The Dreaded Under-The-Tank 4 Pin Connector (85 K100rs)

[robdiaz44]

I have heard that you can replace the 4 pin connector with a trailer connector. Not sure if this can be done on the old (pre 05/85) under the fuel tank connector. I've been scouring the forum to find out, but can't seem find anything. Looking for some input here...thanks in advance.

Here are pictures of: 1) the old female connector that I have since replaced with the "spare" connector that was in the relay box...the 2 "fried" connectors are the pos and neg to the fuel pump; and 2) the male part of the connector...my concern is that the 2 darker connectors (pos and neg connections to the fuel pump) are not becoming glitchy and compromising the necessary electrical connection/power to the fuel pump.

Again...wondering if I can replace the whole thing with a trailer connector.?.?

[Laitch]

my concern is that the 2 darker connectors (pos and neg connections to the fuel pump) are not becoming glitchy and compromising the necessary electrical connection/power to the fuel pump.

You're concerned that they're not becoming glitchy? Pour some salt on them and they'll be glitchy soon enough. :hehehe

Anyway, read this post and the two after it to allay your fears and get you going.

[robdiaz44]

Thanks Laitch...ya, I kinda worded that part of my post as if I was hoping for some glitchiness, in which case, I should take your advice and pour some salt on those connectors  :falldown:

From reading that post, sounds like I will need to pursue getting a new fuel sender (since my '85 K100 can't be modded with the trailer connector). I've already replaced the female part of the connector, but I don't think I trust the male connectors of the sender. From the looks of the burnt plastic on the female end, there maybe unseen damage hidden behind the plastic of the male end.

[Freccia]

old thread- does anyone have a part number for this plug? thx in advance

[rbm]

This connector was recently proposed on another forum as meeting the need.

https://www.ebay.ca/itm/4-Pin-Grade-IP68-Waterproof-Electrical-Connector-Cable-Plug-Socket-Black-M14/262771837834?hash=item3d2e6c0b8a:g:chEAAOSwNnRYlXIm

NOTE:  It's not yet been confirmed that this plug actually works with the 83-85 fuel level sender / fuel pump connector.

[johnny]

greetings...

i have used 4 pin flat trailor wiring harness connectors with 100% positive results...


4pinFlatConnector.jpg (4.27 kB . 200x104 - viewed 1762 times)

j o

[rbm]

Johnny, that'll certainly work for the post-85 fuel sender but this thread is about the early 83-85 sender.  The plug has to be compatible with the receptacle.  There's no alternative.

[Freccia]

This connector was recently proposed on another forum as meeting the need.

https://www.ebay.ca/itm/4-Pin-Grade-IP68-Waterproof-Electrical-Connector-Cable-Plug-Socket-Black-M14/262771837834?hash=item3d2e6c0b8a:g:chEAAOSwNnRYlXIm

NOTE:  It's not yet been confirmed that this plug actually works with the 83-85 fuel level sender / fuel pump connector.

Thanks rbm. Looks like it's worth a try/whittle.

ATBT

[RobP]

if you need to replace both sides anyway, consider a Delphi WeatherPak connector.

[gard]

I know this is an old post but is pretty much exactly what I am seeing. The plug falls out, insulation has failed. How can I connect a newer style plug to the tank without having it leak gas?

If I remember correctly the electrical connectors on the tank side are incorporated into the fuel gauge assembly which is non serviceable and sealed into the bottom of the tank with a O ring and large nut. Al least some sources say it is no longer available new.

I guess I can try prying at the female terminals on the harness end to see if I can get a better connection.

[Laitch]

How can I connect a newer style plug to the tank without having it leak gas?.

You cannot connect a new style plug to that fuel level sender. The solutions earlier in this thread were for fuel level senders in tanks made after 1985.

These fuel level senders are no longer available, as you seem to have discovered.

You could try squeezing the plugs sockets slightly for them to get a better grip on the pins. In conjunction with that, you could line the perimeter of the sender cap's pin opening with some tape to get a better grip on the plug. The sockets need to be thoroughly free of corrosion. Use an electronics cleaner, the best of which is DeoxIT D5. Have you verified that you get 12V from the green/white wire connect to the plug when you crank the engine? Those old plug can be tender.

[gard]

Thanks, that is kind of what I expected. I reformed the female electrical connectors by jamming a metal pick in there, it seems nice and snug when installed and the pump works now. I am going to spend some more time cleaning things up.

I am guessing there is some kind of commercial solvent proof electrical bulkhead tank fitting that could be made to work with a machined adapter if I need to go there in the future.

I was also not getting any voltage to the pump fuse, cleaning and reseating the relay and ICU connector under the front of the tank seems to have fixed that one. I had been riding it for awhile with a jumper between the horn fuse and pump fuse.

The fuel gauges have not been reliable for about the last 30 years and recently the odometer stopped being reliable before it died completely at about 145k miles. So I need to either fix the odometer or figure out something different. Remember when you could just reach down and flip the lever to the reserve tank?

[Laitch]

I had been riding it for awhile with a jumper between the horn fuse and pump fuse.
. . . I need to either fix the odometer or figure out something different.Remember when you could just reach down and flip the lever to the reserve tank?

Using the horn fuse for power was a resourceful step! Your speedometer needs new gears. There are vendors that sell gear sets and singles specifically for the Brick and there are hobby stores and online vendors that sell assorted batches and random singles.

There are some helpful videos online specific to the Brick odometer repair. You'll set closed captions and voice translation to English for this excellent tutorial if Spanish isn't one of your languages. The link I posted might already have them set.

If you haven't yet, get a can of DeoxIT D5 electronics cleaner to clean all the electronic connectors' guts including the ICU and the FICU plugs. Most electronic cleaners help loosen corrosion and flush it away. DeoxIT does that but also leaves a corrosion-resistant protective residue when it drys.

My first moto was a Honda CL77. It didn't have an electric starter either. It also didn't require a gin pole to lift it after a drop. 

[Edward]

the speedy gear replacement is pretty straight up easy. Just be sure to have a clear work area. Those OEM gears eventually crumble apart with age.

[gard]

I used the last of the little aerosol can of deoxit yesterday, I have ordered some more with the needle dispense this time. I guess I will wait on that before disassembling the instrument cluster. I also used a tiny diamond coated drill bit to clean up the corroded connectors.
 
Interesting video on replacing the gears, thanks for that. The recommendation seems to be to disassemble it first to see which gears are needed and verify the teeth count. In the meantime, anyone find a good GPS related app or instrument that will work as a trip odometer that is easy to reset with each fill up? For years I have always gone with fill up at before 200 miles or get really nervous.

[Laitch]

For years I have always gone with fill up at before 200 miles or get really nervous.

That's the distance I fill up, too. The longest I've run before the engine started missing going uphill was 224 on the tripmeter.

[Duckbubbles]

I got replacement gears from speedometergears.com (I believe that's correct).  My mistake was not replacing the smallest drive gear because of the steps involved and sure enough, it fell apart after a couple hundred (or less) miles so I had to get in there again.

Frank

[Edward]

Frank, glad all worked out. 

[gard]

I got the new gears installed in odometer, seems to be working correctly. while in there I replaced all the instrument cluster bulbs with LED, the green backlite bulbs are sensitive to polarity so I checked each bulb with a battery and checked which side of each socket connected one of the 2 ground pins. Some bulbs flicker a little at idle but work fine on the road. The turning indicators are much lower power but they are directed out so it is fine.

I determined the male pins in the tank connector are 0.082" diameter so I used a 0.080" metal pin to check that each of the female pins are compressed to be a snug fit. All connections under tank, fuel relay, ECU, FI and inside instrument cluster cleaned and hit with deoxit.

Bike is running good after all the tune-up work last year, waiting for it to stop raining and get a little warmer.

Need new tires now. Sigh, it seems like every time I turn around its another $100 or 3

[Edward]

Word, great news.

—Just dropped 3 on a water/oil pump rebuild. The gear shaft was worn with age. I have Conti Road Attack 3. As you know, I'm heading up your way soon to the Rally. Hopefully the k75s is road worthy by then. Doing my best. Rain down here as well, every freaking day and night.