Flywheel Sensors

[PorschePassion]

Greetings All - HELP!

I just finished my 1986 3.2 engine rebuild and I am having difficulty getting the engine to fire. This was a simple rebuild with rebuilt heads and new pistons. I checked and rechecked all connections. The cam timing is correct. Checked it many many times.

The current symptoms are as follows: Engine turns over and there is a gas smell there out of the exhaust. I checked and I have spark. The exhaust actually smells as if there is some combustion but not enough. It's not a pure gas smell but gas and bunt fuel. The only thing that I am unsure of is the reference and speed flywheel sensors. They are the original and the rubber insulation was cracking so I peeled it all off and put a band of electrical tape around the wires.

Do you think these are getting interference between eachother? I made sure that the sensors were gapped correctly @ 0.8mm. I just recently heard that there is a dime method gapping technique when replacing with new sensors. Will try when replacing. How sensitive are these sensors to spark strength? And has anyone experienced the rubber insulation cracking as an issue?

Thank You in Advance

[ChrisBennet]

I am not saying that your sensors are the problem but they are due for replacement. It's one of of those things where it is better to replace them now and save yourself the cost of a tow home someday.
-Chris

[johnsjmc]

I had hard starting on a 3.6 install and it turned out to be the 2 sensors had plugs which were close enough that I had interchanged the plugs.After changing the sensor plugs it started up. I then traced long cranking to a dead cyl head temp sensor(results in rich default).I eventually replaced both sensors and it starts much better.

[PorschePassion]

Thanks for the reply -

After some trial and error, I did switch the sensors back and forth. One way the engine just cranks and the correct way the engine sparks and provides fuel with that fuel and burnt fuel smoke and smell.

I checked the timing again. cylinder#1 intake valve begins to open at TDC and 360 degrees (crank) (180 distributor) later #4 begins to open.

Still nothing.

I'm going out of my mind. She looks so pretty down off the jacks on her own feet.

[johnsjmc]

Check the cyl head temp sensor for a short or open. If it is open the infinite resistance causes the DME to go very rich (equals subzero starting mixture)This makes starting at normal temps very near impossible.

[PorschePassion]

I think you are on to something there. Tell me if I am crazy but since the 2 flywheel sensors are techncially not insulated via their own rubber housing(only electrical tape), they are picking up interferance between themselves and the head sensor. I get a very faint popping sound like it is backfiring. I believe this means that the computer is sensing the incorrect reading. Just a thought.

I just put in a new head sensor. Car was running before I pulled the engine with all the existing sensors.

[johnsjmc]

The electrical tape should be as good as the rubber coating as far as insulation. Electrical pulse interference would need to be shielded by a metallic covering.The sensor signal from the crank can be sensed with a analog voltmeter(not digital) You would watch for pulsing(needle swings) as the engine is cranked.The head temp sensor is best checked with a ohmmeter and compared to specs. Are you sure of basics like firing order and if the rotor is pointing at #1 when it is at TDC on compression stroke?

[kühn tune]

I feel your pain, check my thread here, it may give you some ideas.

3.2 rebuild will not start For the love of God please help

I have had electrical tape on one of my sensors since at least 1994. It would be two, but one was replaced in 1997.

[PorschePassion]

Got her started. I was literally dreaming the senario. Woke up this morning in a panic and realized I pulled the most rookie mistake ever. The only reason I realized this is from when I wrote the first thead that mentioned that TDC was #1 valve opening. Should have realized right there. The dizzy was 180 off. So I re-adjusted the valves per the correct TDC and rotated the distributor 180. Started right up and she drives like a dream.

I now have to deal with some oil leaks; one at the left cam cap(crap) and one at what seams to be the right 6# valve cover. I hope its not the cam tower. I really buttered up the loctite when putting the cam towers on and strictly followed the tightening sequence.

Thanks for all your help.

[ChrisBennet]

Congrats!
On the cam tower sealing, thicker isnot better when it comes to these Loctite sealants. Counter intuitive I know.
You didn't say which Loctite you used for the cam towers but I assume you used 574 ("cheeze whiz"). 574 is fine for thin deep cracks but other sealants will seal bigger gaps and remain more flexible.
I've had good luck using Threebond 1104 (aka "Yamabond") or Loctite 518 (Permatex 51813). The Loctite is available at NAPA etc.
-Chris