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70 LS5 454. Frame off reconstruction so everything is basically new. Drove it a bit this winter with no issues. Around Christmas time we had a beautiful day up here in the smoky mountains and I stropped for fuel at the bottom of the mountain and started to head up. About 3/4 up the mountain it started to act like it was running out of fuel. Every time we hit a flat spot it seemed to once again get fuel and we made it home.Move ahead to this weekend. I towed it down to to Pigeon Forge for the Corvette Expo. Every morning I drove it up to my spot and at the end of the day back to the trailer, No issues at all. The group went for a little run and as we were going up a mountain it happened again and I was stuck. The car was not running hot or anything weird, I opened the fuel neck and did see the gasket in the tank from the cap, I figured the was a problem from earlier possibly not enough pressure to pump the fuel up hill with out that gasket, I fished out the gasket and replaced it. After a couple of tries it fired up and i made it to a turnaround and headed back. Thinking it was cured it made it back to the trailer and died. Back home today and after about a 20 minute run (about 75 degrees out side) it started again coming up the mountain. I kept pumping the throttle and when it would get some fuel i just kept flooring it until i got to the top and made it home. Any ideas? Mechanical fuel pump GM, original Q-Jet carb and slight cam with headers and aluminum radiator. Amy ideas would be greatly appreciated. Bill
Unless you were driving in very hot ambient temperature 80s/90s, doubt it's vapor lock.
Did you use the preformed fuel hose from frame to pump?
Have you done a fuel pressure test?
Is the return line from the pump to tank connected and the line is unobstructed?
Is the carburetor float level correct
A common way of troubleshooting this is to tee in a fuel pressure gauge that is visible while driving.
DO NOT run it inside the car. I usually tape it to the windshield, not pretty but it will let you know if the problem is up or downstream.
You could maybe pull the outlet hose on the tank and see if it flows pretty well.
BTW this happened to me recently on my truck with a tank of fuel that must have been heavy on the ethanol.
I immediately loaded some non ethanol fuel and it hasn't happened since.
[QUOTE=Piersonpie;[url=tel:1609525856]1609525856[/url]]Retarded ignition timing can make the engine run hot and boil the fuel out of the carb, especially modern ethanol blends.
not sure what it is. Switched to electric ignition bit I can check on the Dyno sheet.
Originally Posted by Piersonpie;[url=tel:1609525856
1609525856]Retarded ignition timing can make the engine run hot and boil the fuel out of the carb, especially modern ethanol blends.
not sure what it is. Switched to electric ignition bit I can check on the Dyno sheet.
You stated in your original post the engine was Not running hot.
Do you recall the temperature on the gauge?
I would suggest that you might want to inspect the fuel supply line and verify that it has no holes or damage to it. My C3 was running poorly and it turned out to be the fact that it was pulling air INTO the fuel lines.
Park the car and watch closely underneath, we found a pin hole in a metal fuel supply line, at park, the car would leak gas out onto the ground in such a fine spray that it would almost evaporate right away. Under power it was pulling air into my fuel pump and making the engine run poorly. Even old leaky hoses or fuel clamps that are loose can do this as well.
Ignition coils also start to act up when they get Hot or the weather does it for us.
Sounds very low, do you have a thermostat that is stuck open?
If accurate no way did you have vapor lock.
Not that I know of. Brand new thermostat when I went through the engine. Doesn't act like its hot at all. The temp did drop a bunch when I switched to an aluminum radiator. I will put a test gauge and run it to see what the temp goes to just in case i have an original temp gauge issue.
I would suggest that you might want to inspect the fuel supply line and verify that it has no holes or damage to it. My C3 was running poorly and it turned out to be the fact that it was pulling air INTO the fuel lines.
Park the car and watch closely underneath, we found a pin hole in a metal fuel supply line, at park, the car would leak gas out onto the ground in such a fine spray that it would almost evaporate right away. Under power it was pulling air into my fuel pump and making the engine run poorly. Even old leaky hoses or fuel clamps that are loose can do this as well.
Ignition coils also start to act up when they get Hot or the weather does it for us.
I see nothing. All brand new and I don't have the spare tire mounted so great visibility around the tank. Ill keep checking everything...
I know the header is pretty close to the fuel pump lines. Maybe a shield or insulation? Also the pick up tube looks pretty far in front? Any thoughts or suggestions. Thanks
I know the header is pretty close to the fuel pump lines. Maybe a shield or insulation? Also the pick up tube looks pretty far in front? Any thoughts or suggestions. Thanks
That does not look like the factory drop down air cleaner.
Do you sufficient clearance under that air cleaner lid to not interfere with the carburetor bowl vent?
Do you have a Quadrajet or Holley carburetor?
1609527919[/url]]That does not look like the factory drop down air cleaner.
Do you sufficient clearance under that air cleaner lid to not interfere with the carburetor bowl vent?
Do you have a Quadrajet or Holley carburetor?
it’s a quadrajet and it does have a drop down base. Clearance seems good.
Just for ***** and giggles check and see if your choke flap is getting stuck or not adjusted properly .. I had a similar problem and acted the same way also your temp should be from about 175-180 big blocks are slobs and love the heat mine stays at that range
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Higher altitudes I believe will increase chances of vapor lock. When I lived in the mountains of N. Ga I had a vapor lock issue every spring when it began to warm up and the gas companies hadnt yet switched to their summer formula. Once they did I had no more vapor lock issues even though the outdoor temps increased. I chased this issue to no avail but it disappeared when I moved to a lower altitude.
I had an another vehicle with a vapor lock issue that I chased, again to no avail, until I replaced the mechanical fuel pump to a new one and I switched to ethonal free fuel. I'm not sure which solved the problem but It is also my belief that ethanol gas increases the likelihood of vapor lock.
Not that I know of. Brand new thermostat when I went through the engine. Doesn't act like its hot at all. The temp did drop a bunch when I switched to an aluminum radiator. I will put a test gauge and run it to see what the temp goes to just in case i have an original temp gauge issue.
Perhaps not the number one cause of issues on the Forum, but certainly in the top 5, is assuming a new part is "good" when you install it.
I'd pick up a cheap IR temp gun from Harbor Freight or Amazon, and confirm that the thermostat is operating as it should. You have a very shiny engine compartment, so shoot it at the upper radiator hose, as the IR temp gun will be confused by all of the reflections.
I'd also confirm the timing, and not trust a dyno sheet.
Vapor locking I think?
