DDIS and tach

[tjb1231]

I am having power and hesitation issues with my 89 3.0 with the DDIS system. My tach is also frequently thousands of rpm's off. I read a couple places that the correct reading of the tach is important to the DDIS system.

Where do I begin to troubleshoot this? I cannot find much documentation on the DDIS system and what documentation I do find it doesn't show the tach connection anywhere.

Where the distributor usually is, there is a motor sensor. That wires into a control module and I do not know where to go from there.

Is an accurate tach reading necessary for the DDIS system?

 

[Bt Doctur]

Re: DDIS and tach

Ignition systems generate the tach pulse reading not the other way around. section 4B
http://www.boatfix.com/merc/Servmanl/13/13B4R2.PDF

 

[achris]

Re: DDIS and tach

I am having power and hesitation issues with my 89 3.0 with the DDIS system. My tach is also frequently thousands of rpm's off. I read a couple places that the correct reading of the tach is important to the DDIS system.

Crap!!! However, a faulty tacho can effect the ignition system..

Where do I begin to troubleshoot this? I cannot find much documentation on the DDIS system and what documentation I do find it doesn't show the tach connection anywhere.

Where the distributor usually is, there is a motor sensor. That wires into a control module and I do not know where to go from there.

Is an accurate tach reading necessary for the DDIS system?

From the module there are 3 connectors. One 2 wire and 2 three wire. One three wire goes to the coil assembly, the other three wire has a gray wire in it, that is the tacho wire.... You might be able to remove the wire connector from inside the plug, but there doesn't look like an easy place to disconnect it, so I would just cut it and put a female and male bullet connector in the wire. That will give you the ability to connect and disconnect at will....

Chris......

 

[tjb1231]

Re: DDIS and tach

Thanks for pointing me in the right direction. My wording was off but what I was trying to say is, the ddis system relies on a correct rpm reading. I was thinking my incorrect tach was a symptom of the problem.

If I splice into the gray wire, how do I read what is going across it?

Thank You

 

[achris]

Re: DDIS and tach

You're not looking to read anything on it. You need to disconnect it, so the dash tacho is no longer connected to the module.

Chris.....