M50 Cylinder Missing

[Mohammed_A]

Hi Guys..... need some help.... im busy with a m50b25 in my e30, which is turbocharged..... the motor has been overhauled using forged pistons, cometic gasket etc....the problem im having is that cylinder no. 4 is not working at all,im running a standalone management system(dicktator), checks i've done so far - definitely have spark, injector is pulsing.....stripped the head off and sent it for testing, the head/valves are perfect, swapped injectors/plugs/coil packs around and still only no.4 cylinder is not working, when the head was off the no.4 cylinder is still brand new..
when the engine is running obviously it has a terrible miss fire... What else can i check??? please help

[gregslow318i]

its one of 4 things.....air....fuel.....spark....compression

check to see if the air track is open and not blocked, valves are opening closing, in the correct sequences ( cam timing vs crank)

check to see if the injector is firing, trace the wire (injector plug) back to the dme and make sure it is properly grounded and to the correct port on the dme and the injector. since you have a stand alone make sure it (stand alone) knows that injector is on if using it in sequential vs batch. also if the dme is set for high or low impedance (injector dependent) if high check the see if your injector driver is working. if that check out to see if you are getting fuel to that injector and that the injector its self is not blocked (internally)

for spark check once again that the standalone knows that coil is on, that the wiring is all copasetic (ground, 12+, and trigger at the coil dme ect..) , also that the coil its self is good ohm it out and that the resistance is set correctly into the dme, then check that the spark plug wire is also not broken lose ect.. and lastly that the spark plug is good now working condition

then check compression....with a compression tester this should correspond to the first test


but first post pic of your set up

[Mohammed_A]

its one of 4 things.....air....fuel.....spark....compression

check to see if the air track is open and not blocked, valves are opening closing, in the correct sequences ( cam timing vs crank)

check to see if the injector is firing, trace the wire (injector plug) back to the dme and make sure it is properly grounded and to the correct port on the dme and the injector. since you have a stand alone make sure it (stand alone) knows that injector is on if using it in sequential vs batch. also if the dme is set for high or low impedance (injector dependent) if high check the see if your injector driver is working. if that check out to see if you are getting fuel to that injector and that the injector its self is not blocked (internally)

for spark check once again that the standalone knows that coil is on, that the wiring is all copasetic (ground, 12+, and trigger at the coil dme ect..) , also that the coil its self is good ohm it out and that the resistance is set correctly into the dme, then check that the spark plug wire is also not broken lose ect.. and lastly that the spark plug is good now working condition

then check compression....with a compression tester this should correspond to the first test


but first post pic of your set up

thank u very much....

i've tried steps 1 to 3, all fine except u mean air track as in intake manifold ?

i suppose its time to check the compression.... wish me luck..

btw. i will post a pic as soon as i get this thing right....:?