Engine Stalls While Riding at Speed

[AgPete139]

Howdy MotoBrickers,

I am having issues with my 1987 K75C, 4000 original miles. She has a new Wix fuel filter (100 miles since last week),  .024" spark plugs (last week), 20W-50 oil & Purolater filter, BMW fuel pump (as told by the seller 3 months ago), and Shell/Exxon/Chevron/Valero gas 87 octane.

I gave here and Google a search (which referenced iBMW, Flying Brick, and others). The issues I am having are difficult to describe, so that's why I'm finally asking here.

I will be cruising along at 55 mph, and then my engine starts to behave like it's running out of fuel. I will still have ~2-3 gallons left in the tank.

It's initially a loss of power, but within 10 minutes, under moderate throttle input, the engine will "bog down" and almost die. Today,  for the first time, it died twice on me while moving at 45 mph+.

The engine does not totally die. I clutch in, blip the throttle 4 times, and clutch out in a higher gear. I usually do this until I'm safe.

I adjusted the TPS ("click" for open throttle, click for close). Just today I started to get really loud backfires out of the exhaust. Rolling on / rolling off the throttle does not affect the running condition.

This has been happening shortly after I bought it 3 months ago.

NOTE: With a new tank of gas, this does not happen at all.



Could there be something with my fuel pickup & screen, in the left side of the tank? The gas light is always on, even with a full tank.

I thought it was vapor lock or something related, but I tried riding around with the tank lid open and it made no difference. I want to eventually do the "cup" upgrade & flapper removal to the tank.


Please, and thank you very much in advance. Thank you for any insight as to what is causing this.



Peter

[AgPete139]

New fuel hoses and vacuum hoses.

I am going to look at the crankcase breather again today. It had cracks at the end connection, but I did a "shade tree" fix with RTV sealant and electrical tape. This sounds bad, but it is a working temporary fix. There was no change of performance, and no leaks since propane and WD-40 was used to ensure the vacuum was in tact (even at higher RPM). I don't think this is one of the issues, since it seems tank related.

 for cracks. I didn't see any the first time.

All 3 throttle bodies have the vacuum caps on them. They are free of cracks. The TB intake rubbers are good, too.

Also checked the connector under the seat & tank. It all seemed to be connected and looked fine.


People state the electrical connection are bad in situations like these, but it only occurs with 2/3 tank or less. When I fill it back up, the problems go away. It seems to happen when the tank is hot.


But again, spark plug wires are good, connection to plugs are good, proper gapping, connection to tank is good.

How can I check my Fuel Pressure Regulator? Can I clean the FPR with brake cleaner?


Could it be the coolant sensor? How could I know this for certain? The bike starts up every time and idles fine when cold & warm around  1000 RPM +/- 150 RPMs.

[drut]

"NOTE: With a new tank of gas, this does not happen at all."

This would make me look closely at breather &/or whether petrol pump is snugged down in right position before I checked anything else.

[AgPete139]

"NOTE: With a new tank of gas, this does not happen at all."

This would make me look closely at breather &/or whether petrol pump is snugged down in right position before I checked anything else.

The pump is on the left side of the tank, in that cubby hole. The pickup is at the bottom of that. It is NOT secured. I just looked at my manual; how is it supposed to be strapped down? My pickup / pump just sits upright in the tank.

When I get home from work, I will snap a picture of it and post it here in 2 hours.

The fuel level float also does not seem to "float" in the gas, which moves the lever to turn off the gas light. This is unrelated and is just a dummy light, correct?

[drut]

"The pump is on the left side of the tank, in that cubby hole. The pickup is at the bottom of that. It is NOT secured. I just looked at my manual; how is it supposed to be strapped down? My pickup / pump just sits upright in the tank."

On my K100RS it "clicks" into place In a retaining collar.The Lieberry is most helpful: http://www.motobrick.com/index.php?topic=2252.msg29656#msg29656

[Zipster]

My first thoughts were - Is the new fuel filter installed the right way round? And did the fuel pump get bashed or disturbed when changing the fuel filter?

[Inge K.]

All 3 throttle bodies have the vacuum caps on them. They are free of cracks.

Not related to your problem, but you should have caps only on the two frontmost TB's.
On the Third it should be connected a vacum hose for the FPR....could be that the FPR is changed?

People state the electrical connection are bad in situations like these, but it only occurs with 2/3 tank or less. When I fill it back up, the problems go away. It seems to happen when the tank is hot.

Boiling fuel?

[byatesscuba]

My bet is on the fuel pump as well. The pump does snap into the "cubby hole" via a clip on either side. You squeeze these to pull it up and out. The filter sock runs down the lower edge, in the area where heavy things like water would collect. Another think that could be wrong, although I don't get why it matter about fuel level in the tank, is that the rubber boot surrounding the pump has deteriorated due to the new ethanol additives in fuel. I saw this somewhere and it makes a gummy mess, that could be restricting flow intermittently, this could also be gumming up your level sensor, causing bad reads.

[AgPete139]

[AgPete139]

This would make me look closely at breather &/or whether petrol pump is snugged down in right position before I checked anything else.

Breather is still fine. I checked it again with the rest of the carb cleaner I had. Ironically, I needed a breather after doing that. Even with a shop fan, it gets quite fumey. Ha.


The petrol / fuel pump was not secured in the left area. Please see the above pictures for reference. However, with THAT much fuel in there, would this really be a problem? (Not rhetorical)


On my K100RS it "clicks" into place In a retaining collar.

I will look into the retaining collar again. I see what is being referred, but the locking mechanism is lacking. I'm guessing it's a press fit / snug fit with the fuel pump rubber to prevent vibrations from interfering with performance. I'm getting dizzy searching through my Clymers. Ha.


My first thoughts were - Is the new fuel filter installed the right way round? And did the fuel pump get bashed or disturbed when changing the fuel filter?

Definitively, yes. The input line routes from the fuel pump. The output line, which is well secured, connects to the fuel hose that feeds the front of the fuel rail along the throttle bodies.
No, the fuel pump appears damage-free.


Not related to your problem, but you should have caps only on the two frontmost TB's.
On the Third it should be connected a vacuum hose for the FPR....could be that the FPR is changed?
Boiling fuel?

Oh? I think my FPR is actually dumping to the ATM.  I found this in another thread. I will disassemble and recheck this tonight. I think we are on to something. I always just took the current setup as standard. The boiling fuel could be caused the the improper FPR config.



[size=78%]I have 3 caps on the individual TB, where you sync them with a manometer/etc. I suppose that last one should connect to the bottom of the FPR.[/size][/color]

1) Unsure where this is hooked. I replaced these fuel lines, but I replaced them one at a time to not confuse their order. I'm guessing this goes to the TB / fuel rail?
2) This DOES return to the tank on my setup.
3) Depression from air intake? I will consult my manual and find this "depression."

My bet is on the fuel pump as well. The pump does snap into the "cubby hole" via a clip on either side. You squeeze these to pull it up and out. The filter sock runs down the lower edge, in the area where heavy things like water would collect. Another think that could be wrong, although I don't get why it matter about fuel level in the tank, is that the rubber boot surrounding the pump has deteriorated due to the new ethanol additives in fuel. I saw this somewhere and it makes a gummy mess, that could be restricting flow intermittently, this could also be gumming up your level sensor, causing bad reads.

The rubber boot appears to be in excellent condition, and I believe the seller was true to his word regarding it being a new BMW fuel pump. "Squeeze up and pull out." I think this might just be a snug fit in the 6-fingered hole area.

The float sensor was just an arm & resistance electrical connection.  How would flow affect these readings?


***************************************************************************************

I apologize for asking so many questions simultaneously. You guys are being extremely helpful.


In the process of checking for loose connections and solid grounds on the chassis & battery, I came across the 5 prong, white female connector. After looking at the books diagram, I believe it is the Connection For Special Equipment (heated grips, ABS, lights). Mine has none of those. This connector is obviously a standard harness. (Please, refer to images above.)

The "trailer harness" wiring connections under the tank are still rock solid. I will sand and reattach the main ground on the chassis tonight.

[ackgs]

Go here http://www.beemerboneyard.com/k71011k1ak1u.html. I don't know what pump you have but it does not look like the one in my bike. It may well be a pump that can be substituted for the stock pump I have no idea. Others here more knowledgeable than I will know. The black rubber part in beemer bone yard picture bolts into the white nylon part and the pump rides inside the black rubber damper. See the tabs on the white nylon part? Those clip into the square recesses fore and aft of where your pump currently is, that holds the pump in place and at the proper height. Back to pump itself - perhaps, and just a WAG here, it is not providing enough fuel when the fuel level drops as it is just rattling around in there. When I got my non running K the previous owner had a half assed rigged pump in mine too. As the pump in mine was toast I purchased the Beemer Bone Yard pump kit and it has worked well. I will be interested to hear more comments on what kind of pump that is in yours and if it is suitable for use in your K.

I can not seem to get my link to take me directly to the fuel pump page. Go to my link and then click on the fuel pumps and kits section, then choose the K bike pump. That should take you to picture I referenced .

Nice looking bike by the way, get that thing running!

[Inge K.]

On my K100RS it "clicks" into place In a retaining collar.

I will look into the retaining collar again. I see what is being referred, but the locking mechanism is lacking. I'm guessing it's a press fit / snug fit with the fuel pump rubber to prevent vibrations from interfering with performance. I'm getting dizzy searching through my Clymers. Ha.

You have a non OEM pump, the OEM mounting parts is removed.....does the pump stay put, or does it move around?

1) Unsure where this is hooked. I replaced these fuel lines, but I replaced them one at a time to not confuse their order. I'm guessing this goes to the TB / fuel rail?
2) This DOES return to the tank on my setup.
3) Depression from air intake? I will consult my manual and find this "depression."

1. rear end of fuel rail.
2. -------------
3. vacum spigot at TB #3.

[Mongrel]

Yeah, that is absolutely not the stock pump. Maybe it was a "mister fixit" substitute not intended for a K-bike?

[Motorhobo]

Lots of aftermarket pumps work fine with k-bikes...mine's a Ford Escort I think...but it's been running so long flawlessly I forgot which Ford it was. Aftermarket pumps work fine...it's the installation that may be a Mr. Fixit variant. Aftermarket pumps require mods since they're not the same length or diameter as the OEM. If the mod isn't done properly, that's where problems can occur. So it might not be the pump, it might simply be the fit.

[AgPete139]

[ackgs]

So what have you found out?

[AgPete139]

Worked on the bike on Friday evening as the wife stayed inside and snuggled up to a book. We had a busy weekend, so I am just now getting back to uploading Photobucket and adding to this thread.

#1 Hose (from diagram) comes from the fuel tank.

#2 Hose (from diagram) routes to the end of the fuel rail.

#3 As you can see in the above pictures, the #3 throttle body had a cap on it, and the #3 FPR hose (on diagram) rank straight back up to the tank. This MIGHT have been causing the temporary stall / "lean" issue. I have since rerouted the hose from the FPR to the TB.

The tank has also been repainted once, albeit poorly. I'm not complaining, since it still looks good as a 20' bike. However, the bottom insulation was removed. I have since cut and added a reflective insulator underneath the tank. That will radiate heat/energy back downward, away form the gas tank. Boiling fuel should and positive pressure should be less of an issue now.

I called Precision and was informed of the specs and fuel rates. This is a replacement part, so I do not think the brand of pump is an issue.

The pump DOES float around in the left side cubby hole. However, even at half a tank, it is still fully submerged.

I bent the fuel float arm down. I still have a low fuel light. Occasionally this light turns off, but comes back on at the next startup.

UNRELATED MAINTENANCE: While I was in that area on Friday, I replaced the tattered "choke" cable, especially since it's getting colder outside. I also replaced the front brake light switch. It was sticky and semi-corroded, and I already had an OEM replacement.

I filled her back up this morning to a full 5.2 gallons. We will see how she fares at 1/2 tank.

[AgPete139]

Go here http://www.beemerboneyard.com/k71011k1ak1u.html. I don't know what pump you have but it does not look like the one in my bike. It may well be a pump that can be substituted for the stock pump I have no idea. Others here more knowledgeable than I will know. The black rubber part in beemer bone yard picture bolts into the white nylon part and the pump rides inside the black rubber damper. See the tabs on the white nylon part? Those clip into the square recesses fore and aft of where your pump currently is, that holds the pump in place and at the proper height. Back to pump itself - perhaps, and just a WAG here, it is not providing enough fuel when the fuel level drops as it is just rattling around in there. When I got my non running K the previous owner had a half assed rigged pump in mine too. As the pump in mine was toast I purchased the Beemer Bone Yard pump kit and it has worked well. I will be interested to hear more comments on what kind of pump that is in yours and if it is suitable for use in your K.

I can not seem to get my link to take me directly to the fuel pump page. Go to my link and then click on the fuel pumps and kits section, then choose the K bike pump. That should take you to picture I referenced .

Nice looking bike by the way, get that thing running!

Thank you very much! She runs great (for the first 80 miles)  :hehehe

I see the collar you're talking about, and it is not with the bike. If push comes to shove, I'll be forced to buy a new fuel pump with the attaching collar.

I found that the specs are similar, and I think the Precision pump is a suitable replacement after talking to a representative. The issue of it "bouncing" around without the lock down collar is the only real problem I see upon second inspection.

On my K100RS it "clicks" into place In a retaining collar.

You have a non OEM pump, the OEM mounting parts is removed.....does the pump stay put, or does it move around?

It stays in that secluded area, but still moves around. It doesn't travel vertically much. I am looking into a replacement collar.

Yeah, that is absolutely not the stock pump. Maybe it was a "mister fixit" substitute not intended for a K-bike?

It's just a non-BMW alternative. If a Ford pump can be used well, I don't see why this would be any different. Was your Ford replacement able to lock into your BMW lock collar?

Lots of aftermarket pumps work fine with k-bikes...mine's a Ford Escort I think...but it's been running so long flawlessly I forgot which Ford it was. Aftermarket pumps work fine...it's the installation that may be a Mr. Fixit variant. Aftermarket pumps require mods since they're not the same length or diameter as the OEM. If the mod isn't done properly, that's where problems can occur. So it might not be the pump, it might simply be the fit.

I'm looking into a replacement or a solution to prevent it from bouncing around. I am thinking about alternatives. I'd prefer NOT to spend $300 if avoidable. So...duct tape anyone?  :clap:



*********************************

I used 5/8" fuel hose that I had lying around and replaced the crankcase beather. It fits very well with no kinks and the hose clamps. I went ahead and ordered a factory hose from BMW though. It arrives on Thursday.

I am hoping the rerouted FPR hose and the insulation did the trick.

[bocutter Ed]

I see the collar you're talking about, and it is not with the bike. If push comes to shove, I'll be forced to buy a new fuel pump with the attaching collar.

I found that the specs are similar, and I think the Precision pump is a suitable replacement after talking to a representative. The issue of it "bouncing" around without the lock down collar is the only real problem I see upon second inspection.

Another problem is that pump, as is, has a large filter. The stock 'sock' filter fits through the mounting hole to pick up fuel as low as possible in the tank.

[Motorhobo]

Euromotoelectrics has some cheaper pump options but not by much --


http://www.euromotoelectrics.com/BMW-R-K-VDO-Repl-Fuel-Pump-16-14-1-341-231-p/fp-231oe.htm

I think your best bet might be to figure out how much of the original mounting parts you have, replace whatever's missing with the OEM part or an ebay replacement, then follow the instructions on ibmwr.org or here -- http://www.motobrick.com/index.php/topic,2058.msg10840.html#msg10840 -- to replace with a Ford or Purolator pump. It sounds like someone might have started that job on your bike but not done it properly. All I know is that my Ford fits without any free play and has been running for five years or more. The connectors on the US pumps are different and you have to get or make the spacer collar that fits around the pump so that it sits within the OEM housing. It's a one time mod but you'll never have to buy another $300 pump...and that's a good thing.

Or buy the kit from EME...it's plug and play.

[AgPete139]

No interesting updates. This is simply information gathering, compliments of ClassicKBikes, for myself and anyone else that may stumble upon this thread.

BMW Bosch fuel pump P/N: 16121461576

93 & earlier ; 52 mm ; Bosche fuel pump 16121461576 ;
94 & later ; 43 mm ; 16121464696 (complete fuel pump assembly) ; 16141341231 (fuel pump only)

Fuel pump relief valve pressure:  Some where in the 65-80 psi range

Regulated fuel pressure: 2.5 bar (36.26 psi)



*********************************

I replaced the crankcase breather hose with the genuine BMW part.

Bike still dies ; I've been trying to source used parts to no avail. I'm buying a new collar, rubber dampener, screen filter, and fuel pump.

I also learned that the Purolator pump is the 43 mm equivalent, with the sock & spring pickup.

I've gathered that the OEM requirement of 52 mm (from 1985 K75/K100 - 1992 K75/K100) is NOT necessarily better than the newer 43 mm technology & dimensions. However, the Ford 2042 fuel fumps are just as good at only $22.

I will probably get the 52 mm parts and retrofit the Mustang pump with the foam adapter, instead of the 43 mm pieces instead. I'm worried that the 43mm white collar will not readily fit on my 1987 K75. [/u] Hopefully a used K100 part will be able to fit.


*********************************************************




ClassicKBikes.com
"The BMW OEM 52 and 43mm fuel pumps by themselves cost $409 and $374 respectively. A complete 43 mm assembly costs $435 and includes all of the parts you need for replacing everything. This will fit both early and late K bikes.  In my opinion, if you choose to buy new OEM parts then it makes sense to buy the complete 43 mm assembly - #1 in the diagram below. (2013 prices)"


**************************************

I'll be piecing together a kit from EME.

I was waiting for updates from here, but they haven't any new inventory:

http://www.beemerboneyard.com/kfask7510011fp.html

[AgPete139]

Thank you for letting me type out loud and gather my facts straight. If I have anything incorrect, please let me know.

[Conrad325i]

Ok so my issue felt similar...

Ive done so much work to this bike i swear its cursed. I will fix a problem and another unrelated one will creep up after one good ride. Its getting so old.


Rode bike 15miles... Was totally fine. Best ride ive had after fixing ignition switch issue. Bike say in sun for 3 hours. Fired it up and headed for home.
Had NO power. NONE. At first it backfired a little but then it just was down on power. Had to limp it home 15 or 20miles at 25mph on flat ground and 3mph uphill. If i hit a hill and didnt have speed it would die. It almost killed me pushing it up a hill in gear opperating throttle and clutch...

Worst day ever. Haha.

It almost sounds like its on one cylinder but i would think it wouldnt run like that so it must be an afm problem.