Howdy folks,

The old 4v has really been running well lately. Words I used repeatedly when anyone ever talks to me about it and perhaps that has cursed it!

I was real low on fuel yesterday morning and so brimmed it with super unleaded. After around half an hour I pulled over to take a pic of the stunning view with the engine running and it just cut out. Tried restarting - no luck. Just kept turning over. Battery healthy - all the lights on the dash. I put it in gear and rolled it on to compression, turned it on and it started. Away I went and it never missed a beat the rest of the morning.

After work, I started it up and sat on the bike with it idling on 'choke' while I put my gloves on and it cut out. Same thing, wouldn't start. Bumped then it did and seemed fine. Went for a local spin just to check and notice it did 'miss' a couple of times - and once died while riding. Managed to get home by the usual 'bump'.

Does this indicate the fuel pump is on the way out (30 years + 58,000 miles)? 

New fuel filter last month and its been purring along great since.

Could it be that I copped a bad batch of fuel?

Also, during one of the stalls I'm sure I got a sniff of fuel.

UPDATE* Just been to the garage. Switched the ignition on - no fuel pump whirring. Typical that the tank is full of fuel 

I replaced my fuel pump at about 49,000 miles, I noticed a vast improvement on the starting, it took less time on the starter and runs a lot smoother. I bought my pump on eBay, not very expensive but worth the piece of mind.
I also had to replace the gauze filter and rubber mounting.

Stumpy wrote:I replaced my fuel pump at about 49,000 miles, I noticed a vast improvement on the starting, it took less time on the starter and runs a lot smoother. I bought my pump on eBay, not very expensive but worth the piece of mind.
I also had to replace the gauze filter and rubber mounting.

Cheers for that Stumpy.

There's a massive disparity in price for fuel pumps isn't there?

£168 new from Motorworks

Or £230 new on ebay 

Or £22.50 new on ebay

The cheapies look identical. Must be a catch?

considering that it bump starts each time I would be looking for a bad connector, most likely the multi pin connector on the ECU.

RicK G wrote:considering that it bump starts each time I would be looking for a bad connector, most likely the multi pin connector on the ECU.

Cheers RicK,

See the update below original post. The pump isn't playing at all this morning. Completely silent when the key is turned.

Assuming it turns out to be the pump that's shot, has anyone tried one of these copy pumps?

https://www.aliexpress.com/item/32839461036.html?spm=2114.search0104.3.22.3d735c26io6ms1&ws_ab_test=searchweb0_0%2Csearchweb201602_7_10065_10130_10068_10547_319_10546_317_10548_10545_10696_10084_453_454_10083_10618_10307_537_536_10059_10884_10887_321_322_10103%2Csearchweb201603_60%2CppcSwitch_0&algo_expid=20d2f224-ac59-4cb6-ab61-799dc1eb14f3-2&algo_pvid=20d2f224-ac59-4cb6-ab61-799dc1eb14f3

They come with filter too. Good price & all, but not sure if they're the right PSI.

I bought this one: https://www.ebay.co.uk/itm/BMW-K100RS-K100LT-K75-Fuel-Pump-05-1983-10-1992-52mm-Diameter-Made-in-Germany/122825782000?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
and I also bought the gauze and rubber mountings from motowerks

Regards Martin. be along shortly to confirm that Chi-com pump is tip top

Had my share of non-running pumps , at the connector at the tank.
Replaced it with Superseal, and no problem after

Example;

https://kojaycat.co.uk/4-Way-15mm-Series-Amp-Superseal-Connector

here is another alternative to the lady's

Easter Beaver Sumitomo TS090 Sealed Connectors

the 'Sumitomo Not in Catalog Male 4P Connector'  3/4 of the page down sleek discreet connector

get extra pins and seals

Stumpy wrote:I bought this one: https://www.ebay.co.uk/itm/BMW-K100RS-K100LT-K75-Fuel-Pump-05-1983-10-1992-52mm-Diameter-Made-in-Germany/122825782000?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649
and I also bought the gauze and rubber mountings from motowerks

Certainly cheaper than Motorworks - in fact cheaper than their s/h options.

Thanks for the link Stumpy. Just need to make sure mine isn't shot before I replace it.

Arlina wrote:Had my share of non-running pumps , at the connector at the tank.
Replaced it with Superseal, and no problem after

Example;

https://kojaycat.co.uk/4-Way-15mm-Series-Amp-Superseal-Connector

So the pump could be ok - just the connections?

Hmmm 

If you're running the OE Bosch 16121461576 52mm fuel pump your niggled at the wrong thing.
Pumps have been known to last 200K with regular use.

Clean the 4-pin connector and spread out the pins whilst awaiting new connector

volador wrote:If you're running the OE Bosch 16121461576 52mm fuel pump your niggled at the wrong thing.
Pumps have been known to last 200K with regular use.

Clean the 4-pin connector and spread out the pins whilst awaiting new connector

Cheers volador,

I'll try that before ordering a new pump. Have gone for a Superseal as recommended by Arlina (from ebay - that linked seller was closed due to Covid).

I'm glad I asked as I'm not sure how fuel pumps break. If they start playing up (as I described) or if they just stop.

Hopefully its just the wiring. We'll see next week.

Glad it happened locally too, though I do wish I hadn't have just brimmed the tank   

Thanks for your help you wonderful people 

I've been running a Chicom copy for nearly three years, and I have replaced my OEM spare that I used to carry with another copy. It's been run under some pretty adverse conditions and is still fine. There are multiple copies out there and some are probably OK and some could be crap. Most of the OEM pumps that I have seen destroyed were caused either by ethanol laced fuel or rusted out internally probably from sitting.   http://www.motobrick.com/index.php/topic,10054.msg86054.html#msg86054
Regards Martin.

Interesting reading.

Thanks Martin 

Another option not to be overlooked:
https://www.ebay.com/itm/BMW-K1-K100-K1100-K75-1984-1997-Fuel-Pump-Filter-16121461576-16121460452/382307941512

There are at least three different inlet styles on the bottom of the pump, the rest of the pumps are indistinguishable from the OEM pump. The Pabokay is a direct copy and the two Global ones I bought are both different in the inlets.
Regards Martin.

Global Type 1                            OEM and Pabokay

Not to hijack this threat, but my bike gets noisy when the fuel is low.  There is a high pitched ringing in the tank that I assume is the fuel pump as it is uncovered by gas.  Is this normal? or, should I look for a better grade of ear plugs?

How low do you go?

Mine stays the same, but I try not to let it get under quarter full,  guessing its better for the pump. Maybe look inside when it gets noisy.

Some are noisier than others and the noise will increase running a low level of fuel. The OEM pump on mine was a lot noisier the Chinese one. We did a 1400 Km three day run last year in 40 C + temperatures and when I got really low on fuel at one stage the pump noise did increase.
Regards Martin.

brickrider2 wrote:There is a high pitched ringing in the tank that I assume is the fuel pump as it is uncovered by gas.  Is this normal?

It is normal and a modification to make it less likely to occur was contrived. It's here.

RicK G wrote:considering that it bump starts each time I would be looking for a bad connector, most likely the multi pin connector on the ECU.

It seems RicK G is nearer the mark than I first thought. Cheers mate 

This morning I have disconnected, cleaned & reconnected the Motronic and we have lift off. A nice healthy fuel pump whirr when the key is turned and the engine fires up

I'll be honest, I think there's more to it that just that. I think the problem may be related to the ABS 'brain' - but I won't go into that here, I'll open that chapter another day should the issue resurface.

I have ordered a new Pobokay pump to keep as a back up spare on Martin W's recommendation.

Really appreciate the input from you guys.

since you have cleared the Motronic memory by disconnecting the connector plug should do the same with ABS ECU

disconnect ABS brain for 24 to 48 hrs better yet to completely discharge any stored data and start anew

I rode 60-70 miles yesterday, stop/start, switch off/on and it performed faultlessly apart from one stop. Upon turning the key the fan instantly kicked in and the bike wouldn't start (presumably because the ECU cut the fuel injectors?).

This has happened a few times before and I can only get the bike started by either removing/replacing fuse #5 or dis/re-connecting the Motronic connector (clearing the memory). So there's clearly an ongoing issue somewhere.

Bonzo wrote:I rode 60-70 miles yesterday, stop/start, switch off/on and it performed faultlessly apart from one stop. Upon turning the key the fan instantly kicked in and the bike wouldn't start (presumably because the ECU cut the fuel injectors?).

This has happened a few times before and I can only get the bike started by either removing/replacing fuse #5 or dis/re-connecting the Motronic connector (clearing the memory). So there's clearly an ongoing issue somewhere.

In the process of troubleshooting my anti-theft sensor under the seat of my K-100, it appears that the sensor prevents a start by causing an over-temperature fault, which I think should also activate the cooling fan, but mine did not.  As a precaution, I tested the cooling fan circuitry and all is well, but I replaced the cooling fan relay anyway since I don't recall ever hearing the fan run and I already had the relay box exposed.   I also found that the fuel pump was not running and have ordered a new one.   The pump vibration dampner and inlet screen had deteriorated, which probably caused the pump to seize from drawing in debris.   Still waiting on the inlet screen.

Any update to you posting?

Try Quantum Fuel Systems for mounting kits HFP-K437 $40.00 US or kit with pump HFP-437F $90.00 US. I fitted one kit to a mates Brick and the quality seems good. We ordered three kits and got them landed in OZ for $55.00 Au per kit.
 https://www.bing.com/aclick?
Regards Martin.

When you fitted these kits, i see that they have the later filter screens with the hose connection, mine had them fitted but no hose on it. Did you fit a hose and if so where does it go?

The hose was already there to the screen, so it was just refitted. A lot of speculation was posted at one stage as to whether the hose was needed and what it actually does. One theory was it is supposed to stop cavitation of the pump.
Regards Martin.

warmshed wrote:When you fitted these kits, i see that they have the later filter screens with the hose connection, mine had them fitted but no hose on it. Did you fit a hose and if so where does it go?

In the later model Bricks, the hose from the fuel pump pre-filter attaches to a pipe that descends from the vapor collector at the ceiling of the tank. Open the fuel cap or remove the cap assembly and look around. You'll see it if your tank has one but yours might be an earlier model. My '95 K75's tank has that vapor collector but it isn't linked to the filter basket using a hose. Fuel pump cavitation usually isn't likely unless the pump is habitually operated at low fuel levels. I've had no problems in 60k miles.

A pump with a sock-style fuel filter was eventually adopted.

I put a stainless steel screw to plug the unused hose connection. Otherwise unfiltered fuel will enter the mesh basket.