Cam sensor question...

GRWeldon

4th Gear Poster
Joined
Oct 5, 2023
Messages
294
Location
Alabama
Country flag
I have a crank but no start condition on my SC. Suspecting cam or crank sensor but I'm shooting in the dark. I thought I remember reading that the tach won't register when cranking...wondering which one that is?
 
Over at SCCoA they’re always talking about bad crank sensors. No expert here but I’m sure the more knowledgeable people will chime in.

Joe
 
The main job for the cam sensor is helping get the injector pulse on the right stroke, which saves a couple revolutions of cranking during startup.

The crank sensor is the important one; it's how the PCM knows when to deliver spark. The SES light will stay on when cranking and the tach will be dead if there's no CKPS signal. You can also confirm by checking for spark.
 
The main job for the cam sensor is helping get the injector pulse on the right stroke, which saves a couple revolutions of cranking during startup.

The crank sensor is the important one; it's how the PCM knows when to deliver spark. The SES light will stay on when cranking and the tach will be dead if there's no CKPS signal. You can also confirm by checking for spark.
Thanks for the info. Crank sensor is not dead. Tach shows revs when cranking. I could start another thread but I'll try here first. Question 1: I found the Schrader valve on the fuel rail. If I remove the core and cycle the fuel pump a couple of times, shouldn't I see fuel come out this valve? I did not. I removed the fuel filter. There was fuel in the line. I blew through it in the direction of flow. Question #2: Should I feel resistance to the force of air going through? I had to blow hard to get air through.

I did order a fuel filter locally, should be here tomorrow. I'm thinking that if there's no fuel at the rail and the filter takes effort to blow through, possibly could be a plugged filter.

I'm assuming the only thing left in the chain would be a seized/plugged/rusted fuel pressure regulator? I don't even know where that puppy would be. If a new filter doesn't allow fuel to get to the rail, I guess I'm checking there next.

Edit: on a whim I decided to cycle through the pump a couple of times with the fuel filter removed. I expected to find a bit of fuel in the drip pan. I did not.i can hear the pump come on, then shut off after about 2 sec. No fuel at the tube that comes From the tank.

I just installed the pump this morning. I've done at least 3 pump replacements over the years with no issues. I guess I'm going to have to pull the pump and look further. I hate pulling the exhaust on these things. I almost checked to see if it would start before putting it back on. You bet I will this time...
 
Last edited:
One way, you're blowing thru the pump; toward the rail should not pass air at all, unless you remove the schrader valve. Fuel pump failure is likely, at this point, and there are shitloads of fake walbro's out there now. hitting the key with the filter loose, with the tube to the tank in an empty bottle will show pump operation.
 
One way, you're blowing thru the pump; toward the rail should not pass air at all, unless you remove the schrader valve. Fuel pump failure is likely, at this point, and there are shitloads of fake walbro's out there now. hitting the key with the filter loose, with the tube to the tank in an empty bottle will show pump operation.
Yep, see above post. I didn't see your addition. Fuel pump comes on but no pumping. Only 4.5 gallons in a bone dry tank, that should be enough, eh?
 
That should be enough. If you can hear the pump, and no gas, its either dead, of the line in the pump. :( these pumps have gears, like our oil pumps. IIRC, there's a shear pin if the gear siezes. Anyway; you have a fuel pump replacement in your future.
 
That should be enough. If you can hear the pump, and no gas, its either dead, of the line in the pump. :( these pumps have gears, like our oil pumps. IIRC, there's a shear pin if the gear siezes. Anyway; you have a fuel pump replacement in your future.
You mean another one. The one I'm speaking about is brand new and it doesn't pump.
 

Similar threads

Back
Top