S50B30US: no injector pulse

[e30austin]

11/85 325e with S50B30US

car came in with a laundry list of issues, namely, a generally hacked together conversion and an unsightly wiring job. i tidied everything up (dressed the harness up with friction tape, deleted the automatic portion of the harness, installed the e30m3 wiring covers), eliminated the wiring harness adapter (installed a C101 on the engine harness), removed the intake manifold to change the fuel hoses and coolant hoses, and reinstalled everything.

went to go fire the engine and had nothing. had a verified ICV hum, but the CPS tested at almost 1000 ohms (spec is 10% of 565 ohms), and was an aftermarket piece of crap, so i bought a new OE unit from the dealer. still nothing. the fuel pump primes while cranking, so i removed the injector harness cover and found they had 12v, but no switched ground.

the car will fire up on starting fluid, but the injectors are not pulsing. i've never, ever, had spark but no fuel. always been double or nothing. i've torn my hair out all day trying to figure out what the hell is going on... nothing.

i've confirmed the following:
-verified good tach signal at the cluster, tested pins 16 and 43 at the x6000 for + and - signal, verified, new CPS tests at 559ohms, so i think the crank signal is fine
-verified 12v at all red power leads at both main DME and fuel pump relays
-verified 12v at both sides of the injector
-verified 12v at the coil packs
-verified ground at pins 6, 15, 28, 34, and 55 at the x6000, as well as the engine harness termination
-battery distribution block has 12v at the fuseable link and at the battery terminal
-installed known, good working 413 red label DME

welcoming educated suggestions. thanks, guys.

[moatilliatta]

New Cam and Crank sensor?

[e30austin]

crank sensor only. new from the dealer. i don't think the cam sensor would cause the injectors not to fire?

[moatilliatta]

I’d try that before DME. Assuming you have 12V at the injectors.

[mjweimer]

I know this could be considered apples to oranges for various reasons but I'll share in hopes that it helps:

M52 OBD2 - bad cam sensor - wiring harness degraded in connector at the molded end of the sensor body - with ignition on and car not running - wiggling/moving the harness would fire the injectors. It would also cut the injectors with the car running or allow them to fire spontaneously. As I was troubleshooting, the car eventually set a random code but the components would still test OK...only after really moving the harness around did it make a hard failure.

I don't know enough about the signal differences between the OBD1 and OBD2 DME to know if this would apply to your situation...so just carry on if this is not applicable...

[e30austin]

I know this could be considered apples to oranges for various reasons but I'll share in hopes that it helps:

M52 OBD2 - bad cam sensor - wiring harness degraded in connector at the molded end of the sensor body - with ignition on and car not running - wiggling/moving the harness would fire the injectors. It would also cut the injectors with the car running or allow them to fire spontaneously. As I was troubleshooting, the car eventually set a random code but the components would still test OK...only after really moving the harness around did it make a hard failure.

I don't know enough about the signal differences between the OBD1 and OBD2 DME to know if this would apply to your situation...so just carry on if this is not applicable...

Matt, thank you for the insight. it's certainly worth looking at, though i recall the cam position sensor only controlling batch fire to the injectors on an OBD1 setup. thank you!

[e30austin]

i robbed the 4 year old, known good, working, camshaft position sensor, out of my own s50 powered car for testing - made no difference. still have no injector pulse.

i've spent countless hours reading wiring diagrams, old forum posts, and really have not come up with anything.

here's what i need to know so i can not waste any more of my time: what sensor tells the engine controller to pulse the injectors? every post out there discusses the Siemens MS41.1 stuff (cam position sensor), but it's very unclear what works the Bosch M3.3.1 (M50tu/S50US) engines. the test functions in the Bentley manual only discuss if there's a lack of 12v supply, not a lack of pulsing ground.

help, please...

[jbontke]

Have you tried an injector noid light to see if the injector circuit is being grounded on crank? What injectors are installed?

[e30austin]

Have you tried an injector noid light to see if the injector circuit is being grounded on crank? What injectors are installed?

i have a Power Probe circuit tester, it confirms that there is no pulsing ground signal when cranking. i can manually fire each individual injector without issue. stock Bosch M/S50 green top, 17.5# units.

[jbontke]

i have a Power Probe circuit tester, it confirms that there is no pulsing ground signal when cranking. i can manually fire each individual injector without issue. stock Bosch M/S50 green top, 17.5# units.

Has EWS been disabled on the ECU? I am not familiar with the ODB1 ECUs.

[e30austin]

Has EWS been disabled on the ECU? I am not familiar with the ODB1 ECUs.

an aftermarket chip tune will eliminate EWS, so in this situation, yes, it has.

[jbontke]

The wiring harness, have you checked each injector wire back to the ECU for continuity? MS41, right? https://www.adamomotorsport.pl/pinout-m52

[moatilliatta]

an aftermarket chip tune will eliminate EWS, so in this situation, yes, it has.

Pin 7 removed?