Aftermarket Fuel Pump Installation
By: Jeff Dunkle
Bike: ’86 K100RT
The simplest way to be sure the fuel pump is running is to turn on the key and hit the start button. The fuel pump relay activates and the pump will make a very audible whirring sound. Usually the bike starts so fast this sound is masked, but if it doesn’t start, yet the pump is running, you’ll easily hear it for a few seconds.
Other Data and Info:
The BMW fuel pump is a Bosch unit.
BMW Part Number: 16-12-1-461 576
List price as of above date: $248
Bosch Part Number: 0 580 463 999
NOTE! NAPA identified that the above Bosch pump was in their Atlanta warehouse with a unit price of $192 plus $7 for shipping
Bill Z. identified an immersible electric fuel pump that, while not nearly as large as the stock, Bosch unit, will perform satisfactorily. His installation has 100,000 miles on it. Others, including Rick Landi have done the same installation. Rick’s bike has 30,000 miles since this replacement as of this writing. I just completed the same project six days ago and now have 600 miles on the bike with no problems.
|NAPA Part Number:||2P74095||Price: $66.94|
|Advance Auto Part Number:||E-2042||Price: $80.74|
I examined both above units. They are virtually identical.
Also used to fabricate mount shims: NAPA gas neck hose
NAPA Part Number: 1030
Price: $7 per foot
- Disconnect the battery
- Remove the gas cap assembly
- Drain the gas tank – I used a simple siphon
In Tank Test – Optional: do only if you’re comfortable with electrical work. A spark in this situation could be explosive.
- Disconnect the pump power leads. Note that the nut and stud for the white, positive lead is smaller than those for the black, negative one.
- Take a pair of alligator clip leads that are about 3 feet long. Clip one to the small, positive contact stud, and one to the larger negative. DO NOT CONNECT THE OTHER ENDS TO A POWER SOURCE UNTIL THE CLIPS ARE SECURE ON THE PUMP POWER TERMINALS. Otherwise a spark will occur in an explosive atmosphere.
- Touch the positive lead to the positive (+) battery terminal and the negative lead to the negative (-) terminal. Verify that the pump does not run before removal. If it does, look elsewhere for the loss of fuel to your injectors.
Pump Removal Note: A quarter drive ratchet with a universal, several size extensions and metric sockets are very useful during removal and installation.
- Disconnect the power leads to the fuel pump. The positive terminal is smaller than the negative to prevent crossed wires later.
- Disconnect the fuel line from the top of the pump. Note that this is an ideal time to replace the fuel filter as well.
- Remove the six mount nuts and the collar washers underneath that hold the pump mount ring to the tank plate.
- Lift off the plastic hold down ring
- Pull out the pump and rubber mount collar. Be careful not to damage the filter screen clipped to the bottom of the pump.
- If you did not do the in tank direct power test, do that now. Apply 12 volts DC to the pump – positive (+) to the smaller stud, negative (-) to the larger. If it does not turn freely, it’s bad.
Installation of the NAPA Pump
NOTE: the pump has three differences from the Bosch unit. It’s substantially smaller. It has male spade type power terminals. And it has a very different filter, which I still managed to install and use. The main objective is to shim the diameter of the pump in some way so it is gripped by the rubber mount collar enough to hold the pump securely “after” the entire assembly is bolted in place, but not so much that it prevents installation.
- Get crimp on female spade connectors that will fit the two different sized male terminals on the pump. I found some at work so do not have part numbers to relate. I’d suggest opening the box at the store and shopping for connectors before you leave that fit.
NOTE: this entire assembly is immersed in gasoline. Any material used must be gas tolerant. The crimp on connectors had plastic sleeves on them, which I cut off since I did not know how well they’d survive in the gas. I chose not to solder the connectors because of proximity to fuel vapors.
NOTE: Yes….the electrical leads and connections are bare…and in gasoline when the pump is running.
- The barb on the fuel nipple is larger diameter than the one of the Bosch nipple. The existing fuel line will slide over the nipple end but the SS hose clap will not expand enough to slide over the barb. Get a hose clamp that’s bigger before leaving the parts store.
- Electrical connections
- Cut off the eyelet terminations on the power leads.
- Crimp the larger spade connector to the white lead. The positive (+) connector is the larger male spade on the pump.
- Crimp the smaller spade connector on the black wire.
- Orient the filter so that the long end points toward the side where the electrical terminals are located. Press the metal collar of the plastic mesh type filter on the inlet nipple of the pump.
- Cut two pieces of the large fuel hose about 1 1/2 inches wide. These will be used as mount shims. Slit one down through the side.
- Slide the full circle hose segment over the body of the pump…place about 1/3 of the way down from the top. Put the slit hose segment over top of that one.
- Slide the pump with hose shims into the rubber mount collar from the bottom, making sure it protrudes from the top.
- Slide the pump into the mount bracket from the top. It takes a little jiggling to get the filter through the hole where it can then flare out. Note the orientation of the power terminals before pressing the assembly into place. I set it so the terminals were toward the rear of the bike.
- Slide the plastic flange over the mount studs. Put the collar washers in place, then the nuts and tighten the mount flange in place. Check that the pump is firmly grasped by the rubber collar.
- Connect the fuel line to the outlet nipple and install the clamp being sure it does not touch or interfere with the electrical connections.
- Slip the white wire connector over the positive terminal and the black over the negative.
- Reconnect the battery.
- Test start the bike.
- If it runs, remount the gas cap.