Injector Problem 325is - Need Help

[BMW-GA-2005]

I recently purchased a 1995 325is with about 102,000 miles and the car has run great for several months until the Check Engine light came on. When you rev the engine it will bog down and raw gas vapors pour out the exhaust. I pulled the injector rail and noticed that the #6 injector is streaming fuel continuously when the ignition is in the on position (without actually cranking engine). I figured #6 injector is stuck open or otherwise faulty so I decided to make sure by swapping the #1 injector to the #6 injector position to see if it still streamed gas, well it did. Removing the DME and visually inspecting did not show any symptoms of moisture, burnt circuits etc, in fact it looks perfect. Can anybody tell me what would cause the computer to fire the #6 injector continuously?

[BMW-GA-2005]

Somebody...Anybody?

[blkongry]

That's very odd. I've never heard of such a thing. Is it possible the system does this to prempt start up when the ignition is in the 'on' position? Is it a heavy stream? Or just a light mist?

My initial reaction to your saying the engine bogs upon acceleration is that you lost spark somewhere and you are getting unspent fuel going through your chamber; or, you've got a sensor that went bad, or your air intake is somehow getting blocked. If you had a leaky injector, shouldn't it cause the engine to surge at idle? Unless that injector is dumping fuel into the cylinder like mad. Also, with a leaky injector, it should 'clean up' with higher RPMs, since at higher RPMs, the engine now needs the extra fuel and can burn it more efficiently.

I haven't heard of a DME doing this before, and if a sensor went bad, it would adjust the mix across the board, not just on one injector. Did you try cranking the engine over just a bit, then check to see if that injector is still leaking? Perhaps the DME has now moved the leak to another injector since it's on a different firing point. I'd check this first. Turn the key and 'bump' the engine over a bit. Does the injector still leak? Or is another one leaking? Is DME dumping fuel through the inectors, varying along each cylinder's injector during the sparking sequence?

Have you noticed anything else since you made that last post? You've got an interesting problem. The other thing I would suggest is if there is a shop you can take your DME to and ask them to hook it up to their computer and run sequences through it. Make sure everything is working okay. (actually, I don't know what diagnostics they can check, but surely there must be a system check they can run).

Let us know.

[BMW-GA-2005]

Thanks for your reply, I will do the test you suggested ASAP and post results. One thing I want to mention is this, it is a continuous stream that is heavy enough to make the oil on the dipstick smell like gasoline. Also the OBD1 test code was 1222 which I think means O2 sensor lean/rich. I posted this on another BMW forum and this was their response:

Injectors are normally closed and open on a 12v signal. IT sounds like your test was to swap #1 & #6 to see if the injector was stuck open. This was a good test as it showed that the problem wasn't the injector (sounds like you are saying that #6 worked fine in the #1 spot and #1 leaked in the #6 spot). Use a DVM to see if you are getting a constant 12v on the #6 injector leads with the car running. It looks like #6 comes off the Motronic on pin #5 on my wiring diagram for a '94 325is. If it's getting constant voltage you could hope for a short somewhere, otherwise it sounds like a Motronic issue. Seems to be nothing in the diagram between the Motronic and the injector. You could check for continuity between the #5 pin on the harness and injector and and also test the ground on the injector.

And:
The DME controls the injectors by supplying (switching) ground. The "hot" side of the injectors is at +12V any time the car is on, through the DME relay. If the DME-to-injector wire is shorted to ground, the injector will open any time the engine is on.

Here's the test. Look for continuity between the injector control wire and true ground. The injector control wire is brown and another color. If there's a steady low-resistance connection, this is the problem. Turn the car off, disconnect the harness from the DME, and check for continuity again. If, with the DME disconnected, you still see ground on the injector control wire, that wire is shorted to ground. If it now shows open (infinite resistance), you've got a DME problem.

The electronics do a lot of ground-switching where you don't necessarily expect it. Electrically speaking, it's sound (in a car - do NOT try this at home, kids!), but it can be a conceptual pain in the butt.

Does this make any sense? Im not an automotive technician and the tests they advise are technical to me. Do you think someone with basic automotive knowledge could perform these diagnostics? I know if I take it to my local indepedent BMW tech the bill will be over $1000.00.

[blkongry]

Yeah, that makes good sense. I can see how one could get a bit 'drowned' in that explanation, but it's probably right on the money. When he is talking about the 'closed ground' issue, he just means the switch that turns the injectors on and off is on the low side of power (the ground side). It's easier on the switch so it doesn't take so much of a load.

In short, the guy is saying just to take off the plug on the injector in question, turn the ignition to the on position and plug each wire of your multi-meter into the ends of the plug (have the setting on Volts DC). If you get a reading of close to 12V (if it's -12V, that must means your wire are on backwards... no big deal), then you have constant power to the injector and the injector isn't the problem (but I think we already know that since you swapped them). You are getting a ton of fuel out of that injector, so it sounds like it is shorted out full blast. My feeling is that you've got a shorted out wire somewhere. This behavior is even strange for the DME... it would be very remote to turn on the injector full blast no matter what. It's more conceivable to think each time you turn the ignition to the on postion, the vehicle powers up, the short goes live, and the injector dumps fuel. This is good to know, for it narrows down your problem. Still, try bumping the engine and check with your multi-meter if still getting full 12V power. If you are, then follow these steps.

With the ignition in the 'on' position, set your multi-meter to the DC voltage setting. Touch one test wire to the engine block (or equivalent grounding source), then touch the other test wire to one terminal on the plug going to the injector (there should be two terminals on this plug). When you touch one, you should get 12Volts DC; when you touch the other, you should get O Volts DC. You want to remember which one is the O Volts DC terminal. Now, switch your multi-meter to resistance (Ohms, shown by the little upside down horseshoe symbol). Touch one test wire to the O Volts DC terminal and the other test wire to the engine block or ground. If you get a reading of zero or close to it, then you have a short (it means the connection is going right through the wire to the engine block). It means that 0 Volts wire of the injector plug has made contact somewhere down the line.

Now the fun part... you are going to have to search the wiring to see if you can find any melted lookig areas. Wires almost never ground out unless they melt their sheath, especially factory wires.

The other option is that your DME has gone bonkers. Do you know anyone who has an OBDI DME that you can switch out (super easy check, as you know) and check performance? If everything runs great with a different DME, then it's the DME. If it does the same thing, then you've got a hard short in your injector wire.

[Dave at Pelican Parts]

The other test that was mentioned was to repeat that last test (checking the resistance) with the wiring harness unplugged from the DME "brain". If you still get a close-to-zero reading--if in fact you get anything but whatever your meter reads for "no connection"--then the problem is definitely in the wiring. If you get "no connection", then the problem is in the DME.

--DD

[blkongry]

Good Catch, Dave. That will definitely isolate if it's in the wiring or not.

[BMW-GA-2005]

My DME is still out of the vehicle, I will take it to my local BMW tech and see if he can run diagnostics on it. As far a replacing the DME with a known good DME, what about the EWSII preventing me from cranking engine? Can I just remove the chip from my DME and use with the loaned DME? I personally agree with the burnt wiring insulation/grounding out theory due to the fact that when I limped the car home about 5 miles or so I smelled the distinct odor of burnt plastic. I thought maybe the cats were heating up so much that they burnt something underneath the car. What about a burnt O2 sensor wire, it is in that general vicinity. Anyway I will do the checks that you guys suggested and let you know what I find out. Thanks for all the valuable input.

[Dave at Pelican Parts]

An O2 sensor (most sensors on the motor, for that matter) will affect all cylinders more or less equally.

Sounds like a very high probabilty that you have a shorted wire going to the one injector. Run that second check, since the DME is still out of the vehicle. Check the resistance of each pin in the plug to ground. Bet you'll see just about 0 ohms on one of them.

--DD

[Jared at Pelican Parts]

Im with Dave here, sounds like a short...