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R1100 Fuel Pump No Prime / No Low Fuel Light


Jim Moore

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Hi Guys,

 

I took my tank off yesterday to do some other work. Now I'm having some sort of electrical problem with the fuel system. The pump won't prime and I have no low fuel light (tank is almost empty).

 

I have checked several things so far. I'm looking for ideas at this point.

 

The sidestand is up. The RID functions. The engine turns over.

 

I've swapped the fuel pump relay and the horn relay. No help.

 

I briefly have power to the green wire at the connector when I turn the key on. I think that is correct.

 

I have continuity from the green wire to the fuel pump terminal inside the tank.

 

I swapped for a known-good fuel pump. It didn't help.

 

I'm looking for ideas here. I'm wondering about the ground coming out of the fuel plate. Which wire is the ground? How can I check to ensure that wire isn't broken? Other ideas?

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Hi Guys,

 

I took my tank off yesterday to do some other work. Now I'm having some sort of electrical problem with the fuel system. The pump won't prime and I have no low fuel light (tank is almost empty).

 

I have checked several things so far. I'm looking for ideas at this point.

 

The sidestand is up. The RID functions. The engine turns over.

 

I've swapped the fuel pump relay and the horn relay. No help.

 

I briefly have power to the green wire at the connector when I turn the key on. I think that is correct.

 

I have continuity from the green wire to the fuel pump terminal inside the tank.

 

I swapped for a known-good fuel pump. It didn't help.

 

I'm looking for ideas here. I'm wondering about the ground coming out of the fuel plate. Which wire is the ground? How can I check to ensure that wire isn't broken? Other ideas?

 

 

Morning Jim

 

If your problem happened since the tank work then it probably isn't the pump relay.

 

Brown wire is ground so check continuity from pump harness connector brown wire to battery (-) post. If OK there then check right at pump (-) terminal to battery (-) post with pump plugged in.

 

In checking pump prime remember that you only get about 2 seconds of power to the pump then no more power until engine starts cranking.

 

You can do a quick pump 12v power circuit check by looking for power on a fuel injector green/white wire (pump & fuel injectors are on same relay power circuit) but not same low (ground) circuit.

 

 

Edited by dirtrider
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Hi DR,

 

Thanks for getting back so quickly. You reminded me so something that was puzzling me earlier. If the brown wire is the ground I should have continuity from one of the fuel pump terminals to the brown wire at the connector, right? I think I have an open there.

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Hi DR,

 

Thanks for getting back so quickly. You reminded me so something that was puzzling me earlier. If the brown wire is the ground I should have continuity from one of the fuel pump terminals to the brown wire at the connector, right? I think I have an open there.

 

Morning Jim

 

Yes the brown wire should have continuity from pump (-) to pump pass through terminal then on to pig tail brown wire terminal.

 

I have seen more the couple that had an open in the pump pass through connector (usually a failed solder connection) right where it passes from inside tank to outside of tank.

 

If yours is failed there post back as there is bubba type fix for that.

 

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That's it. No continuity between the negative post and the brown wire. How would bubba fix this?

 

Morning Jim

 

First off, see if you can find a solder connection failure. Maybe you can repair that.

 

The bubba fix is to find an open spot on the pump pass through plate that won't interfere with other things , then drill a hole to accept a brass stud (# 6 or #8 long brass screw with head cut off).

 

Put the stud through that drilled hole with a fuel proof sealing washer on each side with brass nut on each side (use fuel proof sealer on the stud in the pass through hole & on the threads where the nuts tighten on the stud & bear on the fuel proof washers)

 

You should end up with a leak proof brass stud sticking out each side of the pump pass through.

 

Now cut the brown wires & crimp (& solder) an eye ring on the brown wires & install on brass stud.

 

I have also seen the brown wires inside the tank cut, small eye ring installed then screwed to the pass through inside the tank, then the brown wires on the outside cut with an eye ring installed & bolted under a pass through retaining screw with a star washer to assure good continuity.

 

You get the idea per the above so be creative with what you have on hand to work with.

 

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I'm picturing what you're saying, but I have another question. The pump is grounded to the plate itself, via a white wire, so the plate itself becomes the ground. Can I just put an eye ring on one of the existing fasteners and run a new wire to the connector?

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I'm picturing what you're saying, but I have another question. The pump is grounded to the plate itself, via a white wire, so the plate itself becomes the ground. Can I just put an eye ring on one of the existing fasteners and run a new wire to the connector?

 

Afternoon Jim

 

You can sure try it, most BMW pump pass through's of that era do have a secondary ground to the pump pass through plate.

 

If your low fuel light or fuel gauge doesn't work then you have to verify those is on the ground lug also.

 

 

 

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The wiper and the pump are both grounded with a single wire to a small screw on a bracket on the plate. I don't see any other grounding points or wires. I'm gonna try it.

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The wiper and the pump are both grounded with a single wire to a small screw on a bracket on the plate. I don't see any other grounding points or wires. I'm gonna try it.

 

Afternoon Jim

 

Just make darn sure that the external ground connection to the pass through plate is solidly TO the plate & not just the screw (or to screw with resistance to the plate).

 

The pump draws a fair amount of current so you don't want the screw connection to heat up & melt the screw seat in the tank.

 

 

 

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OK, thanks. Well, at first glance it looks like that worked just fine. The pump primes and the bike starts and runs. Interestingly I have a low fuel light, but no fuel gauge. So something isn't quite right. Oh well. On a 24 year old bike with 157K miles, that's not a problem. It's a feature.

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OK, thanks. Well, at first glance it looks like that worked just fine. The pump primes and the bike starts and runs. Interestingly I have a low fuel light, but no fuel gauge. So something isn't quite right. Oh well. On a 24 year old bike with 157K miles, that's not a problem. It's a feature.

 

Afternoon Jim

 

Did you plug the fuel gauge float pig tail plug into the connector on the inside of the pass through (easy to forget).

 

If the float is plugged in then make sure that you didn't lose the float assembly ground as it comes out of the tank on the other little separate pig tail then ties into the main ground brown wire outside of the tank.

 

 

 

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Thanks for the info. It's actually working fine. I didn't put enough gas in to register on the gauge so I thought the gauge wasn't reading. I just filled up and it's working perfectly. Thanks again for all your help.

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Eckhard Grohe
Put the stud through that drilled hole with a fuel proof sealing washer on each side with brass nut on each side (use fuel proof sealer on the stud in the pass through hole & on the threads where the nuts tighten on the stud & bear on the fuel proof washers)

 

D.R.

 

Have you got a name brand for the fuel proof sealing washer and sealer???

 

Thanks

Edited by Eckhard Grohe
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Put the stud through that drilled hole with a fuel proof sealing washer on each side with brass nut on each side (use fuel proof sealer on the stud in the pass through hole & on the threads where the nuts tighten on the stud & bear on the fuel proof washers)

 

D.R.

 

Have you got a name brand for the fuel proof sealing washer and sealer???

 

Thanks

 

Evening Eckhard

 

Sort of, maybe, guidance only/

 

Personally I have a very large collection of assorted copper washers, small carburetor washers (remember those?), etc. So I just search my stock for something that works.

 

Without access to a good junk drawer then probably trip to the auto parts store or online to find a couple small diameter copper washers, of make a couple by drilling copper stock (we know this is fuel proof).

 

For the fuel resistant sealer I have a good product but it is a commercial offering that doesn't have a consumer name or part number on it but it is real close in looks & feel to Permatex PermaShield Fuel Resistant Gasket Dressing so I'm guessing it is some sort of a commercial version of that product.

 

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