Car died while driving now no spark.

[spdracrm3]

yea i was thinking about this last night and the number of things you changed can add to the diag dilemma .was thinking just to be sure if you have all the old parts it might be good to just put them back to eliminate unnecessary headache . (like did you use a factory coil?)

also did you plug the OBC 4 pin back in (not jumpered)and confirm that you still dont get power at the coil ?(this is a great diagnostic porcess to confirm problem) want to make sure that really was an issue and not just a loose connection or diag glitch and that we arent looking in the wrong place . just seem weird that what started as a stall no start can be so many issues at once .....

[spdracrm3]

oops

well its a good thing i asked for yr/model as the 87 IS is set up differently that i thought and the OBC does NOT control power to the coil per the ETM. the two pins at the OBC control a voltage signal that is sent to the ECU which then controls the main and fuelpump relays . power to the coil is direct from the ignition switch per diag page 1360-3 of the 87 3 series ETM)


so now we need to confirm that there is power at coil with key on (jumping those pins should not make a difference if the ETM is correct....
and then see if ECU is controlling main and fuelpump relays(do they click when cranking?) .also check power at relays pins 30 86 of main key on, pin 30 of fuelpump key on and pin 86 while cranking (with main relay installed) per diag 1360-5. or did you confirm that your fuel pumps run while cranking? that would let us know main relay and fuelpump relays are being controlled..

[Skoobeesnak]

I've done some testing on the ECU pins and here is what I can test by myself.

1- Verified power on at all times to pin 18.
2- Verified good grounds on pins 2, 14, 19 and 24

Pins 47 & 48 go to the CPS correct? Should I be able to test ohms here and shouldn't it read between 540-600ohms?

[spdracrm3]

I've done some testing on the ECU pins and here is what I can test by myself.

1- Verified power on at all times to pin 18. thats good as it is the same power feed to main relay and fuelpump relay per 1360-5 diagram
2- Verified good grounds on pins 2, 14, 19 and 24 ohm testing i assume?

Pins 47 & 48 go to the CPS correct? Should I be able to test ohms here and shouldn't it read between 540-600ohms? yes if wiring is good (you can also check for an AC voltage signal while cranking at those two pins)

here is a scope pattern of the crank sensor ,it should produce an AC voltage during cranking

[Skoobeesnak]

Power is on the coil with the key on. Verfied.

I replaced the main relay suspecting that could be the problem a few weeks ago. I do get power on pin 30 and power at pin 86 on the main relay.

I do get power on the fuel pump relay on pins 30 and 86 and when I replaced the in tank fuel pump I did verify power was switched onto the pump with the key.

[Skoobeesnak]

So today I went to the BMW dealer and picked up a new relay for the fuel pump. I will test it tonight and post my results. I am not very optimistic about it since I am getting voltage at the coil I should be seeing a spark shouldn't I?

Could be the DME I bought as a replacement is bad as well?

[spdracrm3]

So today I went to the BMW dealer and picked up a new relay for the fuel pump. I will test it tonight and post my results. I am not very optimistic about it since I am getting voltage at the coil I should be seeing a spark shouldn't I? no it takes two things for coil to fire. voltage and a control signal from ECU (which you dont have).dont think a Fuel Pump relay will make any difference as you have power at coil but no spark FP relay has nothing to do with this.

Could be the DME I bought as a replacement is bad as well?entirely possible but highly unlikely ,they are pretty bulletproof. did you ever test crank signal at the ECU? Ohm test and AC voltage while cranking?

[Skoobeesnak]

"entirely possible but highly unlikely ,they are pretty bulletproof. did you ever test crank signal at the ECU? Ohm test and AC voltage while cranking?"

I am not sure how to test these. Disconnect the ECU and check the pins? What ohms and voltage should I be seeing at the ECU harness?

I bench tested the replacement CPS and I am getting an open circuit between pins 1-2. The Bentley says I should be getting around 540 ohms +- 10%. The old one is reading 513 ohms so just for kicks I put that one back in. Still no spark. I am about ready to throw in the towel and tow it 20 miles to a Euro shop.

[spdracrm3]

"entirely possible but highly unlikely ,they are pretty bulletproof. did you ever test crank signal at the ECU? Ohm test and AC voltage while cranking?"

I am not sure how to test these. Disconnect the ECU and check the pins? What ohms and voltage should I be seeing at the ECU harness?

I bench tested the replacement CPS and I am getting an open circuit between pins 1-2. The Bentley says I should be getting around 540 ohms +- 10%. The old one is reading 513 ohms so just for kicks I put that one back in. Still no spark. I am about ready to throw in the towel and tow it 20 miles to a Euro shop.

yes you can disconnect the ECU and remove the wire cover then backprobe the correct pins (looks like 47 & 48 per ETM ,page 8500-5 toward end of ETM shows ECU pin locations in connector) should have pretty close to the same ohms reading you have testing at the sensor itself if the wiring is good all the way from sensor to the ECU connector . then if you have a DVOM that can read AC voltage test at the same two pins while cranking and the sensor should output an AC voltage if its working correctly. if you dont have the correct ohms reading or AC voltage then there is a wiring issue between ECU and sensor

[Skoobeesnak]

OK I did some testing last night and this is what I found.

When unmounted the old CPS when tested reads around 516 ohms. When it is mounted and I test it from pins 47 and 48 I get 0 ohms resistance.

The new replacement CPS reads 0 ohms mounted or unmounted so I think it is bad.

I looked at the wiring harness and it looks like it is in great shape for a 27 year old car. I then put a wire to jumper the pins on the connector to the CPS and was able see there was connectivity to the connector with no problems. So this leads me to think 2 things.

1- My old CPS is bad.
2- The new replacement CPS is bad as well.

Are there any other tests I could do to test the CPS other than an unmounted ohms check? As I am writing this I realize should be checking for ohms change at the pins while cranking correct? I was looking for voltage but it seems obvious to me that I would never see any there now.

[krazykraut]

Ive had this problem while on the track. Check your fuse in the trunk going to positive terminal. I have had my ignition coil read that I am getting power before, but would not create spark. Check that this fuse is wrapped in black heat shrink tubing has not welded itself to the car or just flat out blown. It is located about 18" up the positive battery cable. You may have to cut the shrink tubing and test is with an ohm meter both sides of the flat fuse.

[spdracrm3]

OK I did some testing last night and this is what I found.

When unmounted the old CPS when tested reads around 516 ohms. When it is mounted and I test it from pins 47 and 48 I get 0 ohms resistance.

The new replacement CPS reads 0 ohms mounted or unmounted so I think it is bad.

I looked at the wiring harness and it looks like it is in great shape for a 27 year old car. I then put a wire to jumper the pins on the connector to the CPS and was able see there was connectivity to the connector with no problems. So this leads me to think 2 things.

1- My old CPS is bad.
2- The new replacement CPS is bad as well.

Are there any other tests I could do to test the CPS other than an unmounted ohms check? As I am writing this I realize should be checking for ohms change at the pins while cranking correct? I was looking for voltage but it seems obvious to me that I would never see any there now.

well something must be wrong with the wiring or connector (be sure your testing the right pins ,see below ,pins 1 and 2 ),confirm the wire colors at the ECU pin 47 ,48 and at the CPS and make sure they match the two pin on the CPS that are getting the 516 ohms as you should see the same resistance as you have at the sensor .something strange is going on with wiring . if you jumpered the same two wires that are the same color as those at ECU and got very low resistance at the ECU pins 47 ,48 then you know they are good ,so it might be at connector pins at the CPS if you dont find the wires routed wrong or something else .
agree with you if your testing the same pins on the new sensor and not getting the 520 OHMs or thereabouts resistance then replacement sensor is bad (swap leads when testing pins 1 and 2 also to make sure reading are good/bad)

and no you wont be checking resistance while cranking ,you will be looking for AC voltage across the pins that have the 516 ohm resistance . the sensor generates an AC voltage as the bumps on the tonering mounted to the crank pulley pass by the sensor (this is the signal the ECU uses to determine RPM and TDC

[spdracrm3]

87 injection diagram

this is off the diag from ETM im using ,dont know if the wire color for the CPS right or not it hard to read but looks like one is blk(pin 47 ) and one yellow (pin 48 )

[spdracrm3]

ECU pin location

[Skoobeesnak]

Thanks for the replies. I am sure I am testing pins 47 and 48 since I had a really good diagram and I can see that there isn't any metal pins on either side of them so even if I was 1 off I could see that it wasn't connected to anything.

Here is what I have found.

Double checked the ohms on the old CPS and got 516 again. Checked pins 47 & 48 and was able to see the same 516 ohms to the CPS. Once the CPS is mounted though I get 0 resistance which from what I read in the Bentley manual should be normal.

Interesting thing I noticed is that when I held the CPS away from anything metal while probing pins 47 & 48 I could see that the the ohm load would range wildly from 516 down to 25 or so. I put the multimeter on the setting that will beep when the circuit is completed while moving the CPS around and it would predictably beep then not beep while moving the wire around. This makes me sure that my old CPS has a short in it.

The new replacement CPS shows infinite resistance on pins 1 & 2 or pins 2 & 3 on the connector. So no change there. One thing I did notice on the new CPS is that the pins were numbered above each one so they are labeled 1 2 and 3 left to right with the cable coming out of it nearest to pin 3.

This points me back to getting a new CPS. Unfortunately the old one was ordered online so I can't easily swap it out but I can to see if one of the local places has one if you think that is what it is.

Thanks again for your help.