Im been a mechanic assistance for six yrs i never seen this My brother learned there was two different pumps for the 98 the hard way, haha The tank is horrible to pull and you will need help or if it's a beater the last parts truck that we got some one just cut a hole in the box to do it!!! Have fun. The newer style has plastic tubes from the plastic pump casing and uses those quick connect fuel fittings and you'll need the disconnect tool. The older model has steel lines coming off of the top of the pump to the frame rail and then connects to the frame steel lines with short hoses, you'll need line wrenches and the ability to curse. Halfway through 1998 GMC switched to a new fuel pump style. If you have spark with no pressure it is the pump. If you don't have spark check the cam position sensor in the distributor. If you have fuel pressure after the above tests pull a spark plug and check for spark. But because the pump is in a horrible spot check the regulator easiest way is to pinch the return line and start the truck if it doesn't die the reg must be replaced. If it bleeds off quickley and doesn't spray your fuel pump is most likely shot. With the motor off check the pressure, start it and let it run until it dies then check the pressure and shut the key off. Be careful if the pump is good there will be 40 psi. If not I've used good safety glasses a rag and a screwdriver to check for pressure. ![]() The best thing would be to buy or rent a fuel pressure test gauge as it would thread onto this port. You will have to check the fuel pressure at the rail, the test port is ontop driverside about 3/4 the way back. I believe that truck runs at about 40 psi at the fuel rail. The pump maybe pumping but it might not be putting out enough pressure for your efi system.
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