The Stovebolt Site Forums The Shop Area The Electrical Bay HELP!

You're right about the new parts but the carb wasn't off the shelf. It was professionally rebuilt but I'll check anyway. We're all human. This has got to be the most frustrating ordeal I have ever encountered.

I'm adjusting the valves first thing today.

well I was until I realized I don't have a valve cover gasket to put back on. So, I said I'll wait to do that next Saturday.

I did what you said and adjusted the vacuum to the highest point and then backed it off. Then I reset the timing and all of the carburetor backfiring went away and it ran smooth. You can still hear a "dead" miss at the exhaust but it was running pretty good so I decided to take the test drive but not too far.

as I mentioned before, I have a steep circle driveway, so I thought I'd start there just going around and around. Up the hill down the hill about 6 times. Then I headed down the straight away from my house, perfectly flat and low and behold, the same crap! It acts like it's running out of fuel. It dies and won't take the gas. It'll start using the choke and then cut off again.

Interesting note, I think. I raised the hood and looked at the filter and there was very little gas in there. I then towed it back up the hill to level ground and let it sit. I gave it about 5 minutes and the filter was full. It started right up and ran. I'm lost for now.

Next Saturday I'll take the pump off again and see how the wear marks look.

Great work with the timing change.
Eliminating the backfire lets the focus on the real problem.

Just a note on the "dead" beat in the exhaust.
Take a strip of soft paper (newspaper etc.)about an inch wide and 8" (not critical) and tape it on top of the exhaust pipe so it hangs down over the open end.

Start the engine and watch the paper for a while.

The exhaust will blow the paper out away from the pipe. The paper will drop when a "bad" cylinder fires.
If the paper just drops on that beat, it is a weak cylinder. If the paper is drops back against the end of the pipe or even sucked into it, It is a totally dead cylinder.

Very good observation about the filter.

Think about how the fuel pump works.
There is a chamber with 2 poppet valves (in and out)below it is a diaphragm and below the diaphragm is a spring and the lump arm.

When the cam rotates the lobe pushes the arm up which pulls the diaphragm down and compressing the spring. This pulls gas into the chamber. When the cam lobe moves by, the spring pushes the diaphragm up forcing the gas out to the carb.

If the carb is full and the float valve is closed there is no where for the gas to go so the diaphragm stays down. The spring keeps the fuel pressure up waiting for the carb to need some.

The pump can't pump when the engine isn't running.

The filter is above the level of the fuel tank so gas can't run into the filter by gravity.

So the only way the filter can fill up is if the diaphragm was holding the spring down when it stopped and something released the the back pressure so the gas could flow as the diaphragm came up.

Possible answers:
Outlet side
Float valve stuck closed and then released
Vapor lock
Inlet side
Blocked fuel line
blocked tank air vent

If there is a blockage on the inlet side a vacuum will form in the pump when it can't draw in gas. As the blockage slowly leaks by or air slowly leaks into the tank the vacuum will draw the gas into the tank and will be pushed through until the pressure is equalized.

1. Try driving it with the gas cap off (I know you changed the cap)

2. Wrap wet rags around the gas line and filter after the pump.

3. Wrap wet rags just around the float bowl and fuel inlet. Do you have a heat spacer under the carb?

4. When the problem happens and the filter shows little gas, tap the float bowl sharply a couple times with a screwdriver handle or plastic hammer.

That's interesting! I also feel a real "urge" to order an electric fuel pump..

Easy way to eliminate everything from the gas tank to the fuel pump.

Disconnect the fuel line at the pump and plug it.

Attach a hose to a small gas tank that you can put somewhere safe. An outboard motor tank, tank from a lawn tractor, etc.

Don't do what I would do like just sticking the hose in the top of a 5 gal gas can and putting it in the bed or on the floor cab.

UR radical! I like it.

Thank you for this thread....I'm learning alot....especially the diagnostic steps that Jim Sears is providing.

I may have missed something about the condition of your engine, especially the crank. Are you fairly certain that the cam the fuel pump rides on is not worn? Because I'm like you jim911, I would have put an electric fuel pump on by now, just to eliminate what seems to be a fuel "starving" issue.

Actually after all of this, I think it still comes back to fuel delivery.

I'm pretty sure the cam is worn and as far as the engine condition, I'm not really sure of the internals. What I do know is when it's running, it's strong! Tons of pull.

I'm really leaning towards the electric pump after finding a few on Summit Racing in a 6 volt low pressure. I also have to adjust the valves next.

And yes, Jim has been very helpful along with many others. What a great bunch of guys that understand and aren't judgmental!

I had a similar fuel delivery problem that was likely from a worn cam, fixed by building up the pump lever with a spot of weld

Bill

Been there done that! I added 3/16" yesterday and put it all back together but I still don't feel like it's pumping enough. I'm pulling it out next Saturday to check wear marks. Too much football today!

Just a thought. Had a very similar experience this summer. Rebuilt the carb and fixed a leak. Feeling good about my self until I took a test drive. Fuel starvation and stopped. Tools were in the cab and my neighbors are used to me at the side of the road with the hood up. Nice folks. Any way I took the top off and the needle was stuck in the seat. Had to pull it out with a pair of needle nose. New viton tip and new seat????? So I still had the old one and put it in. Started and ran just fine. No leaks. I did check and recheck the float adjustments cause I was worried. Still good. Drove towards home and it did it again. Pulled the top and the needle was stuck again....pulled with the pliers and set in the back of the truck with a bit of 600 grit paper. Burnished the old needle and put it back. Drove home with no more problems. Modern fuel is not a lubricant. I did the same to the new needle and saved it for later. Been 1000 miles and still running strong. Go figure. Yes the bowl was empty each time and now? I can pull that top off in record time.

I can picture that whole scene. So I need to throw more tools in the box along with some 600 grit?

I have great neighbors too. They stopped this morning to make sure everything was ok and could they help, since I was on the side of the road again and I said yes, "buy this truck"!

My jockey box is sitting on the floor with a bunch of stuff in it. And still have that bit of 600 grit in there as well. Gotta get a new box and put it in the dash,,,some day.

Before you pull it, you may want to check the output. Don't know what gpm is on that pump, but that would let you know if it's pumping up to spec.

Ditto on the football!

Easy to check the output.
Start the engine and run for a minute and shut it off. That will make sure the carb is full and will start right up.

Disconnect the fuel line from the carb and slip a piece of gas hose over the end. Put the other end of the hose into a plastic gallon bottle. (not balanced on the fender)

Check a watch and start the engine. When the engine stops check the time and see how much is in the bottle.

Jim: That is a good test. Sop watch..who would have thought I needed a stop watch? Truck is slow enough that counting works for most things...:)

I feel like I'm losing my mind! Installed the Carter electric fuel pump today and we've got fuel! Unfortunately, the pump is leaking around where it's "clinched" together. It looks like a manufacturing problem. So for today it runs great. no backfires, taking the gas but a major leak. The next step is to see how good Summit Racing return policy is...

Jim, Summit Racing is usually pretty good about returns. Been doing business with them for about 30 years now.

You're right they couldn't have been better about it. They're sending UPS return label and as soon as they see it shipped, they'll send me another one. Maybe by then the snow will be off the roads for a test drive!

Where do I begin to end this thread? After all the things I've tried and all the help I've gotten diagnosing the problem, it turns out it was "fuel starvation". I know the purest are not fond of an electric fuel pump but buddy, it did the trick! If you look under my hood you'd still see the mechanical fuel pump but with a fuel pressure gauge before it. FYI 4# is the magic number for the old Rochester to be able to keep up. I know the danger of the electric pump so I put a "redundant" switch after the ignition switch to be (what I feel) is safe. I drove "RUSTY" for the first time a little over 2 miles after installing the new pump and adjusting the valves (thanks SWEET AND FOURBRADS) then I came back and adjusted the valves again and went for another ride. He's running and idling like my grandmother's singer sewing machine!

To keep with originality, if and when I rebuild this 216, then and only then will I go back to mechanical fuel pump. "It's only weird, if it doesn't work" (BUD LITE)

Thanks to all you guys, you know who you are, for hanging with the Stovebolt Rookie and getting me on the road.

Now all I need to do is put the brakes on and tires and see some "flowers" popping up! Come on spring!!

good deal Jim, thanx for reporting back .... and yes on the soonest return of spring

Bill

Thanks Bill/DADS50/Jim Sears/ and all my "brothers" from another Mother!

Jim we feel your pain. Looking back through these threads, you had the nightmare of everything gone wrong all at the same time. This makes diagnosing so much more difficult. Good job on sticking to it.
Carl