No Injector Pulse

[DJFartBox]

Howdy ya'll. Been lurkin' for a while trying to diagnose a very strange issue with a car I purchased from a frustrated owner who couldn't get her started after the car had been sitting for 12+ years.

I have tested everything from CPS to AFM to DME and all the acronyms you can think of and I have narrowed it down to no pulse on the injectors. Also, when I pull the spark plugs, dry.

I am about 97% sure of this because if I apply +12v to the cold start injector, the car fires up right away.

1986 325eS, has the 13 button OBC - I say this because I suspect this may be preventing the DME from allowing the injectors to pulse, but I could be wrong.

Any advice/suggestions is much appreciated!

...and before you ask, I have done all major maintenance before I even attempted cranking the motor; fogged pistons, WP, thermostat, timing belt (tensioner/spring), sparks, cam seal/s, valve adjustment, gasket and shaft plugs. Coolant, oil and filter.

[peterman]

there are two connectors under the C101 connector. one goes to the CPS and the other goes to the Pulse sensor on the spark plug wires. (I think it's there on the ES) If the connectors are switched you will not get fuel or injector pulse.
The c191 connector could be bad as well. That is located under the intake manifold, next to the bitch tube.

If the OBC is flashing CODE, it could have cut the fuel from the injectors.

[DJFartBox]

there are two connectors under the C101 connector. one goes to the CPS and the other goes to the Pulse sensor on the spark plug wires. (I think it's there on the ES) If the connectors are switched you will not get fuel or injector pulse.
The c191 connector could be bad as well. That is located under the intake manifold, next to the bitch tube.

If the OBC is flashing CODE, it could have cut the fuel from the injectors.

Thanks, perterman. I checked the impedance of both connectors and both came back with readings of ~250 ohms. They are connected correctly as well (black on left , gray on right) I am under the impression that that may stop spark altogether if bad, which I do appear to have.

I think what I will do now is rent a noid light to confirm pulse. Although unlikely, but a possibility; all injectors may be stuck...

I don't believe that c191 came in the 325e's either, at least not one I could find...

[peterman]

There are two cps' on that motor. One is in the bell housing on the flywheel. Did you change that one too?

Sent from my SM-G935V using Tapatalk

[DJFartBox]

There are two cps' on that motor. One is in the bell housing on the flywheel. Did you change that one too?

Sent from my SM-G935V using Tapatalk

There are two sensors in the bell housing the other is the speed reference sensor and both showed good impedance. I wasn't aware of another CPS, besides the one in the bell housing...

I did pull #1 injector plug and tested for voltage, both leads on the plug showed +12v. Is that normal?

I ended up pulling all the injectors too. Going to clean them up and see if that helps...

[jlevie]

There are two cps' on that motor. One is in the bell housing on the flywheel. Did you change that one too?

Close, but... There are two timing reference sensors mounted in the bell housing of this engine. A third may be present on the front of the engine, but its output only goes to the diagnostic connector.

Ohming out the reference sensors will tell if they are open or shorted, but won't necessarily tell if they are good. On rare occasions the timing slug can separate from the flywheel. That can be checked by removing the sensors and watching for the slug while someone else turns the engine over.

[jlevie]

I did pull #1 injector plug and tested for voltage, both leads on the plug showed +12v. Is that normal?

That is normal. 12v is supplied to all of the injectors and the DME grounds the injectors to fire them.

Does the engine have spark when cranking?

[DJFartBox]

Close, but... There are two timing reference sensors mounted in the bell housing of this engine. A third may be present on the front of the engine, but its output only goes to the diagnostic connector.

Ohming out the reference sensors will tell if they are open or shorted, but won't necessarily tell if they are good. On rare occasions the timing slug can separate from the flywheel. That can be checked by removing the sensors and watching for the slug while someone else turns the engine over.

I was trying to figure out how to look for that. Thank you!

That is normal. 12v is supplied to all of the injectors and the DME grounds the injectors to fire them.

Does the engine have spark when cranking?

Good to know, thank you! And yes; if I apply +12v to the cold start plug, I can get the car started and running so as long as the +12v are applied.

I am cleaning out the injectors, they do seem pretty gunked up and hoping that will address the issue. I will keep you guys posted.

Thank you, again!

[jlevie]

Another check would be to measure the fuel rail pressure while cranking by tee'ing in a pressure gauge on the rail supply line. This engine should have 2.7bar (~39psi) at the rail.

[DJFartBox]

Another check would be to measure the fuel rail pressure while cranking by tee'ing in a pressure gauge on the rail supply line. This engine should have 2.7bar (~39psi) at the rail.

Noted! That will definitely be my next step if cleaning the injectors doesn't help.

Thank you.

[DJFartBox]

Well, as I suspected; all 6 injectors were gunked up and some stuck shut. A quick DIY cleaning and replacement of the o-rings have brought them back to life.

Once installed the car fired right-up and purred like a... little roughly. But that is a discussion for another topic.

Thank you, peterman and jlevie for all your assistance, you guys are the real MVPs!


Glad to be part of a helpful community!

-David