Mystery intermittent rough running

My 2006 has run, well, like a Honda since I got it 5 years ago.

Long 5-week-4-visits-to-the-shop story made short...it runs perfect but then starts running rough to the point of being unrideable. The trigger appears to be heat and possibly vaporizing fuel in the tank.

On opening the cap on the last episode, the fuel was at a rolling boil and spewed out of the filler. The tank was almost too hot to touch. Yet the temp gauge has never moved from 3 bars, despite me being able to often feel temperature changes on my legs while riding.

I suspect the fuel rail is picking up vaporized fuel and sending into the injectors resulting in the rough, jarring performance.

The bike has baffled the techies and consultations to Honda Canada. I've changed plugs, coils, fuel filter, tested fuel pressure (100%).

Is it possible to have the motor run so hot as to boil the fuel while the temp gauge remains static at 3 bars?

Next steps: power flush the cooling system and possibly change water pump.

When you tested the fuel pump pressure did you also do the volume test? It has been known to pass the pressure test and fail the volume test. That can cause rough running and surging. A failing fuel pump tends to act up more with low fuel and a hot bike but that's not a given.

Might be a good idea to check if there's any pinched fuel, return, vent lines etc.


The manual lists a ECT sensor test but I'd tend to believe the gauge.
2.1-2.6 Kohm 68?F 650-673 ohms @ 248? F.
Book says replace if more than 10% beyond that.

You can a least verify some flow with the bike cold. Take the radiator cap off and start the bike you should see a decent amount of flow that follows throttle position in the small line from the thermal wax idle advance that attaches just below the overflow siphon at the top of the filler neck.

This doesn't sound like a cooling issue though. If anything the pump seal may leak but that's about it.
.02 a pinched line or a fuel pump.

"it runs perfect but then starts running rough to the point of being unrideable"
Sounds like a classic fuel pump on the way out.

I had the gas spew out of the cap when I opened it. I believe it was caused by a vapor canister filled with gas. I had just run out of gas. I filled the bike with a gas can with no nozzle. Gas ran all over the tank and even down the vapor recovery hose to the canister. I filled the tank and rode it home. I heard the noise in the tank so I opened the cap. Gas came out like a geyser. All that said I am not sure if it is connected in any way to your issue. Your situation does sound like the fuel pump with a low volume issue. Let us know what happens. You can get a fairly cheap, maybe $70, fuel pump for a Honda car. Do a search on this forum to find out which pump works. It would be cheaper to throw a pump at it than have the dealer try to diagnose it.

Thx for this.

Part of the long story short story...I normally parked the bike when it acted up. The last go round I was 350kms from home and decided to run 'er till she blew up. It started while stuck in traffic at 35degrees C but after running at speed for 20 minutes, it smoothed out and ran like a Honda.

About an hour up the road and at the top of the snowshed hill (Coquihalla Highway aka "Highway through Hell") running up at 120kms/hr, it acted up again. 10 minutes later it smoothed out and ran...like a Honda. At the next big hill, same thing, 10 minutes later, running like a Honda. Next hill, same thing. It ran the next morning fine until stuck in traffic and nearly gave me whiplash trying to climb the 800 foot elevation to my house. It was after this climb the gas blew out on opening the gas cap.

I thought fuel pump as well. But I it will do it despite full or empty. The fuel rail test was only pressure not volume. The following comment by woodybelle is good and I will likely swap out the fuel pump just for good measure. But my gut says it's the heat has something to do with it. And hey..this is Canada eh! The frozen north! You guys run these bike in Arizona and Nevada and don't have them buck like a mule. So me thinks there must be a blockage, kinked line or waterpump issue (always good coolant and swapped out every 3years/30,000kms)

Thx for this woodybelle.

I remember reading something about the fuel pump crossing over to the automotive side...just like the oil filter ($17 at Mr. Honda, $5 at Canuck Tire). I'll hunt it down and swap the fuel pump...just cuz.

Just an update...mystery solved.

ST1300r above gets the Academy Award. It was the fuel pump going bad. Although the pressure tested fine, the flow volume was way down at about 70 cc's. Normal is about 180cc. The new pump (OEM from the Honda store) is putting out over 200.

The fuel boiling is gone. I think the reason for that is that the fuel under low volume is exposed in the fuel rails close to the block longer and has time to heat up.

I just wish I had time to test a generic pump at less than $200 Canadian. The OEM part was over $500 Can. The shop would not put in a generic for liability reasons. So...$3,300 total, 4 months off the bike, 5 visits to the shop and the world is right again.

Wow,. Thanks for sharing. Sorry you had to go through this........

Now ride !

ToddC

geoqwest said:

So...$3,300 total, 4 months off the bike, 5 visits to the shop and the world is right again.

Click to expand...

holy smokes! Glad you got this issue resolved! This figure scares the heck out of me, I can't imagine spending half what I paid for my bike to get it running again (my 7k price tag was a stretch for my budget) stories like this make me think that I am over budget on my bike and that initial cost was just part of what it costs to own it.... of course I expected tires, fluids, insurance, gear, plates, title..... but a major repair bill like that and I don't know what I'd do....


The saving grace here is that this site accurately and quickly diagnosed the issue, and had he done the work himself the cost would have been significantly cheaper

Hi Geoqwest) Just a quick question, how many kms on your ST before fuel pump failure, as I am approaching 125000 kms and am thinking replacment this fall may be in order as a preventative thing?

I question as to how low some people run their tanks... the pump is cooled by the gas. Wondering if low tank usage could cause early pump failure

Tom I think that has a lot to do with it. my 03 has 172k on it and still on the original pump however I got one of these just in case but I try not let mine go below 2 bars before I gas up.
http://www.highflowfuel.com/i-14521145-new-intank-efi-fuel-pump-honda-st1300-2003-2013.html

Tom Mac 04a said:

I question as to how low some people run their tanks... the pump is cooled by the gas. Wondering if low tank usage could cause early pump failure

Click to expand...

Would be hard to quantify.
I'm at about 80k, just about every tank fill is down to one bar flashing when I do. 3 roundtrips to work get me to that point each time. I won;t fill at the 2.5 trip point due to taxes in the work state.

I'm currently waiting on my new (cheap) fuel pump to be delivered. Mine is running just like the original poster with bucking going on big time!! I milked it home from a trip 520 miles. The last 150 were just like his, it was very bad. It seemed to be boiled fuel running down the fuel rails but stayed at 3 bars all day on the engine fluid temps.

FYI I've ran mine down to empty almost every tank in it's 196,000 mile life.

The pump is cooled by gas running through it not by gas around it.

If low fuel levels shorten pump life my two teenagers disproved that theory by constantly running their 230-250,000 mile Hondas around on empty as does the amount of engine heat transferred to gas in the ST's lower tank. If it caused problems Honda and other manufacturers would warn against operation at low fuel levels or they would calibrate gauges to show E when a "cooling amount" of gas remained in the tank. Popular theory though.

FWIW I proactively replaced my fuel pump at 120,000 miles to prevent problems on long rides. It seems to be common enough at those miles and more to have a problem. It's cheap and easy to do with aftermarket pumps like the HFP-382 kits

geoqwest said:

Just an update...mystery solved.

ST1300r above gets the Academy Award. It was the fuel pump going bad. Although the pressure tested fine, the flow volume was way down at about 70 cc's. Normal is about 180cc. The new pump (OEM from the Honda store) is putting out over 200.

The fuel boiling is gone. I think the reason for that is that the fuel under low volume is exposed in the fuel rails close to the block longer and has time to heat up.

I just wish I had time to test a generic pump at less than $200 Canadian. The OEM part was over $500 Can. The shop would not put in a generic for liability reasons. So...$3,300 total, 4 months off the bike, 5 visits to the shop and the world is right again.

Click to expand...

I think I would have a discussion with the shop about charges for the first 4 visits where they accomplished nothing. The failing fuel pump issue is not a new one. You shouldn't have to pay to teach them how to do their job.

My ST1300 bike is running great after replacing the fuel pump yesterday. I bought the cheapest ebay kit I could find with the "Custom Parts High Quality" brand CSTP-382 HFP-382 pump in the kit. Nothing was used but the pump so it all worked great. I'd link the ebay seller but the item I bought for $18.78 is now shown as $118.78???

the job took about two hours. I didn't remove the upper tank. I tried to remove the pump unit without breaking the fuel line banjo fitting loose. It won't come out that way. you have to remove the banjo and return fuel line. That's not a big deal as I reused all the gaskets and none leaked. My bike had 196,800 miles on it at replacement.

If you want to carry a spare I'd suggest you order the cheapest HFP-382 kit off ebay. Like I said, mine was only $18.78 with shipping!

View attachment 176308

Same part $19.92 today. Second pump replacement pump for me already, not quite 80k miles on my bike. Had boiling roiling fuel on our recent North Carolina trip - opened the tank because of all the noise in there, fortunately the top tank was only about half full, so no explosion. Lots of surging and stumbling when railing through the hills, then it would behave during steady state cruising. Was slowly getting worse all this summer already, so I figure proactive replacement is in order, and for < $20...

grrr...

I don't think there is any particular mileage these things go out. My ole '05 has the original fuel pump still in it and running just fine at 185K. The only fuel pump I have had to replace in all my other bikes was the '04#2 that sat for six years in a shed (it wasn't stored properly either). And I put in a used ebay ST1300 pump for that.

Even my 2012 with only 7,300 miles on it gets that boiling tank issues when riding in really hot weather. One thing I did that helped some was to put a heat shield between the tank and air cleaner box.

I also think that the 2008 and newer run hotter than the pre '08s do. I have a lot less issues with the boiling gas in the tank with the '04s than I do with the 2010 & 2012.

Hmm. I may need to think about the heat shield idea. I know a lot of folks complain of heat from under/around the tank, but that's never been an issue with my '03. Still won't hurt to insulate it. The boiling issue wasn't even on a particularly hot day, and was still occurring after a half hour cruise back to the house. All the heat from mine that I notice comes from the cats. No way I would survive riding this bike without heavy boots - I'm pretty sure my ankles would burn.