Engine quit - request for diagnosis assistance

You know on my Pacific Coasts, I had this trouble and the shop couldn't find the issue. They sure charged me though. Anyway, I found the problem myself. The problem was that there is a safety diaphragm that would shut off gas flow if the bike went down so that it didn't fule the fire. The problem was that the diaphragm would wear and get a leak and then it would develop the problems you described. Replacing the diaphragm resolved the issue. If the ST1100 has the same setup, then I would look for that as the culprit. It is quite easy to find and quite easy to check.

Gator6 said:

You know on my Pacific Coasts, I had this trouble and the shop couldn't find the issue. They sure charged me though. Anyway, I found the problem myself. The problem was that there is a safety diaphragm that would shut off gas flow if the bike went down so that it didn't fule the fire. The problem was that the diaphragm would wear and get a leak and then it would develop the problems you described. Replacing the diaphragm resolved the issue. If the ST1100 has the same setup, then I would look for that as the culprit. It is quite easy to find and quite easy to check.

Click to expand...

The 1100 has the same system and it is a known issue. I think it is the ethanol in the fuel that causes the failure as it is known to break down rubber. Many people out there have by passed it. I mentioned that to him but I am not sure if he has looked into this further.

I agree with everything so far.

The symptoms do sound like fuel delivery. If the float bowls start to run down you'll get that symptom where it starts on choke but won't keep running. Also, the fact that it stops completely suggests that it's not fuel flow to just one carb, but to all of them. I don't know the fuel system on the 1100 at all, but if you can open it at the last point before it splits to feed the different carbs, that's probably the place to start, then work back toward the pump. (Or is there just one carb on the 1100?)

My guess would be the issue got resolved since the thread is a year old......just sayin....

Brant said:

My guess would be the issue got resolved since the thread is a year old......just sayin....

Click to expand...

Cant get it to edit...........my bad all, sorry.

Definitely got a bad diaphram in the shut-off valve.

Brant said:

My guess would be the issue got resolved since the thread is a year old......just sayin....

Click to expand...

We are not that sure.

Yesterday he posted that he was stranded on the Dragon that the issue was back.

I texted him about the possible fuel cut off issue because he was in poor cell coverage and only TXT messages would get through. I got a response a while later that he got it going and was at his destination. He is going to post more here later. I haven't seen him post on what he did to get it going yet. My other recommendation was to open the gas cap to see if it ran better. Possible plugged vent or bad gas cap.

Hey gang - thanks for the continued discussion! Definitely not a solved problem...and now have some new data for everyone to consider.

My ride from Indy to ATL on July 3 went something like this:

1. Indy to Lville. Stop for breakfast for ~35 minutes. Bike starts up and runs fine afterwards.

2. Lville to somewhere just south of Lexington. Stop to use restroom and top off tank (because keeping the tank topped off on my way back from CO a month ago seemed to help, but now I'm not so sure the fuel level is a factor). After this quick stop of less than 10 minutes, I hit the interstate and the bike started exhibiting the same fuel starvation symptoms within a few miles. A short stop on the shoulder of less than 10 minutes and the bike fired back up again and ran fine once I got going.

3. South of Lexington to Rest Area near KY/TN border to deal with a phone call. Kept the bike running during this stop because this fuel starvation issue has only seemed to pop up after shutting the bike off for a quick stop. Since I knew this would be a quick stop, I kept it running, the temp gauge increased as normal, fan kicks on etc...and once back on the road I have no problems.

4. Rest Area to South Knoxville - fuel stop. Turned bike off to fill tank at gas station near intersection of 129 & 411 before heading towards the Dragon. Less than 15 minute stop. Bike fires right up and starts as normal. Turn onto 129 and bike starts exhibiting symptoms within 2 miles. Pulled over before it died completely and gently revved throttle listening for the bike to "correct" itself which it eventually does. Back on the road and by the time I get another few miles to the intersection of 129 & 72 where the Dragon BBQ Pit and the 129 Motorcycle Garage Restaurant are, it is wanting to die again. Since it is starting to rain and lunchtime, I pull in figuring that by the time I have lunch the bike will have sat longer than it usually needs to sit when I've been on the side of the interstate and might be ok after lunch.

5. After lunch it fired right up again, but died on me twice before I could even get to the Harley Davidson shop just a few more miles down the road (this is all still before the official start of the Dragon). Pulled in there, let it sit for another 25 minutes and decided to start heading back towards 411 where I would at least have cell service again. Died on me twice more by the time I got the few miles back to the 129 Motorcycle Garage Restaurant at 129 & 72. That is when I posted the stranded rider post from a Gold Winger's Verizon phone that had service (my Sprint phone did not). However he decided he needed to roll before I could really get a full post created, which is why it was so vague. I eventually was able to call my wife from the restaurant phone and she updated the post with a bit more info. Also had her pull up the RAN list and after seeing that there wasn't anyone in/around Knoxville (and the bike had been sitting for an hour or more), I decided to try it again to get back towards 411 where I had cell service.

6. Fired up as normal and as I rode 129 back towards 411 it ran without any issues whatsoever. Turned left on 411 and headed to ATL which was 120 miles away and decided that I wouldn't shut the bike off until I got there. Ran completely fine the entire way.

ATL to Indy on July 4th

I was in ATL to carry a videocamera guy on my motorcycle for the Peachtree 10k road race. So my morning consisted of the bike starting right up, moving it over to the start line 2 minutes away from my hotel where I turned it off and it sat for 90 minutes or so. Fired it up for the race and rode the 10k distance at just under 10mph or so covering the athletes. Once done, I kept it running as I said my goodbyes and then hit the road for home.

After seeing the day prior that fuel level didn't make any difference, I decided to keep the bike running the entire way home. So my 550 mile ride included 2 fuel stops where I refueled with the engine running and one additional stop where I did the same. The bike didn't skip a beat the entire day...nearly the entire ride was in the rain and temps were in the low 70s eventually dropping into the 60s as I got further north. One of the stints I ran the tank all the way down until the low fuel light came on - something I hadn't done since early May when I thought that there was something related to fuel level tied into all this. Had no problems running the fuel that low...

Looking for consistencies across all occurrences of this issue, it seems that it happens after the bike has been running for awhile (engine has a chance to get hot), the bike is shut off for a short period of time and then restarted.

It appears that over the last 2 days I proved that it does NOT happen when the bike has been running for awhile (engine has a chance to get hot), the bike sits for a short period but I leave the engine running and then I take off again.


Is there a component that is engaged during the process of starting the bike that would affect fuel delivery a few minutes later?


A few reminders regarding my bike: vacuum shutoff has been bypassed for a few years, no "air suck" venting occurs when I open the gas cap after the bike dies or any other time. Fuel pump has already been replaced with an Airtex that fit exactly as the OEM. Fuel filter assembly has been changed to the glass Purolator version and filter element was replaced last month as a precaution although the first one looked fine.

Have not tried running the bike with the gas cap unscrewed.

The only similarity to a hot re-start issue is my wife's KZ750, and it's air cooled. We would be out for however long, make a fuel or "quick" stop, would crank and crank and crank, finally start. When it was cold it would start with the choke on, then turn it off after the engine warmed enough. It ended up being the float levels. Two out of the four carbs were 1/4 inch low and the other two 1/8 inch low. Have not had a restart issue since float levels brought to spec. The floats should be set at 7mm on the ST. I can't imagine why float levels change from spec once they're set, unless the carbs were disassembled and something happened the their setting after they were taken apart that shouldn't have happened. Leaving the engine running was as a slick trick due to hard restarts if the engine was hot.

After reading your update I would not think that it is the fuel cutoff diaphragm. It is bypassed anyhow but the symptoms don't fit that if it were in place. The blocked vent/bad gas cap doesn't really fit either. You mentioned that if you shut it off to get gas you might have issues when trying to start it again. Well unless you have some magical way of putting gas in the bike without opening the cap you would have released any vac/vent issue with the tank.

So what does this leave. You mentioned you are on an aftermarket pump. What about adding an inline aux pump where the fuel cut off would go. I have seen where people have used an inline fuel pump to boost pressure. Were the specs of your aftermarket pump in line with OEM in terms of GPM and pressure? Before jumping down this path I would consider this thread.

https://www.st-owners.com/forums/showthread.php?127541-ST1100-won-t-start-when-hot

It is a long read so if you want to skip to the end of the book and read the last chapter it sounds like it might have been just a filter. I am assuming it is an air filter based on what he is also talking about. However I would recommend flipping through all the posts. I know he is in Columbia and I want to say he was at high altitude so that might be part of it. Also there is talk about float adjustments that were made like what Moddy just said. It just seems like what he was describing is in line with what you are. Fairly close at least. Of course we started with all the usual suspects, fuel cut off, fuel pump, fuel filter. Kind of like what you have been through.

So how old is your air filter? If you don't know (I don't recall how long you have had your bike) or it is a few years old, you wouldn't be out much by throwing a new one at it to see what it does. You are likely about to end of life anyhow. Kind of like my charging issue the other day on my 1300. My battery was about 4 years old so before really digging into things I threw a new battery in it. Things seem better now.

I mentioned in that other thread that I had a car doing the same thing to me once. Turned out to be a coolant temp sensor. I would shut off the car. The computer would think the engine was cold so the FI system would do enrichment. It was hot though and it would flood the engine. Of course it was a FI system where the 1100 has carbs.

Hope some of this information helps out.

moddy said:

The only similarity to a hot re-start issue is my wife's KZ750, and it's air cooled. We would be out for however long, make a fuel or "quick" stop, would crank and crank and crank, finally start. Leaving the engine running was as a slick trick due to hard restarts if the engine was hot.

Click to expand...

Moddy - the difference between what you describe and what I'm experiencing is that I don't have any problem restarting the bike the first time after a short stop. It starts as normal...but then just a few miles down the road starts starving for fuel. When it dies, THAT is when I have trouble restarting. Leaving the engine running the entire day on my way home was just my way of seeing if the situation was tied specifically to shutting the engine off, restarting as normal and getting going again. It would appear that I've proved that the restarting the bike part is a consistent contributing factor...

Thanks - thinking through all of the possibilities with other mechanically inclined minds will eventually lead us to a solution...and we'll all learn something (I hope!). Taking a few of your thoughts one at a time...

sennister said:

You mentioned that if you shut it off to get gas you might have issues when trying to start it again. Well unless you have some magical way of putting gas in the bike without opening the cap you would have released any vac/vent issue with the tank.

Click to expand...

Just to clarify - I have never had any trouble restarting after refueling or after stopping for other short periods of time (rest area etc). It starts up just fine...but just a few miles down the road is when it starts to starve for fuel. When it dies a few miles after getting back on the road - that is when it won't restart.

When it dies a few miles down the road, I have unscrewed the gas cap and listened for any rush of air and have never heard any sign of venting when doing so. It also has never helped the bike restart.

sennister said:

So what does this leave. You mentioned you are on an aftermarket pump. What about adding an inline aux pump where the fuel cut off would go. I have seen where people have used an inline fuel pump to boost pressure. Were the specs of your aftermarket pump in line with OEM in terms of GPM and pressure? Before jumping down this path I would consider this thread.

https://www.st-owners.com/forums/showthread.php?127541-ST1100-won-t-start-when-hot

Click to expand...

I was following that thread as well and was especially interested in the fuel pump relay post regarding the very small heat cracks that develop over time. That was about the time I wrote post #35 in this thread after my ride to Colorado and back and wondered out loud if the fuel pump relay could be the issue. If I would have had known this trip to ATL was going to be on my calendar, I would have buzzed down to GaryZR's place and swapped it out to test it. But the ATL opportunity came up quickly and I didn't have a chance to. So unless someone can convince me otherwise - it is still on the list of potential causes.

To answer your fuel pump questions - I installed the Airtex E8371. The symptoms that led up to that decision are over here on this thread. You'll see my last update there was in August 2011 - I replaced the pump at our IN Tech Day in March 2012.

https://www.st-owners.com/forums/showthread.php?87984-Engine-dies-at-speed-diagnosis-assistance-request&highlight=

According to the info over on Advance Auto Parts website, it pumps 30-40 G/Hr at 2-4 psi:

http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_electric-fuel-pump-airtex_3150151-p#fragment-2

sennister said:

So how old is your air filter? If you don't know (I don't recall how long you have had your bike) or it is a few years old, you wouldn't be out much by throwing a new one at it to see what it does.

Click to expand...

I replaced my air filter last year with an EMGO filter. I need to pop the cover off to remind myself if I added a piece of tubing to create a good seal or if it was the correct height straight out of the box. Thing is that I've done plenty of riding between then and April of this year when this issue started...so it doesn't initially seem the different air filter would be the culprit, but it would be easy to buy an OEM Honda air filter and swap it out to test.

Nathan, we are in Branson MO right now, and have been following your situation. But we will be back sometime on the 8th. Any parts that I have left that you want to try and switch out, one at a time, including the carbs, or coils, and relays is OK with me. I'll update when we get back home, so you can call or msg. me then to get together and come up with something that will help figure this out.

Gary.

If this has already been explored, sorry for the repeat. If the fuel pump is is working properly, what about the backtracking from there to the "unit" that tells the fuel pump to run intermittently. If you have symptoms of fuel starving then it shuts off, I can see the level of fuel disappearing from the float bowl without a dose of fuel soon enough until it runs out. Then, for some reason, it will eventually start, because I can see this mechanism that makes the fuel pump run intermittently keep the float bowls charged. If all of this fails, and you're not able to figure this out. I took my machine to a guy from when I was working on my ride earlier this year. He charges 30.00 an hour for diagnostic and labor charges. He figured out I had a clogged #3 carb jet. It would have only cost 30.00 from that point, but I was out of town and had him fix it while I was gone. He pulled the carbs, cleaned out what he could because it would not all come out, greatly improved my performance, 45.8 mpg going to OhSToc, total charge 80.35. 1 hour diagnostic labor 1.5 hours labor. He's in the Southeast Indy area http://www.lightslefton.biz/.

My parts are from the 1991 standard, not abs model. I think they should be able to switch and fit. Does anyone know any reason why they would not?

Gary.

smunderdog said:

Thanks - thinking through all of the possibilities with other mechanically inclined minds will eventually lead us to a solution...and we'll all learn something (I hope!). Taking a few of your thoughts one at a time...

Just to clarify - I have never had any trouble restarting after refueling or after stopping for other short periods of time (rest area etc). It starts up just fine...but just a few miles down the road is when it starts to starve for fuel. When it dies a few miles after getting back on the road - that is when it won't restart.

When it dies a few miles down the road, I have unscrewed the gas cap and listened for any rush of air and have never heard any sign of venting when doing so. It also has never helped the bike restart.

Click to expand...

Ok I was thinking you couldn't get it started. Either way it isn't the fuel cut off.

I was following that thread as well and was especially interested in the fuel pump relay post regarding the very small heat cracks that develop over time. That was about the time I wrote post #35 in this thread after my ride to Colorado and back and wondered out loud if the fuel pump relay could be the issue. If I would have had known this trip to ATL was going to be on my calendar, I would have buzzed down to GaryZR's place and swapped it out to test it. But the ATL opportunity came up quickly and I didn't have a chance to. So unless someone can convince me otherwise - it is still on the list of potential causes.

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Ok. I didn't read all the posts but wasn't sure if you had seen or followed the thread.

To answer your fuel pump questions - I installed the Airtex E8371. The symptoms that led up to that decision are over here on this thread. You'll see my last update there was in August 2011 - I replaced the pump at our IN Tech Day in March 2012.

https://www.st-owners.com/forums/showthread.php?87984-Engine-dies-at-speed-diagnosis-assistance-request&highlight=

According to the info over on Advance Auto Parts website, it pumps 30-40 G/Hr at 2-4 psi:

http://shop.advanceautoparts.com/webapp/wcs/stores/servlet/product_electric-fuel-pump-airtex_3150151-p#fragment-2

Click to expand...

How does this line up with the OEM pump's Spec? I don't have my Service Manual in front of me. Have you tried to verify the flow rates? It is possible the pump is bad even though new. 30GPH is 0.5 GPM 40GPH is 0.66 GPM. So if you had a 1 gallon gas jug, jumper the pump output to the gallon jug and let it run for a minute. If it is about half full your pump is working to spec and as long as that in spec with the bike you can rule it out. Be careful doing this though. I know of one member that had a small fire in doing this.

I replaced my air filter last year with an EMGO filter. I need to pop the cover off to remind myself if I added a piece of tubing to create a good seal or if it was the correct height straight out of the box. Thing is that I've done plenty of riding between then and April of this year when this issue started...so it doesn't initially seem the different air filter would be the culprit, but it would be easy to buy an OEM Honda air filter and swap it out to test.

Click to expand...

I am not saying this is the issue. Your symptoms may be different. With that thread do you recall if he could get it to start and it died shortly after when hot like you mentioned or was it simply that it wouldn't start when hot. Like I said as well, I want to say he is dealing with an altitude issue that you don't have. That may have been a contributing factor to what seems to have ended up to be an air delivery issue and not a fuel supply issue.

I don't recall if you took a good look at your spark plugs. They will typically show how clues as to what is going on in the cylinders. Run it till it is hot on a hot day then once home shut it down and see if you can get it to die while there. Pull your plugs and see what you can see. Comparing them to each other and comparing them to the diagnosis charts. It might show a too rich (air delivery issue) or too lean (fuel delivery) issue. Someone posted a really good diagnosis link here somewhere the other day. I can see if I can find it.

I think this is the page that someone linked to.

http://honda-tech.com/showthread.php?t=2502308


Of course you don't need to cut up your plugs like this but it gives you an idea.

So to help me stay organized, here is a list of items brought up as potential culprits. My bike is a non ABS '96...

Pending investigation:

ECM - as suggested by Superzuki in post #56

Fuel Pump Relay - potential heat cracks as outlined by ladder106 on this thread? (https://www.st-owners.com/forums/showthread.php?127541-ST1100-won-t-start-when-hot/page8)

Coils - crimp connectors affected by heat (suggested by ST1100Y in post #40)

Carbs - Synched at the March 2012 IN Tech Day. Have not torn into them since I purchased the bike with 22,000 miles in 2008 (currently has 53,000 miles on it).

Fuel Pump - No longer running OEM pump. Replaced with the Airtex E8371 in March 2011. Have not tested it's flow rate and if I end up doing so will make sure I don't catch fire like George did.

Not Likely

Vaccuum Bypass Valve - it was bypassed back in 2010 when I was seeing similar symptoms that eventually I diagnosed as the fuel pump seizure syndrome.

Fuel Filter - No longer running OEM. Replaced in 2012 with Purolator Pro 806 that has replaceable cartridges. Although it didn't look like it needed it, I went ahead and replaced the cartridge in early May 2013 before my BBG run to CO.

Air Filter - Replaced in 2012 with EMGO filter.

Spark Plugs - they were pulled and looked at when Gary came up to my place and we found the loose electrical connection to the fuel pump in November 2012. To my recollection, they looked normal and although I had purchased new ones with the intent of replacing them, we put them back in so we didn't introduce another variable to the mix. I would have to pull them again to match their coloration up against the thread you are referencing. I've seen that thread as well somewhere...

Gas Cap & Vent tube - have opened the cap without hearing any rush of air when the bike has died on me, so it doesn't appear to be a venting issue.

smunderdog said:

Fuel Pump - No longer running OEM pump. Replaced with the Airtex E8371 in March 2011. Have not tested it's flow rate and if I end up doing so will make sure I don't catch fire like George did.

Click to expand...

I wasn't going to throw George under the bus like that.... But hey, at least he has healed up. Though his service manual has a bit more character now...

Here is what I would do if you opt to do a flow test. Try and include the filter as part of the test. Or do the test with and without the filter as a comparison. I assume you have the filter mounted where the OEM one goes so it should be pretty easy. Never know how much restriction something adds. I want to say that there is a spec that the fuel delivery needs to meet in the service manual. I have a Haynes and a factory manual if you need me to look and see what they say. They are out in the shop though. I am just thinking that the filter may be clean and fine but if it is too restrictive by design it could still cause an issue. Same goes for the air filter since it isn't OEM. Maybe there is one that you could swap out for a test as well. If you can't find one, if you can get it to fail while home, get it to fail and try and pull the air cleaner while it is failing and see if it starts. That would eliminate that as a possible cause. While not recommended to ride without an air cleaner you can see if it will start. Carb Syncs are done that way anyhow. It isn't a bad idea to do another one since it has been a while but odds are they don't go out of spec all that often. Though I spot check mine with a SK Flowmeter whenever I have the air cleaner off on my 1100.