Bad Ignition Coil Help!

[mintscorpion]

So I came out of the movies this afternoon with my girlfriend and got in my car. To my dismay and slight embarrassment my e30 wouldn't start. The first thing I did was check the fuses, they were all good. Next I disconnected the return fuel line on the bypass and had my girlfriend crank it over, there was a steady stream of fuel. So there is no spark. Next I disconnected a sparkplug wire and held it against the valve cover while my girlfriend cranked again, there was no spark. Then I disconnected the coil wire to the distributor and did the same. There was no spark so I'm thinking it is the coil. That was all I could do before the tow truck got there and now it's dark.

I have misplaced my bentley manual and I am not sure how to test the coil. Beyond that, what else could be bad? DME? Ignition switch? Crank position sensor? How do I test those?

Any help would be greatly appreciated. Thank you in advance.

[ZombiE30]

break out your ohmmeter and go to it!

The coil is easy: the resistance between the outer terminals should be .5 ohms. resistance between the + and the center terminal should be 5k ohms.

Crank position sensor: should be 540 +/- 54 ohms

(if your car is an 'e' also check the reference sensor connections on the rear portion of the valve cover. these sensors should be at 960 +/- 96 ohms)

DME: this you will need the bentley for. it's easy enough to get to the DME by just pulling the upper panel out of the glovebox, and it's not that difficult to test....there are just a lot of little tests of the inputs that you can do from here and I don't want to type them all right now. it takes about 20 minutes to do the tests.

ignition switch: unlikely......does it crank? if it cranks, the switch is fine.

good luck!

[blck325is]

Hmm I might need to check my ignition coil as well. The starter won't turn, it just clicks once when I turn the key. I've been parking on hills so I can get a rolling start and start it that way. Ideas anyone. Oh sorry for the threadjack.

[ZombiE30]

if your starter won't turn, that's a different issue entirely.
You get just a single click?

First, look at all the starter cables for any disconnection/corrosion. It sounds like your solenoid is engaging, but no power is getting to the starter itself. Keep in mind that it is grounded through the body (ie directly to the block/bellhousing).

Next, turn on your headlights and everything and try to start the car. Does the lights go dim when you do this? If it doesn't, then you have an open circuit somewhere on the starter side of things (or a dead starter). If it does go dim, then you have a nasty short somewhere.

Also, try to start it with someone hitting the starter/solenoid with a hammer/wrench/broomstick. It could be pitted contacts inside the thing, and this usually works to get it going.

Also, check all applicable relays and fuses if you haven't already. Don't know offhand which ones they are, but that's always a good place to start.

[mintscorpion]

I just tested the coil and it's 0.7 ohms between the pos and neg. It is 6080 ohms between the secondary and the positive. Is that in spec?

Also, am i blind because i can't find the crank position sensor.

It cranks over just fine and it gets fuel. Which relays could i test?

1986 325e in case itmakes a difference.

[gotaloveRWD]

id say go with the coil next its only 60 bucks or so. if the ohms vary at all that should def be next on the list good luck!

[lennon]

On your car the crank position sensor is on the bellhousing of the transmission. There are two identical reference sensors there. If that sensor was bad you would not get fuel either. The sensor tells the DME that the engine is spinning so that it will pulse the injectors and spark.

Your coil resistance is a little high, but that could be an erroneous reading from your meter or something. Should be 0.50 ohms and 5-6000 ohms

[jlevie]

Just a click from the starter could be a bad starter, or it could be a discharged battery. A very low, but not dead, battery might result in the system voltage being too low to have spark. Check the battery voltage, anything under 12.4v could be a problem.

[ADEN]

Just a click from the starter could be a bad starter, or it could be a discharged battery. A very low, but not dead, battery might result in the system voltage being too low to have spark. Check the battery voltage, anything under 12.4v could be a problem.

Sometimes my car cranks well when battery voltage is 11.5v maybe he need to load test the battery ,sometime 12.5v battery gets down to 8v while cranking.