gone haywire then this could be a cause and possibly the temperature sensor needs looking at. If a substitute coil is available, take both to an auto electrician and ask for an insulation test on both units for comparison, There may be a short circuit in the primary circuit to the coil pack that is sending a false trigger to the other side of the coil. That will be hard to track down. I assume that the coil and leads are spotlessly clean? By all means check the injectors first but I would be interested in knowing the history of the starting problem that set you off down this sorry path. Perhaps this will enable us to pinpoint the problem. Sorry this is inconclusive but intermittent faults are like that.
Hot wire anemometers burn off their deposits by raising the wire temperature to red heat. on Saabs, this happens at switch off but if the design has changed or is different in Cits then this may be the source of ignition; does it happen just as the engine is cranked or as the ignition goes on?
Another possibility is that an intake valve is not closing properly and the compressed mixture is forced into the manifold. The spark does the rest. This is not very likely but it should be ruled out with a compression test. More likely is a spark happening at some time that it shouldn't. Most ecus will advance the ignition to start the engine using a temperature sensor to control enrichment. If the advance had gone haywire then this could be a cause and possibly the temperature sensor needs looking at. If a substitute coil is available, take both to an auto electrician and ask for an insulation test on both units for comparison, There may be a short circuit in the primary circuit to the coil pack that is sending a false trigger to the other side of the coil. That will be hard to track down. I assume that the coil and leads are spotlessly clean? By all means check the injectors first but I would be interested in knowing the history of the starting problem that set you off down this sorry path. Perhaps this will enable us to pinpoint the problem. Sorry this is inconclusive but intermittent faults are like that.
Thanks for the input folks.
In answer to the question of "Does this happen as I turn the ignition on or when I crank the engine ?" The answer is that it happens as i crank the engine. But only if I do so imediately without waiting for the dash illuminations and guages to register.
The dash guages and illuminations do not register imediately when I turn the ignition on, they dont just move slowly, they seem to have a pre defined waiting period folowed by normal dash illumination and then the guages kick in.
If I wait 2 to 3 seconds for this to happen all is OK and off I drive.
And in this beast that can be a rapid takeoff.
More and more it looks like there is a short delay while the ecu resets. Maybe failing to wait means that it hasn't fully reset and cant workout where in its cycle it should be.
It seems a logical assumption that as there is, I believe, only one trigger indent on the flywheel the ecu must calculate how long to wait before firing each coil once it's tdc sensor finds that indent. This calculation must take into account the rpm, air flow, temp etc.
If the ecu were attempting to fire before that calculation was complete then it may fire completely out of time.
There, you see, I should have been a Vulcan. As comander Spok once said "Once you have eliminated the impossible, whatever remains, however unlikely, must be the truth"
I'll keep on testing, looking for clues, any further ideas are welcomed.
Paul.
In answer to the question of "Does this happen as I turn the ignition on or when I crank the engine ?" The answer is that it happens as i crank the engine. But only if I do so imediately without waiting for the dash illuminations and guages to register.
The dash guages and illuminations do not register imediately when I turn the ignition on, they dont just move slowly, they seem to have a pre defined waiting period folowed by normal dash illumination and then the guages kick in.
If I wait 2 to 3 seconds for this to happen all is OK and off I drive.
And in this beast that can be a rapid takeoff.
More and more it looks like there is a short delay while the ecu resets. Maybe failing to wait means that it hasn't fully reset and cant workout where in its cycle it should be.
It seems a logical assumption that as there is, I believe, only one trigger indent on the flywheel the ecu must calculate how long to wait before firing each coil once it's tdc sensor finds that indent. This calculation must take into account the rpm, air flow, temp etc.
If the ecu were attempting to fire before that calculation was complete then it may fire completely out of time.
There, you see, I should have been a Vulcan. As comander Spok once said "Once you have eliminated the impossible, whatever remains, however unlikely, must be the truth"
I'll keep on testing, looking for clues, any further ideas are welcomed.
Paul.
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uhn113x
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1997 ZX 1.9D Dimension. - x 1
Voyager quoth:
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">
There, you see, I should have been a Vulcan. As comander Spok (sic)once said "Once you have eliminated the impossible, whatever remains, however unlikely, must be the truth"
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
I think that Sherlock Holmes was reputed to have said this - Spock must have 'borrowed' it
At £240 a throw, I would be inclined to wait the three seconds! No good if you have HS (hurry sickness) though
<blockquote id="quote"><font size="1" face="Verdana, Arial, Helvetica" id="quote">quote:<hr height="1" noshade id="quote">
There, you see, I should have been a Vulcan. As comander Spok (sic)once said "Once you have eliminated the impossible, whatever remains, however unlikely, must be the truth"
<hr height="1" noshade id="quote"></blockquote id="quote"></font id="quote">
I think that Sherlock Holmes was reputed to have said this - Spock must have 'borrowed' it
At £240 a throw, I would be inclined to wait the three seconds! No good if you have HS (hurry sickness) though