Diesel Place banner
1 - 7 of 7 Posts

·
Registered
1985 c10, N/A 6.5, 4l80e
Joined
·
2 Posts
Discussion Starter · #1 ·
Hello, I have a na 6.5 and 4l80e in a 85 c10. The power train didn't come with the pcm so I got the atomic tcm. My issue is it requires a tach signal. It has the engine speed sensor on the back of the engine but I can't find any information that explains how it's wired and if I can use it for the tcm. Any info or easier ways to do this would be greatly appreciated.
 

·
Registered
Joined
·
264 Posts
The speed sensor in the valley, passenger side? The output is a low voltage alternating current. I believe it is an 8 cycle per revolution output. I don't know if your controller can accept such signals. TISS and TOSS on a 4L80 are similar, only from a 40 pulse per revolution tone ring.
 

·
Registered
1985 c10, N/A 6.5, 4l80e
Joined
·
2 Posts
Discussion Starter · #3 ·
The speed sensor in the valley, passenger side? The output is a low voltage alternating current. I believe it is an 8 cycle per revolution output. I don't know if your controller can accept such signals. TISS and TOSS on a 4L80 are similar, only from a 40 pulse per revolution tone ring.
No it's where your distributor would be on a gas engine.
 

·
Administrator
Joined
·
22,669 Posts
Hello, I have a na 6.5 and 4l80e in a 85 c10. The power train didn't come with the pcm so I got the atomic tcm. My issue is it requires a tach signal. It has the engine speed sensor on the back of the engine but I can't find any information that explains how it's wired and if I can use it for the tcm. Any info or easier ways to do this would be greatly appreciated.
Welcome to DieselPlace
(y)
 

·
Registered
Joined
·
4,061 Posts
I think you should contact whoever made the PCM to find out what they say what you should do.
Maybe they make or know of an adapter.
As Keith said in post 2. The speed sensor uses a totally different wave length than a normal Tach signal.
FYI tachometer in 6.5 are operated by a signal from the alternator. It also has different wave length than a standard tach signal. Which requires the special 6.5 only tachometer.
 
  • Like
Reactions: Kylcldwll

·
Registered
Joined
·
264 Posts
Alternator field winding output is a roughly AC signal which is much higher frequency than the original tachometer drive. Most alternators have between 6 to 16 poles, all spin much faster than the crank.

On my 1986 K30, the Delco 27SI has 16 poles and spins at a 2.583:1 ratio to the crank. That is about equal to a 40 tooth reluctor wheel spinning at crank speed.
 
1 - 7 of 7 Posts
Top