So I ran out of gas. I think. Maybe.

[Mack B]

Alright, I've taken this ol turd out every weekend since this occurred and put a few miles on it pretty uneventfully. Christmas Day on a stretch of highway it started feeling like I was pulling a heavy load, I was at my destination before I could investigate further, but I did take the gas cap off when I stopped the truck. Truck probably sat for an hour, when I left it fired right up and ran fine the rest of the trip.

Today. I took the truck out for a drive. After I warmed it up with some spirited driving the problem came back full force. Under load in 4th gear the truck stopped accelerating. I reached out and removed the gas cap. No change. I came to a stop. Fuel pressure at the carb was 5.5-6 psi. When I got back on the road it was the same in every gear, it was like I was pulling a super heavy load. I couldn't go above 2,000 rpm. Roughly 45mph. No backfiring, or missing. Just failure to thrive. I limped it home. Tried unplugging the vacuum advance, no change. Checked timing, no change. It will crank, idle, rev, even move around the yard fine. I checked the plugs, they are light tan.

Cliffs:
Problem came back after 10 mile cruise, again after high rpm romp
Not gas cap
7" of fuel in tank
5.5 psi of fuel at carburetor
Plugging vacuum advance didn't change anything

This sound like anything in particular?
Incase it wasn't mentioned earlier the truck has an hei distributor

[Captainfab]

It sounds like it is not a fuel issue, so I would think it is ignition related. Does the HEI have a full 12 volts to it? Have you had the cap and rotor off and looked at the advance weights?

[Mack B]

Originally Posted by Captainfab

It sounds like it is not a fuel issue, so I would think it is ignition related. Does the HEI have a full 12 volts to it? Have you had the cap and rotor off and looked at the advance weights?

It was wired as such. I was separated from my volt meter today, so I wasn’t able verify that it hasn’t changed. I will verify that.

I didn’t consider an issue with the mechanical advance, I’ll inspect that first

[61K10]

coil over heating? this a gm hei?

[Mack B]

Originally Posted by 61K10

coil over heating? this a gm hei?

If it’s not the weights seized up that’s what I’m leaning toward. I couldnt find my exact symptoms by searching for overheating coil issues. Most say they backfire and miss.
I assume I would have to get the coil hot and take an ohm reading?

It’s a summit branded HEI. Likely Chiwaneeze.

[andyh1956]

To check mechanical advance unhook & plug your vacuum advance & get your timing light out & see if the timing advances by the light when you rev the engine. It should advance outta sight.

[Mack B]

Originally Posted by andyh1956

To check mechanical advance unhook & plug your vacuum advance & get your timing light out & see if the timing advances by the light when you rev the engine. It should advance outta sight.

Yes sir, it was working when I checked the timing, my thoughts is this may be engine heat related or just intermittent, I may get lucky and find the weights and springs in a rusty mess by taking a look.

[raidmagic]

Depends on what your neighbor looks like...

[Mack B]

Originally Posted by raidmagic

Depends on what your neighbor looks like...

This is akin to looking a gift horse in the mouth .

[Mack B]

update:

I had a few hours to mess with it this evening, the advance weights move freely,
I had a cap, coil, rotor and module on the shelf.







It was none of those things.

[rvrfoot]

Wow, what could be next?

[Mack B]

Originally Posted by rvrfoot

Wow, what could be next?

It’s probably something simple I’m overlooking.

Biggest problem for me is I can’t replicate it in the shop where I can be under the hood and see what’s going on the instance it happens.

T..this is fun right?

[Mack B]

Progress! It turns out you can have fuel pressure without fuel volume. I found a large amount of silt in the filter, inlet screen on the carb, and in the bowls. Apparently I done a $@!t job of cleaning the tank. I’m assuming this is rust or is this what happens to varnish that gets left behind?

[rvrfoot]

Wow, That is dirty.

[Captainfab]

Looks like rust to me.

[rideblue00]

Ha, my sisters 72 Chevelle went through this until we installed a new tank. Very fine sediment from rust makes it past most filters as i found out

[The Rocknrod]

Ya, you'd need a larger Donaldson or Cat 2 or 3 micron filter to get all that out of the fuel. Also there is more in the tank that will continue to come out over time. Even then over time heavy silt will build up again eventually. I would change the tank and the lines as well. But that's just me.

[Mack B]

Originally Posted by The Rocknrod

Ya, you'd need a larger Donaldson or Cat 2 or 3 micron filter to get all that out of the fuel. Also there is more in the tank that will continue to come out over time. Even then over time heavy silt will build up again eventually. I would change the tank and the lines as well. But that's just me.

I’ve got a Boyd’s tank that has been on the shelf for years, I think my excuses just ran out.