NO SPARK, New owner please help!

[Back2Basix]

EDIT:::: CAR STARTS!!!!!!!!!!!!!!!!!!!!

Yes yet another no spark issue post for an E24 -___-

This is my first bmw and i have the slightest idea about electrical issues.

Heres the story. I bought the car not running for dirt cheap. 1986 635csi sunroof, that diamond black color, fridge in the back, red interior. Anyway the story the seller told me was that the fuel pump was bad and needed changing. Took a risk about bought it. brought it home and took off the distributor cap and boom it was so worn out. changed to new cap ad rotor and YAY it started up. idled really crap and then would eventually shut off. after about a week of staring and bogging off. it wouldnt turn on anymore. i moved to the next thing which was to check the fuel to the rail and nothing was getting to the fuel rail. changed the fuel pump and had fuel to the rail BUT still no start. changed out the ignition coil with a brad new one and still no spark. took a look at the cam shaft and speed sensor connected to on that metal bar like thingy and it seems like the harness had disintegrated from old age and the pins were resting on the metal with burnt marks left on the metal bracket. i changed out both sensors with new ones and still no spark. i am left to believe it is the ECU???? could the ECU have fried from the camshaft sensor harness grounding out while i tried starting the car?? cranks perfectly fine btw just will not start up again!

please help!!!

[dwal95008]

No 86' 635csi has the fridge in the back as far as I know... Maybe if there were an L6 in 86 but I dont think the L6 was out that year.

Here is the most commonly linked DIY no start page I have seen.

http://hiperformancestore.com/Motronic.htm

[Back2Basix]

No 86' 635csi has the fridge in the back as far as I know... Maybe if there were an L6 in 86 but I dont think the L6 was out that year.

Here is the most commonly linked DIY no start page I have seen.

http://hiperformancestore.com/Motronic.htm

maybe it was swapped in because there is in fact a fridge in between the two seats. lol

thanks for the link i will diagnose accordingly!

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UPDATE!!!!!!!!!!

was going through said link given to me above and i came across this harness while checking the coolant temp sensor. . . .this harness was not mentioned in the diy no start link. what is this and could it be the reason for a no start / no spark????

[dwal95008]

Put your VIN in this website and look for the thermostat housing sensor diagram.

It will give you an idea of what that is.

http://www.realoem.com/bmw/

[Back2Basix]

Put your VIN in this website and look for the thermostat housing sensor diagram.

It will give you an idea of what that is.

http://www.realoem.com/bmw/

i checked it out and it didnt mention that harness in the thermo housing diagram.

its a square harness that doesnt plug to a sensor on the housing but plugs into a wire that reaches down below passed the housing to what looks like a ground but cant really see. (idk if a harness to a ground even makes sense)

any other ideas on what it could be?

[88m53453]

What year is this beast according to the previously mentioned link ?

[Back2Basix]

What year is this beast according to the previously mentioned link ?

1986

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[rlkrlk]

Offhand that looks like an AFM or ICV plug...

Good luck,

Ray

[Back2Basix]

Offhand that looks like an AFM or ICV plug...

Good luck,

Ray

thank you i will do some more research on those plugs. do you know if they can cause the no start /no spark?

[Sprocket]

Yes, you need that. Pretty sure that is your crank position sensor, and required for ignition. You may be able to jump those leads to the connector if you can solder, but you would be best to get a new sensor with attached connector, or I guess you could get a used one and splice on the connector. If you get under the car, you will see where that lead goes.

[rlkrlk]

Oh indeed the CPS plugs look the same. And yes, they're all needed, as Mr. Sprocket said.

Well actually on the S14 I understand one CPS just goes to the diagnostic port, so... consult your wiring diagram...

http://www.armchair.mb.ca/~dave/BMW/e24/

Cheers,

Ray

[RSheiman]

The male portion of that connector had disintegrated on my 86 (no fridge BTW) leaving those three prongs standing free. I just plugged them into the female portion and use liquid electric tape to insulate. Been 4 years without an incident even though I often think of replacing it. The location gets esposed to a lot of heat so check regularly. The orientation of the prongs in your photo indicates how you need to plug them into the female end.

[Sansouci]

Hoses look a little spongy. What's all that red crap? Did you notice the old liquid gasket stuff coming out of the T-stat housing?

[Back2Basix]

Hoses look a little spongy. What's all that red crap? Did you notice the old liquid gasket stuff coming out of the T-stat housing?

thanks for all the input guys i will move forward accordingly!


also all that red you see is peeling red paint. the block seems to be painted that red color. i dont know if thats how they come or if the seller painted it. i did notice the ugly gasket job!

[88m53453]

1986

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Let me restate, what is the production date, year and month ?
Thanks

[pete9903]

Well actually on the S14 I understand one CPS just goes to the diagnostic port, so... consult your wiring diagram...

http://www.armchair.mb.ca/~dave/BMW/e24/


+1 on that being the diagnostic port sensor. According to Bentley, it's only required for the BMW proprietary diagnostic tool to function, it has nothing to do with normal driving. I removed mine entirely and car operates no differently. The magnetic sender at the other end of those 3 male pins is underneath the coolant pump housing and is only attached by one machine screw, easy to get to if you stand on the passenger side of the engine bay.

FWIW, sounds like you have an '87 if you have the rear A/C.

Good luck with your troubleshooting!

[Back2Basix]

Let me restate, what is the production date, year and month ?
Thanks

sorry haha according to my vin and real oem production date was 09/1985

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Well actually on the S14 I understand one CPS just goes to the diagnostic port, so... consult your wiring diagram...

http://www.armchair.mb.ca/~dave/BMW/e24/


+1 on that being the diagnostic port sensor. According to Bentley, it's only required for the BMW proprietary diagnostic tool to function, it has nothing to do with normal driving. I removed mine entirely and car operates no differently. The magnetic sender at the other end of those 3 male pins is underneath the coolant pump housing and is only attached by one machine screw, easy to get to if you stand on the passenger side of the engine bay.

FWIW, sounds like you have an '87 if you have the rear A/C.

Good luck with your troubleshooting!

thats interesting so from what youre telling me that plug has nothing to do with the no start. i have yet to look further deeper into the matter with my work schedule. i will update really soon.

does anyone think the ecu could*** be the problem?

[flyfisherman]

I thought my no start problem on my 1987 was the ecu and it ultimately was that the code function on the on board computer was malfunctioning. I could bridge the main relay with a Y wire and it would start every time. I bypassed the code function (the relay is located under the dash on the driver's side and have not had further issues with the car not starting.

[dwal95008]

I looked under my hood and that plug is indeed the diagnostic only front crank sensor. You can leave it off if you dont mind the look.

Mine is 4/85 and I have never heard of one before 87 that had a cooler.

[Back2Basix]

I looked under my hood and that plug is indeed the diagnostic only front crank sensor. You can leave it off if you dont mind the look.

Mine is 4/85 and I have never heard of one before 87 that had a cooler.

ok thanks for that info!! I don't mind leaving it off I just want the car to start lol and as for the cooler it could have been swapped in I guess

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I thought my no start problem on my 1987 was the ecu and it ultimately was that the code function on the on board computer was malfunctioning. I could bridge the main relay with a Y wire and it would start every time. I bypassed the code function (the relay is located under the dash on the driver's side and have not had further issues with the car not starting.

hmmm my on board computer doesn't even work. It is plugged in but either it's bad or the screen doesn't work , however *** the car did start with the onboard computer "not working" again either it's the screen or the actual onboard computer that's bad

[dwal95008]

If you can find a spare ecu near you try to plug it in and see if anything changes. Beyond that anything I could guess at is wild speculation.

[mauryc]

don't overlook the main relay. Always carry a spare (and fuel pump relay also)

[CW6er]

It could be several things; the electrical portion of the ignition switch (it is replaceable and you keep the key cylinder), the OBC relay, The Main relay, etc. You need to narrow it down. Here is a list:

This "No Start" procedure is for '83 to '87 cars; the '88/'89 cars have their main relay wired slightly different and different Ref. and Speed Sensors.

Break down of components needed to get spark to the engine:
Ignition Switch, OBC Relay, Main Relay, Coil, Reference Sensor, ECU
____________
• The Engine Cranks Over

First check for spark:

Pull a plug wire and get an extra spark plug* and plug it in. Position the plug so that the metal shell is grounded and try to start the car. Watch the plug to see if you are getting a spark. If you are getting spark, skip to the next section to check for fuel.

If you are not getting spark at the plug, test again at the coil tower. if you get spark at the coil but not the spark plug, check the Distributor Cap and Rotor.

(* or use a spark tester, these can be had from an auto parts store. You may also need an extra plug wire to plug in and test at the coil tower.)

If no spark from either the Coil or Spark Plug:

Checking the ignition Switch and Coil:
• Check, with the key on, for voltage at terminal 15 (+) on the coil (voltage will appear at Term 1 also). If no voltage, the ignition switch or wires to it may be bad. Wiggle the ignition switch to see if it is intermittent**.

• Check, with the key off, the resistance between Terminals 1 (-) and 15 (+), of the coil. It should be around 0.50 Ohms. The resistance between terminal 15 (+) and the high tension center tower should be around 6000 Ohms. Replace the coil if it has high or infinite readings (Open) or little or no resistance (Short).

Checking the OBC Relay:
• Next, pull the Main relay and with the key on, check for voltage between pin 86 & Ground and pin 30 & Ground, in the relay holder (the numbers are molded into the bottom of the relay).

• If there is no voltage at pin 30, check the Red wires at the Positive Battery terminal (Clean and tighten them regardless).

• If there is no voltage at pin 86, check the OBC relay box under the driver's side kick panel, by jumping:

◦ New Style OBC (10/'84):
◦ the two green wires (pins 3 & 4) in connector C2.
◦
◦ Old Style OBC:
◦ pins 14 (GN) and 15 (GN/RD) in the black connector C1 (See page 116/117 in the ETM for pin locations).

• If there is no voltage at pin 3 of C2 (New Style), or pin 14 of C1 (Old Style), the ignition switch may be bad (both terminal 15 on the coil and the OBC pins above are powered from pin 15 of the ignition switch).

• If voltage is present at pins 86 and 30: It is easiest to just jumper the Main Relay as in the Photo below or swap in a new/good main relay and then skip to the "Checking the Speed and Reference Sensors" below. Otherwise check the main relay as in the "Checking the Main Relay" steps after the Photo.


Jumping the Main and Fuel Pump Relays:

•
_________


Checking the Main Relay:
• Check the circuit diagram on the side of the Main Relay to see if it has two separate contacts for the output pins 87 and 87b or if it just has one contact going to two pin 87's. Clean the relay prongs and the sockets in the holder base and plug the Main relay back in.

• If there is just the one contact: With the key on and the Main relay plugged back in, check for voltage at the RD/WH wire in an fuel injector plug (or use a "noid" light on the injector plug).

• If there are two contacts: With the key on, check for voltage at BOTH terminals 87 and 87b of the Main relay. (You have to wrap a wire around each pin and plug the relay back in and test for voltage at each wire. Don't short between the pins!! One terminal can be good, suppling power to the fuel pump, and the other bad, not suppling power to the ECU, or vice versa.

◦ Alternately, to check both relay contacts and the Start Input: With the key on, check for voltage at Pin 4 (Start Input) and Pin 35 in the ECU harness plug, and at the RD/WH wire in an fuel injector plug (or use a "noid" light on the injector plug).

•
• If there is no voltage in the tests above: replace the Main Relay. As stated, it might be easier to just replace the Main relay out of hand in the first place, instead of doing the testing. It is also a good idea to keep a spare Main relay in the trunk Tool Kit and just replace it (and the Fuel Pump Relay) out of hand if the car stops out on the road.

Checking the Speed and Reference Sensors:
• Check the plugs to the sensors first, the plastic can get brittle with age and they can crack around the wire locking bail leaving them loose. Then check their resistance as below (won't hurt to check them both hot and cold if the car's hard starting is temperature sensitive):



_______________

The resistance test above is simpler, and gives you info on the condition of the crank sensors, but the AC voltage output test below is a bit more conclusive, as it also checks for the rare instance of a missing Ref. pin for the Ref. Sensor in the flywheel (Automatic transmission only):

• 1. Pull rubber boots back off of the two plugs on the sensor lead side (not the harness side). Pull the main relay & fuel pump relay to disable the FI system.
• 2. Set your voltmeter to AC volts and back probe the black and yellow wires while cranking the engine.

◦ Speed Sensor (Black Connector - reads flywheel Teeth) -- 4.0 AC volts max while cranking the engine.
◦ Ref. Sensor (Grey Connector - reads flywheel Ref. Pin) ------ 0.4 AC volts max while cranking the engine.

____

** (To start with a bad ignition switch: run a jumper wire direct from the battery to term 15 (+) of the coil and jump pins 11 and 14 in the diagnostic plug to engage the starter.)

[MylesPH1]

Listen to this man, he will get your 6 going.

I really like putting in new main and fuel relays. They tend to gather moisture over time in their housings, and things corrode and make starting an intermittent thing.

[dm635]

No 86' 635csi has the fridge in the back as far as I know... Maybe if there were an L6 in 86 but I dont think the L6 was out that year.

Here is the most commonly linked DIY no start page I have seen.

http://hiperformancestore.com/Motronic.htm

There were some 86's with rear AC. I had a non rear AC on my '86. My son during the time I had my '86 picked himself an '86 and it did have the rear AC. Ended up that the VIN between our cars was less than 100. Thought that was kinda cool.

If I remember correctly the last 7 from my VIN is/was

0606816