DOZENVALVE

So my "wait to start" light is not coming on sometimes, and when I fire the truck it starts super rough and runs rough for 15-30 seconds.

I replaced the KSB on this pickup before, but I can't remember if that's what I need to replace this time or if this is the intake heater grid. I seem to remember
Replacing my KSB (cold start advance) because my truck would not shut off when I pulled the key out, due to it being wired in series with the fuel cut off switch. (It's been a while but this is what I'm pulling from memory) what's the issue I have now with the wait to start light and cold starts? Even when temp is definitely cold this is happening.

thrashingcows

Might be your air temp sensor in the intake is toast?

DOZENVALVE

Okay

Any others before I start ordering parts?

Angry Johnny

Really guys, unless the problem is crying out to you as soon as you open the hood the first step should be checking for codes. I know the PCM's on these old trucks aren't much but they are something.

DOZENVALVE

Wellllll okay. Not a guru with these trucks, but I don't see any check engine light...

oliver foster

You should be able to hear the grid heaters "kicking in", as it loads the idling motor with the two 30 AMP heaters.

You should be able to hear them switch on before you start it cold, and the wait to start light is on as well.

You should also be able to see the headlights dim and the voltage meter dip when the grids kick on.

That should be an easy way to see if they are working.
I could tell you from 20 feet away and the hood closed using this technique.

Mopar_Aaron

Yes it's true what Oliver is saying (I started out by just buying my first gen as soon as I saw one for cheap and learnt by reading and some trail and error, you'll learn as time goes on) the grid heaters make a very noticeable sound and can be heard very easily. And depending on the temp the grid heaters will cycle on and off, which you will hear and notice just by looking at the voltage fluctuate. I wouldn't freak out by a pcm issue. And even so a bad pcm will show signs of needing to be replaced. There's a write up in the sticky's about our grid heaters check it out before you start throwing $$$ at your truck.

DOZENVALVE

I can hear the grid heaters when they are working. And then j can clearly hear the clicking off as the light goes away. But they are only working like, 10% of the time, and the other 90%, no light, no grid heaters, no click. Nothing.

Jim Lane

A tidbit of information.
The grid heaters are rated at 200-amperes each but due to the excessive resistance in the circuit in reality both only draw little over 200-amperes combined, this is why you might notice your headlamps to dip as the relays cycle, they draw 80-amperes more than your alternator can provide.

https://www.dieseltruckresource.com/...d-t297761.html

Jim

DOZENVALVE

Interesting.

Is there a switch or fuse for the grid heaters somewhere?

j_martin

The grid heaters are connected to 2 relays that look like the starter solenoids in a lawn mower. Those are driven by the PCM, which looks at the air temp sensor for info.

With a wiring diagram, the whole system is quite easy to diagnose.