No Spark / No Fuel 93' E30 325ic

[Crow1970]

Hi All,

I have a 93' E30 325ic and have exhausted all my attempts to get this thing running, the DME checks out on all pins except for pin 3 in which I don't have any voltage with the ignition on. From what I understand the DME will ground pin 3 when the CPS sends signal of a rotating engine, also it seems there is no DME signal getting to the main relay at terminal 31 under the relay (brown wire) this should be a ground I've read and has no continuity. I'm hoping somehow these two faults correspond, please help before I dump gas on it and light it on fire!

Here is a list of everything I've done so far.

Checked for a fuesible link but I read the converts don't have one, I'm guessing since the battery is under the hood instead of in the trunk.
New BMW CPS (Ohms at 510)
The fuel pump is new and had to be replaced anyway, the original died. I jumped the F/P relay and it spun
New main relay
Tried jumpering the main relay
went through all DME pins for ground / continuity and voltage where needed.
Bypassed the Onboard Computer Relay / jumpered the green and green and red wire together
All fuses checked
Unloader relays checked
Getting 12V at the coil
Checked continuity of the coil seems to be in spec
Car cranks over beautifully.

Could the ignition switch have something to do with this issue? I'm great with anything mechanical but electrical always seems to kick my a$$!

Thanks in advance for any input I receive.

[bmwdirtracer]

Pin 3 won't be a ground until the DME activates the main relay. Relays do not have a pin 31. The activation (ground signal) from the DME comes in on pin 85 of the relay.....yes, after the DME is happy.

Is your DME properly mounted in its bracket, or at least, externally grounded?
Is your tachometer moving when the starter is spinning?
Does pin 27 of the DME go hot (12+volts) when the starter is turning?
Pin 30 and pin 86 of the main relay should be full time hot....are they?
Pin 18 of the DME shows full time hot?
Pins 19, 14, 2, and 24 of the DME should have full time grounds....do they?


Do you have the factory wiring diagrams?
http://wedophones.com/Manuals/BMW/19...g%20Manual.pdf
(You'll have to use '92, no E30 is shown in '93 diagrams)

[Crow1970]

Thanks for your input Chris, I just ran your recommended checks and here are the results.

Is your DME properly mounted in its bracket, or at least, externally grounded? Yes
Is your tachometer moving when the starter is spinning? No
Does pin 27 of the DME go hot (12+volts) when the starter is turning? Yes
Pin 30 and pin 86 of the main relay should be full time hot....are they? Yes
Pin 18 of the DME shows full time hot? Yes
Pins 19, 14, 2, and 24 of the DME should have full time grounds....do they? Yes

Checked again for ground on terminal 85 of the main relay while the relay is plugged in and nothing it has a voltage of .887
Also no voltage on pin 3 of the DME
I also plugged my OBC back in

Any other help is certainly welcome

Thanks again

John Crosetto

[ross1]

Thanks for your input Chris, I just ran your recommended checks and here are the results.

Is your DME properly mounted in its bracket, or at least, externally grounded? Yes
Is your tachometer moving when the starter is spinning? No
Does pin 27 of the DME go hot (12+volts) when the starter is turning? Yes
Pin 30 and pin 86 of the main relay should be full time hot....are they? Yes
Pin 18 of the DME shows full time hot? Yes
Pins 19, 14, 2, and 24 of the DME should have full time grounds....do they? Yes

Checked again for ground on terminal 85 of the main relay while the relay is plugged in and nothing it has a voltage of .887
Also no voltage on pin 3 of the DME
I also plugged my OBC back in

Any other help is certainly welcome

Thanks again

John Crosetto

Sounds like a dead crankshaft position sensor
Also, please clarify if E30 or E36 chassis. My understanding is the E30 ended in '92, verts only.

[Crow1970]

Hi Ross1,

It is an E30 I believe last year of that chassis was 93' and only offered in verts at least in the states.

The CPS is a new unit from BMW has 510 Ohms I also have a known working used one as well that did not make a difference.

Thanks

-John

[Crow1970]

On pin 47 - 48 of the DME I had the same Ohms coming from the CPS, cranked the engine and saw fluctuations through my meter. I'm guessing since I also tried a used one that is good and had the same results that the new unit is fine.

[bmwdirtracer]

Hi Crow,
I wish Jim Levie were here, to confirm. There's never been a better E30 guy in the world, but he's not been here for a while; health issues I think.

I can't remember the last time I called an early Motronic DME bad, but I think yours is. You've been very thorough in tracing all the wiring and inputs, and it would seem that in spite of all the correct signals, the DME's not turning on the main relay.

Maybe someone else will see something I've missed?

[Crow1970]

I bought a supposed good used DME off eBay just for a backup, swapped it in with the same results. I'm thinking somewhere in the harness I have some sort of a short, oh well I appreciate the feedback. I'll keep working on it but In the interim if any ideas pop into your head I would love to hear them.

Thanks Chris
-John

[ross1]

Rather than checking for voltage at DME pin 3 I'd be checking to see if it is connecting to ground. A test light with the clip to 12v+ and probe pin3, if it lights while cranking you have ground, at the DME anyway. Next check at pin 85 of the main relay.

[ross1]

A thought; It's been a while since I've had hands on an M20 but think they use the cylinder identification wire like the M30 does. That connector and the CPS are same and situated near each other. Any chance these are swapped?

[Crow1970]

Hi Ross1,

Thanks for your input, I'll use my test light on pin 3 when I get home from work, good advice! As for the CPS it is plugged in correctly since I get a reading from pin 47 - 48 on the DME. It was a good thought though considering it's easy to flip flop plugs in the wrong sockets.

Thanks!

-John

[jclausen]

We just had an e30 that had no spark replace very worn cap and rotor, the had weak spark come to find out the coil gets basically a switching signal from the ground on the dme and signals very erratic. Swapped out dme started right up

[bmwdirtracer]

Actually, John, it would be worth checking out Ross's suggestion. If it's possible to plug the cylinder identification sensor into the plug for the crank sensor, you would still get a "signal" at pins 47/48. Both sensors are very similar. Maybe do a continuity test between the crank sensor plug and pins 47/48 ? Then do the same for cylinder ID and pins 8/31 ?

[Crow1970]

Hi Guys,

Thanks for the suggestions, I just got done putting my test light on pin 3 and still nothing,it didn't pick up a ground. I'll do checks based on your recent info, this is really driving me nuts.

Thanks again
-John

[Crow1970]

Hi Guys, I have continuity from pin 8-31, I get a reading .5 ohms and again on pn 47-48 I get a reading of 510. It's gotta be some sort of a short in that harness, I have no idea what else it could be.

Thanks
-John

[bmwdirtracer]

John, you obviously have a very good grasp of what's involved, and what you're looking for. However, I'm not sure that you understood the test I was asking you to try.

Rather than testing continuity between pins 8 & 31, and between pins 47 and 48, you should test the continuity between the wire which plugs into your crank sensor's plug, and pin 48 of the DME's plug. The object is to find out whether the plugs to the crank sensor and the cylinder identification sensor are reversed. Also, I believe that you are seeing the wrong reading from your cylinder ID sensor. I don't have an M20 or M30 nearby to check, but I'd expect ~500 ohms, not 0.5 ohms.

Lastly, have a close look at the round connector that lives a foot below your throttle body. And wetness or corrosion there? I forget which signals go through this connector, but it will definitely keep your engine from starting.

[Crow1970]

Hi Chris,

Yeah I totally didn't understand what you were explaining before, now I get it, LOL Thanks for the input and because of guys like you helping guys like me I have a chance of getting this thing road worthy, I appreciate ya! I'm like a caveman banging a stick against a rock when it comes to this sort of thing, I'd rather pull a motor rebuild it and stuff it back in instead of tracing down electrical issues. At least I'm learning as I go along, thanks again for all your input!

-John

[Crow1970]

Hi Guys,

I performed the continuity checks as prescribed, all checked out and examined the plug for the fuel rail as well. It looked to be in good shape but cleaned anyway. I've just gained some new info, my main relay that I bought from NAPA seems to be the wrong one. I replaced the original a while back due to no continuity and hopefully this will be my issue. The one from NAPA which is a BMW relay has pin 87a, I read this is the wrong relay and should have pin 87b. I'm going to replace it today and see what happens, seems mine is a high beam and blower select relay. Wish me luck!

-John

5 pole relay.jpg

[bmwdirtracer]

That is the wrong relay, but not because it says 87a. It's the wrong relay because it switches between pin 87 and 87a, instead of activating BOTH, simultaneously.

And, yes, that will prevent your car from starting.

[Crow1970]

That's what I get for going to NAPA, I told the guy exactly what I needed and that's what he ordered. My fault though, I should have compared the old one to it. But never having experience with 5 pole relays, I assumed they were all created equal. No one had anything in stock so I ordered a genuine BME unit from eBay.

[MIKYZZ4]

My reasoning behind recommending only BMW OE or OEM Replacement Parts,
for all electronic sensors or electrical parts!
You should have cross-referenced the BMW part# before ordering at NAPA,
but it's just better to order from a reputable and reliable BMW parts supplier,
as they are familiar with BMW specific parts.

[ross1]

John, I see you are local.
I have a boatload of spare relays on hand. you are welcome to scrounge through them. Pm if interested.

[Crow1970]

Hi Ross1,

Thanks I think I will take you up on that, I appreciate it!

-John

[Crow1970]

Hi Guys,

Installed a new relay compliments of Ross1 and now I'm one step closer, I have spark, but no fuel. Can't figure out why the pump is not getting power, I jumpered the relay the pump spun, the relay I have has been triple checked. Not sure what is going on here also my tach is not moving when the car cranks over, any suggestions are welcome.

Thanks!

-John

[323i E30]

Here's a bit of electronic troubleshooting, posted way back by Jim Levie. Might provide some helpful details.
Electrics are not my cup of tea, so I'll just wish you good luck

The DME, engine harness, coil, and CPS are all that is required to run the engine. The car provides power to the coil and the START input of the DME via C101 and the fuel pump relay output is routed via C101. Since the ICV doesn't buzz with the key in RUN, my first suspicion would be that the DME has no power or isn't getting a START signal. A trouble shooting guide is:

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.
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.

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