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 Jim Grant's Tech Tips ‘94 Ford Ranger, Hesitation to Repair Q: I have a ‘94 Ford Ranger EFI 4L with California emissions. When you accelerate, the vehicle falls on its face and is not drivable. It acts just like an accelerator pump failure in a carburetor. If you bring the throttle up very slowly, the RPM's will gradually increase. No Error codes are found and Check engine light hasn’t lit up. I replaced the air and fuel filter and checked for vacuum leaks. The exhaust system and converter checked good for restrictions. A local shop said it might be a fuel pump or camshaft sensor. They weren’t sure and said the repair estimate if they fixed the cam sensor was $600, but they weren’t sure if that was what was wrong. I am a bit confused at spending that much money as just a guess. Any Suggestions? A: I would be hesitating to spend that money too, with the information you've been provided. Let’s start with the fuel pressure. On your vehicle there is a test port on the fuel rail right by the fuel injectors. Any shop worth its wrench set has a fuel pressure gauge with an adaptor that will connect directly to this test port. Once connected the tech should check the fuel pressure with the key on and engine off. Then check, the fuel pressure with the engine running followed by a fuel volume test. But, the best test of all is to duct tape the fuel pressure gauge to the windshield. Be sure the hose to the fuel gauge is safely routed, not pinched in the hood (there's a trick to it), drive the vehicle and monitor fuel pressure while the problem is occurring. The fuel pressure, should be in the area of 30 psi at idle and climb to about 45 psi when accelerating. If the fuel pressure drops while accelerating then you have a fuel supply problem that is either the filter, fuel pump or possible damaged (pinched) fuel line. Most cases if the filter is new and the pressure drops it's the fuel pump that has the problem. As for the camshaft position sensor being the cause? Let's put it this way. If you want to upset your vehicle's computer, just take away the camshaft position sensor signal. The check engine light will be on in a flash and there will be a hard code to retrieve from the computer's memory. The camshaft sensor only has to screw-up for a few milliseconds to set a trouble code. So after a few milliseconds of reading this you may want to find a different repair facility.
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