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1988 Ford Ranger 2.9 Engine. Truck runs fine until you get between 25 and 35 and then it bogs down. If you floor it, it goes, but that is hard to do with the police behind you while you are trying to maintain a steady speed. Gas gauge does not work. I am told that there is a low pressure pump in the gas tank. Could this be the problem, or the main fuel pump Any suggestions would be a great help. I reset the inertia switch breaker under the carpet, No Luck. HELPPPPPP... Thanks GMRockin@hotmail.com
Part throttle problmes can be a number of things, but some common ones are the fuel pressure regulator and/or clogged injectors.
After driving, pull the vacuum line off the fuel pressure regulator. If the line is wet or full of gas, the fuel pressure regulator has failed and needs to be replaced.
Since your setup is more likely to use a MAP sensor, you need to pay close attention to vacuum leaks. MAP sensors are a bit more finicky than MAF and a small vacuum leak will cause a part throttle problem. You can pull codes for your EFI without a code scanner and some things that would cause your problem would show up as a code but not turn on the "check engine" light. instructions are at http://www.troublecodes.net/Ford/
Finally, when was your last tune up? A shorted spark plug will cause a part throttle drivability problem as well as a shorting distributor cap or rotor. Don't get me started on what a clogged air filter can do.
It is not typical for a low pressure/high pressure fuel pump set up unless you have a truck with dual fuel tanks. If you only have one fuel tank, you only have one fuel pump.