1988 K75 C Fuel Pump Problem

1988 K75 C Fuel Pump Problem "UPDATE"

Took bike out for a ride and it suddenly stopped. Got it back home and done the following.
1. No gas to fuel rail
2. Checked fuses and NO JUICE going to the fuel pump fuse.. All other fuses have juice , bike cranks lights work etc.

Where is the fuel pump relay found? Is there one ?
Someone mentioned a connector by the tank may be loose ?? Location? Size ?
Thanks for looking

bikerboy108 said:

Took bike out for a ride and it suddenly stopped. Got it back home and done the following.
1. No gas to fuel rail
2. Checked fuses and NO JUICE going to the fuel pump fuse.. All other fuses have juice , bike cranks lights work etc.

Where is the fuel pump relay found? Is there one ?
Someone mentioned a connector by the tank may be loose ?? Location? Size ?
Thanks for looking

Click to expand...

The fuel pump connector comes from the bottom rear of the tank, crosses under the right frame rail just forward of the engine computer holder and plugs into the harness near the right rear of the fuel tank.

Bikerboy,

Be aware, power goes to the fuel pump ONLY when you are pushing on the starter button (and for a couple seconds after) OR when the engine is running (engine is spinning without the starter button being pressed). This shuts off the pump if the engine is not running or trying to be started.

98lee said:

Bikerboy,

Be aware, power goes to the fuel pump ONLY when you are pushing on the starter button (and for a couple seconds after) OR when the engine is running (engine is spinning above around 750 rpm which is above starter speed). This shuts off the pump if the engine is not running or trying to be started.

Click to expand...

but there was NO power indicated to fuel pump fuse .. shouldn’t that show hot with key on????

that 4 wire connector is a known problem area. I had to replace mine on a K75 I used to have. I used a flat trailer wire connector. Check that you are getting continuity .

bikerboy108 said:

but there was NO power indicated to fuel pump fuse .. shouldn’t that show hot with key on????

Click to expand...

Bikerboy,


No. The fuel injection relay (which provides power to fuse #6) is only activated when the Ignition Control Module sees that the starter button is being pressed OR that the engine is running (spinning without the start button being pressed). The Ignition Control Module provides the ground for the pull in coil on the relay.

The more I learn about my K 75 RT electrical system the more I think it was designed during Oktoberfest.
YMMV
Nick

nickrides said:

The more I learn about my K 75 RT electrical system the more I think it was designed during Oktoberfest.
YMMV
Nick

Click to expand...

By the intern they left in the office.

Update

Took pump out of Tank and put 12 v to it No Go it doesnt spin

1. Is there and automotive pump that fits?? Dont really want to spend alot as its only a runner.

2.The pigtail that runs to the fuel gauge and and supplies power to the pump also looks comprimised. I seems like you have to buy the whole unit ??? $379 ?? WTF any alternatives?

3. Before I put the whole thing back to together I would like to test the new pump in the tank to make sure pigtail still transmits power to the new pump what two wires transmits power to the pump ? Green ?? and ??

Bikerboy,

Check out the Kbike DIY/Tech Library at the top of the Flying Brick Section for the answers to your questions.

https://forums.bmwmoa.org/forumdisplay.php?54-K-bikes-DIY-Tech-Library

98lee said:

Bikerboy,

Check out the Kbike DIY/Tech Library at the top of the Flying Brick Section for the answers to your questions.

https://forums.bmwmoa.org/forumdisplay.php?54-K-bikes-DIY-Tech-Library

Click to expand...

2 great articles in the tech library Thanks but 2 questions one on Fuel pump and one on the fuel pump/level sensor wiring..

1. Fuel Pump - the link to Euro moto electric for the 37 mm no longer works and it seems the company no longer sells the 37 mm fuel pump ? Neither does BB.... So is there a auto one that fits and reduces the 52 mm damper opening down to 37 Or another aftermarket motorcycle company that does...

2. Level Sensor wiring.. So no way to fix that wiring except buy new or DIY ?? I saw one response said they use a trailer connector and wired it in
Thanks for the articles

If the issue is the connector, then replacing it with any 4 pole connector works fine. If the issue is the pass-through at the tank then that does nothing. I have had both conditions and just this spring had to spend the $$$ for a new tank assembly.

PGlaves said:

If the issue is the connector, then replacing it with any 4 pole connector works fine. If the issue is the pass-through at the tank then that does nothing. I have had both conditions and just this spring had to spend the $$$ for a new tank assembly.

Click to expand...

thanks for # 2 any swaps for the pump to a 37 mm electric moto no longer sells them

1. Fuel Pump - the link to Euro moto electric for the 37 mm no longer works and it seems the company no longer sells the 37 mm fuel pump ? Neither does BB.... So is there a auto one that fits and reduces the 52 mm damper opening down to 37 Or another aftermarket motorcycle company that does...

Bikerboy,

The passthru part of the fuelsender assembly can be repaired. The failure is usually a broken wire or solder joint. The inside solder terminals are visible. The outside terminals require breaking apart the outside plastic cover and then covering the exposed terminals with some non-conductive potting or silicone.


Either of the aftermarket pumps that Euromotoelectrics sell will work fine if you couple them with the correct size damper and bracket. There are loads of aftermarket pumps on fleabay, but you still need the correct damper assembly for whatever size you choose.



:

bikerboy108 said:

thanks for # 2 any swaps for the pump to a 37 mm electric moto no longer sells them

1. Fuel Pump - the link to Euro moto electric for the 37 mm no longer works and it seems the company no longer sells the 37 mm fuel pump ? Neither does BB.... So is there a auto one that fits and reduces the 52 mm damper opening down to 37 Or another aftermarket motorcycle company that does...

Click to expand...

'Er ya go mate....
https://www.ebay.com/itm/3823079415...r3CcWUqhLotEwBRnGm6olyYp7RX0|tkp:BFBMzM36lvtg

I put one of these in last night. It sure looks like the one that EME sells. Now we see how long it lasts.
This has all of the goodies to make the inside sparkle again except fuel line. I priced the hose at O'Riley's at $80 for 3'!!! I know I live in a cave, but when did submersible hose become a precious metal? Our local Beemer parts person sent me out the door for $44.

It's worthwhile to just zero time the tank components for piece of mind. One more thing to cross off the list.

Good hunting.....
Dan'l

K75 fuel power line test

For most of these K75, the petrol gauge electrical connector at the flange goes bad. I have this problem now, trying to solder the wire is tough because there is very little to solder too. That's another issue. If anyone has a used one for sale (PETROL GAUGE - 62162305558), I would be interested in buying. I am still going to try to fix that terminal issue. But as for testing the fuel pump, here are couple of ways.

The standard wiring on the 4 wire connector for the fuel pump is brown and green. The brown goes to ground (large terminal on the pump), green to the pump power (small terminal on the pump). While it is true that the relays and all the safety circuits work to only allow the pump to run under the correct conditions, for purposes of testing that the pump, and the fuel lines are working you can do the following.

The resistance test method:
Take an ohm meter and first check large terminal on pump and that it goes to ground, metal from and or battery black terminal, if you get a low resistance under 1 ohm (test your meter by shorting the two wires to get your baseline resistance through your cable). Once that is confirmed continue. Next test the green wire to small pump terminal the same way. Next use the meter, the resistance between the green and brown should be 2-4 ohms. If it is more, most likely the pump maybe be the issue.

First the Safety cautions: don't connect power and then attempt to connect a wire inside a tank with fuel as a spark could cause serious harm and/or death.

The power test method:
If you are not getting a good ground, make and connect a ground wire from the pump large terminal to the frame. Make a wire with the correct crimp connector (small terminal on pump), connect to pump, put a fuse in-line with a switch and then wire to +12v. If you turn power switch on, then the pump should turn turn on and if you have the ignition switch on, the bike should run, if it does, you have to repair or replace the float assembly, if it does not run, you may have a bad pump.

Hope that helps. Just be careful when connecting wires inside the tank if there is fuel.