Mechanics

POSSIBLE THAT LENGTHENING WIRES TO THE ECU CAN MESS UP THE RESISTANCE?

1989 BMW 525i • 10,000 miles

Is it possible that lengthening wires to the ECU can mess up the resistance that much that the ECU is unable to send a signal to the coil to spark?

Hi, recently I have lengthened the wiring on my bmw 525i from 1989 with the m20b25 engine.

However now it will not start. I have only lengthened the wires to the ECU. The engine cranks over and I can hear the fuel pump buzzing during cranking. Main relais and fuel pump relais are good. Cps checks out fine and the coil is good aswell.

There is no spark getting from the coil to the distributor. I have heard trouble when lengthening wires from the ECU. Is it possible that the resistance from the coil - to the ecu has changed in a way that the ECU is unable to send a signal to make the coil spark? I have only lengthened the cable by about 30 cm?

Regards

W. Van den kerkhof
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Woutvandenkerkhof
August 21, 2012.




Lengthening wires? Why would you ever do something like that? Any additional splices made to those wires can cause real problems. Lengthening them would mean that you have made 2 additional splices. That spells trouble.

Wrenchtech
Aug 21, 2012.
Well because the m20 engine was put into an E21, and I wanted to protect the ECU from heat and moisture in the engine bay by putting it in the glove box. I do not have an e30 wiring harness so I tried to use the e34 one.

Tiny
Woutvandenkerkhof
Aug 21, 2012.
For some vehicles it is acceptable but for some it is not. You should be checking why you are not getting sparks from the ignition coil for a start.

KHLow2008
Aug 21, 2012.
Every single splice made to a wire is a potential for a new problem, especially if they weren't soldered and heat shrinked which would be the only acceptable method of splicing. Butt connectors are definitely not OK but I agree with KHLow2008 that you should be approaching the issue at the source of the problem and see where that takes you.
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Wrenchtech
Aug 21, 2012.

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