Stranded (Fuel Pump shutoff from overheating?)

[RetroTexan]

Yeah, I read through that thread which is what made me believe checking the pins was the next step in diagnosis.

[RetroTexan]

Ok, well I set the Acewell to 185F thinking it would start warning me well before the fan is supposed to kick on. I rode it around the area (feeder road speeds) for a little over 45 minutes. The warning light never came on and neither did the fan. As I was putting it into the garage, I noticed quite a bit of black smoke coming from the exhaust when it was on the side stand. It's running very rich. Which also leads me to believe that it's running much cooler than normal thus not getting hot enough for anything to be happening.

I hit the engine with an infrared thermometer and it only read 165F, which seems very cool for being ran at 50+ mph for almost an hour.

I'm very confused at this point. I'm guessing now there is some issue with the injectors adding too much fuel. These are the upgraded injectors from an M3 with the 4 holes instead of OEM 1-hole injectors. Anyone else with upgraded injectors getting black smoke and very low running temp?

[Laitch]

You haven't indicated the results of your sensor test. What were they?

[RetroTexan]

I haven't proceeded with diagnosing the sensor issue yet. This issue supersedes the temp sensor. It's going back to the fuel delivery, hence it takes priority over the fan issue I was asking about yesterday.

One problem at a time... and right now it looks like I still have a fuel delivery issue. Do you have experience with black smoke issues?

[Laitch]

Is your engine a 2-valve or a 4-valve model?

[RetroTexan]

It's a 2-valve model

[Laitch]

Put that information in your signature right now so it will show up with every post. The 4-valves operate somewhat differently.

[RetroTexan]

Well mine is a 2-valve so if anyone has insight into the diagnostic process after a fuel pump rebuild that would result in black smoke, I'm all ears

[Laitch]

You were guided to test the coolant temperature sensor because it plays a role in the timing of fuel injection. A cold engine needs more fuel than a warmed engine. If the sensor sends a signal that the engine is cool when it is actually warm, the injectors will overfuel it. If it sends a signal that the engine is warmed when it's actually cold, it will be hard to start.

So the engine can start great in the morning and wind up blowing coal in the garage when you're finished.
 



The air flow meter is another essential ingredient in correct fueling. It also houses a critical component—the air temperature sensor. If these items were mishandled during the hacking of the Brick into a scramble, they, too, could be involved in this malfunction. If the temperature sensing switch has gone cactus—as is said in Australia but I don't know if that's said in Texas and I doubt it because fecked or one of its other permutations is probably used—a malfunction there would have multiple effects.

Diagnosis is an orderly process of elimination. Checking the sensor in an overfueling or hard-starting engine is part of the process and a simple one.

[RetroTexan]

I'm looking at 1.7kΩ @ 89.5°F and 232Ω @ 174.5°F after 20 minutes of idling on the stand. Slight hiccups around the 15 minute mark, when revved it billowed a big black cloud of smoke but did not produce more billows on subsequent revs until I let it idle again for another 5 minutes, then another big black cloud.

[Laitch]

After reviewing your odyssey, including the news that your coolant temperature sensor reading is okay, in conjunction with the rain here ending this morning, along with the fact that this smoke seemed to be a new occurrence and the fuel pump has been disassembled and reassembled previous to its appearance, you might want to consider checking fuel delivery pressure at the rail—a straight forward and relatively uncomplicated procedure. Fuel delivery over-pressure and/or one or more injectors stuck open could cause the smoke you describe.
Verify the air flow meter's wiring plug contacts are clean and its connection is tight.

[RetroTexan]

In case anyone in the future has an issue with black smoke, poor gas mileage (18mpg), and the radiator fan not kicking on here is my update:

It was 100% the 'upgraded' fuel injectors I had installed from the M-series cars. The extra injector atomizing holes (4-hole) were spitting too much fuel into the engine and instead of the Jetronic picking up on this and adjusting the fuel delivery it was just coming out the exhaust as unspent fuel (aka black smoke)

I found the old 1-hole injectors that come standard with the bike and the smoke turned from black to white (which is normal for k-bikes). Also, since the engine is burning the fuel completely, the engine is able to heat up to temperature and the fan kicks on as normal now.

Hope this might be of some use to someone in the future!

[Laitch]

It was 100% the 'upgraded' fuel injectors I had installed from the M-series cars

That "upgrade" didn't seem to be mentioned in your Brick's history, Tex. This discovery of yours is a reminder for all of us to ask about injector swaps when fueling problems seem to be happening. Thanks for the update.

[Martin]

A mate of mines son was an injector specialist. After looking at a cutaway view of the K's engine he said stick to the 1 hole injector. The 1 hole injector is designed to spray onto the back of the inlet valve cooling it. It also breaks up the spray allowing it to atomise. The 4 hole injectors will not give you more performance but will increase your fuel consumption. If the 4 hole injector is so superior to the one hole injector why hasn't the companies selling the 4 hole injectors done a dyno comparison.
Regards Martin.

Cutaway K Engine Injector angle .jpg.png (59.96 kB . 768x568 - viewed 291 times)

[frankenduck]

If the 4 hole injector is so superior to the one hole injector why hasn't the companies selling the 4 hole injectors done a dyno comparison.

Yeah, the 4 hole injectors are really popular with the Jeep crowd for some reason. Yet I've never been able to find anyone running actual dyno runs that show any real performance improvement.

JMHO: I'm not a fuel injection expert but the FIs spray fuel onto the back of a hot intake valve which should cause the fuel to mist well just from the heat.

[RetroTexan]

That "upgrade" didn't seem to be mentioned in your Brick's history, Tex.

I'm very confused at this point. I'm guessing now there is some issue with the injectors adding too much fuel. These are the upgraded injectors from an M3 with the 4 holes

@Laitch: yes I did mention them. You were focused on the results of my sensor while I was still focused on the fuel delivery issue. This can be a reminder that there are plenty of incorrect suggestions and advice out there about these bikes.

The 4 hole injectors will not give you more performance but will reduce your fuel consumption.

@Martin: I can report that I had the opposite occur. My fuel consumption INCREASED dramatically and I was only getting 18 mpg with the 4-hole injectors, instead of the 55+ mpg that some riders have reported with the stock injectors. The bike also ran like crud with much higher and very noticeable vibration. Not to mention the black smoke that originally lead me to believe something was wrong.

That edited cutaway you posted is a great visual, thanks for posting it! It looks like the 1-hole injector is able to shoot fuel directly at the back of the valve to help atomize it like Frankenduck mentioned. When I performed my bench tests on the injectors, the 1-hole shot straight out, parallel with the injector itself. But the 4-hole had a spray pattern that was angled outward like a radial crown which leads me to believe, based on that cutaway you provided, that the 4-hole was spraying into the air intake chamber instead of directly onto the hot valve as designed which lead to the poor combustion.

When building the bike, I shouldn't have tried to upgrade anything before getting it up and running. Moral of the story, and say it with me kids: "Don't believe everything you read online.”

[Laitch]

@Laitch: yes I did mention them.
@frankenduck:That image you posted is a great visual, thanks for posting it! I

I finally found that reference, Tex. It should have penetrated my concentration. Most disappointments with them involved lackluster performance "improvement" and slight increased fuel consumption.

The helpful cutaway diagram posted by frankenduck is one of a series of excellent Brick engine system images provided by BMW in its 1988 K100/K75 Repair Manual that has been available for download by members of this site for years.

Your observation of getting the engine running before trying to modify it should be taken onboard by other aspiring customizers.
Your persistence has paid off! I hope you will post more photos as you complete this project.

[Martin]

Retro I had a typo, dyslexic fingers it was supposed to be increased fuel consumption. A lot of the bum dyno reports of increased performance when fitting the 4 hole injectors can be put down the fact that the 1 hole injectors were blocked or faulty. I had a feelable increase in performance when I finally got my injectors clean after doing them myself. The first two attempts by a local shop were only partially successful. I ended up having to use thinners in my wife's ultrasonic jewelry cleaner with the injectors connected to a pulser multiple times before I got the correct spray pattern. Unfortunately the lid on her jewelry cleaner sort of melted in the process. I upgraded to a 10lt stainless steel one.
Regards Martin.

[RetroTexan]

A lot of the bum dyno reports of increased performance when fitting the 4 hole injectors can be put down the fact that the 1 hole injectors were blocked or faulty.

Honestly, what other explanation is there?! From this experience, I can't possibly understand how anyone would find benefit in running 4-hole injectors on these bikes.

The difference is night and day: my bike just runs so much better with the stock 1-hole injectors! No more black smoke, much less vibration, MUCH better fuel economy, the fan now kicks on properly at temp, no more bogging down on hard throttle at stops.

The only "negative" difference I've found so far is it back fires a bit when twisting the throttle after deceleration while in gear which I'm pretty sure is a result of my after-market exhaust anyways. And I put that in quotation because honestly, it just sounds badass to me

[frankenduck]

What's the Bosch number of the FIs?

I think the best 4 holes for Ks are 0280150415

[Martin]

The best 4 hole injectors for a K bike are the 1 hole injectors. Also as TMG pointed out the 4 hole type will be more prone to blocking.
Regards Martin.