Engine Will Not Start Now After Insulating Fuel Rails

[JDP530]

After insulating fuel rails this past weekend and re-assembling yesterday engine will not start. I have looked at all of the fuses I could find, including the heavy fuses on right side battery, and none of them were blown. Engine spins easily but it doesn't pop at all on either side. I haven't had anytime today to do any trouble-shooting, but I have been told that sensors on front of engine could be reversed. I am pretty sure I have wires plugged in same as before when engine ran fine because plugs are oriented to go in one way and I didn't change anything.

One factory diagram shows the sensor connectors (black and grey) in a different orientation than on my car, but, according to George Fontes article on his 750i top end rebuild, my connectors are in same position as his. But, my sensors on left side of engine are reversed compared to his. I haven't changed anything and I have compared plugs and connectors to old photos when I first started working on the car and I don't see anything different.

George (shogun?) shows both sets of sensor connectors on brackets positioned with black connectors on top and the tan connectors on the bottom. This is how mine are mounted. But, as I mentioned above, the cylinder ID sensor is mounted to top (black plug) on right side standing in front of car. According to his article, both cylinder ID sensors should be plugged into both the tan connectors.

So I am quite confused now! Is it possible that the alarm on my '91 model has disabled the ignition/ fuel system that is preventing engine from starting? Seems like engine should start on one bank even if sensors on other bank are reversed.

This first photo from a couple of years ago shows orientation of connectors that are still the same now.
IMG_20171221_125736877_HDR (1).jpg

This is photo showing orientation of colored connectors as they are today.
IMG_20200915_173031.jpg

This photo shows orientation of sensor plugs. The top plug on left side of engine is the cyl ID sensor for 7-12. But, according to George, this plug should be plugged into tan connector on bottom like that on right side of engine. The bottom plug is the crank sensor plug.
IMG_20200914_182809.jpg

Here is a factory diagram of the connectors which is different from those on my car and George's 750. This diagram shows grey connectors on one side and black on the other. The orientation of sensors is the same as those on my car though.
IMG_20200915_173652.jpg

I would appreciate any help! Electrical diagnostics isn't my forte.

[ChrisFuture8]

JDP530, see if my picture help.

If you are in front of the car facing the motor, the passenger CID is plugged to the bottom on the passenger side. The driver's CID is plugged in the top position on the driver's side.20200611_160300.jpg

Sent from my SM-G965U using Tapatalk

[JDP530]

JDP530, see if my picture help.

If you are in front of the car facing the motor, the passenger CID is plugged to the bottom on the passenger side. The driver's CID is plugged in the top position on the driver's side.20200611_160300.jpg

Sent from my SM-G965U using Tapatalk

That's how mine are positioned same as yours. It's just that the connectors are not the same color as indicated in other photos and diagrams. In George's article he indicates that both CID sensors are plugged into the same color connectors on either side.

Is it possible my alarm in this '91 model could prevent the engine from starting?

[ChrisFuture8]

I don't think the 91 has the EWS module (the gurus chime in here if I'm wrong). Corrupted EWS module will prevent your starter not to turn among other things.
Are you getting fuel? Is the exhaust tip wet with unburned fuel? Are you getting spark when you crank? Do you have a spark tester?
Try pulling each fuel line at the injector rails (and placed the line into a glass jar and have someone crank the motor a few seconds to see if you're getting fuel.

At one time when both of the CPS sensors on my car went bad, the motor would not catch. If one is good and one is bad, the motor will start but run rich and extremely lumpy.
Trace back your engine wire loom from the plugs at the front of the motor to the injectors and back to the end of the motor. Make sure nothing was badly kinked when you lifted the wireloom off to get the injector rails out.

[shogun]

Maybe this thread helps: Crank-and-Cylinder-Index-Sensors-M70 https://www.bimmerforums.com/forum/s...identification
I will also copy some of these posts in that thread in the E32 forum, so that members can help.

From my website, this shows how George marked the CPS and CI connectors on his E32 750 http://twrite.org/shogunnew/files/fo..._Refurbish.pdf he mentions from page 20:
Pulse Sender/Cylinder ID (right)
This is a view of the right side Pulse Sender [top plug ] (circled). This connector block is black and the cable goes to the left side of the block) The connector beneath it is the Cylinder Identifier (1 through 6 ) and leads to spark plug wire No. 6 on the right bank. This connector block is tan/white.

Pulse Sender/Cylinder ID (left)
This is a better view showing the left side Pulse Sender (top plug). This connector block is black and goes to the right side of the block) The connector block beneath it is for the Cylinder Identifier (7 through 12 ) and leads to a spark plug wire on the left bank. This connector block is tan/white

Pulse Sender/Cylinder ID : NOTES
To help me remember where the connectors went, I labeled a couple prior to unplugging. As you can see to the right, these unplug in the same manner as the temp. sensors on the intake manifolds. Squeeze the bail in and pull out the plug. Don’t cross these plugs when reassembling!

Cylinder ID
This view shows the right Cylinder ID plug with its “doughnut” around spark plug wire No. 6.

Pulse Sender/Cylinder ID connector Removal (Circled)
This shows the location of the four 10 mm (socket) bolts that hold the connector retaining clips to the cylinder head. They’re hard to see as they’re covered in grunge.

Connector Blocks in Clips This shows the bolts removed with the connectors (still held by their mounting clips.) I chose not to separate the connectors from the clips because I didn’t want to get them mixed up. I carefully threaded them under the oil filler spout when I removed the injector wire harness.

on page 26 is also a very good pic showing all 4 connectors.

[JDP530]

I don't think the 91 has the EWS module (the gurus chime in here if I'm wrong). Corrupted EWS module will prevent your starter not to turn among other things.
Are you getting fuel? Is the exhaust tip wet with unburned fuel? Are you getting spark when you crank? Do you have a spark tester?
Try pulling each fuel line at the injector rails (and placed the line into a glass jar and have someone crank the motor a few seconds to see if you're getting fuel.

At one time when both of the CPS sensors on my car went bad, the motor would not catch. If one is good and one is bad, the motor will start but run rich and extremely lumpy.
Trace back your engine wire loom from the plugs at the front of the motor to the injectors and back to the end of the motor. Make sure nothing was badly kinked when you lifted the wireloom off to get the injector rails out.

I need to check for spark and fuel possibly later today.

Brian sent this photo to me that shows same arrangement as your sensors, Chris, which is like mine:
-3162607202303992195.jpg

So I dont think this is where the problem is. I also double-checked wiring for coils and they are correct.

[JDP530]

Page 27 of owner's manual states that ignition circuit is interrupted if attempts are made to open doors, lids, when alarm is set. This must be the reason my car is not starting. Because over the period of four days while working on fuel rails, I had car locked with hood unlatched, and at times I would unlock car to roll down windows to keep from heating up interior, then I would re-lock it. So I may have alarm system messed up. Manual does state that alarm can be reset with key in ignition position 1, but I was using position 2. So I need to see if I can reset it. I have batteries disconnected now to see if that will help.

I reconnected batteries, re-programmed radio. Tried disarming alarm with key in both doors. With car unlocked 'anti-theft' light on radio continues blinking until ignition is turned on with key. As soon as key is removed light starts blinking again.

[shogun]

Just to make sure, I now checked on 2 cars, 1 x on my 11/88 E32 750 pre-facelift engine and on a E32 Alpina B12 750 with facelift engine, both are the same. Same as explained in the site of George.
Black connectors are op top, white ones are on bottom, also look at the cable loom, the upper cable goes to the upper black plug on each side. Here a pic from the B12 where we just reseal the intakes

[CD05001CIA]

Check for spark first. Remove easy-est plug wire. Put a good spark plug in it. Have wifey / buddy crank engine while you touch thread of temporary spark plug to head or heat shield. Don't do this in full sun cause you can't see it. You'll feel it if you don't touch the threads of plug to metal.