The Fuel Pressure Regulator, High Temperatures and Vapor Lock 94 K1100rs

[cheetah]

It's Texas, it's hot down here and my bike has quit on me in traffic and while traveling 80mph  :falldown:

It idled fine, but when I went to take off, it just died.  Let it sit for 5ish minutes, starts right up and good to go.  Same remedy on the highway.

So, can high temps cause the FPR to act up, or is it vapor lock?  I did run high amounts of Techron fuel cleaner and Marvel Mystery oil in the last few tanks and it has not happened recently - leads me to consider the FPR...?

Any thoughts, suggestions and solutions are welcome  :clap:

[Scott_]

Is your cooling fan running during this time? Or do you have a manual fan switch that you can turn the fan on?

[johnny]

i donts know of any motobrick fuel pressure regulator failures...

anybody know differently...

j o

[JamesInCA]

Heat-linked engine failure, starts up again after cooling off?

Is this not the textbook symptom of Hall Effect sensor failure?

[lhead]

Vapor lock seems to have gone the way of burnt points now that bikes (including ours) are sporting fuel injection. I don't recall the last time I've seen or even heard of an engine developing vapor lock.

However, if the fuel in the tank is being heated past the state change point and is developing bubbles, it's a possibility. One sure way to tell is if you could find a piece of clear reinforced fuel line to install on a temporary basis leading from tank to FI. When the symptoms occurred again, just glance down and check for gas bubbles.

[Grim]

Heat-linked engine failure, starts up again after cooling off?

Is this not the textbook symptom of Hall Effect sensor failure?

Id agree that its probably ignition and not fuel if you can hear the pump running. FI typically doesn't get vapor lock. Regulators usualy just stop ramping up pressure when the diaphragm cracks. Not a problem that would go away when cooling down. And typically it wouldn't kill the engine dead just start missing or getting a bad ping from being lean under load.

Read a post where the paste under the ignition module dried out and not getting good heat transfer. Symptoms are similar and I seem to recall the guy was in Phoenix. Cheap stuff at any auto parts store.

I had some intermittent problems that seem to have been dirty ECM connections. I took a Q Tip cleaned the ECM side and a jewelers screw driver to make sure there were no burnished spots on the plug. Been a couple weeks since I had the problem.

[Scott_]

Heat-linked engine failure, starts up again after cooling off?

Is this not the textbook symptom of Hall Effect sensor failure?

Read a post where the paste under the ignition module dried out and not getting good heat transfer. Symptoms are similar and I seem to recall the guy was in Phoenix. Cheap stuff at any auto parts store.

I think his bike is to new for that. That heat sink issue dealt with an ignition amplifier on the earlier K's. I'm thinking only like the 92's and 93's possibly or something close. 94's and later shouldn't have that.

[JamesInCA]

Here's a decent thread on some K1100 bikes cutting out in the heat: http://www.k11og.org/forum/viewtopic.php?t=5246&postdays=0&postorder=asc&start=0

It reminds us to check a few other common failure points:
-- Thermostat
-- Fuel sender (esp. the ground connection on the outside)
-- Tank connector (wired to the fuel sender)

[racinrich]

don't kid yourself vapor lock can happen. reed vapor pressure is lower with fuel saturated with alcohol.usually vapor lock happens at hot soak restart when fuel pressure drops in rail.fuel under has a higher boiling point so unlikely while running. I have heard of fuel boiling in the tank in arizona.sounds like a pickup or ecu.take a heat gun to the pickup while running ,use a ir temp gun to monitor component temp ,don't melt the wires

[johnny]

the bugeye motobrick would stop running... i would open the gas cap and relieve the vacuum... start it up and be on my way... it would do it on hot days when i would roll out a tank of gas without stopping...

j o

[cheetah]

Is your cooling fan running during this time? Or do you have a manual fan switch that you can turn the fan on?

The system runs temperature wise where it's supposed to.  With the exception of a hot day.  Then the temp needle will be slightly more right - but not near the red.  The fan works well and does what its supposed to.

[cheetah]

the bugeye motobrick would stop running... i would open the gas cap and relieve the vacuum... start it up and be on my way... it would do it on hot days when i would roll out a tank of gas without stopping...

j o

The times it happened in town, I was sitting in traffic idling.  Light goes green, and as soon as I give it sime power, it cuts.  On the highway I was doing almost 80, well, until it died  :dunno2:

[Scott_]

Sounds like its time to get the hair dryer(or carefully use a heat gun) and check the HES sensors on the front of the engine. They can fail under extreme heat conditions.