BMW K bikes (Bricks)

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MikeisonTV

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Bottom 7.5 fuse keeps blowing and now fuel pump isn't working. Are these too the same problem? As in, does the fuel pump need that fuse to power (spin)?

What can I do to figure out why that fuse keeps popping?

Thanks gents.


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RicK G

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The #7 fuse feeds the horn relay and the flasher unit. It should have no bearing as to the fuel pump working or not.
Check the 4 pin plug that goes to the tank they are noted for problems, you may need to squeeze the female pins so they make good contact or just cleaning it may work. I have replaced two of those over the years with 4 pin 6mm automotive type connectors and have had no more trouble.
As for the fuse blowing you will need a good circuit diagram to chase the problem down. If you need one PM me and I will give you a link.


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If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

MikeisonTV

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I'll try the 4 pin under the tank in the morning and see if the pump will spin. She just slowly choked out and died. Gas was pretty low so I hoped that was the culprit turns out to be more. Please do send the diagram link for the fuse when you get a second. Thank you so much Rick.

PM sent


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kennybob

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The fuel pump runs on fuse #6, which it appears you are missing.

    

Holister

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MikeisonTV wrote:Bottom 7.5 fuse keeps blowing and now fuel pump isn't working. Are these too the same problem? As in, does the fuel pump need that fuse to power (spin)?
I think Mike is referring to the "bottom 7.5amp fuse" which is #6 (the missing one).
If this is the case then the fuel pump windings or fuel level sender may be shorted. Fuse #6 also goes to the temperature controller. Try pulling the temp controller first and see if the fuse blows. Then disconnect the pump or visa versa. It's likely going to be the pump. When did you last change the fuel filter?


__________________________________________________
1988 K100RT VIN No. 0094680
1989 K100RT VIN No. 0097367 (naked)
1996 K1100RS VIN No. 0451808
Fuel: 95 Octane
Engine Oil:Nulon Full Synthetic 15W50
Gear Box Oil: Nulon Synthetic 75W90
    

duck

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To test the fuel pump you can jump 12V directly to it. The smaller diameter terminal on the pump is 12V+.

Probably a good idea to make a point of not creating sparks in the fuel tank when doing this. i.e. Connect leads to the fuel pump first, then your power supply outside of the tank.


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Current stable:
86 Custom K100 (standard fairing, K75 Belly pan, Ceramic chromed engine covers, paralever)
K75 Frankenbrick (Paralever, K11 front end, hybrid ABS, K1100RS fairing, radial tires)
86 K75C Turbo w/ paralever
94 K1100RS
93 K1100LT (x2)
91 K1
93 K75S (K11 front end)
91 K75S
14 Yamaha WR250R
http://www.ClassicKBikes.com
    

kennybob

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delete



Last edited by kennybob on Thu Jun 23, 2016 10:33 pm; edited 5 times in total

    

Holister

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Mike. Does the fuse blow....

  1. As soon as you put it in
  2. When the ignition key is turned on
  3. When you press the starter







EDIT: due to kennybob's post being completely altered, I've deleted my response because it was not relevant.



Last edited by Holister on Thu Jun 23, 2016 8:16 pm; edited 1 time in total


__________________________________________________
1988 K100RT VIN No. 0094680
1989 K100RT VIN No. 0097367 (naked)
1996 K1100RS VIN No. 0451808
Fuel: 95 Octane
Engine Oil:Nulon Full Synthetic 15W50
Gear Box Oil: Nulon Synthetic 75W90
    

Inge K.

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kennybob wrote:The radiator fan is likely locked up and the stall current is blowing fuse #6.

The fan motor is protected by fuse #7, beside the fuel pump fuse #6 protects the PCB inside the temp management relay.


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Inge K.
K100RS -86. (first owner), K1100LTSE -94.
    

MikeisonTV

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I meant to update sooner. RICK nails it again...tighten up the 4 pin connector under the tank...she fired right up.Cool


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Yep! I'm flipping through the air....that ain't good.
    

Holister

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kennybob wrote:Just to quickly test if the pump is working and to avoid sparks in the tank, with the key off, you could put a jumper wire from the right-hand side of fuse 4 to the left side of fuse 6 to put power to the fuel pump.

This is a test, it is only a test. Do not try to operate in such a manner.
The proper way to test the pump is to isolate it first, away from the circuit that's causing the short. In any case the fuse would blow straight way again so you'd be none the wiser. Don't even think about trying that without a fuse.


__________________________________________________
1988 K100RT VIN No. 0094680
1989 K100RT VIN No. 0097367 (naked)
1996 K1100RS VIN No. 0451808
Fuel: 95 Octane
Engine Oil:Nulon Full Synthetic 15W50
Gear Box Oil: Nulon Synthetic 75W90
    

Holister

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MikeisonTV wrote:I meant to update sooner. RICK nails it again...tighten up the 4 pin connector under the tank...she fired right up.Cool
most often its the simple solution. Onya rick.

So whats causing the fuse to blow?


__________________________________________________
1988 K100RT VIN No. 0094680
1989 K100RT VIN No. 0097367 (naked)
1996 K1100RS VIN No. 0451808
Fuel: 95 Octane
Engine Oil:Nulon Full Synthetic 15W50
Gear Box Oil: Nulon Synthetic 75W90
    

MikeisonTV

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Holister wrote:
MikeisonTV wrote:I meant to update sooner. RICK nails it again...tighten up the 4 pin connector under the tank...she fired right up.Cool
most often its the simple solution. Onya rick.

So whats causing the fuse to blow?
The fuse seems to be ok now

I reconfigured my DIY mustang fuel pump design by:

1: gutting a dead BMW fuel pump for the metal housing
2: I bought a Carquest E2024 fuel pump from eBay seller Herko andGenuine Walbro Fuel Pump Sleeve 122-3074submersiblefoam noise suppressor sleeve oneBay
3: the pump fits super snug in the sleeve, the sleeve then super snug in the gutted BMW pump housing. Since the black rubber on the pump mount has been falling apart over the years...I cut the "distended rubber off at the bottom. I added a screw tightening o clamp to the top for addedsecurity.


My guess is the first shitty design I had was maybe shorting the fuse as one of the wires might have touched the other when it fell through theorginal mount...but I'm more of a designing brain and a wrench than an electrician...


Finally bought a TRUE RMS multimeter so I can stop shying away from electrical gremlins like you pros


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Yep! I'm flipping through the air....that ain't good.
    

MikeisonTV

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duck wrote:To test the fuel pump you can jump 12V directly to it. The smaller diameter terminal on the pump is 12V+.

Probably a good idea to make a point of not creating sparks in the fuel tank when doing this. i.e. Connect leads to the fuel pump first, then your power supply outside of the tank.
That's exactly how I did it. I clean the pumps using the same DIY method used for cleaning the fuel injectors.

Using a battery, carb cleaner, and a tire valve stem like this:
(no need to melt if you drill the hole in the tire valve stem one size narrower than the red straw)


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