All injectors firing besides cylinder?

[Gabeisrad65]

So on my 1998 328i E36 i have spark at cylinder 3 but no combustion for some reason i feel like the 3rd injector is not injecting fuel at all? I even swaped out the injector for a newer one and the problem is still there, so im assuming its maybe the wiring harness? Btw i did the coil pack swap test to verify it wasnt the coil pack. If anybody has ever experienced this i would really appreciate any help 😎

[MarcoZandrini]

The injectors (and the ignition coils) get a constant 12VDC as long as the ignition switch is in the run or start position. The engine computer (DME) provides the ground in both cases. So check for power on a pin of the injector connector.

[Gabeisrad65]

So if there is no power on third injector your saying it could be the dme not grounding the injector or maybe the positive lead wire is shorted some where? Cause what im thinking is if all the injectors are working but one then maybe its just the ground?

[ross1]

What Marco is saying is that the DME supplies the ground path, not 12v. The ground pulse is VERY brief.
12v+ is provided via the DME relay to all the injectors full time, if there were a short in that circuit likely that none would work and since an un-fused circuit there would be smoke.
A simple test to see if the injector is "firing" is to use a stethoscope( a long screwdriver will do) pressed to the injector and the handle to your ear. It can be heard clicking when it opens. Assuming it is not clogged and has a fuel supply hearing it clicking is fairly fool proof. This say nothing about spray pattern, etc. although a gummed up one will have a sound duller than the crisp click of a clean one. With experience you can tell more from the sounds they make.

[MarcoZandrini]

Ross, if the injector connector is bad the injector may not be getting 12VDC. So, OP, check the engine harness connector for cylinder 3 injector to make sure 12VDC is there. The injector won’t fire if it’s not getting power.

[ross1]

Ross, if the injector connector is bad the injector may not be getting 12VDC. So, OP, check the engine harness connector for cylinder 3 injector to make sure 12VDC is there. The injector won’t fire if it’s not getting power.

good point