Questions and Answers
T-Bird Fuel System
Q. Dear Mr Vincent Ciulla, I have a 1991 Ford T-Bird, 5.0 liter V-8 engine, Automatic transmission, 110,000 miles, Fuel injection, A/C and Cruise Control. When parked on HOT sunny day on parking lot, the T-Bird will not start until may 10 to 20 tries and within half an hour.
I changed fuel filter, this improved it, but problem came back in couple of months. I have found “bicycle valve” on the top of fuel injection manifold located on top of the engine. When activated, gasoline, then foam, and then air (vapors) came out of it. Ford dealer checked the flow and pressure and found nothing wrong, but suggested to replace fuel pump. At the dealer, our car started okay, and he could not duplicate our problem.
Because the sound of pump was not healthy, I found an independent repair shop, bought the fuel pump at Ford dealer, and had the independent install the new pump. Second day the problem was back, now the car does not have to be on HOT sun not to start. I changed fuel filter again, just in case that the taking out the gas tank, in order to install new pump, stirred up some gunk.
I disconnected the fuel line after filter and after turning key switch to ON position, solid burst of fuel came out of filter outlet, and then stopped, and then nothing. That baffled me because I thought that the no pressure in fuel line should trigger fuel pump to pump. After installation of filter I could hear air, originating from the new filter, to escape to fuel tank every time the key switch was cycled. After while there was no air. Now there is also no air coming out of the“bicycle valve” on the top of the fuel manifold.
My hunch is that the pump controller does not know that there is low or no pressure in the line, or the pressure regulator keeps pressure too low for gas to be injected in combustion chamber.
- What gives?
- Is there a Fuel Pressure Sensor?
- Is there a Pressure Regulator, other than the one on the Fuel Pump/Sender Assembly? Ford Parts department says there is one on the top of the engine, but I could not find it. However, there must be some valve bypassing the extra fuel and air back into the tank.
- Where could I get fuel line (piping) schematic?
Peter
A. Well, let's do this by the numbers.
1. It sounds like you have a case of vapor lock. Vapor lock occurs after the engine runs and then sits and the heat soaks into the fuel lines and actually boils the fuel inside the lines and injectors. The fuel pump has to circulate enough fuel to cool down the lines so liquid fuel once again fills the lines. The other possibility is a bad ignition module. They will fail at high temperatures and start working when they cool off. Both are distinct possibilities in your case.
2. There is no Fuel Pressure Sensor.
3. Yes, there is a fuel pressure regulator. The fuel pressure regulator controls fuel pressure supplied to the injectors. The regulator also traps fuel during engine shutdown, thus eliminating the possibility of vapor formation in the fuel line, and provides instant restarts and initial idle speed. It is located on the fuel rail. It has a single vacuum hose connected to it. You might want to replace it and see if that helps the vapor lock problem.
A Chiltons Service Manual will have the fuel piping diagram and locations of all the components of the fuel system.
Additional Information provided courtesy of ALLDATA
