help

[boogie67]

My sons 72 is giving him a problem.It will run for a while and then act like it runs out of gas.He's already changed the fuel pump,filters and carb.Theres is no dirt in the gas as he has a clear filter on it and the gas looks clean.When it sets awhile it will crank right back up and run for awhile and do it again.Im the one that works on his truck but I've been sick lately and can't help him.Any ideas.Thank You

[jdwhitlo]

Sounds like you might have a vapor lock problem.

[boogie67]

Not to sound dumb but what does that mean?[vaporlock]A guy on another site was describing the same thing on his 56.They told him to try running it with his gas cap off.Does that sound right?

[jdwhitlo]

Try routing the fuel lines away from the manifold/header's and anything else that gets really hot.. If it is vapor lock this should help.

[jdwhitlo]

Got this from Wikipedia,
Vapor lock is a problem that mostly affects gasoline-fuelled internal combustion engines. It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling. Restarting the engine from this state may be difficult. The fuel can vaporise due to being heated by the engine, by the local climate or due to a lower boiling point at high altitude. In regions where higher volatility fuels are used during the winter to improve the starting of the engine, the use of "winter" fuels during the summer can cause vapor lock to occur more readily.

[Shyguy]

You might want to check all the rubber fuel lines.

I had one on the suction side of the fuel pump that was collapsing causing similar problems.

If the gas tank or cap are not vented a vacuum can happen causing problems and losing the cap can remove the vacuum affect allowing the gasoline to flow.

Danny - Southeast Missouri

[race18]

I would start looking at the ignition system. Does it have Electronic Distributor? Could be Coil or Module.

[60ratrod]

i would check the timing as well

[Botietruck]

Back to the basics. It takes fuel, air & spark (electrical) to make an engine run. Usually vapor lock will not occur until the fuel temp rises significantly. Make sure he has plenty of gas in the tank - remember simple things first.I would also check the gas cap. remove it and see what happens. Also check that fuel filter one more time. He could have a tank full of trash. If you're getting fuel, check the components of the electrical system. I've had a coil to cause the same symptoms that you're speaking of. Let us know what you come up with, and good luck! Hope you get to feeling better fast!

[boogie67]

Talked to my son.He is going to try some of the things ya'll said to try in the morning.Tonight were making tamales oh yeah can't wait to taste them.Happy New year Guys& Ladies.

[cdowns]

theres a filter sock on the fuel pickup inside the tank not unusual for that to be clogged with crap

[BLACK AND BLUE 67-72]

I had a problem like this, I would start the truck and it would run fine for a minute or two then act like it ran out of gas and die, I could pump it and it would restart and do the same thing over and over. I replaced all of the fuel lines and it would still do it, I got a wild hair one day and took off the air breather while it was running and looked at the choke butterfly and it would start to open too soon and the truck would die, so I bent the choke rod so it would stay closed a little longer. It fixed it and I haven't had it happen since, so you might check that also.

[El Bombero]

Here is my .02 And Im not too cool to admit this happened to me. I was having the same problem and here is what it was. I have a C-20 with two fuel tanks. When I was getting in and out of the cab my foot accidentally hit the Tank selector valve on the floor between the door and the seat. I hit it just enough to put it in between the two tanks. I dont even want to tell you how long it took me to figure out that one. I havent felt that stupid in a while...

[ChevLoRay]

Originally Posted by cdowns

theres a filter sock on the fuel pickup inside the tank not unusual for that to be clogged with crap

I was laid off from my long-term job, back in '75, and ended up going to work for Sears Auto Center. One of the jobs I was given, was on a '72 Mercury Montego Brogham, that was loaded....429, and all the bells and whistles. It was a "come-back" job....it had been brought in for a tune up/carb overhaul. Shop manager gave it to me (don't know why me) but the only description of the reason was that it would run and die. Shop chief told me to "rebuild the carb, new points, plugs, wires, fuel filter, rotor and cap". After I got all that done, I drove it. After a couple of miles, I exited the freeway, and headed back to the shop. Within a mile of the shop, it died. It died at least four more times before I was within sight of the shop. I finally made it back, and drove it onto one of the lifts. At that point, I dropped the tank, removed the fuel pick-up and (to this day), I still have the sock that was on that pickup tube. It never came back for that problem.

But, there's a deeper problem with Sears.....that being the simple fact that they could fix anything, as long as your credit was good and you had ample room on your credit limit. I saw other issues besides that one. I seemed to be the one to get the stuff nobody else could fix, and never did I get one that hadn't been muffed up, leading the customer to spend more money than he/she should have had to spend.

Just read a Custom Classic Truck (Jan) issue that tells of taking a '95 Camaro in for plugs/wires, only to find that the six used plugs he got back were what got changed. The other two plugs in the V-8? Still there. Plug wires were routed too close to the exhaust manifold, and they didn't live 200 miles.

Vapor Lock? I have not seen such since my dad sold our '50 Plymouth, in '59. Used to see people come in the station I worked at, with clothes pins clamped onto the steel fuel line, to "prevent" vapor lock. Not gonna say it doesn't happen, I just don't have any experience with it, and I try to stay true to the routing of fuel lines, as the factory intended.

My '69 had a problem in which it would die. Being I am older and not as agile as I once was, I let someone I trusted work on it. Only thing is he wasn't doing the work, just one of his employees. After replacing the ignition module in the HEI, it seemed okay, until New Years Day, 2003 (about a month later). To make a long story short, I put in a new Accel HEI. The problem with the old HEI? The wire to the reluctor had an intermittent break in it that would become an open circuit when you let off of the gas and the vacuum advance would move it enough to break the circuit.

Don't know if you have HEI, but don't let this tidbit throw you off. I only put it in here JUST IN CASE you exhaust all the normal options and have questions. In the medical world, the problem I had is a zebra, when you should be looking for horses when you hear hoofbeats.

[Sport/Truck]

Nobody backs you like Sears! Anybody remember the problems they had with there brake jobs in the `80's?
s/t

[james w]

had that problem on my 71 custom10 turned out to be rubber fuel line on fuel pump suction side was collapsing