BMW Repair: 1986 UK E30 325i SE - No ignition spark, bmw specialist, car breaker

Question
Very interesting, Rob.

I phoned my local BMW specialist breakers today and they want £150   VAT   postage for a USED ecu of the same number as mine. I argued that it was a big rip off considering it was at least 20yrs old and most likely on the later stages of it's working life. The guy said that i CAN'T use anything other than the EXACT Bosch part number, however i can get a 325i Sport ecu off eBay for around £40. You've been most helpfull Rob, is there any way i can make a donation to your beer funds?


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Hi Rob.
My '86 325i has served me well for 9years  without any faults until recently. About a month ago, i was travelling to work (about 3 miles) and the engine just died on me with a backfire and wouldn't restart. I walked to work and returned 30min later. Car started 1st time and has ran as smooth as always up until a few days ago. Same thing happened again, only this time the car won't restart. There is always a strong smell of unburnt fuel.

I assumed an ignition fault and sure enough, i have no spark at the plugs. There is also no spark directly from the coil centre when cranked. I have full battery voltage to the coil at the  15 terminal to ground. The Primary tests at 0.8ohms and the Secondary 5800ohms, which varies from my Bentley book (0.5/5000) so i replaced the coil with a used one but it's resistances match my original one. The car breaker is a family friend and the coil is a known runner as the vehicle it came off blew the head.

Next, i checked the Speed and Reference sensors. Both return 970ohms so seem ok. The main relay appears ok because i have 12v at the centre pin of the idle stabilizer valve which is 0v when i remove the relay. Now i'm thinking that the ECU has gone bad but want to be sure before spending more money.

What yer reckon Rob?

Answer -
Hiya!

Sounds like either the DME/ECU busy packing up or the crank sensor, both a common issue with the E30 325i. Can you get access to a ECU from a scrappy or a mate and try this without buying? Check the wiring to the crank sensor and clean it off while you are there. Chances are its the ECU but if you have a 'help yourself scrappy' nearby, it's always handy to have one anyway on a car of this age. A mate of miine had a similar problem and his turned out to be the fuel pump relay, but it's a bugger trying to determine where an intermittant fault comes from without trying a process of elimination. I opened the ECU on one of my other cars and found a bit of burning on the PC board and this had the same symptoms (no spark at centre of coil, and power to it).

You should only pay about £20.00 for an ECU from a scrappy or on Ebay anyway.

Good luck!

Regards

rob


Hi Rob.

Thanks for the fast reply. Numb nuts here thought that the ECU was positioned above the passenger glove box so was getting some weird test results this evening from the ABS controller. Anyway, now that i've found the ECU by the steering wheel(!!!), i did all tests as per Bentley manual and everything is ok back to the plug, including the Ref and Speed sensors.

I'm now after an ECU. Mine is a 0 261 200 073. Which other models are compatible as a direct plug in without having to swap chips?

Thanks for your time,
Birchy

Answer -
Hiya

Good question! Thing is, most of the ECU's for similar models will have differing numbers but do the same job. When the cars are built they are given a part number for the ECU (and any other part for that matter) and this is to identify that part to the guys who actually build the car on line. But if there is a slight change, even one as silly as changing the mounting bracket (or re-mapping etc) or the series of the part, the number is changed to reflect this. As the manufacturing life of the car continues and options are added this will also affect the part number on the ECU but will have no effect on the workings of it for the earlier cars. Chances are you could try any ECU from a similar car and it would work. Some might be geared more toward economy and others toward performance but as long as they are for the same car and similar spec then you should be ok.

Hope this helps.

If it sets your mind at rest, I did an ECU swap with one of my cars for a much later ECU with a completely different number and it still runs fine.

Let me know how you get on.

Regards

Rob

Answer
Hi

No doubt he has the Exact part number in stock. This is exactly what I was told and is usually a lot of rubbish.
Mine was also a Bosch unit and the dealer said only to use the exact same number as well. I build cars all day long and am involved in the process of changing specification and the like and I can tell you that we can change a part number five times before the part even hits production! (and I work for BMW).

I will call a mate of mine in the morning and get back to you tomorrow night if thats ok? £40 for an ECU sound okay.

Regards

rob