Author Topic: Did I fry the Motronic? (Read 3595 times)

Bmw02er · « **on:** November 01, 2010, 12:36:07 AM »

Afters doing some work on the intake manifold I turned the key to drive the car out of the shop. Poof! Shortcut. Turns out the wiring to the injectors got stuck between the U-shaped profile for the right-hand side bolt of the manifold, between the engine and the fire wall. Now the car won't run anymore.

I fixed the wiring - no great damage, I only had it on "run" for a second, mostly new insulation. Then I checked the fuses but could not find a single broken one. I put new ones in 10 and 11 to be certain, but to no avail. I'm fearing I may have toasted the ECU, or perhaps the main white relay?

I'd like your views before I dig into this and buy a new Motronic or take apart the wiring.

bmwconnect · « **Reply #1 on:** November 01, 2010, 01:09:20 AM »

Hi Bmw02er ... Your cheapest option is to find a spare DME off ebay or if you are good at soldering you can find the blown components and replace them yourself ... very good chance you have blown resistors

MLM · « **Reply #2 on:** November 01, 2010, 03:42:14 PM »

Injectors have two wires to them one a power supply the other goes to the ecu and switches to ground.

If you shorted the ecu wire it should only have seen ground potential and no damage would have occured.

If you shorted the power supply a fuse, wires or possibly relay may have burn out as these are pre ecu.

Check all your fuses and relays and a few continuity checks before shelling out for a new ECU

DesktopDave · « **Reply #3 on:** November 01, 2010, 05:40:26 PM »

The Kiwi is right...you might have had full power running to your DME injector drivers for a second or two, likely isn't a problem. Unfortunately, they're not fused from what I recall.

Check for power to the DME first. You should see the CEL come on for a bit when you turn the key. If not, did you check the little fusible linky in the DME cable from the battery?

It's the smaller red wire running off the battery positive terminal along the side of the trunk to the distribution block. Check for continuity or resistance. If no continuity (or infinite resistance), strip the last few inches of heat shrink tubing until you find the fusible link & replace it with a bolt, solder, wire, whatever you have. It carried a fair bit of current, 50 amps IIRC.

Here's a thread:
http://forums.bimmerforums.com/forum/showthread.php?t=939668

bmwconnect · « **Reply #4 on:** November 01, 2010, 08:04:22 PM »

I had a customer do the same thing and ended up being the DME so I will be surprised if its any of the above but desktop and kiwi are correct for getting you to check those before you dish out for a used DME... Good luck BMWo2er

Bmw02er · « **Reply #5 on:** November 02, 2010, 01:34:43 AM »

Thanks for the tips. I'll check all this today. I already sourced a spare DME for 30,- which I only need to pay so can't go wrong there.
What I can say is, that the spark plugs work and so does the fuel pump. After cranking over several times I don't smell any fuel, neither in the inlet or on the dipstick. The injesctors clearly aren't squirting. Silly me, small mistake, big consequenses.
I'll post an update when I figured it out, for future reference.

Bmw02er · « **Reply #6 on:** November 05, 2010, 01:20:40 AM »

Well, it turns out it wasn't any fuse or DME. The plus (R/W wire) of the 3-pole plug was fried. There was no 12V going to the injectors. Fixed it, put everything back together, ca drives like a dream again.

bmwconnect · « **Reply #7 on:** November 05, 2010, 07:54:26 AM »

lucky! nice job on tracking the problem down