Need a m20 wizard

[hyd3official]

Hello i was wondering if someone can help me out with this problem. Well last sunday i finally took out my old m42 engine that had 279,000km from my 1990 german 316i and replaced it with a m20b25. Everything is hooked up i get fuel to the engine the battery is sending the voltage but it is not starting at all i mean nothing at all! But i noticed i have three wires from my ECU that are not connected which i cannot find out what to connect to please help for this is my first bmw swap.

Bless :)

[jlevie]

What was the production data of the car the engine and harness came from? My suspicion is that the DME isn't running because it isn't getting the START signal.

[hyd3official]

316i/m42b16/MT. i am thinking it is the started because everything is hooked up right it all comes down to wiring i believe.trick is the fuse box is from the m42 should i go to the junk yard and pull the other fuse box for the engine?

[paperplane94]

How about a CPS input?

[hyd3official]

Thats what i will check pictures will be taken.

Thanks

[hyd3official]

Battery Voltage / DME Main Relay? Maybe it could be my voltage on my battery is to low. I did use the same battery from the m42.

[hyd3official]

ok so the car cranks but no spark at the spark plugs i checked the coil and it read 12.43 volts i don't know what to do now accept get another wiring harness out of a 525 and rewire everything.

[paperplane94]

ok so the car cranks but no spark at the spark plugs i checked the coil and it read 12.43 volts i don't know what to do now accept get another wiring harness out of a 525 and rewire everything.

That would be the easiest thing.


What you describe is a classic sign of no CPS input. Maybe if you can fix that it will start.

[SpeicherBimmer]

Well I put a multimeter on the CPS and I got a signal from it. I can't figure out what the issue is. The wiring harness he has that came with the M20 had some kind of relay wired to the ignition coil, which I have never seen before ( of course, I have only worked on my own 320/335). I cut it off and ran it the way the stock set up is and still no spark. I have a feeling that some how the ECU isn't sending the start signal, but I don't know why. Is the C101 connector the same for late M42 cars as the M20 connector?

[jlevie]

Okay, use what is below to find out what is wrong.


For the engine to run the following conditions must be met:

Power on DME pins:
27 Start Input
18 Un-switched Power input
37 Power Input from Main Relay

Ground on DME pins 2, 14, 19, 24

Timing data from the CPS on DME pins 47 & 48 from a rotating engine

To have spark power must be present at the coil positive and ground pulses
from the DME's pin 1 must reach the coil negative. Power to the coil is
controlled by the ignition switch via C101. When checking for spark, use the
output lead from the coil to eliminate the distributor, rotor and plug wires.

To have injector firing power must be present at each injector and ground
pulses from the DME's pin 16 (Bank1) and pin 17 (Bank2) must reach the
respective injector bank. Note that the injectors are wired as two banks of
three. With cylinder 1,3,5 being bank 1 and 2,4,6 being bank 2. Power to the
injectors is controlled by the main relay. Injector firing is best checked
with a noid light.

The fuel pump relay must have power on pin 86 (relay coil) from the main relay
output (pin 87) and power on pin 30. The DME will ground pin 85 to turn on the
relay and power the pump(s) via pin 87. Of the above, only the fuel pump power
is fused. So if the there's power at pin 87, but not at the pump, check fuse
11.

The main relay and DME pin 18 receive power from the smaller of the two wires
that connect to the battery's positive terminal. That wire incorporates an
in-line fuse. When the DME is presented with a start signal, it grounds the
main relay pin 85 and furnishes power to the fuel pump relay, injectors, and
DME.

Troubleshooting:

Disconnect the battery and the DME cable. Then:

1) Disconnect the coil negative and check continuity from that connector to
DME pin 1. Also verify that from DME pin 1 to ground is an open circuit.

2) Check the resistance across DME 47 & 48, which should be 500-560 ohms. If
the CPS is dismounted, the resistance can be seen to change from about 500 to
540-560 ohms when a ferrous object is brought to the face of the
sensor. Neither pin should be grounded.

3) Check for continuity from DME 36 to main relay 85 and from DME 3 to fuel
pump relay 85.

Reconnect the coil, remount the CPS (air gap should be 1mm), plug the
relays back in, reconnect the DME, and connect the battery. Then do the
following checks:

1) With the key off, verify that power is present at DME pin 18 and main relay
86 & 30.

2) With the key on, verify that power is present at DME pin 27 and pin
18. Power to pin 18 is from the main relay and there should be power to the
injectors and fuel pump relay.

3) With the key on, verify that no voltage is present at the DME grounds (2,
14, 19, 24).

4) Verify that power is present at the coil positive and at fuel pump relay
pin 30. Those get switched power from the ignition switch via C101.

The engine will start and run (if poorly) with only those connections to the
DME in place. The other signals from Cylinder ID, AFM, temp sensor, etc., are
necessary for proper operation. But they won't prevent the engine from firing.

IMPORTANT:

A power check means seeing a voltage within about a tenth of a volt of what
you measure across the battery terminals, which should be at least 12.6v on a
charged battery.

A continuity check means seeing less that 1 ohm of resistance.

An open circuit means seeing a resistance of at least 100k ohms.

A good quality auto-ranging digital multimeter will make these tests much
easier.

[hyd3official]

still in the works me and Spiecherbimmer have been tag teaming this project for our drift missle.

[mikeedler]

easiest solution.....

go to the strip yard and get a wiring harness from a facelift (plastic bumpered 320i/325i)
your problem is the harness you are trying to run is from the older cars.

also make sure to grab a harness from a car with ABS if your car has ABS. and if yours doesnt have ABS, make sure the new harness is also without .

give me a call 01715300150

[hyd3official]

thanks mike apreciate that will keep in touch with more feedback!---- SPIECHERBIMMER THE 525i harness will ignite my black b#@%(e30) on fire.

[SpeicherBimmer]

Please don't ever associate me with your "Drift Missle" again.....