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I purchased a New/Used 1998 Chevrolet S10 LS, with a 4.3L it had 87,000 miles it now has around 130,000 on it. Recently I had all my tail lamps except the one on top of the cab. While I was in the process of tracking the problem my fuel pump goes out "Bad Luck" I guess. I replaced the pump and it is pumping the fuel to the test port on the fuel rail and still the truck will not start! If I manually put gas in to the Throttle Body it will run. What would you say the problem is? I have heard everything from airlock, the timing being off to the computer..... I think maybe the injector could be gummed up…

Without knowing the fuel pressure that you are producing I can just guess what the problem is. You said it was running fine until you started working on a taillight problem. Then the fuel pump quit pumping and you changed it. My question is did you put the right fuel pump in the truck? You said you have fuel pumping up to the service port, so I know the fuel pump is not wired backwards. It is possible that you may have installed the wrong type fuel pump for your truck! A throttle body fuel pump will look just like a Vortec fuel pump in appearance (you have a Vortec V/6). The difference is in the fuel pressure they produce. The throttle body fuel pump puts out around 20 pounds of fuel pressure. The right fuel pump for your truck will produce about 100 pounds of pressure! You should have a fuel pressure reading of 60 psi when you hook up your fuel pressure gauge and try to start the truck. If your truck doesn't have enough fuel pressure then you have found the problem! If you don't have a fuel pressure gauge and you are working on today's cars, invest in one! Most problems on today's cars deal with fuel delivery. A fuel pressure gauge is indispensable when working on finding these type problems. There are several tests you can perform on fuel pumps: 1) Pressure test. (What is the pressure when you crank the car?) 2) Static pressure test (does it hold pressure when shut off?) 3) Volume test (does it pump 1/2 pint of fuel in 15 seconds?) 4) Quality of the fuel (does it smell like gasoline or diesel fuel?) 5) Voltage drop to fuel pump (is it less than 1/2 a volt?) 6) Wave pattern test (does it have a good wave pattern?)

 

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