Testing Crank Position Sensor

[Kobe Diesel]

Just completed major overhaul of M20 motor.

Ok, everything is put back together but now the car does not fire.
No spark, no fuel. (The car was running before the overhaul except it was running tired).
So Im thinking the crank position sensor could be damaged.
I had it out, and the jacket covering the 2 wires is cracked. I re-installed it not thinking that this cracked jacket which I think serves as a shield could be a problem - now I think it is.

I tested between pins 1&2 and got a reading of .55ohms. Between pins 3&1 and 3&2 are both open "OL" circuits. Pin 3 to the chassis ground is open "OL".
Isn't the resistance too low? and shouldnt I get continuity from the #3 pin to ground?

I have juice up to the coil, removed a spark plug and have no spark when it cranks, and I dont hear the fuel pump running.

If this sensor is not faulty, is there anything else I should check for?

For reference, new parts installed: rotor, distributor, ignition wires, water pump, headgasket, timing belt and pulley (triple checked the timing belt setup and adjustment and the marks match each time).

Any help is greatly appreciated. TIA

[Dr. evil]

before you start buying parts i would recomend that you check the fuel relay and the main relay. could be something simple


i lost my bently so wouldn't be able to help you with test procedures for your CPS

[E34-520iSE]

Are you sure you plugged the sensor into the right socket? I got caught out by that once! There was no spark, no fuel etc. If you need a helpful picture let me know.

HTH,

Shaun M

[Kobe Diesel]

Ive considered that, but the length of the wires will not allow the plug to reach further back to the plug where the ignition current sensor plugs in.
So it cant be in the wrong position.

[E34-520iSE]

Erm I'm stumped now! That was why M20 never ran after it's rebuild. The 'ground shield' on my sensor is also split, and has been for 4 years (45000 miles) now. In your case it really does sound like the most likely suspect. Have you checked the gap between the sensor and the front flywheel? Is the sensor nice and clean?

Shaun M

[Kobe Diesel]

Tested CPS = 550ohms
Tested independently the coil, distributor/rotor, wires to see if there was a disruption in the high voltage path - none, I get spark.
Plugged the CPS back into the harness, cranked, no spark.
Im running out of ideas here. But Im convinced the CPS is ok.

[Blitzkrieg Bob]

Tested CPS = 550ohms
Tested independently the coil, distributor/rotor, wires to see if there was a disruption in the high voltage path - none, I get spark.
Plugged the CPS back into the harness, cranked, no spark.
Im running out of ideas here. But Im convinced the CPS is ok.

Just did that test last week

How is the inductive sensor on the plug wire?

[E34-520iSE]

Have you checked the circuit to the CPS at pins 47 & 48 of the DME? The wire colours (should be) yellow & black, according to the Bentley diagram.

HTH,

Shaun M

[Kobe Diesel]

have not checked it DME
is there a pdf of the bentley manual?

[E34-520iSE]

Sorry I can't figure out how to copy the page of the Bentley pdf that you need. Adobe acrobat will only only let me copy the whole document. Do a little googling and you should be able to find the complete manual somewhere. When you get it (it's a 64 MB download!) look at page 117 section 120-7. This shows the I/O connections of your DME.

Hope that helps,

Shaun M

[Kobe Diesel]

Ok still at a standstill...
Checked the CPS, measures 550 ohms. If I were to cross another magnet past the CPS and collapse the field, what kind of reading should i get?

Now, I taped up the broken shielded insulation on the sensor cable, and re-installed. Turned the key on, got a very weak spark, this tells me the coil is grounding to allow the juice to get to the distributor. But when I cranked it, no spark.

I am at a point where I think I need to replace the sensor. If that doesnt work, Im going to have to suck it up and have the f*cking thing towed to a indy mechanic. It's been one year since I last drove her and she was running before I did all this work, now she doesnt.

[Kobe Diesel]

car now runs.

[E34-520iSE]

So what did you do to make it run then Kobe?

Cheers,

Shaun M

[Kobe Diesel]

i studied electrical schematics and poked around with a meter until i stumbled on something incorrect. had i not had the cd with schematics, i'd be stuck.

the crank sensor and cyl. ID sensor were plugged into the wrong points. strange enough how the cps wiring didnt reach in length back to where it should have been connected. the new cps wiring was long enough to reach to the mating point. swapped - started.

-bedded in the brakes to chip off the rust.
-bled the air out of the coolant system
-adjusted idle
-ran like **** for the first few minutes, then the DME had probably recognized the new injectors and AFM. I still havent installed the EAT chip, b/c i didnt order it yet.
-the engine revs good
-put some fresh fuel in the tank, the other stuff was a bit stale.
-drove the car up to 125 mph, and could have gone a little more, but i have 2 pending speeding tickets.
-will see what happens when the chip is installed.

very happy now~

[E34-520iSE]

the crank sensor and cyl. ID sensor were plugged into the wrong points. strange enough how the cps wiring didnt reach in length back to where it should have been connected. the new cps wiring was long enough to reach to the mating point. swapped - started.


See, I was right all along lol! You're dead right about that CPS connector though - I had to rip it out of the loom to get it to mate up with the semi rigid sensor wire. I never did figure out the 'correct' cable route!

ATB,

Shaun M