Ok, I'm about to rip my hair out! I have a 69 351w in my 57 F100. I have replaced or redone just about everything on the truck. I have a factory gas tank with no vent that I did a POR15 tank kit in. It has a new tank pickup and I bent all new gas lines. New mechanical fuel pump and a never used 600 cfm Edelbrock carb that sat on the shelf for a while. Here's my problem. I static checked the timing then set it with a light. It fired and idles GREAT. I can put it in gear and move it around just fine. When I went to take it out, I got about 1/2 mile from my shop cruising about 40 mph and it started to stutter. It stalled and would not start back up. I pulled the air cleaner on the side of the road and looked in the carb and it wasn't getting any gas. I started checking fuel lines to see if any were hot and none of them felt hot. Part of the frame rail the fuel line is attached to is getting hot from the exhaust but the line did not feel hot. I tried to start the truck again after messing with it for about 10 minutes and it fired and idled perfectly. I turned around back to the shop and right as I was pulling back in it died again. I checked the filter and it is clear, and wasn't getting gas to the back of it either. What the hell is it doing?!?!?!?
You said the tank is not vented. Is the cap? Do you have any loose hoses that might be pulling air in before the pump. Also does your pickup tube in the tank have a strainer or screen on it because in tanks that have been lined ive seen the screens get covered with a film of dissolved liner that gloggs it up.
I had a similar problem...and the only thing I could really pinpoint was a tiny air leak at a rubber to hard line connection. Seems it was sucking air into the lines but wasn't big enough to leak. I could be totally wrong but when I tightened the hose clamp the problem when away.
Yeah, the tank could be vacuum locking, after a couple minutes air seeps into the tank and allows fuel to exit the tank until it the fuel pump sucks a bit of fuel and creates another vacuum situation. Also, I have heard of the coating in tanks dissolving from high percentage Ethanol/Gasoline blends. Marty McF.
unvented tank MUST use a vented cap - probably the problem based on the time it takes to stall the engine - as said, remove the cap and see if the problem is gone - if so get a vented cap.
you running one of those glass and chrome fuel filters with the replaceable element? chuck it and put a proper fuel filter on. i had two that would clog up so quick i couldn't get the car out of the driveway. fresh lines, newly cleaned and sealed tank, new pickup tube. never did discover what the hell was wrong with the filters. i just won't use them anymore.
I agree put a vented cap on, sounds like it took the same amount of time to stall both times. Drive it with the cap off, and see if it happens again. Easy todiagnose and you have an excuse to drive it again. Brandon
Those old 351W were notorious for vapor locking! I had a '71 Ranger that would do it intermittently and leave my ass sitting by the side of the road all the time. The fuel pump itself would get hot and cause the problem. An aftermarket electric fuel pump solved the problem.
Simple test here. Back off the cap until loose, run it. If it runs okay, get a vented cap. If it still dies, it's probably an air leak in the line or connections somewhere. It's running fine until it looses it's prime.
So I went through and checked everything again and tried it without a cap and it was still doing it. I decided to pull the sending unit out and see if I could see something clogging the pickup. When I looked in the tank I saw that the POR15 sealer was peeling off the whole inside of the tank and had melted to the bottom. Obviously clogging the pickup. I pulled the tank and started cleaning it out. Not sure if I did something wrong while coating it or if that stuff just SUCKS, but what's done is done.
At least you isolated the problem. Take your tank to a radiator shop and have them re-seal it. It's cheap, and it will work. Good luck...
With some of those sealer products, if you dont follow the instructions down to double dotted "i" misprint. It wont work worth crap.found out with garage floor peel..oops, I meant paint!
Glad you found the problem but as said above get rid of the glass see thru fuel filter, they may look cool but when that thing fails instead of sitting on the side of the road waiting for your truck to start again you'll be waiting on a fire truck to extinguish the flames. Rick