2002 Blazer 4dr fuel pump R/R lessons learned

[reefgeorge]

Thanks to all of the posts before me that got me started. Here is some of the better tips from others as well as my experience. I hopes that this helps someone. Gotta give some back.

My fuel pump problem started as an occassional buck in the drivetrain at highway speed. Then it took longer to start. I should have suspected the fuel pressure and put a gauge on the schrader valve. I am sure that It would have failed the pressure tests and given me the chance to replace the pump before I had a most inconvienient breakdown, a tow charge, a missed business meeting, etc. Oops. BTW, my first pump lasted 151K miles.

When shopping for a pump, do not use the cheap after market varieties like Airtex or Carter. Get a Delphi/AC Delco. Mail order they are not that much more expensive. This is a PITA job and you don't want to have to do this again in a month.

If you suspect the fuel pump, check the pressure at the schrader valve on the fuel rail in the engine compartment or tee into the filter position. The specs on my truck were 58-64 psi at key on , then 3-10 psi drop at start up. Also check the leakdown after key on (couple of different targets in these forums). Mine went from 61 to 56 pounds after 5 min. after replacement. Mine is 56 psi at running after replacement. Mine were all 0 before with clean power everywhere.

If functioning pump and improper pressure check the regulator. If the regulator is OK check the fuel connections, then the injectors. The last possibility is the pump running but leaking inside the tank. If no pressure at all, check the electrical. Make sure that the fuel pump relay has 12V at the input to the relay contacts. If not check the fuse upstream or the wiring. Make sure that the relay has 12v at the coil input pin and comes on for 2 sec at key on and stays on during cranking. If you have power to the coil and no power across the relay contacts, swap out another relay in the box and try it. Make sure that you have 12V at the grey wire at the fuel pump connector. Make sure that all three grounds on both connectors have less than 5 ohms to chassis ground. My deal was <1 ohm grounds, clean 12v at the pump, no pressure at the rail, no fuel pump sound for 2 sec at key on = need to r/r the pump.

Watch the considerable gas fumes (ventilate), watch flame/spark sources/lights. Remove the spare tire. Jack the car up on the left side, make sure it's rock solid on flat firm ground. Have at least one fail safe support. Remove the left rear wheel. Loosen the strap bolts to drop the tank slightly and disconnect the 3 fuel lines on top of the tank facing aft. Squeeze the little side white plastic keepers if quick disconnect. 2 pipe wrenches if threaded (watch for the little o-rings). Pitch them down drain them into a container. Wrap the ends with tin foil to prevent leaking and fume build up.

Disconnect the tank fill hose at the aft end, the tank vent hose at the forward end, the TWO vent hoses at the aft end on the left side, the 2 electrical connectors near the fuel connections facing forward, and the strong tape holding the electrical wiring to the top of the tank.

Get a siphon bulb with a very small hose to drain the tank with the aft end still hanging down. Place a thin stiff wire in the hose to keep it from curling up and push it past the check flap just under the fill nipple on the tank until it clunks on the bottom and take out the gas. I only had around 5 gallons. A full tank may need greater care in gas removal before dropping the tank.

Finish unhooking the two tank straps with a floor jack holding the tank up and drop the tank.

Remove the old pump by using a block of wood/hammer (no sparks) and rotate the keeper flange CC (watch the little latch). Pull out the pump/sender. Slosh the rest of the gas around and get it to the end near the pump hole. Then siphon the rest of the gas and wipe out the crud that you got to the end for a nice clean tank.

Test the sender output (40 - 200 ohms), assemble the sender arm, lube the rubber seal with a little oil, place the unit in the tank (align the tab) and rotate the flange ring clockwise to latch. Transfer any quick connect white plastic latch/seal pieces to the pump pipes. Mine had 2 on the outer pipes.

Cover all of the holes with tin foil so that crud does not drop in the tank while you bang it around under your dirty truck.

Cut the wires on the old 4 pin connector in a staggered fashion (and the new connector to match) so that the new connector will end up at the same position and the solder points will not be next to each other. Solder all connections and heat shrink (heat gun) the connections with adhesive heat shrink tubing from West Marine (Ancor). After you forget to put the heat shrink tube on the wire before the first solder joint, you can mutter an expletive, unsolder the connection and do that one over again. Make sure that you have good clean solder joints. Nice hot gun, wipe the end clean with a wet rag. Pre-tin the wire ends. Always heat the wire until it draws the solder onto the wire. Solder nice and shiny. Then place the wires together, heat the wires, let additional solder draw in and stop with no movement in the wires until they set up. Make sure that the joint is shiny and uniform around the wires. Dull looking solder joints or incomplete coverage can lead to high resistance, a joint that falls apart or worst a solid mechanical joint that has high enough resistance to cause a connection failure (cold solder joint).

Get the tank back in position on the floor jack and get it most of the way up in to place. Have your wife hide the kids because for the next 30 minutes you are going to say a few x-rated things. Start the straps back in their holes in the frame rail. Put them back in every time they fall back out. Barely connect the forward strap and leave the aft end of the tank hanging down. Reconnect everything, making sure that every fuel connection clicks if quick connect, o-ring first if threaded. Push the tank all the way up. The real PITA part is trying to get the aft strap bolt started in the floorpan. This would be easy on a lift with a helper, easier under the car with a helper, or easier under the car with the aft end of the drive shaft removed. Just be careful because if you drop the driveshaft, you loose the safety of a firmly planted right rear wheel in park. I did not have any of these things and starting that bolt was tough. The strap is kept from moving into position due to a bulging tank side and no leverage. If I did not have such long arms it would have been literally impossible without dropping the drive shaft.

Double check all of your fuel, vent, and electrical connections. Put in a few gallons, check for leaks. 2 seconds on, 10 seconds off, then start the car (assuming that you heard the whirring of the pump). Run the car for a while, then check again for leaks. Pressure test as above. Change your fuel filter after some miles.

Say to anyone who asks why you did such a PITA job yourself - because I saved $500!