If you are having fuel pressure-related problems, use these tests to narrow down the problem. You will need a fuel pressure gauge. You can either make one, using the instructions on the Make A Fuel Pressure Gauge page, or you can buy one for between $20 and $40. They are available at most larger auto parts stores. The better ones have brass fittings, bleed valves (to relieve the pressure), and metric adapters. Here you can see a picture of mine.
For information on upgrades, see the Upgrading The Fuel System page.
If you are having fuel flow problems, try replacing the fuel filter. It is fairly cheap and is mounted next to the gas tank in front of the rear, right wheel well. There are also tiny screens in each of the injectors. Most injectors can be disassembled and the screens can then be cleaned. Also, look for any pinched or kinked fuel lines. If this is not the problem, then the fuel pump may be getting weak.
Some pumps will only fail after warming up, so they appear to work fine after they have "rested" for a while. This is the sign of a dying fuel pump motor. Some pumps have a defect where a hose clamp is missing on the short fuel hose between the pump and pump bracket, inside the tank. The hose will pop off and will suddenly produce very low pressures. Other pumps will still run strong, but the gear pump itself is worn and cannot produce enough flow at high pressure (usually accompanied by a loud whining sound from the tank). You can verify a weak pump (at idle) by pinching the fuel return line on the regulator. If the pressure does not rise, then the pump is the likely culprit.
Fuel regulators don't often fail, but if they do, it may result in low pressure. You can verify this by pinching off the fuel return line to see if the pressure rises. More often the diaphragm will develop a leak and while the fuel pressure is not effected, fuel finds its way into the vacuum lines causing any number of problems (usually MAP sensor related).
To test for leaking fuel injectors, remove the fuel rail and reconnect all the fuel lines. Repressurize the fuel system by cycling the ignition key to "run" once or twice. No fuel should flow or drip from the injectors. If the injectors are leaking from the tips, you can try to disassemble and clean them. If the are leaking from the connection to the rail, remove the injector and inspect the o-rings. Replace any bad o-rings. Injectors sometimes crack along the back or sides and must be replaced. Always replace the fuel injector in sets to maintain equal fuel flow (in a pinch you can try replacing it with a used injector).
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Copyright © 1996-2003 Russ W. Knize.