Fuel problem again

wjbertrand · Jul 16, 2015

Seems like Honda added the ground wire to the tank to ensure a positive connection. The tank itself is probably not designed to be grounded to the frame, hence the increased resistance upon removing the ground wire. This assumes you are testing to the frame or ground terminal of the battery. If so I suspect this is normal.

Anna'sDad · Jul 17, 2015

Bill144 said:
I notice I get a resistance from the top of the reserve tank to ground IF the ground wire is disconnected.

This should not come as much of a surprise as the lower fuel tank is mounted to the chassis in four places with rubber isolation grommets, which make for poor electrical conductivity. The Green conductor is essential to the fuel pump circuit, as it provides the required connection to chassis ground.

Perhaps a more useful test would be to check for voltage (+12vdc) between the Brown conductor and chassis ground (as well as the Green conductor) the next time the bike quits running. If voltage is not present on the Brown conductor and chassis ground, then the Fuel-Cut Off Relay (or some component of the power source circuit) is suspect. On the other hand, if voltage is present on the Brown conductor and chassis ground, but not present with the Green conductor, then the Green conductor (or some component of the chassis ground circuit) is suspect.

The Fuel-Cut Off Relay inspection should include an examination of the condition of the connectors inside the socket that the relay connects to, a few members have noted discoloration/corrosion in this area.

Of course if the voltage checks out, and +12vdc is present between the Brown conductor and the Green conductor, then the Fuel Pump (or some component of this circuit inside the fuel tank) is suspect.

One final thought, when the bike quits running, check for voltage (+12vdc) between the Brown conductor, and chassis ground whilst the conductors are still connected to the Fuel Pump, if there is low or no voltage present, check for voltage again, but this time with the Brown conductor disconnected. If voltage is present only with the Brown conductor disconnected, that would be an indication that the fuel pump circuit cannot pass sufficient current (amps). The usual suspects in this situation are dirty, or corroded contacts, and connections.

Bill144 · Jul 17, 2015

Anna'sDad said:
This should not come as much of a surprise as the lower fuel tank is mounted to the chassis in four places with rubber isolation grommets, which make for poor electrical conductivity. The Green conductor is essential to the fuel pump circuit, as it provides the required connection to chassis ground.

Perhaps a more useful test would be to check for voltage (+12vdc) between the Brown conductor and chassis ground (as well as the Green conductor) the next time the bike quits running. If voltage is not present on the Brown conductor and chassis ground, then the Fuel-Cut Off Relay (or some component of the power source circuit) is suspect. On the other hand, if voltage is present on the Brown conductor and chassis ground, but not present with the Green conductor, then the Green conductor (or some component of the chassis ground circuit) is suspect.

The Fuel-Cut Off Relay inspection should include an examination of the condition of the connectors inside the socket that the relay connects to, a few members have noted discoloration/corrosion in this area.

Of course if the voltage checks out, and +12vdc is present between the Brown conductor and the Green conductor, then the Fuel Pump (or some component of this circuit inside the fuel tank) is suspect.

One final thought, when the bike quits running, check for voltage (+12vdc) between the Brown conductor, and chassis ground whilst the conductors are still connected to the Fuel Pump, if there is low or no voltage present, check for voltage again, but this time with the Brown conductor disconnected. If voltage is present only with the Brown conductor disconnected, that would be an indication that the fuel pump circuit cannot pass sufficient current (amps). The usual suspects in this situation are dirty, or corroded contacts, and connections.

I do have everything ready for the tests the next time it quits. My problem is where do I want to be when it quits again? One the side of a country road - on the side of the highway - how close to home?
Undiagnosable problems are never easy on my stress level. I think I will modify the three wires going to the pump so I can have easy access to test points. I did run another ground from the tank to the frame just in case it is the original ground feed.
Thanks again for your input.

Anna'sDad · Jul 17, 2015

Bill144 said:
I think I will modify the three wires going to the pump so I can have easy access to test points.

You may never know what the problem is/was if you begin modifying the current environment.

I think if this were my situation, and I couldn't reproduce the problem, I would carry a volt meter with me, and just drive around the local neighborhood.

If Vernon is anything like the Canadian cities I've visited, I can't imagine there isn't a Tim Horton's shop on every other street corner, at least you won't want for nourishment.

Bill144 · Jul 19, 2015

Anna'sDad said:
You may never know what the problem is/was if you begin modifying the current environment.

I think if this were my situation, and I couldn't reproduce the problem, I would carry a volt meter with me, and just drive around the local neighborhood.

If Vernon is anything like the Canadian cities I've visited, I can't imagine there isn't a Tim Horton's shop on every other street corner, at least you won't want for nourishment.

There are only 4 Tim Hortons in Vernon so you are correct about the nourishment. I'm kind of in a holding pattern right now. I have an email off to the fuel pump manufacturer. The pump has a lifetime guarantee. I want to know if they have heard of this problem. I also want to remove the pump and see if its a connection in the tank.
Tomorrow is a hot day so I will try and replicate the problem. I will remove the side tupperware and take it for a run. I do hate working with gas in my garage. I live in a townhouse complex so I worry about gassing out my neighbors.

Bill144 · Jul 22, 2015

Well due to many forest fires in my area yesterday I decided not to go for the test ride. Lots of smoke. Instead I tore the fuel pump out of the reserve tank and did a thorough check of the wiring. All looked good.
Today I am going to go for the test ride.

gsforster · Jul 22, 2015

Bill I would love to have a look at it see if I can help you out. I'm an auto tech by trade but fairly well versed in electronics. I also am fairly close

First determine if there is still power to the pump module when it acts up. That will point to next direction either relay/supply circuit or something inside the tank or pump itself. I find best tests are voltage drop tests measured on a loaded circuit, as resistance tests with an ohmeter are usually next to useless in finding bad connections (high resistance does not show up until circuit has a load on it.) Getting it hot enough to start showing the problem is key. Should wire up a simple bulb/socket pigtail maybe with a switch in line and hang it out from under the seat. Connect it to the fuel pump connector (backprobed) at least then when it acts up flick the switch and see what you got. What kind of pump did you replace it with? I've seen many auto fuel pumps do this when they get hot, what happens is they run slower and slower as they heat up kind of like they are siezing up. Then after shutdown they wont start turning again until cool. Can do a current probe / labscope to get the current waveform of that pump and then can figure the rpm of the motor itself. Example - there are usually 8 segments on a fuel pump commutator so you would see 8 distinct patterns on screen before the set repeats. When the pattern repeats, that is one revolution. Take how many milliseconds that revolution took, multiply by 60,000 gives you pump rpm. I have used this method to call out fuel pumps on these troubling intermittents.

Bill144 · Jul 24, 2015

gsforster said:
Bill I would love to have a look at it see if I can help you out. I'm an auto tech by trade but fairly well versed in electronics. I also am fairly close First determine if there is still power to the pump module when it acts up. That will point to next direction either relay/supply circuit or something inside the tank or pump itself. I find best tests are voltage drop tests measured on a loaded circuit, as resistance tests with an ohmeter are usually next to useless in finding bad connections (high resistance does not show up until circuit has a load on it.) Getting it hot enough to start showing the problem is key. Should wire up a simple bulb/socket pigtail maybe with a switch in line and hang it out from under the seat. Connect it to the fuel pump connector (backprobed) at least then when it acts up flick the switch and see what you got. What kind of pump did you replace it with? I've seen many auto fuel pumps do this when they get hot, what happens is they run slower and slower as they heat up kind of like they are siezing up. Then after shutdown they wont start turning again until cool. Can do a current probe / labscope to get the current waveform of that pump and then can figure the rpm of the motor itself. Example - there are usually 8 segments on a fuel pump commutator so you would see 8 distinct patterns on screen before the set repeats. When the pattern repeats, that is one revolution. Take how many milliseconds that revolution took, multiply by 60,000 gives you pump rpm. I have used this method to call out fuel pumps on these troubling intermittents.

Hello Geoff - On Wed I took the bike again to see if it would fail. It did fail near Armstrong. I had previously knicked the feed cable to the pumps insulation so I could directly feed it power so I could take a faulty relay out of the equation.
Previously with the pump I tested the jumper to the feed wire and it ran the pump. When I did it again with the bike down it blew the fuse in the power source I was using. It was like the pump had grounded.
about 40 min later all was OK, I didn't trust it so I had BCAA haul it home for me.
When I pulled the connection apart the resistance of the pump was 20 ohms. When it is cold it is about 1.3K ohms.
I don't understand.
I also have an electrical background being a Industrial Electrician for 30 years in mining.
I definitely would accept your help.

gsforster · Jul 24, 2015

Bill144 said:
I definitely would accept your help.

pm sent

winston lee · Jul 25, 2015

Have you checked the venting to atmosphere of the fuel tank. If the tank can not vent properly, at some time after starting and running the engine there could be a partial vacuum in the tank and then the fuel pump will be unable to supply the injectors properly.
When you have stopped, After some time if the fuel tank gets back to normal atmospheric pressure then the pump will work properly and supply fuel to the injectors as it should.
Cheers Winston Lee , Northampton, Western Australia

Bill144 · Jul 25, 2015

winston lee said:
Have you checked the venting to atmosphere of the fuel tank. If the tank can not vent properly, at some time after starting and running the engine there could be a partial vacuum in the tank and then the fuel pump will be unable to supply the injectors properly.
When you have stopped, After some time if the fuel tank gets back to normal atmospheric pressure then the pump will work properly and supply fuel to the injectors as it should.
Cheers Winston Lee , Northampton, Western Australia

Thanks Winston - I did check for that possibility and did not hear any suction when I opened the gas cap. The bike still refused to start.

JDM ST1300 · May 19, 2016

Did you ever get this resolved I'm having a similar problem

SilberPfeil · Jul 26, 2016

JDM ST1300 said:
Did you ever get this resolved I'm having a similar problem

I may be experiencing a similar problem. I just returned from a trip "out west". On the 3 days coming home, the bike would sputter (cut out) in high temperatures (over 95 degC), but ran flawlessly when temps were around 90 or lower. I tried some Sea Foam when it first happened but I don't think it affected anything. I ended up riding at night the last 2 days to get home.

Some other symptoms:
- much of the last good day was spent in 95+ temps with no problem
- when it happened, riding faster (70+ mph) seemed to lessen the effect
- even when it was hot, taking a break (half hour fuel stop) would make the problem go away for a while
- the bike never completely stalled
- the bike always idled fine
- the bike had around 111K miles when it started. I've never been in the lower tank (original fuel filter).

I haven't done any investigating yet. I got home at around 5am earlier today and spent most of the day sleeping and catching up with family.

It sure seemed fuel-related. I'm thinking of just replacing the fuel pump, filter, and FPR. The difficult part is reproducing the problem. It only happened after riding a while in high heat.

Tdinova · Nov 13, 2022

SilberPfeil said:
I may be experiencing a similar problem. I just returned from a trip "out west". On the 3 days coming home, the bike would sputter (cut out) in high temperatures (over 95 degC), but ran flawlessly when temps were around 90 or lower. I tried some Sea Foam when it first happened but I don't think it affected anything. I ended up riding at night the last 2 days to get home.

Some other symptoms:
- much of the last good day was spent in 95+ temps with no problem
- when it happened, riding faster (70+ mph) seemed to lessen the effect
- even when it was hot, taking a break (half hour fuel stop) would make the problem go away for a while
- the bike never completely stalled
- the bike always idled fine
- the bike had around 111K miles when it started. I've never been in the lower tank (original fuel filter).

I haven't done any investigating yet. I got home at around 5am earlier today and spent most of the day sleeping and catching up with family.

It sure seemed fuel-related. I'm thinking of just replacing the fuel pump, filter, and FPR. The difficult part is reproducing the problem. It only happened after riding a while in high heat.

What was the cure.. I have a 07 acting like your. I replaced the pimp and ordered a relay. Relay should be here tomorrow.. 135xxx km

Fuel problem again

Ventura Highway