got fuel got a spark but wont fire !! 2002 316ti
Discussion
it was driving fine no problems at all. came back from a good run, went back to it a couple of hours later and it wont start
its turning over fine
the plugs are nice and wet with fuel
the spark is nice and brite white when put to the block
ive fitted new plugs today to try that and ive put jump leads on to ensure its not a battery problemive checked each pencil coil and there all giving the same coloured spark
help !!
its turning over fine
the plugs are nice and wet with fuel
the spark is nice and brite white when put to the block
ive fitted new plugs today to try that and ive put jump leads on to ensure its not a battery problemive checked each pencil coil and there all giving the same coloured spark
help !!
Well it might be the ecu, but unless there is a reason, like perhaps it got wet, or somehow it was subject to electrical damage, the injectors are the more likely point of failure.
Mechanical things generally go wrong more quickly than electronic ones.
You said you were going to do a compression test. Again if you suspect that the compression might be a problem, it's worth checking first, because it costs little to do.
If you have an idea that the injectors are at fault, the best thing is to get them checked out. If you're feeling flush, maybe just change them anyhow.
The thing that makes me think this might be the problem is that you said when you disconnect the fuel pump, it begins to try firing. I think that's probably the best indication that you have some sort of fuel problem.
If it is a fuel problem, then it's airflow sensing, ECU, injectors or fuel pressure regulator.
I don't know your particular car, but I have a feeling it has some sort of moving plate airflow sensor. If it's that sort, then you need to check the little carbon track inside the sensor, because they do fail. The alternative is the hotwire system, sometimes the tiny filament wire breaks. In either of these situations it shouldn't prevent the car starting, but there would be more fuel pumped through the engine.
TBH with a car as new as yours, and with a fuel problem, I'd have said it's better to take it to the dealer because they will have fuel pressure measurement guages to test the regulator; A test harness for the injectors; Electronic diagnostics for the ECU.
Mechanical things generally go wrong more quickly than electronic ones.
You said you were going to do a compression test. Again if you suspect that the compression might be a problem, it's worth checking first, because it costs little to do.
If you have an idea that the injectors are at fault, the best thing is to get them checked out. If you're feeling flush, maybe just change them anyhow.
The thing that makes me think this might be the problem is that you said when you disconnect the fuel pump, it begins to try firing. I think that's probably the best indication that you have some sort of fuel problem.
If it is a fuel problem, then it's airflow sensing, ECU, injectors or fuel pressure regulator.
I don't know your particular car, but I have a feeling it has some sort of moving plate airflow sensor. If it's that sort, then you need to check the little carbon track inside the sensor, because they do fail. The alternative is the hotwire system, sometimes the tiny filament wire breaks. In either of these situations it shouldn't prevent the car starting, but there would be more fuel pumped through the engine.
TBH with a car as new as yours, and with a fuel problem, I'd have said it's better to take it to the dealer because they will have fuel pressure measurement guages to test the regulator; A test harness for the injectors; Electronic diagnostics for the ECU.
Edited by dilbert on Thursday 21st August 19:30
Sounds a hell of a lot like a faulty crankshaft sensor, the N42 engine is quite common for this fault. You're probably right in that you've got fuel and spark - but they're at the right time! Unlike the engine it replaced (M43TU) a faulty crank sensor will stop it starting.
Unfortunately it's at the back of the block on the N/S - have to remove inlet manifold to replace it, so a bit fiddly.
The other slightly less common fault (seen a few though) is the timing jumping a couple of teeth. Not as bad as it sounds as it rarely damages the engine, a lot more work to rectify though.
Feel free to email me if you need any more advice/ instructions, i usually check my emails every evening around 6-7pm.
Unfortunately it's at the back of the block on the N/S - have to remove inlet manifold to replace it, so a bit fiddly.
The other slightly less common fault (seen a few though) is the timing jumping a couple of teeth. Not as bad as it sounds as it rarely damages the engine, a lot more work to rectify though.
Feel free to email me if you need any more advice/ instructions, i usually check my emails every evening around 6-7pm.
Hi,I would definately check the engine timing,i've repaired a few n42 engines for the timing chain plastic guides snapping and the timing chain then skipping teeth with the extra play,they tend to make a rattling noise from the front of the engine when cranking over (very faint),you should be able to check the guides once the rocker cover is removed,you'll need to remove the valvetronic motor to get the cover off though.
would the eml light not go out on cranking if its the crankshaft sensor ?
would a crankshaft sensor die just like that with no warning ?ive had sensors die before on other cars and they usually give a little warning
the reason why im thinking the ecu has died is a long story but if your sitting comfortably ...
about 2 months ago the car started to develop a fault where it wouldnt rev. it would start ok but the revs would be limited.if i disconnected a vanos solonoid or a camshaft senso the car would be fine and run no probs obviously what was happening when i disconnected the solonoid was that the engine was switching from using the variable motor to the throttle body flap and using some sort of default map. this is what they do as a secondary system if there is a fault with the vanos so bmw said
after a lot of diagnosis and headscratching by bmw they determined it was the vanos motor sticking in position.
i fitted a new motor and took the car back to them as they need to be reset in position.
now with the new motor fitted i didnt need to disconnect any sensors for the car to drive fine so i was hopefull it had been fixed
when i went back to bmw they could not clear the engine managment light and the ecu would let them reset the vanos motor.
they said they thought the ecu was at fault so reflashed it with an updated map but it didnt change anything
they then said i needed a new ecu . at this point me and my wallet left as the car was driving perfect albeit with the engine managment light on
anyway that was a lot of miles ago and the car has been perfect untill the other day when i went back to it after it had been fine all morning
would a crankshaft sensor die just like that with no warning ?ive had sensors die before on other cars and they usually give a little warning
the reason why im thinking the ecu has died is a long story but if your sitting comfortably ...
about 2 months ago the car started to develop a fault where it wouldnt rev. it would start ok but the revs would be limited.if i disconnected a vanos solonoid or a camshaft senso the car would be fine and run no probs obviously what was happening when i disconnected the solonoid was that the engine was switching from using the variable motor to the throttle body flap and using some sort of default map. this is what they do as a secondary system if there is a fault with the vanos so bmw said
after a lot of diagnosis and headscratching by bmw they determined it was the vanos motor sticking in position.
i fitted a new motor and took the car back to them as they need to be reset in position.
now with the new motor fitted i didnt need to disconnect any sensors for the car to drive fine so i was hopefull it had been fixed
when i went back to bmw they could not clear the engine managment light and the ecu would let them reset the vanos motor.
they said they thought the ecu was at fault so reflashed it with an updated map but it didnt change anything
they then said i needed a new ecu . at this point me and my wallet left as the car was driving perfect albeit with the engine managment light on
anyway that was a lot of miles ago and the car has been perfect untill the other day when i went back to it after it had been fine all morning
Blimey that's a bit bold.
In the old days, you could pin down a fault using your brain and a (small) hammer. These days without the right tools, it's just an expensive gamble. £245 is less than I would have imagined, but it's still a lot of dosh. Hope you're right and I'll cross my fingers for you.
In the old days, you could pin down a fault using your brain and a (small) hammer. These days without the right tools, it's just an expensive gamble. £245 is less than I would have imagined, but it's still a lot of dosh. Hope you're right and I'll cross my fingers for you.
If you have fuel and a spark you ought to be able to get *some* sort of life out of it. I'd suspect from the symptoms that you have got too much fuel and are flooding it. Many engine management systems have a 'flood clear' mode which cuts the fuel off when you hold the throttle wide open, it would be worth trying that. Even if you don't have the flood clear feature, maximum air flow would give you the best chance to get rid of excess fuel if it's over-fuelling. If you can get it to fire at all with the fuel pump disabled then I'd have thought you stood a good chance of nursing it to life by just briefly enabling the fuel pump when it starts to lean out.
Do you know how the fuel pressure is regulated? If it's a manifold referenced regulator, it may be that the vac reference hose has come adrift? Or it may be the coolant temp sensor has failed and the ECu thinks you're at the north pole.
Do you know how the fuel pressure is regulated? If it's a manifold referenced regulator, it may be that the vac reference hose has come adrift? Or it may be the coolant temp sensor has failed and the ECu thinks you're at the north pole.
i tried it with the throtle body held open but it shouldnt be using the throttle body any way so thats the earlier fault
it should be using the vvt system to control the revs
yes its a gamble getting a new ecu but ive got the full kit ( ie ecu chips and transponder ) at a good price so i can always sell it on.
it should be using the vvt system to control the revs
yes its a gamble getting a new ecu but ive got the full kit ( ie ecu chips and transponder ) at a good price so i can always sell it on.
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