Need help with ignition problem

[96blakdroptop]

I have a 1996 Z28 vert, when the car has a full tank of gas it will start with no problem. When it has a half a tank or less i have to hit the key once then let it go then hit it again and it will start. I don't have any problems once it is started it runs like a champ. I have changed the fuel filter and still same problem I need help b4 i start replacing more expensive parts that may not be the problem. By the way i am new to posting on the forum but i have been a visitor for a while and have learned a lot just by reading all the post from the very knowledgeable members. KEEP UP THE GOOD WORK!!!

[N20LT4Bird]

Why are you labeling this an IGNITION problem? If I had to guess, based on just the info given, i'd say fuel pump. If the check valve in the pump is bleeding pressure back into the tank, you would have to prime the pump (cycling the key) to get it to start. The stumper here is why it doesnt happen when you have a full tank???

[ZUL8TR]

Originally posted by N20LT4Bird
The stumper here is why it doesnt happen when you have a full tank???

I agree it is a fuel pump problem. I would say it is quite possible the reason why it doesn't act up when the tank is full is because the pump is cool while submerged in fuel. When the tank becomes less full the pump may be overheating.

[Joe 1320]

Originally posted by ZUL8TR
I agree it is a fuel pump problem. I would say it is quite possible the reason why it doesn't act up when the tank is full is because the pump is cool while submerged in fuel. When the tank becomes less full the pump may be overheating.

That is exactly what I think.

[N20LT4Bird]

Could be..... but how would temperature effect the pumps ability to hold pressure in the system when the car is off??

[tabahr]

could it be that when the pump is NOT submerged air is getting into it when it is not running. If the tank was full, and the pump submerged no air could get in the pump and it woud fire right up.

When the fuel level is lower, below the pump it is able to bleed out and fill with air, then it takes a moment for it to re-prime itself next time he goes to start it.

I would agree, he needs a new pump. Good time to replace some suspension bushings!

[96blakdroptop]

Thanks to all who replyed, will be looking for the best place to purchase a new fuel pump and a few rear suspension components while i'm under there. once again thanks fellas.