A 350 chebbie ....

Doug I · #1 (**permalink**) 03-09-2009, 05:16 PM

Ok - it isn't my truck - it's my uncles

S-10 with a 350 in it

Runs perfectly for a few minutes then acts like it's run out of gas

Wait a few minutes and it fires right up and runs fine for a few minutes then repeats above

New tank
New sender / pump
New gascap
New filters
New carb

Filters are clean, just empty then they refill after a few minutes

Does the above with or without the gascap on, so it's not a lack of air vent issue

Vapor locking ? but we can't see anywhere that is suddenly getting hot enough
Bad fuel pump ?

Ideas ?

Thanks
Doug

tcrist · #2 (**permalink**) 03-09-2009, 05:57 PM

I believe that your car will only vapor lock if it gets hot enough. If it is only running for a couple of min, it should not get hot enough to vapor lock.

That said, Does it have an electric fuel pump? Is it wired correctly? It might be wired to a hot that is only hot when the ignition is in start mode, not in run mode.

If it is a mechanical fuel pump on the engine, You might have some cracked lines and it could be sucking air. That happened to my sons 74 1/2 ton 4X4.

Was the 350 just installed and it just started doing this? What size engine was in it before the 350? V6, 4 cyl?
Maybe you need a more powerfull fuel pump.

Terry

john chesnut · #3 (**permalink**) 03-09-2009, 06:17 PM

Any chance the choke is closing up as it's running?

SP01715 · #4 (**permalink**) 03-09-2009, 06:20 PM

What about a restriction in the fuel line between the tank and the filters. Is there an internal filter in the fuel tank? If the fuel pump is working I would look at these areas.

john chesnut · #5 (**permalink**) 03-09-2009, 07:26 PM

I have seen a rubber fuel line that had an internal piece peeling away. When fuel was drawn through it, it closed up. Took awhile to find that problem.

poboy427 · #6 (**permalink**) 03-09-2009, 07:34 PM

Find someone with an electric fuel pump you can use. Get some clear hose from Menards or Lowes. Rig up a seperate fuel supply using a gas can. At this point I would leave out any filter. MAKE SURE YOU DO NOT HAVE ANY ELECTRICAL CONNECTIONS THAT COULD SPARK. Use 8-10 ft of hose so the fuel pump connections are a long way from the gas can. HAVE A FIRE ESTINGUISHER AT HAND TOO.

If it runs ok then you know you have a fuel delivery problem that goes back to probably a bad supply line as you have tried several other new pieces.

If there is really no differance look at an ignition problem, the way the fuel pump is wired or carb problem-perhaps choke closing like someone else said.

rAY

G_Edmonds · #7 (**permalink**) 03-09-2009, 09:10 PM

Is the new tank or gascap vented?

fastraxsg · #8 (**permalink**) 03-09-2009, 09:17 PM

I had a similar problem and found small bits of gunk in the carb bowl. Motor would run and the gunk would plug the jets, the motor would die, the bits would settle in the bowl, start again and they would get in front of the jet again.

57chevy · #9 (**permalink**) 03-10-2009, 05:04 AM

Doug
I have seen these symptoms a couple of times that were not related to fuel. On old ignition systems a coil or condenser failing will do close to the same thing. In one instance we had a engine that the lifters would pump up and open the valves slightly, that was the hardest to figure out. When the car first started it ran great then after about fifteen minutes it would begin to sputter and die. Car would need to set at least half an hour before it would start again. At the time my uncle was so convinced that it was fuel he even swaped out the carb, but it turned out to be the lifters.
Just some ideas that may add to the confushion. Good Luck
Rip

sdonnel · #10 (**permalink**) 03-10-2009, 09:45 AM

As John said above, check the hose. Having worked for Aeroquip, I have seen many hoses where the inner tube gets cut when the fitting is assembled. You don't see it when you look in the end unless you use some type of light source. Use some type of pick to make sure a flap isn't laying over on you. Also, make sure you are not somehow collapsing the hose from a vacuum as well.

SP01715 · #11 (**permalink**) 03-10-2009, 04:55 PM

Quote:

Originally Posted by sdonnel

As John said above, check the hose. Having worked for Aeroquip, I have seen many hoses where the inner tube gets cut when the fitting is assembled. You don't see it when you look in the end unless you use some type of light source. Use some type of pick to make sure a flap isn't laying over on you. Also, make sure you are not somehow collapsing the hose from a vacuum as well.

I had this happen on a boat. I had the thing in the shop and they checked everything they could think of with no problems found. When I got home I removed the pickups from the tank and removed the fuel line and found a small piece of rubber inside the supply hose.

Ronbo · #12 (**permalink**) 03-10-2009, 06:14 PM

HEI distributor? Might be a flaky module. During the mid 80's GM had a bad run of coils that would usually take the module out.

Doug I · #13 (**permalink**) 03-22-2009, 08:03 AM

Here's an update on what we've done ....

Yesterday we by-passed the tank and fuel lines by feeding the new mechanical pump directly from a gascan and 10' of new fuel line. We had already by-passed the regulator by feeding the carb directly from the filter. So the gas went from a can, to the new mechanical pump, to the filter, to the new carb. Fired it up and after ~10 minutes the filter emptied, but it was getting enough gas to keep running. I'd cleaned out the filter (in line clear glass) as it had a few specks of crud in it.

Reset the trans shift point to 3k and so far it running ok. At 3k the engine can't spin fast enough to run out of gas. But this is only a patch until we can figure out why it runs out of gas. New mechanical pump, new carb, no leaks but it just doesn't work. Drive mechanism for the pump checks out as does the supply pressure. When we had the regulator plumbed into the system the pressure never dropped below 5.5psi which is just fine for edelbrock carbs. We're a little surprised it's running ok without regulated fuel pressure.

Right now we're going "hmmmmm time for a beer"

tcrist · #14 (**permalink**) 03-22-2009, 08:36 AM

Doug,
What about a flat lobe on the cam for the fuel pump push rod.
Maybe a bent fuel pump push rod.
Hook up an electric fuel pump in line with the fuel pressure regulator and the fuel filter.
You want to elminate 1 thing at a time until you find the source.

Terry

Paul F · #15 (**permalink**) 03-22-2009, 08:55 AM

I know you said it is a new carb, but there is a wire mesh filter inside the point the fuel line connects to the carb (at least on my Holley there is) that may have gunked up quickly. Pull the 5/8 fitting off the carb. Its behind that. I doubt it, but worth a check. Don't let that half full clear fuel filter convince you it is fuel and not look elsewhere. My mower runs all day long with the filter half full of air.

Doug I · #16 (**permalink**) 03-22-2009, 10:28 AM

In changing the pump we checked the drive for it from the cam. Everything looked good and the nothing bound up.