89 bmw 325i convertable no fuel or spark.

[DB0778]

Me and a buddy of mine were attempting to reset the oil service light and jumped the pins on the wrong connector. We jumped them on the plug by the firewall that goes into the relay box, as well as the other end of the plug. The wires that were jumped were pin 7 and 18. Now I get no powere to the fuel pump and no spark from the coil. Checked all the relays and they all work, so is there any advice out there about where I need to check next. Also looking for a way to jump the security system and see if it got tripped. Any help would be greatly appreciated.

[thejlevie]

Jumping pins 7 & 18 of C101 (the round connector by the fuse box) shouldn't hurt anything. But I'll bet those weren't the pins you jumped. If pin 7 of C101 got grounded out, you could have fried part of the wiring harness or even the ignition switch. Evidence of that would be a lack of power at the coil positive lead when the ignition switch is in the run position.

[DB0778]

Thanks a lot man. That really helps me out a lot. I will check it all and let you know if that is it. How would I go about checking the ignition switch?

[thejlevie]

Work your way through:

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.

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 to 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 540-540 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 0.040"), 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 batter 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.

[bmwdirtracer]

Holy etm, Batman! You're a walking encyclopedia! I'm hugely impressed, Jim, yet again.

I'd only like to add two things: 1) the pins involved in resetting service lights are 7 and 19, not 7 and 18, and 2) the uninitiated shouldn't do this. It's like a game of "Operation", where the patient can die, if you hit the wrong pin. When all that's wrong is a red light at start-up, why chance frying something by kluging the reset?

[DB0778]

Yeah, Thanks Jim. I told my buddy to just leave it alone, but he kept going anyways. I would have been just fine keeping up with the miles on it. The plug on C101 does not have a 19 wire, so the ones he jumped were 7 and 18 thinking it was 19.

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.
( Checked continuity and it was good, also pin 1 to ground is open. )

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 540-540 when a ferrous object is brought to the face of the
sensor. Neither pin should be grounded.
( Resistance between DME 47 and 48 was 540. )

3) Check for continuity from DME 36 to main relay 85 and from DME 3 to fuel
pump relay 85.
( DME 36 to main relay 85 was good, as well as DME3 to fuel pump relay 85. )

Reconnect the coil, remount the CPS (air gap should be 0.040"), 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.
( DME18 as well as main relay 86 and 30 all had power present with key off. )

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.
( DME18 had power, DME27 however does not have power. )

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

4) Verify that power is present at the coil positive and at fuel [COLOR=blue ! important][COLOR=blue ! important]pump[/COLOR][/COLOR] relay
pin 30. Those get switched power from the [COLOR=blue ! important][COLOR=blue ! important]ignition [COLOR=blue ! important]switch[/COLOR][/COLOR][/COLOR] via C101.
( Have no power to the positive side of coil. Fuel pump relay pin 30 does however have power. )

So now I need to figure out where to go from here. Do you think it may just be my ignition switch?

[thejlevie]

Holy etm, Batman! You're a walking encyclopedia! I'm hugely impressed, Jim, yet again.

I'd only like to add two things: 1) the pins involved in resetting service lights are 7 and 19, not 7 and 18, and 2) the uninitiated shouldn't do this. It's like a game of "Operation", where the patient can die, if you hit the wrong pin. When all that's wrong is a red light at start-up, why chance frying something by kluging the reset?

Hardly anyone does it, but the safe way of jumping the pins for an SI reset is to use a lead that includes a current limiting resistor. Something around 100-200 ohms will do the reset and protect against damage from a short circuit.

I pretty well know my way around an E30. Well, at least those with an M20B25 engine. I wrote that up a few months back to help out a fellow racer who was a couple of states away and was strugging with a no start, no spark, no nothing condition.

Thanks for the compliment.

[DB0778]

So, what do you think it is? Is it my ignition or something else? I posted the results of the test above. The results are in Parentheses below the steps. I would greatly appreciate all the help i can get.

[thejlevie]

No power to DME pin 27 and coil positive with the ignition on says that switched power via pin 7 of C101 isn't reaching the coil and DME or that pin isn't getting power from the ignition switch. My guess is that the problem will on the body side between C101 and the ignition switch, at least that's where I'd start.

[DB0778]

I tested the ignition switch and got power out of both of the green wires that are connected to the switch. Is there anywhere I can get a relay diagram to show me with relay or fuse those wires run to? I am pretty sure I can finish it up knowing which relay those wires go to so that I can check the wires more in depth.

[thejlevie]

http://wedophones.com/BMWManualsLead.htm

[DB0778]

Well, we finally got her back on the road. Turns out that the number 7 wire from C101 ran down through the firewall and in to a box underneath the dash. We ended up jumping the two green wires going into the box and now everything works fine. Thanks for all of the help.

[d0kki]

Im having same problem. Old thread but can anyone tell what is this box and where is it exactly? Im on the road and cant check it now.