89 GMC C3500 454/w FI will not start.

fuel pump, or fuel punp relay mounted on fire wall, check the fuse in relay, also check the ground wire from fuel pump (in tank) to the inlet pipe , under the truck, where you put gas in, fuel pump needs a good ground period. fuel pump could be on its last leg ! reason why I know this is cause I have a 1988 gmc 3/4 ton. to access fuel pump, I cut an access opening in truck bed, 12" square above tank at location of pump. better than dropping tank, besides the truck is how old ? makes a hard job easy. change your fuel filter also. good luck, ken

It sounds like you have a defective fuel pump. The pump is locate inside the fuel tank, the fuel tank must be removed to replace the pump. Please follow this procedure to remove the fuel tank.
Disconnect neg battery cable, safely raise vehicle, place floor jack under tank, loosen gas tank straps and allow tank to slowly drop halfway, disconnect( this is the hard part) fuel lines,and power connections at tank. Drop tank. With a brass hammer/punch carefully remove retaining ring/seal.Reverse to install.A new pump module will cost you $300-$400 at the dealer. Don't use a cheap pump replace the entire assembly because this is a float/sender/pump/ in one. Replace your fuel filter too or the fuel pump warranty is voided..

what motor? is the coil producing spark?? If so, check the fuel pressure, if the fuel pressure is low drop the tank, repace the pump and also replace the filter (located on the frame forward of the tank). If the coil is not producing spark, check for shorts or opens in the circuits as well as the IGN fuses. If there is NO fuel pressure at all check the fuel pump fuses and make sure the fuel pump is plugged in and there are no opens in the circuit

Fuel Pump or starter. Since you say it's turning over but won't start I'd say it's your fuel pump. You'll probably have to drop your gas tank to fix this problem as your fuel pump is in the tank. You might be able to just loosen the straps and lower your tank a little to access it without removing the whole tank. Check around to local junk yards for this part and you'll probably find it for half the price as new. Make sure you can get your money back if the used pump doesn't work before you pay for it though. Don't forget to run fuel system cleaner (2 bottles to a full tank) once a month.

replacing the fuel pump on this truck, requires the fuel tank to be removed. the fuel pump is installed in the fuel tank. you can either drop the fuel tank or remove the truck bed to gain access to the fuel pump

If the pump is in the gas tank,which most new vehicles are, you'll have
to drop the gas tank, to remove the pump and sender. Make sure you
do this with as little fuel in it as possible,seeing that fuel is like 8-10 lbs.
per gallon. Good luck.

Inside the fuel tank where the fuel line comes out.

Unfortunatly, your fuel pump is in your gas tank. It is part of the sending unit. You will need to siphon out the fuel and drop the tank. You may have to replace the tank straps and fuel llines depending on thier condition. It should take 3-5 hrs depending on what you need to replace.

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Hit the bottom of the fuel tank. This jars the fuel pump. If the truck starts You need a pump. Common problems to GM is the pump.