Author Topic: 1990 K75s not starting (Read 17595 times)

wayside · « **on:** June 07, 2015, 02:47:18 PM »

put in new battery yesterday, turns over strong but won't fire. Seems I'm not getting gas. sounds like my fuel pump is running when it turns over. when I turn on the ignition I don't hear the normal buzzing sound. any idea's?

thanks!

johnny · « **Reply #1 on:** June 07, 2015, 02:51:44 PM »

greetings wayside...

welcome to motobrick.com...

wanna make sure i understand... it was running... you installed a new battery... now it doesnt run...

is that right... anything else you oughtta tell us...

j o

wayside · « **Reply #2 on:** June 07, 2015, 02:56:43 PM »

was running when I put it away for the winter, Knew I needed new battery last fall. This is the first time trying to start this year. Only 7200 miles, but I make sure to run it several times a summer. Always runs good. Have the tank off, tried tapping the relay, didn't help.

johnny · « **Reply #3 on:** June 07, 2015, 03:00:28 PM »

so... you have done nothing except the battery...

now you have the tank off tapping the relay...

if your starter relay is stuck it would turn over once you turn the key on and keep turning over and over when you turn the key off...

is that happening...

j o

wayside · « **Reply #4 on:** June 07, 2015, 04:22:04 PM »

nope not happening. guess I forgot what the tapping was for, remember doing it years ago when starting with a worn out battery. Like I said turns over strong but doesn't pop.

johnny · « **Reply #5 on:** June 07, 2015, 04:30:31 PM »

if you are sure you gotts all the battery wires back on and there good their terminations are good... the easiest thing is to remove the jetronic connector... clean all the contacts on both ends and reseat it... do the same with the under tank fuel pump connector... then give it a go...

if it goes... yeeeehaaaaa... if not... gotts to make sure you gotts fuel pumping to the rail and spark at the plugs and go from there...

how old is your fuel... fuel filter... is it no corn ethyl or ethanol regular...

j o

wayside · « **Reply #6 on:** June 07, 2015, 04:44:27 PM »

anything special to clean it with. Gas form last year, I'm sure its 10% ethanol. Plan on empting gas tank.

thanks for the help, I'll let you know what I come up with.

thanks J o!

johnny · « **Reply #7 on:** June 07, 2015, 08:54:45 PM »

this and a toothe brushe...

j o

wayside · « **Reply #8 on:** June 12, 2015, 02:53:13 PM »

Johnny, cleaned the connectors up, still nothing. Just to make sure the Jetronic connector is the silver box under the seat, right? Should have confirmed before I started. If I did it correctly what's my next step?

When I turn on the ignition, shouldn't there be a buzzing sound?

here's a picture of the connector I cleaned. Should there be an empty slot?

Scott_ · « **Reply #9 on:** June 12, 2015, 06:26:24 PM »

From what I have read of others with a K75, the fuel pump won't prime when just the key is turned on.
The pump will energize when the starter button is depressed and will stay energized so long as engine rotation is sensed by the hall effect sensors.

johnny · « **Reply #10 on:** June 13, 2015, 05:22:42 PM »

yes that is the connector... like scott_ said... the pump on a 750 wont pressurize until the you press the start button with the key on...

you gotts spark on the plugs and fuel at the rail...

j o

rbm · « **Reply #11 on:** June 13, 2015, 07:33:00 PM »

You should hear the fuel pump "buzz" for 1.5 seconds after the start button is released. If not, the electrical connection to the tank would be suspect.

wayside · « **Reply #12 on:** June 14, 2015, 01:01:27 PM »

Think I found the problem!

Any tricks for pulling the air filter box?

billday · « **Reply #13 on:** June 14, 2015, 01:47:09 PM »

Quote from: wayside on June 14, 2015, 01:01:27 PM

Think I found the problem!

Any tricks for pulling the air filter box?

Maybe you don't even need to pull the airbox, if you can get a strong vacuum cleaner in there. But if you do need to pull it, my advice is to leave the top half in place. After you get the air filter out and pull the top half up and away (maybe using a couple of bungee cords), you'll have *just* enough room to get a small hand in there with an allen wrench to undo the bolts that fasten the bottom half of the airbox to the top of the engine block.

Search for the threads on intake or throttle body refurb and you'll find more on the topic.

Beemer Boneyard usually has a good price on air filters.

wayside · « **Reply #14 on:** June 14, 2015, 02:53:28 PM »

Thanks, once I got the filter out I was able to get a vacuum and got it all cleaned out. Pulled plugs and have good spark, 1 and 3 were wet, 2 not so much. With gas on the plugs I would think it would at least pop when turning over. I'm open for suggestions.

thanks!

kris · « **Reply #15 on:** June 14, 2015, 05:13:37 PM »

Wow, truly a rat's nest!! Incredible. But still no run, eh?

wayside · « **Reply #16 on:** June 14, 2015, 05:22:57 PM »

Kris, you would not believe what came out! I felt a little relieved too find it, I thought it was going to start. the last thing I want to do is have the BMW dealer trailer it in. there's so much good info here, hope I can get her going, Its always run like a top. Its a clean machine!

Bill

rbm · « **Reply #17 on:** June 14, 2015, 08:33:09 PM »

You still haven't confirmed whether you've checked the fuel pump connection under the right hand battery cover. Can you confirm that, when you attempt to turn over the motor, the fuel pump busses for 1.5 seconds after releasing the start button? Wet plugs might be an indication that the fuel pump and injectors are operating.

If your fuel pump is operating, then the next port of call is to confirm that sparking is happening at the spark plugs.

Have you done anything to the electrics prior to the bike failing? When you use phrases like "...the normal buzzing sound...", I get a sense that everything with the bike was working normally for a period of time and then suddenly it stoped working.

wayside · « **Reply #18 on:** June 15, 2015, 07:53:05 AM »

Robert, I do have spark, all I've done is replace the battery, and new gas. Have cleaned jetronic connector.

wayside · « **Reply #19 on:** June 16, 2015, 08:44:50 PM »

To all, new battery, first start for 2015, turns over strong but not starting. Advice from Johnny, cleaned jetronic connector and connector right side under gas tank. Looking at other post found rats nest in filter box, cleaned out, new air filter, new gas. Have spark on all three plug, 1 and 3 were wet with gas, 2 was hard to tell.

Motorhobo · « **Reply #20 on:** June 17, 2015, 09:58:34 AM »

Check fuel filter -- if flow is restricted you'll get gas but not enough flow at the injectors for sufficient spray.

wayside · « **Reply #21 on:** June 17, 2015, 10:36:17 AM »

Do I need to pull the tank to check the fuel filter?

Motorhobo · « **Reply #22 on:** June 17, 2015, 01:11:07 PM »

No, I don't think so, but I think you should siphon as much gas out as you can. I usually just pull it off -- easier to work on it and get light in there when it's on the bench or a well-lit workspace. It also really helps to hAve one of those miners light things you strap to your forehead.

wayside · « **Reply #23 on:** June 28, 2015, 11:09:15 AM »

Have Bert's guide printed out, tank off, have my ohm/volt meter. I'm on the left side of the flow chart, fuse good, power to pin 86, could use some direction moving down the chart.

is it possible to bump the fuel pump with wire from pos. battery to fuse? If so would that tell me that the pump is bad?

thanks,
Bill

rbm · « **Reply #24 on:** June 28, 2015, 11:40:01 AM »

You should also have a schematic diagram available to reference, most notably to understand the wire colour codes.

At the point you're at in the flow chart, look for power on the Green/Yellow wire (relative to ground) on the FI relay. This is pin 86. Have you successfully identified the FI relay I should ask?

K75 schematic

At the next step, you're looking for 0V on the yellow/purple wire (pin 85) of the same relay and ground on pin 7 of the ECU under the seat.

Next step, if the first two previous steps are passing, you're looking for +12V on either or both of the green/red wires off the FI relay (pins 87 and 87a)

You can apply power directly to the fuel pump BUT first connect a very long wire from the pump positive. Don't start touching a live wire to the pump inside the tank. You could even remove the pump from the tank and test on the bench with another battery. You don't want sparks near the fuel fumes.

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Author Topic: 1990 K75s not starting (Read 17595 times)