Knock Sensor...what did they do pre-ECM?

[usar17]

Just like the title. My current 1985 Carb 305 has a knock sensor on the driver side of the block. It uses one wire for signalling.....what is it talking to haha

I'm pretty certain my truck doesn't have an ECM. So it is talking to the Distributor? The Mixing Solenoid on the Carb? what? haha My carb is a M4MED

The wire for the knock sensor has been melted by the headers and is exposed. That is what spurred my curiosity to its function and what issues I may not know are occurring.

Thanks

 

[Swims350]

nope your truck has an ecm. it also should have the big 4 ot 5 wire weatherpak plugin on the PS of the dist. That is what the knock sensor talks to and reatrds the timing, that and the ecm. You should have a big grommet on the firewall PS behind the dist. that the wires go into the ecm and it's behind the glovebox. Silver box. Our 84 had one(still does but not hooked up) and the 86 we had it had one as well. Both were carbed both had that same dist. setup.

Maybe it's just called esc setup, not ecm on these, I know the dist. crap is all esc or electronic spark control.

 

[Jims86]

Go pull your glove box out, and youshould see your ECM strapped up over the climate control ducting.

 

[usar17]

Ill double check later when i get home. But I'm reading through the Haynes book at work....the sensor I'm talking about is on the driver side between the first two forward exhaust ports. could this be a transmission controlled spark system?

The insulation on the wire is melted. And since I cleaned the motor and noticed this wire I have had some dieseling issues.

 

[89Suburban]

Ill double check later when i get home. But I'm reading through the Haynes book at work....the sensor I'm talking about is on the driver side between the first two forward exhaust ports. could this be a transmission controlled spark system?

The insulation on the wire is melted. And since I cleaned the motor and noticed this wire I have had some dieseling issues.

You mean in the head? That should be a coolant sensor. I could be wrong but it is my experience the knock sensor is usually mounted in the side of the engine block, and usually on the pass side?

 

[usar17]

Ya the more research i did the less i thought it was a knock sensor. It goes into the head.

I'm pretty sure its this hole that the sensor is in. Now the Haynes book pictures something similar and calls it a Transmission Spark Control Switch or sensor



FYI this is a random photo i found.

 

[Stroked]

I was thinking that's where one of my temperature sending units was at.

 

[89Suburban]

From what I can dig up it seems it should be located on the lower pass side of the block. It does not have to be in a water jacket port per say. It can be bolted directly to a threaded boss in the block casting in the starter area or near a block drain plug. Supposedly the lower on the block the better of a signal it picks up? Not 100 percent on this, just looking around the net for this info.

 

[Jims86]

I was thinking that's where one of my temperature sending units was at.

that should be the temp sender for your gauge. Knock sensor should be innthe water jacket in front of the starter.

 

[Swims350]

temp sensors are in the head, knock, not transmission knock, but engine sprak knock are in the block, just above the oil pan, in t emiddle of the motor. They are basically between 3 and 5 and 4 and 6 on the motor.

transmission controlled spark is IN the transmission, we had one of them once had no clue what it was, it has a 2 wire sensor on the PS of the trans.

 

[usar17]

OK that makes sense. I didnt have time to poke around after work, got distracted by the misses

Grabbed a quick photo the of the wire in question that needs repaired.

Found the knock sensor by the starter. Ill trace some wiring tomorrow and look in the glove box.


I want to make sure all the electrical work is up to par before i drop in a 350.

 

[Swims350]

yes that is the temp sender for the dash gauge or light.