Fuel Issue Perplexed

[volador]

So to confuse me further, my repair manual says the FI is the far right relay.  Anyway, is swapped the right relays this morning with no change, so both are functional.  Fuel pump still kicks on, horn still works on either.  So the load shed is what was causing the pump to be non-op or full on.

another member of the VW Microbus club 

Some links for your K journey. Good Luck

Factory Service Manual, Torque Specs & Riders Manual download from the world famous Motobrick library

Just bought a 2V

Just bought a 4V

Check parts compatibility with BMW MAX Microfiche, BOBS BMW, REAL OEM

https://shop.maxbmw.com/fiche/PartsFiche.aspx

https://shop.maxbmw.com/fiche/PartsSearch.aspx

https://parts.maxbmw.com/BMW___BmwMotorradK.html

https://www.bobsbmw.com/store/microfiche/BrowseSeries.aspx

https://www.realoem.com/bmw/select.do?kind=M&arch=1

https://www.ascycles.com/BMW-Motorcycle-Parts-Fiche

Cross reference parts like Bosch pn#'s, etc....  http://partsplusecat.com/
No spaces in the part number

Parts Vendors

https://www.beemerboneyard.com/

https://www.capitalcycle.com/

https://www.euromotoelectrics.com/

https://www.tills.de/

Headlight relay stuff if you chose to add one

https://www.motobrick.com/index.php?topic=268.0

http://www.motobrick.com/index.php/topic,4962.msg30932.html

http://culayer.com/product/matchbox-headlight-relay/

http://easternbeaver.com/Main/Wiring_Kits/H4_Kits/h4_kits.html  Eastern Beaver site is a great reference for electrical connectors,plugs, etc...

http://www.k100-forum.com/

http://www.kforum-tech.com/Tech-page.html

http://www.kforum-tech.com/electrical/EFI/bike-wont-start-EN.htm

http://www.kforum-tech.com/Downloads/electrical/diagrams/interactive_diagrams.htm

http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/k100tshoot/K100.Troubleshoot.Start.2018.pdf

http://kbikeparts.com/index.htm

http://www.kbikeparts.com/classickbikes.com/ckb.tech/ckb.new2k.htm

http://www.kbikeparts.com/classickbikes.com/ckb.tech/ckb.tech.toc.htm

http://www.eilenberger.net/K75S/IgnitionSwitch/

http://www.verrill.com/moto/moto.shtml

this site has a lot of good info and breakdown pictures in the tech and tech resources sections for K1100 alot of the parts are on K75 & K100

http://www.k11og.org/forum/index.php?sid=2df953dde5715fd9001fbe69edec5ad0

https://ibmwr.org/index.php/k-bike-tech-articles/

This site has all kinds of technical specifications on all the BMW models    http://www.bmbikes.co.uk/mechanicalpages/kseriesmechanical.htm

http://largiader.com

http://bmwk10075abs1fix.web.fc2.com/index.html  Toshi ABS site

[Cherokee2072]

Thanks Volador for the comprehensive list. 

I removed my relay holders again just to verify vs the wiring harness/schematic.  The 5 pin relay on the left (at least on my 1987 k75s) that is extremely stock, is the FI relay.  That at least makes me feel a little less insane in my explanation for what gremlin I am chasing down.  TMG, your schematic as it refers to this particular motorcycle stands as correct.  Thanks! 

[daveson]

The relay box drawing in my Clymer manual (2007 edition) is wrong. The drawing in your earlier post is right, especially if it matches your bike. If you have ABS or something odd, it will be different again.

I know you said there was no power "to" the fuse,  but if no power at the fuse, replace the fuse. Prob good to replace regardless.

The horn relay shouldn't effect the pump,  if it really does, that points to an earth problem I think.

When it next fails, I'd test with a test light (a substantial one) to find where the power fail is.

[Cherokee2072]

I verified the actual wiring from the socket onward to eliminate any confusion.  100% confident in the FI relay location being correct at left hand position now.  Regarding  the fuse issue.  That was due to the faulty relay.  The issue now has been that the replacement relay was not the proper replacement.  Right one is on the way.  I’m still at a loss as to what started the issue in the first place.  Everything was well sorted and The bike was running pretty much perfectly.  Cannot find any rubbed wires, loose connections or corrosion.  Hopefully it was just time for the old relay to pass into the afterlife and all will be well. 

[daveson]

Check for a click if you connect a battery to pins 85 and 86, and give enough power (or at least continuity) from 30 to both 87 pins.

[Cherokee2072]

No click on the old one.  New one doesn’t have the correct internal bypass so it seems to be killing the pump circuit after the bike starts and it loses fuel pressure.  Going to update after I install the new (correct) relay. 

[daveson]

OK, looking good.

[Cherokee2072]

Update....


Received the correct spec relay today.  Started, ran perfectly.  Backed out of the shop.  Before the end of the drive, new relay is gone.  I am pulling it and testing tonight to find where the problem is which will hopefully lead me to what keeps eating them.  I have replaced the new fuel pump with a new fuel pump, verified grounds and checked for any frayed/rubbed wires.  If anyone has experienced this please chime in or make me an offer, lol. 

[Laitch]

If you haven't performed the ignition control unit and fuel injection control unit tests that were recommended back in Reply #4, now might be the time to do them. Post the results here that are not within the specified ranges.

[Cherokee2072]

I have initially, and they were in range.  I suspect I will have to purchase another relay to perform the tests again as the system will not power up properly without it. 

[Laitch]

One of the purposes of those tests is determin malfunction of either of the control units. According to your results, they're ok.

[Cherokee2072]

Laitch I’m leaning towards a possible short under the tank or in the sending unit.  It runs perfectly until it doesn’t, lol.  No miss across rpm range or cold/hot issues with idle so I believe all FI systems are functioning properly, it’s a simple short causing the issue.  Hopefully. 

[The Mighty Gryphon]

Is the failure in the relay's coil or the contacts? 

Did the coil burn out causing an open circuit so it can't close the contacts?  It's hard to believe a 12v relay coil would burn out on a 12v electrical system.  You need to check the continuity across the coil.

Or was it a heavy current that may have burned the contacts or possibly melted a solder joint in the relay? 

An autopsy on the failed relays is a good place to start troubleshooting.  It's the only way to know where you should be looking.

[daveson]

If it passes the click test out of the bike,  maybe it's just a failed earth (or power) On the bike.

[Cherokee2072]

In the process of disassembling both defective ones to sort it out now TMG.  The issue that prevented proper running with another relay didn’t lie in the coil, it was with pin(s) 87.  I left my electrical engineering degree in my other pants, so I’m reading up on this as I go.  I’m much better with points and a magneto than Jetronic.  But I am learning to read quickly. 

[The Mighty Gryphon]

Did you have continuity between pins 85 and 86?  What is the resistance across them in ohms?

Can you apply 12v to pins 85 & 86 with the relay out of the bike?  When you do do you get a very quiet click?  Do you then get continuity across pin 30 to the 87 pins?

[Cherokee2072]

TMG I am getting 105 resistance and I do get a click across 85/86.  No resistance from 30 to either 87 pin. 

[alexg]

If a heavy load is the cause to be frying the relays, why a fuse is not blowing? THere must be a fuse feeding pin 30. Can you check the rating of that fuse compared to the factory spec?

[The Mighty Gryphon]

Okay, the coil seems to be good.  I'm guessing that you are reading 105 ohms which means that the coil is getting about 125ma which sounds about right.

When you say no resistance between 30 and 87 do you mean it's infinity or is it 0.0 ohms?  When the coil is energized the resistance should be about 3-4 ohms or less, depending on how good your ohmmeter is.  My Harbor Freight meter never reads less than 3.5 ohms when the probes are connected together.

Another thing to check would be the resistance between the 87 terminals in the socket and ground.  That might help us see how much current is going through them.  That would give an idea of whether the loads on the contacts are shorted or open circuits.  Make sure the + lead of the meter is on the 87 pin and the - is on the ground.

[The Mighty Gryphon]

Alex, I was going to ask that same question.  It would be odd, though, that high current would be burning contacts rated for 30 amps.  Still, it wouldn't hurt to check the fuse ratings.

I need to check the schematics, but I'm starting to suspect the tank connector is whack.

[Cherokee2072]

Sorry guys, wife is under the weather, I had to abandon the cause.  The fuse is a 10 amp, without looking at my manual I believe the OEM was 7.5.   I hope that wouldn’t cause the sky to fall but the way this week/month/year has gone I wouldn’t doubt it.  I’ll get back to it tomorrow evening and dig deeper.  I did get to look at the wiring diagram and that 87 circuit basically runs the gamut of every Red/green wire from the fuse block one one side of the relay to the injectors/tps/all the way through on the back end.

[rbm]

@alexg:  There is no fuse on the Red wire going to Pin 30 of the FI relay. So, if there is a large load (i.e. short circuit) on one of the circuits being fed from pin 87, then there is nothing to limit the current flowing through the relay contacts. 

@cherokee:  Your task should be to isolate all the circuits fed by the FI relay and start searching for a short to ground.  It's probable that the high current situation may have melted insulation on the wiring inside the harness.

Pull fuse 6, pull the temp sensing module from its socket and and disconnect the tank connector. Start testing the continuity between the Green/White wire and ground on that isolated circuitry. You're looking for a short to ground.  You shouldn't read any shorts with all this circuitry disconnected.  Once you've verified the harness wiring, then start testing the fuel pump.  It is highly probable that the insulation on the wires inside the tank have hardened and deteriorated.  That may cause short circuiting.

Pull the connector that joins the injectors to the harness, pull all injector connectors and the EFI computer.  Do the same tests for shorts as above.

To test the relay contacts, you need to first energize the relay coil, to cause the contacts to close.  Then measure the resistance between 30 and 87 (both 87's individually).

It's possible that you might be able to resurrect one of the relays by opening it up and seeing if the contacts are not too far gone to be reconditioned.

[Cherokee2072]

@RBM, Thank you Robert.  Very much what the wiring diagram pointed toward.  Your experience probably saved me hours in simplifying the process.  Definitely a weekend project.  I did replace the pump wires when I installed the new pump during the rejuvenation process, sending unit wiring is suspect. I’ll let you know what the culprit is.

Thanks
Kevin

[The Mighty Gryphon]

You can take the search in baby steps.  With the relay out, pull the fuse.  Unplug the tank.

Check the resistance between the #87 contacts on the relay socket and ground.  It should be very high.

Check resistance between both #87 contacts and both contacts on the fuse socket.  Only one contact on the relay socket and one contact on the fuse socket will have a low resistance between them.  All the rest of the combinations should have a very high resistance.

Check the resistance between the fuse socket contacts and ground.  It should be be very high on one of them(the feed from the relay #87) and at least a couple hundred ohms on the other.

Get back to us with the results of these checks, especially if any readings are not what was expected, and we'll figure out the rest of the troubleshooting.

Don't neglect the relay.  Carefully pop the cover and check the operation and try cleaning the contacts with Deoxit.  See if you can get the contacts to work. 

[Cherokee2072]

Finally had time to do these checks.

Front 87- no resistance to ground
Rear 87 254 resistance to ground

Front 87-Front #6 no resistance
Front 87-Rear #6. High resistance 700
Rear 87- Front #6 no resistance
Rear 87-Rear #6 no resistance

Front #6 to ground 350
Rear #6 to ground no resistance

I will say that even with cleaning I had too much difficulty getting a good reading from the fuse plugs.  I am suspecting a loose connection in the wiring at the fuse connector, it looks good and nothing obviously visible, I will have to pull the fuse block out and look at the crimps/solder however it was connected.  I’m going to give that a look over now.