My '83 chevy with the rebuilt IP has been working great untill a few days ago. I went fishing for about 3 hours and no start, there were are bubbles in the line, I jumped it and crank a few more times and it started and ran great.

In the morning it stared, but didn't really want to to. It had a chug and chug the chug,chug,chug then running.

When hot still no start without a big fight and a recharge still air in the return line from the IP.

I looked it over and there is no wet lines. Is there a check valve in the tank that could cause this?

you don't need wet lines for an air leak. air sucks easier than fuel.could be leaks at fuel filters, tank pickup, the return lines. vent fuel cap can also plug up, making it worse because the tank will vacuum .somewhere in the facts sticky i think there was a procedure for pressurizing the return line and looking for the leak.

I tried that, there was no leaks anywere. I was wondering if it could be a check valve leaking back on the feed line. Is there on in the tank or the manual fuel pump?

When I did the preassure check it oozed out the return nipple on the IP, it's no suppose to do that is it? The key was off and the engine was over 100 degrees.

The fuel system must be leak free to hold fuel in the system. I use the soda straw illustration to explain.

If you put a soda straw into a glass of water, put your finger over the end of the straw, lift the straw up out of the glass and the water stays in the straw, you have a leak free system. If the straw has a pinhole anywhere in it, the water will drain out, even with your finger held tightly over the upper end.

The same is true of a fuel system. Any leaks in the system, fuel will drain back down toward the tank, the lowest part of the system. The lines, filter, etc., will be dry and the air will be forced into the pump on startup, Often, it will start and run for a second or two until the air hits the pump, then it dies and is very difficult to restart.

The check valves in the lift pump help but will bleed down in time. Many new lift pumps will not hold vacuum when tested new out of the box. If the system is absolutely leak free, the fuel will not drain back and the engine will start, even after sitting for months.

I figured it out, the air was just from the return side of the pump. When you move the clear line a few bubbles come up. The one battery was shot and was turning too slow to fire up when warm. Got that and bam, fires right up all the time. It seemed to be turning fast enough to start, but I gues not.

man i just fixed the same problem in my truck,
the air was getting in because the clear return line i had coming out of the pump had a tiny crack at the bottom and when you moved it air would come in. I found this out of course after i replaced all of the fuel lines between the lift pump the IP and all the OTHER return lines. Amazing how something that slight could cause that much trouble starting