Can't maintain fuel pressure

[JSM]

I have one of the clear Mr gasket filters that folks don't recommend coming right off the fuel line before the mechanical pump. Supposedly my tank was cleaned and I'm shocked at the amount of crap in that filter. 

[SteveJ]

I have a BUNCH of fuel filters on the way. They should arrive tomorrow or Saturday. I might still take off the filter that's on the car now and cut it open.

[SteveJ]

I am quickly beginning to think there's much more going on than just a fuel pressure issue. Today I drove the car. It started up and ran great. I stopped for a few minutes to buy some Harbor Freight supplies, and the car ran like crap. I continued on to my destination where the car sat for about 3 hours. Starting out from there, the car ran great, but showed some hesitation after having some stop-and-go traffic for a couple of miles.

When I got home, I pointed a fan at the carburetors and let it run for a few minutes. I took it for a drive, and there was some hesitation. I went back home and sprayed the ignition module (ZX distributor) and coil with a can of air held upside down. The car ran worse, so it wasn't an overheated ignition. I drove back home and put the fan on the carburetors again. About an hour later, I checked, and the intake was nice and cool. Going for another drive, the engine pulled great, with no hesitation. 

I feel that there is a big-time heat soak issue going on here. By the way, the car had ceramic coated headers and 4 screw SUs.

[siteunseen]

Summer gas?

[SteveJ]

Not sure. I just buy ethanol free gas. While I did experience vapor lock with the flat tops & stock exhaust manifold on one summer day, I didn't have these issues before the swap. I had this issue to some degree with the L26. The L28 is a higher compression motor, but I don't know why it would run hotter than the L26 with respect to the exhaust. I'm using a 160 degree thermostat. 

[Mark Maras]

 The various hydro carbons that make up gasoline have boiling points from 100` f - 400` f. The formula for gas is not precise and the quantity of components can vary from refinery to refinery. If the problem is new to a known working engine, Cliff may be right. The question now is how to cure it. A tankful of gas from a different station might be an easy fix or eliminate gas as the problem.

[SteveJ]

I can give that a shot.

[Captain Obvious]

You could also blast your carbs with the liquid from the upside down can of Perri-Air and see if that helps.

[SteveJ]

8 minutes ago, Captain Obvious said:

You could also blast your carbs with the liquid from the upside down can of Perri-Air and see if that helps.

No, President Skroob took my last can.

[djwarner]

I can't help with your primary problem, but a heads up on the magnet. Rust is not magnetic.

Can we assume now that you have focused on heat in the engine compartment that you have solved your fuel pressure problems and it still reads 3 psig during the heat soaks.

[Captain Obvious]

11 hours ago, SteveJ said:

No, President Skroob took my last can.

Haha!! It's in his desk drawer with all mine as well! 

Good luck with the problem hunt. On that front, when the issue arises, do you think you're running rich or lean? Rich could be from percolating the fuel in the bowls and forcing additional fuel past the needle, and lean could be from boiling the fuel in the rail and pushing vapor pockets into float bowls expecting liquid. Any guesses as to which direction you are going? How do the plugs look?

[jalexquijano]

On ‎04‎/‎08‎/‎2017 at 6:35 PM, SteveJ said:

I am quickly beginning to think there's much more going on than just a fuel pressure issue. Today I drove the car. It started up and ran great. I stopped for a few minutes to buy some Harbor Freight supplies, and the car ran like crap. I continued on to my destination where the car sat for about 3 hours. Starting out from there, the car ran great, but showed some hesitation after having some stop-and-go traffic for a couple of miles.

When I got home, I pointed a fan at the carburetors and let it run for a few minutes. I took it for a drive, and there was some hesitation. I went back home and sprayed the ignition module (ZX distributor) and coil with a can of air held upside down. The car ran worse, so it wasn't an overheated ignition. I drove back home and put the fan on the carburetors again. About an hour later, I checked, and the intake was nice and cool. Going for another drive, the engine pulled great, with no hesitation. 

I feel that there is a big-time heat soak issue going on here. By the way, the car had ceramic coated headers and 4 screw SUs.

THis is exactly the same problem i have!! Heat Soak after getting stucked in traffic for several minutes. Cant seem to find the solution!! I even read some crazy ideas of driving with the engine lid off!!