Riding fine, then bike died

[rocketbrick]

So, I was riding about two weeks ago on a fairly hot day to a local bar. The parking lot was gravel/dirt and I didn't have good leverage for center stand, so I popped it on the side stand. It sat there for about an hour or two before I rode about 15 mins home. About 10 mins into my ride, the bike died and wouldn't start back up. Cranked, battery charged and fine, but it wasn't getting fuel. I suspected vapor lock because I left it overnight and returned in the morning, and was able to get it home.

Cut to today - charged the battery, changed the fuel and vacuum lines, changed the pump, still no start. It got close a couple times, and started a few times in the past few days, but it was in my garage. Today, it was sitting outside.

Bike is a 1988 BMW K75C. I heard it could be the hall effect sensor, but I've got no idea. ODO is at approx 67,500

Where do I start? Any advice?

UPDATE: 9:43PM. Tried starting, nothing. Cleaned the connections on the ignition switch and it made no difference.

[Laitch]

If a Brick cranks but doesn't start, check the spark plugs. Are they wet or dry? That's the place to start. When you crank it then stop, can you here the fuel pump whine for a couple of seconds? That's normal. If you don't hear it check fuse # 6 to verify if its wire is broken. If you suspect vapor lock, open the tank and try starting it. Sometimes that overcomes the lock.

[rocketbrick]

What's up, Laitch?

The plugs are dry and getting spark - I tested them last night. I can't hear the fuel pump whine at all, so that makes me think it's something electrical after all. Fuse # 6 you say? I'll check it shortly.

[rocketbrick]

If a Brick cranks but doesn't start, check the spark plugs. Are they wet or dry? That's the place to start. When you crank it then stop, can you here the fuel pump whine for a couple of seconds? That's normal. If you don't hear it check fuse # 6 to verify if its wire is broken. If you suspect vapor lock, open the tank and try starting it. Sometimes that overcomes the lock.

Fuse #6 is the 6th one down on the side fuse box, yeah?

EDIT: 8:02AM - I’ve got an update. It’s 100% not getting fuel from the pump. I was able to start it for a split second today and it ran before it inevitably died. Some fuel must have slipped down the line past the pump. I unplugged the pump and still got a momentary start and run out of it.

So, fuel pump is not getting power. It's a new pump and it's hooked up correctly, so that has to mean relay or fuse, right?

[frankenduck]

Fuel tank connectors can be an issue.

Take that connector apart. You should get 12V on the GRN/WHT wire when the starter button is pressed and the engine is turning. That will tell you if the problem is upstream or downstream of the connector.

[rocketbrick]

Fuel tank connectors can be an issue.

Take that connector apart. You should get 12V on the GRN/WHT wire when the starter button is pressed and the engine is turning. That will tell you if the problem is upstream or downstream of the connector.

I've got the cranking volts of the GRN/WHT wire, so it doesn't seem to be the issue. I did just recently replace the fuel sender since this bike came with it deleted. I suppose the issue could be there, since used parts?

[frankenduck]

You can use ring terminals to jump power to the fuel pump from the green/white and brown wires in order to bypass the connector and fuel level sender. (The smaller diameter terminal on the fuel pump is 12V so should connect to the green/white wire.)

[rocketbrick]

You can use ring terminals to jump power to the fuel pump from the green/white and brown wires in order to bypass the connector and fuel level sender. (The smaller diameter terminal on the fuel pump is 12V so should connect to the green/white wire.)

Gotcha - I'm a bit of a backyard mechanic, so I'm learning a little at a time. What should I use to jump from the connection wires to the fuel tank? Should I just splice them?

[frankenduck]

I used Posi-Taps when I did that. (DO NOT use Scotchloks.)

[rocketbrick]

OK! I've got some new fuses I'm going to try first, then I'll give this a try. Thanks for the info - I also checked the relay and it looks brand-spanking new, so definitely no problem there.

[frankenduck]

If you're getting 12V at the GRN/WHT wire when the engine is turning then #6 fuse and FI relay are working.

[The Mighty Gryphon]

You can have 12v at the tank connector socket on the harness, but it might not be getting to the pins on the plug that comes from the tank.  That is a fairly common problem.  Clean the connector with Deoxit and tweak the pins a tiny bit to help them make better contact in the socket.

It's also possible that a wire is broken where it enters the tank.  That is a tougher problem to fix.

[rocketbrick]

The bike came w/ the fuel float deleted, so I still have the plate I can replace it with.

I'm really hoping it's not the dumb fuel float, I spent too much money on that thing  time to get some posi-taps!

[frankenduck]

You can have 12v at the tank connector socket on the harness, but it might not be getting to the pins on the plug that comes from the tank.  That is a fairly common problem.  Clean the connector with Deoxit and tweak the pins a tiny bit to help them make better contact in the socket.

It's also possible that a wire is broken where it enters the tank.  That is a tougher problem to fix.

A lot of times it fails inside of the tank side connector. Hence the trailer wire repair:
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/fls.connector/fls.connector.htm

[The Mighty Gryphon]

A lot of times it fails inside of the tank side connector. Hence the trailer wire repair:
http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/fls.connector/fls.connector.htm

True.  Good point.

[rocketbrick]

So, going to get the posi-taps and give testing the connector a shot.

I'd like to replace the connector - can it be done with something like this?

https://www.amazon.com/Lonlonty-Aviation-Connector-Industrial-Waterproof/dp/B09YLP4JFY/ref=sr_1_28?crid=RM82IIAPNFQ9&keywords=4%2Bpin%2Bconnector&qid=1691453372&sprefix=4%2Bpin%2Bconnector%2Caps%2C84&sr=8-28&th=1

[Laitch]

I'd like to replace the connector - can it be done with something like this?

That's a helluva connector there, rocketbrick, and is likely to work fine, but it's overkill. There are less complex connectors than the one in your link and these are some examples of them.

The trailer connector that frankenduck links to in Reply #13 has done the job for generations of trailer lights working in much worse conditions than being tucked under your Brick's fuel tank. It will be easier to disconnect than your example when you're lubing the rear drive splines—a task done yearly if your ride is a tool, not a toy. If it were me doing this, I'd use the difference in price for a meal in some far flung destination.   

[rocketbrick]

That's a helluva connector there, rocketbrick, and is likely to work fine, but it's overkill. There are less complex connectors than the one in your link and these are some examples of them.

The trailer connector that frankenduck links to in Reply #13 has done the job for generations of trailer lights working in much worse conditions than being tucked under your Brick's fuel tank. It will be easier to disconnect than your example when you're lubing the rear drive splines—a task done yearly if your ride is a tool, not a toy. If it were me doing this, I'd use the difference in price for a meal in some far flung destination.

Hah! The beefier the better for me. You mean the solder joint job, right? I'd go with that, but I just want the ease of removable connection. Plus, with my luck, I'd rather be bulletproof. But I like your thinking with the meal savings ;)

[Laitch]

You mean the solder joint job, right? I'd go with that, but I just want the ease of removable connection.

The 4-pin trailer connector is a removable connector. Those connectors replace what is there now. You could use Posi-locks to join the connectors to the wires, and rather than cut across the wires at the same place, the cuts could be staggered to make the total joint less bulky. Please post a photo of the job when you finish it and maybe a brief description of what you did.


Rather than worry about the connectors being bulletproof, maybe you should install a kevlar tank bra if there's that kind of threat where you ride. 

[Martin]

I recently purchased a kit of heat shrink waterproof connectors. Very easy to use, slide the connector over the wire, twist the wires together, slide the connector over the join and heat carefully with a lighter or mini gas torch. It produces a really nice waterproof connection.
Regards Martin.

Heat Shrink Connector Kit.jpg (36.75 kB . 768x432 - viewed 337 times)
Heat Shrink Connector.jpg (11.71 kB . 768x432 - viewed 321 times)

[rocketbrick]

The 4-pin trailer connector is a removable connector. Those connectors replace what is there now. You could use Posi-locks to join the connectors to the wires, and rather than cut across the wires at the same place, the cuts could be staggered to make the total joint less bulky. Please post a photo of the job when you finish it and maybe a brief description of what you did.


Rather than worry about the connectors being bulletproof, maybe you should install a kevlar tank bra if there's that kind of threat where you ride. 

Ahhhh, couldn't tell - only saw the soldered wires and not the connector in the background. Makes sense, I'll give that a shot!

[rocketbrick]

Hey y’all, did the trailer connector fix. Everything is getting power but it’s still not starting. I’m at a loss, no idea where to go from here 🤷

[Laitch]

Everything is getting power but it’s still not starting. I’m at a loss, no idea where to go from here 🤷

Does that mean you can hear the fuel pump whine for two seconds after you quit cranking the engine?

[rocketbrick]

Sorry, I wasn't clear - still no fuel pump power, I mean.

I used the voltmeter on the new trailer connection and I see it's getting the proper amount of voltage

[Laitch]

So everything doesn't mean everything, eh? I'll keep that in mind. 
Under what conditions is the connector to the pump getting 12V? Which wires are getting 12v? Is the starter running? Is 12V on both sides of the connector?