Camshaft position sensor

[RawbDidIt]

You nailed it. I was hoping to everything holy it was just the sensor, but that's simply not the case. No oil pressure when cranking, and just to be sure I set up my boroscope to look at the rotor while cranking... nothing, nothing, nothing, caught a tooth and spun, then more nothing. Video below, no sound because the boroscope doesn't have audio.

Guess that's it, I'm not going through the work of putting a distributor into this one, and fishing out all the metal shavings with this engine in the truck. I'll get to work on my new engine and replace. It was a good 240k mile engine, and could probably go another 50k but it's got low oil pressure and needs the bottom end rebuilt anyway. Time to build my 383. If anything this forces my hand to do something I've been wanting to do for a while. Thanks for the help, glad I didn't throw another $40 at it and not solve the problem.

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[stutaeng]

Yikes! Excellent diagnosis.

I was going to suggest you just buy a new distributor. Mine did that around 187k miles or so. My mechanic replaced the camshaft sensor, and just a few thousand miles later entire distributor failed.

The thing is, a new distributor comes with a new camshaft sensor for about $150 or so. Camshaft sensor alone is like $50 or so.

 

[RawbDidIt]

Yeah, I was debating on reusing my distributor anyway. No longer an option, so there's that.

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[evilunclegrimace]

Yeah, I was debating on reusing my distributor anyway. No longer an option, so there's that.

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Why not? throw a new gear on the distributor and run it until you finish the new engine

 

[RawbDidIt]

I'm using the heads and intake off my existing engine. Once I get the rotating assembly I'm taking everything in to be cleaned up, and machined so it's not going to be running for a couple weeks while I assemble everything anyway

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[RawbDidIt]

I had some things come up that necessitated me solving this issue before I could get the new engine built for it. Other projects require the truck running, and they're more important than having a louder, faster truck. The 383 will have to wait. In the meantime, I got the beast running again, so I thought I'd post my process so those looking after me will know the solution.

As previously discussed, it was the distributor gear. It got chewed up pretty bad throughout the 220k miles that are on the truck, and eventually failed completely. It didn't completely shatter from the looks of it, just got chewed up, I'm sure a bit of that was from the repeated attempts to start the truck after it died. A visual inspection of the cam gear looked pretty good, so I'm not too worried about having it fail as well.

So I pulled the distributor cap, wires, and spark plugs. Removed the rotor from the distributor. Removed the distributor clamp and pulled the distributor. Pulled the gear off, and replaced with a new one from Rock Auto. It has an odd number of teeth, so make sure you put the notch on the same side, not 180* off.

Grabbed a telescopic magnet and tried to fish out as many metal pieces as I could. No big chunks, but a fair amount of shavings, as expected.

Removed the radiator fan shroud. Rotated the crank to the timing mark next to the harmonic balancer. Checked to ensure I was on compression stroke with a boroscope on cylinder 1 (no valves open, on exhaust stroke, exhaust valve will be open). Lucky me, I was on the compression stroke first try.

Align rotor on distributor with window marked "8" to triangle marked "6" on the housing. Dropped distributor in. The rotor rotated a few degrees clockwise at this point as expected due to the gear meshing. Distributor at this point was not fully mounted as the oil pump was not fully engaged. Hand rotated the engine until I saw the distributor drop fully, then rotated back to TDC on first cylinder. Double checked I was properly aligned, installed rotor, distributor cap, the distributor clamp a new set of wires I had laying around in the garage. Checked spark plugs. Running a little dirty on cylinders 2 and 6, probably oil guessing by the fact that burning oil, and the mileage of the engine. Re-install the plugs (they're still fine, brushed them and double checked gap before reinstalling). Buttoned everything back up and gave her a crank. Ran it for just a couple minutes to throw the metal into the oil filter. I'm sure there's a better way to flush them out, but I'm not aware of any.

I'll be pulling the pan to fish out any shavings that didn't make it to the filter and do a filter and oil change before I run it again. I'll do another oil and filter change after 500 miles and check for more metal shavings.