Checking for spark on an M50

[88E30M50]

Hey Guys,

I've been banging my head against the no-start issue for a couple of weeks now and am not getting anywere. I think the wiring is correct and have traced every wire in the connectors through the ETM and then back probed the wires to verify what I've found. I've checked the crank and cam sensors and the resistance values I get from the ECM connector match what I get on my running 525. I've swapped MAF sensors, checked coil packs, replaced the plugs and still get nothing but an occasional backfire and lightly fouled plugs when I try to start the beast.

So, I back to the basics and need to verify spark. The issue is, I have no idea how to do that on an M50. Bentley's is of no use except to warn about ECU damage. Does anyone have a good way to check for spark? I was thinking of pulling the coil pack connector, attaching a spare coil and boot and grounding both the coil pack attachment point and the plug. Will that work or am I asking for a fried ECU?

Any help would be greatly appreciated. I'd really love to get the car running before fall sets in.

[gregslow318i]

yeha just pull a coil and plug in a spark plug and ground the tip and turn it over. try not to shock the sh*t out of your self!

[evil_twin]

IF you hold onto the coil and it shocks you a little bit, then it's good. So hold onto it. :)

Are you sure you're getting fuel into it? Do you hear your fuel pump. When you pull off the lines and crank it does fuel come out of 1 line?

[Jay325]

I would lean more towards a fuel issue.....You could spray some starting fluid through the TB and see if it starts. You could buy an inductive coil on plug tester, I have seen them in many tool catalogs or online (autotoolmart, toolsource, autospecialtytools) To me it sounds more like lack of fuel if it stumbles and fouls plugs.

[88E30M50]

Are you sure you're getting fuel into it? Do you hear your fuel pump. When you pull off the lines and crank it does fuel come out of 1 line?

I think I'm Ok with the fuel pump. I have a fuel pressure gauge attached and am getting around 50psi while cranking. If spark checks out Ok, I'll take a look at the injectors themselves.

Thanks,

[evil_twin]

Well there's is a feed and a return line. Do you have that plugged in correctly? Even if you have 50psi at the gauge, you might be just running into a brick wall by having the lines flipped incorrectly.

[88E30M50]

Well there's is a feed and a return line. Do you have that plugged in correctly? Even if you have 50psi at the gauge, you might be just running into a brick wall by having the lines flipped incorrectly.

Good thought but, I think I've got that right. Feed at the front, return at the regulator. The gauge is connected at the front of the rail and is measuring rail pressure.

Thanks,

[evil_twin]

Okay, now did you pull apart your DME to put a chip in?

[88E30M50]

I did pull the DME to put the chip in. I have a 525iT that I've swapped DMEs back and forth between several times. The DMEs all seem to work in the 5'er, but no joy on the 3.

Thanks,

[JGood]

Man, I'm in the same boat. 85 325e with 94 525i m50. No spark, but everything checks out... and I mean everything.

It's fucking bullshit.

I'm about 2 days away from swapping the m20b27 back in... no joke.

[88E30M50]

I hear you on that. I've tossed that idea around a couple of times, but need to press on. Tonight, I swapped fuel rails, injectors and FPR, checked the injector pulse via noid lights and checked spark. Still nothing. I'm convinced that it must be the cam or crank sensor and am about to pick both up. If that does not do the trick, I don't know where I'll go from here. I'll let you know what I happens when I swap the sensors in. I checked both of my sensors via the ECU plug and get almost identical readings to the ones in my 525iT. I figure $150 is easier to swallow than the $500 an oscilloscope would set me back (and that's for a cheap one).