Help with 528i start but not run

[Lenny D.]

This is a used one:



I am beginning to think your ICU is functioning enough to fool you into thinking it works.


In the dart-throwing dept.:

Did the distributor somehow get bumped? Timing?

[Peter Florance]

I do realize reisitors get hot, but this one looks seriously overheated. As I said the ICM does still seem to be functioning, so I'm going to leave it alone for now.

Oh and thanks for the link, and the continuing advise from everyone. If I was on my own on this the car would be at the crusher by now.

The nice thing is when you're done, you'll understand how simple Ljet is. I wonder if you live near another owner that could test your ecu in their car?

[turbo-rampage]

Yes the L-jet is certainly simple, it really can't get much more basic. I have dealt with fuel injection on various vehicles, and have an overall good understanding of fuel injection, but it's simplicity has been a snag. FI is so complex these days, I was always looking for things that were more complicated than they really were.

But without good information, troubleshooting is still nearly impossible no matter how simple. All systems have thier own nuances that you need to know.

These days the system will spit out a code to atleast get you going in the right direction. L-jet really leaves you blind. I can see why the OBD code system was developed, this has been incredibly time consuming.

The FAQ section on this website has been a tremdous help. I probably spent 8-10 hours before I even posted on here thinking I could solve this issue myself based on all that information. My hats off to those who compiled it. It is nice to see this info on basically "old school" cars are being preserved somewhere. Until I found this website, I came up with almost no information whatsoever.

So now to the current situation

I cleaned, re-connconnected all the grounds I could find, including the ones on the intake manifold. Confirmed resistence basically zero back to the battery by stabbing the wire before the connection to confirm a true good ground.

Clean the coolant temp sensor i think. Is it located under the intake manifold in a big mess of hoses? Kind of hard to get at.

Tried a different coil for spite.

Checked continuity from the single wire connector in the glove box to the ECM.

Checked voltages at the AFM. Voltage to the unit is about 6.5 volts. I assume this is OK because the battery is running low due to all the attempted starts. Found this interesting however, the voltage out of the AFM drops a full volt when the flapper door is in the engine off position. The voltage decay as you open the door is dead on steady to zero. This brings me to problem #2. Is the voltage supposed to decay as you open the door, or vice/versa? The wiring diagram leads me to believe it should increase, not decay. However, I'm not sure how this switch in resistence could physically happen anyway.

Can anyone confirm on thier AFM what voltage should read with the door fully closed? To me that 1 volt drop may be too much. Again the wiring diagram gives me the impression it should be same voltage in to the AFM.

Just a point of interest, while working on the AFM with the key on, I can slightly smell the resistor in the ICU since I have not epoxied the cover on yet, so it still functioning.

Lenny, you may be right about the ICU. I can't see your picture right now, my work internet blocks most all images.

After all this still the same old vrooom, and dies.

Next plan it to inspect the ECM for any obvious broken solder joints etc.

[Peter Florance]

I thought I confirmed that it increased. I'd have to check again; only one of my e12's has ljet. The other is MegaSquirt; that one won't help.

Did you try moving the door to see if it changes

[turbo-rampage]

When you open the door, the voltage starts at about 5.5 volts (6.5 volts going to the AFM) and steadily drops to zero as you open the door. I was thinking maybe it was how I was checking it that made it backwards.

Also could you check voltage at fully closed. As I said there is a 1 volt drop already, and it decays from there as you open the door.

I would think volts with the door closed should be nearly, if not exactly the same as the voltage to the AFM. That 1 volt drop makes me think the ECM is seeing the door partially open when it really is not.

[turbo-rampage]

Latest update...

I took apart the ECM and it is fried. One component in it is completely blown apart ( a capacitor I think), and another had the top blown off. That one I managed to push back together but I'm not sure it would still work.

I would post pics but I can't figure out how.

I wonder if someone could ID the components, and maybe a trip to the electronics store my get it going again.

Peter, don't worry about checking your AFM. I think we found the primary problem

[Peter Florance]

Latest update...

I took apart the ECM and it is fried. One component in it is completely blown apart ( a capacitor I think), and another had the top blown off. That one I managed to push back together but I'm not sure it would still work.

I would post pics but I can't figure out how.

I wonder if someone could ID the components, and maybe a trip to the electronics store my get it going again.

Peter, don't worry about checking your AFM. I think we found the primary problem

email pics to peter@firstfives.org

Also which part # ECU is it? I could probably sell you a used tested one fairly cheap

[turbo-rampage]

Pics and PN sent.

[1st 5er]

Well, I made it just in time for the happy ending.

Great read though.

Congrats, hopefully are in order.

[turbo-rampage]

Just thought I would give one final update.

Just got the ECM in the mail. Put it in and it lives once again.

Special thanks to Peter and all who helped out. Couldn't have done it without you.

[1st 5er]