Service Procedure
TO BE PERFORMED BY CHEVROLET OR GMC TRUCK DEALERS ONLYDealers should first inspect each C/K or R/V vehicles fuel tank(s) and fuel tank straps for evidence of recent replacement and/or excessive corrosion as well as evidence of existing leaks prior to performing any repair or replacement.
If it does not appear that the fuel tank(s) or straps have been recently replaced and there is evidence of excessive corrosion to the fuel tank(s) and straps, and if the owner does not have proof that a replacement fuel tank was purchased/replaced between December 1, 1993 and September 12, 1994, the owner should be advised that their vehicle may not be involved in this campaign. The owner should also be advised that any repairs made to the fuel tanks, other than repairs to correct fuel tanks with defective sender unit retaining ring projection welds, would be at their own expense.
Once this inspection has been completed, the dealer should then perform a pressure test on the suspect tank to determine if their are any leaks. If the tank does not pass the pressure test, the fuel tank should be removed and the sender unit retaining ring inspection visually for evidence of any "Lifting up" or unevenness from the tank surface. "Lifting up" or unevenness of the sender unit retaining ring is an indication of fractured welds. Further verification of fractured welds can be made by trying to pass a "feeler gauge" through the welds. Tanks with fractured sender unit retaining ring welds should be replaced at no charge to the customer.
1. With ignition key in run position, check fuel gage to insure there is no more than 3/4 of a tank of fuel in vehicle. For auxiliary fuel tanks the fuel tank transfer switch in the cab will need to be switched to "right side" position.
NOTICE:
In cases where fuel gauge indicates above 3/4 of a tank of fuel, remove enough fuel from tank so that a 3/4 gauge reading is indicated. Drain fuel tank as described in Section 6C of service manual.
2. Disconnect negative battery cable after noting all electronic device settings.
3. Disconnect radiator test cap from Radiator Pressure Test Pump (Kent Moore Tool J-24460-01 or equivalent) at hose to cap fitting.
4. Pressurize fuel tank(s) in question following the applicable procedure shown below:
Trucks With One Fuel Tank:
Insert threaded end of radiator pressure tester hose fitting into fuel vapor line at fuel tank fuel vapor canister (figure 1).
Trucks With Dual Tanks (RPO NL2)
Remove shield covering the electronic fuel tank transfer valve which is located inside the frame rails next to the auxiliary (right side) fuel tank. Under the shield there is a T-connection, which connects each fuel tank vapor line to the fuel vapor canister line. For the fuel tank which is going to be pressure tested, disconnect fuel tank vapor line from the T-connector. Insert threaded end of radiator pressure tester hose fitting into vapor line (Figure 1).
5. Pressurize fuel tank system to 1-2 psi. Note position of radiator pressure test pump gauge needle.
6. Monitor pressure change which occurs. Note that a slow rate of pressure bleed off is normal due to radiator pressure test pump to fuel vapor canister connection. Pressure may also bleed off as a result of fill cap pressure relief valve.
^ If the test indicates that pressure bleeds off in a period of 1-2 minutes, the fuel tank will need to be removed and the sender unit retaining ring welds inspected for evidence of any "lifting up" or unevenness from the tank surface. "Lifting up" or unevenness of the sender unit retaining ring is an indication of fractured welds. Further verification of fractured welds can be made by trying to pass a "feeler gauge" through the welds. If tank replacement is required because of fractured sender unit retaining ring welds, skip to Fuel Tank Replacement Procedure below.
^ If fuel tank pressure tests indicates that fuel tank holds pressure, go to step 7.
7. Reconnect fuel vapor line. If fuel was removed from fuel tank in step 1 of service procedure, refill tank to previous level with fuel that was drained.
8. Reconnect negative battery cable and reset all electronic devices as noted in step 2.
9. Install Campaign Identification Label.
Fuel Tank Replacement Procedure
1. Drain remaining fuel from fuel tank following procedure in section 6C of appropriate service manual.
2. Disconnect clamps connecting fuel filler neck hose and vent line to fuel tank.
3. While supporting fuel tank, remove fuel tank retaining straps.
4. Disconnect fuel tank sending unit wires, hoses and ground straps from fuel tank. Tank will need to be lowered to gain access.
5. Remove fuel tank from vehicle.
6. Loosen sending unit tank locking cam using Kent-Moore tool J36608 or equivalent and remove fuel sending unit assembly from fuel tank. This procedure is described in detail in section 6C of appropriate service manual.
7. Install fuel tank sender unit into the replacement fuel tank.
^ Inspect and replace sending unit gasket if necessary.
^ Tighten sending unit locking cam using Kent-Moore tool J36608 or equivalent.
8. While supporting fuel tank, install fuel tank sending unit wires, hoses and the ground straps.
9. Reconnect the existing fuel tanks filler neck hose and the vent pipe to the fuel tank using existing fasteners removed in step 4.
10. Using existing fuel tank anti-squeak strips, install existing fuel tank retaining straps with existing hardware. Torque bolts or nuts as follows:
^ Base Tank Nuts - 6 Nm (48 lb. in.).
^ Auxiliary Tank Bolts (If Applicable) - 33 Nm (24 lb. ft.)
11. Reconnect fuel tank vapor line. Refuel fuel tank with gas removed in step 1 of this procedure.
12. Reconnect negative battery cable and reset all electronic devices as noted in tank inspection procedure (step 2).
13. Install Campaign Identification Label.