Author Topic: Location of fuel injection relay? (Read 24498 times)

Quiltzig · « **on:** March 16, 2019, 06:08:41 PM »

I have a K75S cafe racer. It was running fine till I took off the tank to repair a pinhole leak. Upon reinstalling the tank I could not get any fuel supply to the injector rail. I bench tested the pump and it works fine. It was a new pump last year when I completed the project. I found that I am not getting any voltage at fuse #6, so according to the wiring diagram the voltage to this fuse is fed from the fuel injection relay. I can’t find any info on where this relay is located, and the green/red wire is tricky to trace as the loom is very nicely & tightly bound. Anybody able to assist?

Filmcamera · « **Reply #1 on:** March 16, 2019, 06:30:05 PM »

I would check the 4 pin connector...

Quiltzig · « **Reply #2 on:** March 16, 2019, 06:42:41 PM »

I already checked the connector and the problem is further back in the electrical system, as I am not getting voltage at fuse #6 which feeds the power to that connector.

Laitch · « **Reply #3 on:** March 16, 2019, 06:52:14 PM »

The relay is in the relay box under the tank on the left side of the moto. The fuse panel is attached to it. Three relays are located adjacent to the front wall of the box—the horn relay, the load shed relay and the fuel injection relay. If you have a wiring diagram, you should be able to identify it by its connections.

rbm · « **Reply #4 on:** March 16, 2019, 07:03:34 PM »

What's the state of Fuse #1? Blown or intact?

Quiltzig · « **Reply #5 on:** March 16, 2019, 07:17:32 PM »

All fuses incl #1 and #6 test OK and are intact.

rbm · « **Reply #6 on:** March 16, 2019, 07:21:50 PM »

Was that a visual check or a Ohms measurement. AGC fuses are known to fail internally in a way that is not obvious when visually inspecting the fuse.

I believe the source side of the fuses are on the left, so check both sides of the fuse for voltage to determine if the contacts in the fuse holder are not loose.

Quiltzig · « **Reply #7 on:** March 16, 2019, 07:31:58 PM »

I checked all with multimeter, and all are OK. I am not getting supply +12v at fuse - hence my original question about location of FI relay because schematic shows supply coming from this relay to the fuse.

alexg · « **Reply #8 on:** March 16, 2019, 11:26:11 PM »

at least in my K75, the fuel pump is only energized when pressing the start button. I assume that stays energized above certain RPMs or another way of detecting engine running. It does not energize with the ignition key ON.

Quiltzig · « **Reply #9 on:** March 17, 2019, 12:01:01 AM »

Yes, I realise that. I should have said that I get voltage at the female side of the 4 pin connector to the tank when the starter button is pushed, and the fuel pump tests OK, but still no fuel to injector rail.

Scott_ · « **Reply #10 on:** March 17, 2019, 06:56:18 AM »

Post #2 in this thread...
http://www.motobrick.com/index.php/topic,536.0.html

rbm · « **Reply #11 on:** March 17, 2019, 07:39:12 AM »

You posted two contradictory statements about the condition of your fuel pump electrics. In Post #1, you wrote "I found that I am not getting any voltage at fuse #6" and then in post #10, you post "I should have said that I get voltage at the female side of the 4 pin connector".

The implication in your first post was that there is an electrical problem that is preventing the fuel pump from working, but your 10th post confirms all the pump electrics are working properly, including fuse #1 and fuse #6. Voltage should only appear at fuse #6 with the engine turning over. Did you take your measurements at fuse #6 with the engine spinning or at rest?

Your problem is now sounding to be more mechanical in nature than electrical. Can we assume that you've put the hoses back on the tank correctly?

The Mighty Gryphon · « **Reply #12 on:** March 17, 2019, 11:32:04 AM »

I vaguely recall the rear frame loop being part of the fuel pump circuit.

johnny · « **Reply #13 on:** March 17, 2019, 03:52:49 PM »

greetings...

the fuel injection relay is no longer available from bmw... you gonna have to getts one from...

https://www.jaycar.com.au

now to the matter at hand... is this the no start moto you speak of...

B53732D7-64B0-4066-8EC4-1D8A071C6467.jpeg (75.66 kB . 768x576 - viewed 1007 times)

or is it this one..

photo 1.jpg (80 kB . 768x576 - viewed 1110 times)

j o

Quiltzig · « **Reply #14 on:** March 17, 2019, 04:20:53 PM »

its the purple one

Quiltzig · « **Reply #15 on:** March 17, 2019, 04:22:46 PM »

Quote from: rbm on March 17, 2019, 07:39:12 AM

You posted two contradictory statements about the condition of your fuel pump electrics. In Post #1, you wrote "I found that I am not getting any voltage at fuse #6" and then in post #10, you post "I should have said that I get voltage at the female side of the 4 pin connector".

The implication in your first post was that there is an electrical problem that is preventing the fuel pump from working, but your 10th post confirms all the pump electrics are working properly, including fuse #1 and fuse #6. Voltage should only appear at fuse #6 with the engine turning over. Did you take your measurements at fuse #6 with the engine spinning or at rest?

Your problem is now sounding to be more mechanical in nature than electrical. Can we assume that you've put the hoses back on the tank correctly?

True - I did not realise initially that the pump only runs when the starter is pressed. Hence I was testing the power at both the fuse and the connector with just the ignition turned on. later I realised my mistake. The hoses are connected correctly.

johnny · « **Reply #16 on:** March 17, 2019, 04:42:05 PM »

greetings...

is the black one also yours...

j o

Quiltzig · « **Reply #17 on:** March 17, 2019, 04:45:58 PM »

The black one was my wifes bike - but we sold it a year ago when she got her R9T.

johnny · « **Reply #18 on:** March 17, 2019, 04:48:16 PM »

greetings...

id ask the new owner if you could try his fuel injection relay... you can eliminate that from the equation... that way you wont have to ping jaycar...

j o

Quiltzig · « **Reply #19 on:** March 17, 2019, 04:51:49 PM »

I would but he is in the South Island and I am in the North - so its just not feasible.

daveson · « **Reply #20 on:** March 17, 2019, 04:56:08 PM »

Can you hear the pump turn on and then off, after you press the start button?

If not, maybe revisit filmcameras' idea.

If so, did you remove the pump for your repairs? You may have forgot to tighten one of those hose clamps (or wires)

Provide 12V to pin 86 of the relay and earth to 85, you should hear a click as the contact closes, and should have continuity between 30 and both 87 pins. It makes more sense if you look at the illustration on the relay.

Quiltzig · « **Reply #21 on:** March 17, 2019, 11:31:00 PM »

It is hard to hear the pump over the sound of the starter motor cranking, but no fuel is coming to the injector rail, that much is certain.
Which relay is the one that you are referring to? I can't find any data on which is which.

daveson · « **Reply #22 on:** March 18, 2019, 12:55:28 AM »

Just a quick jab of the button, when you let go the starter will stop, but the pump should continue for about 2 seconds. As Scott and Laitch said, the relay is at the front of the box, on the left side, it has five pins.

You have Voltage on the female side of the four pin (therefore the relay is supplying Voltage) do you have Voltage on the male side? This can be done outside the tank. Check earth too.

If working, with the filler cap openned and the starter continuously pressed for say five seconds, you should see fuel returning to the tank

By the way, what is the cylindrical thing between the air filter and the crank cover?

rbm · « **Reply #23 on:** March 18, 2019, 06:39:26 AM »

If you can't hear the pump over the starter, you can check for correct pump signal using the following method:
1. unplug the 4-pin tank connector
2. use a multimeter on DCV range, stick the positive (red) probe into the socket for the Green/White wire on 4-pin harness side. Fasten the negative (black) probe onto a ground point.
3. Crank the engine and observe the multimeter. It should read +12V or there abouts.
4. Release the start button while continuing to observe the multimeter. It should continue to indicate +12V for about 1.5 seconds AFTER you release the button, then drop to 0V.

Laitch · « **Reply #24 on:** March 18, 2019, 10:06:52 AM »

Quote from: Quiltzig on March 17, 2019, 04:22:46 PM

True - I did not realise initially that the pump only runs when the starter is pressed.
Quote from: Quiltzig on March 17, 2019, 11:31:00 PM
It is hard to hear the pump over the sound of the starter motor cranking, . . .

It seems you are closing in on the problem but just to clarify, when you let off the starter button on a K75, the pump will still run for approximately two seconds and you'll hear its whine.

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Author Topic: Location of fuel injection relay? (Read 24498 times)