Dead Opti

[compyelc4]

Can anyone tell me if the water temperature sensor harness (on front of LT1-'95) needs to be plugged into water pump in order for Opti to work.

I'm in process of replacing water pump, so I thought I would clean the opti up a bit. The opti was running fine when I pulled her off but now she will not fire at all. Just as I expected, the spark distribution pins and the rotor (at 5,000 miles!) were crudded up real good due to the fact that my fresh air line was bent at a right angle preventing opti from venting fresh air. That coupled with the fact that my waterpump leaked a small amount before I caught the problem. I cleaned the pins and rotor up real well with emory paper. I did not even go into the optical portion of the opti. Then I reattached the opti and all belts, tubes, wires and harnesses but I left the water pump off (and the water temperature harness that goes into the front of it). The opti will not fire at all. Do I need that temp sensor harness plugged into the waterpump in order for the opti to work?

I'm at a loss. I need help.

Thanks

 

[Steve92LT1]

no... not for the opti to fire.. should be fine as long as the opti itself is plugged in.. I tested my 95 Z28 the same way when I changed the opti. Thats the coolant temp sensor for the ECM.

Steve

 

[Mako]

It is entirely possible to put the opti on incorrectly.

There are 3 holes the cam drive pin will fit into on the rear of the opti. The correct hole is elongated and looks different from the other two.

There is no simple way for me to describe a test that will allow you to detect if the opti is installed in the correct position or not.

If your getting spark at the output of the coil, the opti is the logical place to look.

Good luck,
Allen

 

[compyelc4]

Thanks for the reply Allen. Yes. I am very aware of the mounting configuration. I sure she slipped into the right hole (the funny looking one), but I suppose it might be possible to get her off 1 hole. You would think that if I were a hole off I would at least get a sputter. Nothing! I'm putting my timing light on the primary wire tonight. I full expect to find input from the coil, but no output. I cannot, for the life of me, figure out what I might have done wrong to cause her not to even "pop". May find out tonight.

Ted

 

[Steve92LT1]

I know a kid with a 96 Trans Am that put his opti on wrong.. We couldnt get a sputter out of it.. Just turned over and over. Then we pulled it apart and sure enough, the pin was in the wrong hole. Put her in the right hole (the one with the little notch) and she fired right up.

Good Luck!
Steve

 

[compyelc4]

Just pulled her off. The pin was in the correct opti hole. Before I did that I check for spark at plug=none. Then checked spark primary to optt=none. You would think it was the coil or coil module. No. They and the opti were working just fine before I pulled the water pump and opti. I actually have 3 optis on my bench now. The one GM says was defective at 15,000 miles. The new one they put on at 15,000 miles (which worked fine when I pulled it off to clean the secondary pins and rotor) and a rebuild which I purchased today but have not put on yet. I can take it back for full refund if not used. I checked resistances on the first and second optis with the new one (at the PCM to Opti 4-pin plug) and all resistances are identical. I am beginning to think that all optis are good, especially the one I just pulled off cause it was working perfectly then!

Why, when I hook everything back up do I get no spark. I am 100% sure that the coil and coil module are fine.

Can anyone on this site give me more troubleshooting help. It has got to be something simple

Ted

 

[Steve92LT1]

Check the harness that goes to the opti. On the LT1's I have worked on (not sure about my vette though) there was a place that it plugged into a bigger 4 pin weatherpack connector on the top of the intake manifold. I have heard of this harness causing problems. Check the wires from this plug to the opti plug for continuity.

Steve

 

[Steve92LT1]

Actually try plugging in the temp sensor, I was reading on another forum about a no start condition that was realated the the coolant temp sender..

Sounds strange, but hope this helps!
Steve

 

[compyelc4]

Steve92lt1-

<Check the harness that goes to the opti.>

That is a good suggestion. Actually, when GM said the first opti went bad, they replaced both the opti and that 4-pin ecm-to-opti harness. Seems that the opti end of the harness, while sealed to the outside elements, is "open" to the inside of the opti. What this means is that even though the harness weather seal (blue) might prevent moisture from entering through the external harness it can migrate inside of the opti itself and compromise the external 4-pin set from the inside! I remember those 4 pins on the opti and the harness were a powdered blue copper sulgate mess at the time. Well when GM replaced the opti they forgot to replace the harness. I know this because the service manager searched the place over at the time and could not find my old harness. Guess where that was? Right- he put the corroded old harness on the new opti. I figure there was just enough of an improved connection that the opti worked great for about 100 miles. Then I lost spark again. Another tow back to the dealer revealed what had happened. They replaced the harness for real that time and covered all expenses, including tow. At least she held for 5,000 miles before I realized that a slow leak in the water pump was the root cause of the moisture inside the opti. I remember at the time that GM said the pump seal was in good shape. Really coincidental that she decided to leak after I pulled out of the garage. The leaky water pump by itself might not have caused such an early corrosion if there had not been a SECONDARY PROBLEM. When I was reinstalling the opti yesterday I noticed that my fresh air vacuum line from the manifold to the opti was mashed at a right angle preventing the circulation of fresh air. I would advise any '95 or '96 LT1 owners check that vacuum line regularly.

One final thing...and this may be the root problem now. To keep corrosion of the pins at a minimum I coated each pin of the external opti connection and the end of the ECM harness with a dielectric high-frequency tuner lube. By mechanic bro suggested that that crap may have cause current bleedover between the pins. What do you think? I am in the process of getting all that crap off of the connections.