Okay. I thought aafter replacing cracked rubber fuel lines,moving the metal line away from the block to prevent vapor lock, installing an electric fuel pump(5.6PSI), fuel filters and setting the timing properly, I had this issue licked,....but no. It is the strangest thing. The car runs solid and start every time. However, somewhere between 7 to 15 minutes sitting hot, the car refuses to start. Turns over, but won't start. Let it sit 20 and it fires. Here is what I notice; fual filter will not stay full (even when pump is running and in order to get it to start you must pump the gas (20-30). Also, the engine temp guage displays the engine running at the top of the acceptable range. I've also changed the thermostat to a 180* in hopes to lower the temp, but I'm not exactly sure it is running that hot. Let it sit 30-40mins and it fires like thers no problem at all.
Stumped?? I do have a high flow thermostat that I will be installing (180*) in hope it will lower the over all temp, but I do not think that is related to the starting issue. BTW. I've checked the plugs and they look perfect, like a well cooked marshmellow.
Anyone???

 

Just curious, do you have a return line?

 

Boy it sounds like your doing everything right. I would take off fuel line to carb and pump into bucket, then do the same with gas tank cap off, compare the two levels. This can tell a if your tank vents are relieving any vacum properly.
This one might be kinnda out there but can you see if your distributor vacum canister is locking after high vacum idleing and shut down. If it is you'd be starting with 40 or more advance. Hang in there we'll get this with you and your boys.

 

This sounds like classic vapor lock to me, "todays gas."

On my 67, I actually installed a vapor return. What year model are we working on, here?

Adding one is made easier by using a Wix fuel filter no 33040/ 41, 5/16 or 3/8" respectively, or equivilant interchange

These have a 1/4" return fitting with a built in orifice, so "all you have to to" is get a 1/4" line installed back to the tank.

An insulated spacer under the carb might help, and I'm considering "going against" all my years of experience and blocking the heat crossover in the intake on mine. (I don't drive this car in inclement weather, anyhow.)

After installing the return and carb insulator, mine is now managable. I have headers, and it is obvious that "they are a problem." I eventually plan to "find" some flexible (glass?) insulation to go over the fuel line from the torsion bar up to the pump, and from there to the carb.

I'm running BOTH a Holley "red" pump and the original mechanical.

 

Next time you have the "no start" condition when hot retard the timing some and try.

If it starts you have your issue,

If it doesnt start, use a small bit of starting fluid past the carb blades and start, if it runs even for a couple seconds you know its fuel issue.

If it doesn't fire on starting fluid you have an "hot"ignition problem, coil boiling or resistance in the system.

Forgive me if you already know its definitely fuel, I'm late to the post..

It sounds like vapor lock for sure but 180 t stat isn't doing it... headers or block heat, sure.. but you said you moved it all..

 

not sure if i have the same issue.
im running the old edelbrock single plane torquer. heat crossovers are blocked. my car starts up on two pumps. runs great,
its just a pain in the *** to start when its hot. starts fine if i turn the ignition on and hold down on the gas about 1/4 throttle or less.

 

Thanks BTW for the responses. 69' 440CID stock 4bbl(edelbrock 600CFM)

1) No return line, but have two vents at the tank. One short snorkel and the other goes up into the trunk somewhere. I know the fuel line itself and short snorkel are not clogged, as I can blow air through them without issue.

2) I will try pumpgas into a tank both with and without the gas cap on, but seems odd that if it were a vent issue that it would only happen when hot.??

3) Really thinking vapor lock for two reasons. a) seems its the only time the upper fuel filter is not chock full. b) when I watch the gas spray into the carb, I see fog come out. I'm running a 5/16's line thought a full 3/8 might help. (more fuel to heat up)??? Do you think the wix filter will help this?
4) Don't have headers just the factory manafolds. Any one have any pics of fuel line routing that avoids heat sources? Right now the line runs between the block and the alt, right by the exhaust manifold. I can't seem to think of any logical way to avoid heat....

I'll let you allknow if I ever figure this crap out or the weather down here drops below 98* which ever comes first..LOL THANKS AGAIN!

 

I dont want to POO-POO anything about vapor-lock, cause I've never had it, or seen it. But if his carb is set anything like a Holley, then I dont understand it. First off, most carbs have a fuel inlet at the top of the float bowl. That will not let an issue with the fuel tank venting, vacuum the float bowl empty. The float bowl is vented, this aids in avoiding a vacuuming issue. So I am saying, the fuel SHOULD be in there, and available for a pump-shot for a hot motor. Tried a float-bowl sight-glass yet? Handy on ANY car! BTW, when you do get it started after a HOT sit, does it blow rich at first? I'm leaning to a carb that leaks-down very fast. Wont notice that if you put it in the garage and try it again the next day. The fuel has already washed down the cylinders. Do you have very gassy smelling oil?

 

I know this kinda sounds dumb, but when I bought my first dodge I had a similar problem. I found that the previous owner had put the fuel filter in front of the pump instead of behind it. swapped around and problem solved. Hope this helped

 

That may very well be it. I just re-read and saw filter was plural. For an electric it should have a screen only style high volume "filter" before the pump and then the usual style fuel filter after the regulator and before the carb. Multiple paper filters
would be too much of a restriction.

 

My intake manifold would get real hot...if I stopped to get gas it would start up fine then start to stumble as though it was running out of gas...I added a phenolic 1 inch spacer and it solved my issue...mechanical fuel pump and Holley carb..