# No spark 88 750il



## 750il broke me (Mar 15, 2008)

This thing is killing me.......I tried stomp test and got no check engine light flash, I found "the hidden fuse" it was ok....it cranks fine thanks to new starter.....I am at the end of my rope and getting ready to attach a noose.

I pulled out both rear seats and checked all of the fuses........the vehicle has 2 MSD spark controls and I don't have a clue what to do.

I downloaded the wiring manual but my eyes kind of glazed over at about page 450 or so.

I just bought this car (not running...it needed a starter and I got that) still no start, you can hear the fuel pump.......and slightly smell gas but no fire.

My friends say I have lost my mind (buying a car that don't run) and I would just love to drive past them and at least be able to race the motor a little.

Someone...anyone save me......

By the way I was going to buy a PEAKE code reader...but since I never get a check engine light (even when I turn the ignition to on) I thought that a code reader would not help me....at least yet.

I am 52 years old and feel that I should be able to fix it.....after a diagnosis.

Help me ......I'm falling.

PS: The car has a "M" on the front grille, the instrument panel, and before the 750il letters and looks like this.
//M 750il 

1988 ///M750il Vin # WBACG8314J2765899


Carlos


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## 750il broke me (Mar 15, 2008)

I also replaced the Battery.........does anything other than the clock need reprogramming at the "stealership" ?


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## Dave 330i (Jan 4, 2002)

750il broke me said:


> This thing is killing me.......I tried stomp test and got no check engine light flash, I found "the hidden fuse" it was ok....it cranks fine thanks to new starter.....I am at the end of my rope and getting ready to attach a noose.
> 
> I pulled out both rear seats and checked all of the fuses........the vehicle has 2 MSD spark controls and I don't have a clue what to do.
> 
> ...


Hum, bought a car that doesn't start. How about checking the compression? If my hunch in right, you're in serious trouble. Maybe you could unload it to another guy and tell him it just needs a tune up?


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## 750il broke me (Mar 15, 2008)

*Compression?*

What does Compression have to do with spark......I need spark man spark.

You could have 3 dead holes and 5 burned valves....but without spark you can't start.

So tell me friend...........HOW DO I GET SOME SPARK?


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## Dave 330i (Jan 4, 2002)

750il broke me said:


> What does Compression have to do with spark......I need spark man spark.
> 
> You could have 3 dead holes and 5 burned valves....but without spark you can't start.
> 
> So tell me friend...........HOW DO I GET SOME SPARK?


Where did you say there is no spark? Did you isolate the problem to no juice to the coils? Seems like there is juice to the starter and the fuel pump, and you checked all the fuses.


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## TerryY (Jul 20, 2003)

Where in Portland?

MSD? replacing the coils or a separate system from stock?

Are their little donut sensors on the two back spark plug wires?


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## 750il broke me (Mar 15, 2008)

*I got no spark...how about you?*

Ok, there are 2 Mallory MSD boxes located under the passenger side windshield cowl, these 2 boxes have a common red wire going to a spot under the hood I am going to call a battery hot......or a B+...which is connected under that terminal.

Now of course the MSD controls are of course an aftermarket item...and it appears as though they simply fire the stock coils.....I have no voltage at either of the coils........and I assume that I should have 12 volts with the ignition in the on position at one of the terminals and like any other coil the trigger for spark is when the other terminal is grounded or opened from grounding by the MSD's electronicly to create the spark at the stock factory coils.

I checked for voltage at he stock coils with my Fluke meter and have none, and tested for spark with my Lisle spark tester and have of course no spark.

And Terry (thank you) I live on 110th and SE Division in Portland...of course now that I have moved from 173rd and TV Hwy in Aloha (ain't that life) and being in your neighborhood I got this darn problem.

Now you are asking me about 2 sensors at the 2 back cyl on each side donut shaped and I will find out that information when the sun comes up and post it in the early am.
Thanks to everyone for the help.

Heck I know that you wouldn't ask Terry about the donut sensors.....if it weren't inportant so I am getting dressed and getting out my flashlight right now.....and will post an update in a few min.........thanks to both of you guys.


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## 750il broke me (Mar 15, 2008)

*I don't see anything*

Terry, I don't see anything connected to the rear plug wire on either side....and my hands or any hands can't fit in there to feel. I will post some pics after work as it will still be dark when I leave from home to get on (TRIMET).:thumbup:


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## 750il broke me (Mar 15, 2008)

I had so much fun ridding the bus at 6:00am this morning that I forgot my keys at work so I can't post anything till Tue evening.


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## 750il broke me (Mar 15, 2008)

I couldn't find anything attached to the rear plug wires on either side of the engine.

What should I do next?

Also when I turn the key to the on position shouldn't I see a check engine light for a few seconds or untill the vehicle starts?

I know on OBD11 that is the case but OBD1 ?

I never have seen a check engine light go on yet.

Also when I turn the key to the on position.......the EML light comes on for just a sec. or so then goes off............but if you touch the accelerator the EML light will come on and stay on till you turn the key off. Then if you turn the key on again it will come on and go off as before..........long as you don't hit the pedal.

Any more ideas folks???????


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## TerryY (Jul 20, 2003)

If the sensors are not present the next thing would be to trace out how the aftermarket ignition boxes are wired in and how much of the original system has been wired out.

When you turn on the ignition what do the throttle motors do? Do they move by themselves as the ignition is turned on? Do they move when the throttle is pushed or does the EML light just come on?


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## 750il broke me (Mar 15, 2008)

Ok folks.....here is the latest......
No Power at fuel Pump 1 or 2 with ignition on.
No Spark.
Both Fuel Pumps work when powered directly.
How do I bypass this damm anti-theft module?
Battery Voltage is above 11.5 volts when cranking.
I bet this is a simple problem I am making complex.


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## TerryY (Jul 20, 2003)

The start up sequence is:

At switch ON the fuel pumps run for 3 seconds to pressurize the fuel rail.

At start the starter is engaged (transmission position switches willing
). Fuel pumps are off.

The computers check for "resistance" and signal from the crank position sensors and cam position sensors (the spark plug wire donuts on #6 and #12) The spark system should be powered up and sparking at this point. If it isn't the fuel pumps will not run to prevent the motor from going into hydraulic lock from unburned fuel.

IF it sees cam/spark and crank sensors the fuel pumps are turned on. If it fails to see the sensor output then the fuel pumps remain off. If it sees all of the inputs on one side then the fuel pump for that side will run and the motor will start and run on 6 cylinders.

The EML is checking the DK motors (Throttle) during this period.

Remember that the Air flow sensors and throttle motors are on the opposite side from the side that they feed.

Check the coils for signs of damage or overheating. If they show any signs they will need to be replaced. If they pop they take the ECU output driver with them. That may be what started the modifications trying to get spark.

Out of curiosity did you buy it in Beaverton?

BTW NOTHING seems simple on the V12


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## 750il broke me (Mar 15, 2008)

*Have I solved the puzzle.......or opened a can of worms?*

I have located and checked both Crankshaft position sensors....the Bentley book says test between terminals 2 and 1 and I should read 540 ohms+or- 10%

My left bank reading is 10.2 ohms.

My right bank reading is .2 ohms.

Do these values change depending on just where the crank is stopped at the moment or have I located my problem Terry?

By the way I bought it off a car lot on 82nd......they say it was running fine then they sold the car to a young man..........who brought it back the next day as he could not remove the key from the ignition........they sold him another car then sent it to their mechanic to get the key removed.........well he got the key removed.........but it hasn't run since.....I saw the car and asked about it and diagnosed the problem as a starter..........I towed it home and later to a shop to have a starter installed.......

Now my guess is now that the car has been in "LIMP" mode due to one of the sensors basicly wearing out...........then it was driven for a peroid of time in "LIMP" mode and everyone just told each other that it needed a "TUNE-UP" .......then the vehicle became harder and harder to start as the second crank sensor was also old...............so they cranked and cranked and cranked till the starter died.

Have I solved the problem......I got to know Terry.

If this does fix it Terry I am going to buy you the biggest steak they have at "THE RINGSIDE" you know that giant porterhouse...........and if you don't like steak........please feel free to watch me eat mine.


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## 750il broke me (Mar 15, 2008)

Oh.........by the way she does pump fuel for 3 seconds like you said she shoud.......and the throttle bodies seem to move as well.


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## 750il broke me (Mar 15, 2008)

Oh and the sun.........yes the sun was out in Oregon today and I did find the "donut" rings for the rear cylinders.........they were at the front of the engine close to the dist cap.


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## 750il broke me (Mar 15, 2008)

*The Bentley Book is "WRONG" ?*

Quote from another forum.........

"M70 engine only: at page 120-10, 2nd picture down, the picture shows the plugs for the crankshaft sensor and cylinder identification sensor (pulse wire). According to Bentley, the 2 top plugs are the crank sensor plugs, and the bottom 2 are the ones that go to the spark plug wires. This is obviously wrong. Looking at the picture, the left top plug is the crank sensor bank 1-6, left bottom plug is the spark plug sensor bank 1-6, right top plug is the spark plug sensor bank 7-12 and finally right bottom plug is the crank sensor bank 7-12. Also this is checked in the factory manual."

So at first I was actually testing the wrong sensors.

I think I tested the correct sensors now..........the BOTTOM ones.....and here are the readings.

Left Bank tested between 1 and 2.....59k ohms.
Right Bank tested between 1 and 2...9.94k ohms.

The book says again 540 +or- 10%

So I still may have identified the culprit..........I understand as a sensor wears the resistance increases.

Now the book says the above readings are @ 20degrees C.
And our outside temperature is currently 58degrees F or about 17 degrees C.

I used a good FLUKE meter with a new battery.


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## TerryY (Jul 20, 2003)

The crank sensors tell it when to spark and the cam/plugwire mounted sensors confirm that it did.

If in doubt then change the crank sensors. Beware that you may have to remove the crank damper to do it. Just the small bolts not the big one.

This is where I buy my parts http://www.autohausaz.com/html/autohaus.html

Have fun!


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## 750il broke me (Mar 15, 2008)

*Crank Sensors Re-Tested "GOOD"*

I re-read the Bentley and the other bulletin that identifies the error in the Bentley book regarding testing "CRANKSHAFT SENSORS".

Both sensors tested within factory specs.

Also I found that the 1988 model does not do the "STOMP TEST" as that feature was not available till 1989.

Terry said the crankshaft sensor "TRIGGERS " the spark and the camshaft sensors "CONFIRM" the spark.........

How do you "TEST" the camshaft sensors ?

Also any other ideas...........like I posted earlier........key on = fuel pump for three seconds but no spark........ever.

Suggestions?:dunno:


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## 750il broke me (Mar 15, 2008)

*These things are complicated*

I am still pulling out my hair.:dunno:


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## TerryY (Jul 20, 2003)

Sent you the two main E32 references that I have.


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## 750il broke me (Mar 15, 2008)

Terry I got your E32 (DME/EML 1.2) diagrams and thank you very much. Ok, so I tested the Black shielded wire disconnected from the coils to the following results. Mind you I disconnected the Motronic Relays as well as the main connectors at the "E BOX".
I read .2 ohms between terminal #1 of the Motronics on both coil leads to their respective Motronic unit........this makes sense to me....however I also test 39.5k ohms between Ground and the same leads.......I don't understand why I would have any continuity between these leads and ground.

Also when I test between terminal #1 on the large connector for Unit #1 and terminal #1 on unit #2 I get that same 39.5k ohm resistance.......and nowhere on the diagrams do they show a connection.

It just seems to me I should have 0 ohms where I am getting this 39.5k ohm reading.

And by the way I have removed all of the MSD crap from the engine and I can see that previously this is where the MSD crap was spliced to the harness.

Should I just replace both the shielded wires to the coils? Or are the above readings "NORMAL" ?


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