ST1300: Fuel Indicator Problem

Interesting, Scooter. I was wondering about the possibility that the Fuel Pump could be repaired... the whole assembly is probably going to be spendy, and I'm not even sure it'd offer a cure.

I did notice last night, right after topping off the tank, that the fuel indicator will not indicate full, either. It stops short of the final bar. Anyone else experiencing this, too?

So far, I've concentrated on the easy things:

1) Topped off the tank and added ~8oz. of Sea Foam to see what happens. Sea Foam has had curative effects on other motors for no explainable reason. I figure it can't hurt.

2) Pulled the battery out. Turned the ignition on and then off to bleed any residual power. I have a feeling that I did something unknowingly wrong, electrically, when I was working on the ST this winter.

All I can do now is watch the fuel gauge run down and see if it holds at two bars again. I have a terrible feeling that this will be an intermittent problem, though, and hard to catch. If the simple solutions don't work, I'll pull the fuel pump and check the voltage.
 
Mellow said:
If it's not showing full when you fill it up, it could be the upper sending unit

This thread may help: https://www.st-owners.com/forums/showthread.php?t=23849

maybe, this will fix both the full tank and lower reading issues.
Click to expand...

Would that be the "Fuel Unit Set"? Part 37080-MCS-G00?

At $73, it'd be a cheaper than the $329 Fuel Pump Assembly for the lower tank. Assuming that was the problem, of course.

Great observation, Joe. :yes:

I hope that would be the worst case scenario fix.

It actually makes sense considering that I lifted the upper tank off and disconnected it this winter when accessing the throttle bodies. It's more likely I messed up the upper tank than the lower.
 
Hey Erik, just to throw something else out there but isn't there a known issue where the fuel gauge isn't really that accurate when you are doing lots of shorter trips and the bike is on the sidestand? I thought I read something about that but it may have been limited to the rage to empty estimate may not be accurate. Just throwing it out as another posibility.

You could run for a few tanks, running it down and see how much gas it takes subtracting from 7.7 gal to see how much was really in there. Of course while doing this watching the trip odometer and the MPG so you don't run it dry again.
 
Ordinarily, Dave, I'd see that as a possibility. However, I've used the ST as a commuter for years (~12 mile ride to work), and haven't seen the problem until now.

However... Rich and I did put Hyperpro suspension into my ST this winter, and it definitely "stands" different on both the side and center stand (putting the ST on center stand requires about half the effort it used to). This could be affecting the sensor. I'd like to compare my ST to yours on side stand this Wednesday to see the lean differences.
 
EASt said:
Ordinarily, Dave, I'd see that as a possibility. However, I've used the ST as a commuter for years (~12 mile ride to work), and haven't seen the problem until now.

However... Rich and I did put Hyperpro suspension into my ST this winter, and it definitely "stands" different on both the side and center stand (putting the ST on center stand requires about half the effort it used to). This could be affecting the sensor. I'd like to compare my ST to yours on side stand this Wednesday to see the lean differences.
Click to expand...

That is if I have one :p:

Oh wait the game is over. ;)

I figured that when this happened it wasn't like you were doing something new and I know you have had the bike for a while so something changed. As I mentioned I was just throwing it out there. I have read something about the issue but since I have never experienced it I don't know if it would be related. Typically fuel gauges in newer vehicles work so that the change in level isn't instantly read. Otherwise your gas gauge could be all over the place depending if you were sitting on a hill, leaned over on side stand or whatever. I think that with these newer bikes and cages the computer gets involved to smooth out the reading but it may take the initial when started reading as fact. If the bike is leaned over on sidestand when this is done it would possibly explain a high reading. You mentioned that the bike is easier to get on centerstand. That makes me think that your bike must sit higher when upright and so you don't have to lift it as much. Well this would mean on sidestand it would lean further. This could throw off the reading a little more and possibly give you a high reading.

However all that said, if your lower tank holds 2.2 gal and you ran out of gas partway through a 12 mile commute something isn't right or you are getting some seriously bad mileage. It would make me think that it was empty for a while and empty is empty if you are on a sidestand or not. I don't know enough about how the system passes the reading from one tank to the other. Maybe the float has to drop a certain amount before it triggers that the upper tank is empty and tells it to read from the lower. If when you were doing your work your tank got banged around a little it may have bent the arm. From that post that Mellow posted it sounds like it may not take much. There was one report that it may be caused by pointing the stream of fuel in the wrong area when gassing up. I haven't seen the float design on this bike but it could be little more than a float on the end of a flimsy piece of stamped steel. When moving the tank around empty maybe it was enough to bend it a little to where it is getting hung up and not passing off the reading to the lower tank.

Of course most of this is speculation.

We can do some comparisons tomorrow.
 
sennister said:
We can do some comparisons tomorrow.
Click to expand...

Count on it.

Eating Pie makes people smarter, so I figure we'll be able to toss it around easier in the parking lot, and I'll be able to pick a few [superior] brains about the subject.

I'm pretty eager to see what the fix is - there are more than a few people with similar problems on the board, and it'd be nice to get it resolved as a group. Let's win one for the Kemp-er.
 
EASt said:
If the simple solutions don't work, I'll pull the fuel pump and check the voltage.
Click to expand...


You don't need to pull the pump to measure the voltage. You simply lift the seat off and the three pin connector is on the left side of the bike. You might need to remove the small side panel. (I did'nt have to on mine).


Mellow said:
If it's not showing full when you fill it up, it could be the upper sending unit

This thread may help: https://www.st-owners.com/forums/showthread.php?t=23849

maybe, this will fix both the full tank and lower reading issues.
Click to expand...


You could measure the fuel level sensor in the main tank when the tank is full to see if the resistance value is OK. You wouldn't have to remove the tank to make this measurement either.

Since your bike is a 2003 model, did you get the recall performed on the ground harness? Wondering if you have a ground problem?
 
Scooter said:
Since your bike is a 2003 model, did you get the recall performed on the ground harness? Wondering if you have a ground problem?
Click to expand...

Uh, no. I suppose it's too late for that now. :roll:
 
EASt said:
Uh, no. I suppose it's too late for that now. :roll:
Click to expand...

If it's a safety recall, I think it can be done anytime, within reason... 20 years from now might be too long.
 
Recalls are covered in or out of warranty. They are a safety issue.

I thought about this initially but didn't say anything assuming it was long since completed. If not I would start there if there is anything goofy going on with an 03.
 
Mellow said:
Give them a call and with your VIN number they'll be able to determine if that recall was done on your bike.
Click to expand...

Thanks Joe.

And, no, I won't check it in before RTE/Pie Happy Hour, Sennister.
 
Erik, here is a link to more info on the recall. I don't know if you found this or not.

Link

Edit: I was going to pour over the electrical diagrams for you as well. Today you mentioned high beam issue. Which side was getting stuck? Also when it is "Stuck" do you recall if the indicator lamp on the dash was stuck on as well or was it just one of the bulbs? Also no modulator right? And did you mention things were fine with OEM bulbs? I think you said a relay swap didn't change anything.
 
sennister said:
Erik, here is a link to more info on the recall. I don't know if you found this or not.

Link

Edit: I was going to pour over the electrical diagrams for you as well. Today you mentioned high beam issue. Which side was getting stuck? Also when it is "Stuck" do you recall if the indicator lamp on the dash was stuck on as well or was it just one of the bulbs? Also no modulator right? And did you mention things were fine with OEM bulbs? I think you said a relay swap didn't change anything.
Click to expand...

  • Left Bulb sticks on high.
  • Indicator lamp sticks on too.
  • No modulator.
  • OEM bulbs work fine.
  • Relay swap did nothing to fix it.

I'm beginning to [-]think[/-] hope that all of my electrical woes in the fuel indicator and lighting systems are tied together. It seems too coincidental. However, the headlight sticking started last summer and the fuel indicator didn't begin until two or three weeks ago.
 
EASt said:
  • Left Bulb sticks on high.
  • Indicator lamp sticks on too.
  • No modulator.
  • OEM bulbs work fine.
  • Relay swap did nothing to fix it.

I'm beginning to [-]think[/-] hope that all of my electrical woes in the fuel indicator and lighting systems are tied together. It seems too coincidental. However, the headlight sticking started last summer and the fuel indicator didn't begin until two or three weeks ago.
Click to expand...

While it is possible that it is related I am not convinced. Rich did mention his gauge was flaky as well after doing the work that you did. He said it returned to normal after a few tanks which you haven't been through yet. You also mentioned that the gauge issue is new where the light is an old issue.

Here is more good info on the recall. Take a look at the pdf of the install directions.

ST Wiki

Now I happen to have a somewhat strange ability to recall enough about what I read to do pretty good searches so I can dig up things pretty well here. I recalled reading a post a while back about why the left bulb seems to burn out more often than the right. It had to do with the fact that the left and right bulbs are in fact wired differently for High/Low. This seems odd to me but they may have done this so that it would be unlikely that something like a relay failure would leave you in the dark if you will. Rather it would kill just your left bulb. While they could have skipped the relay on both sides this would require heavier gauge wire to the switch pod. The post that I was thinking of is this one.

Link

There is likely more information here than you want to know about the way the headlights work and the interesting point is that there are errors in the diagram that are mentioned if you read the fine print. But from looking at the diagram only the left beam is run through the relay where the right beam gets its power directly through the switch. So this would tell me the issue is either the relay or the ground. Now if it is the ground then it is possible it is the grounding cap recall. If you looked at the directions in the PDF above you could see where the grounding cap issue is exactly and maybe look at it to see if there are any signs of melted wires or that of the connector. Here is another good test. Pull that highbeam relay and check continuity to ground in the socket with a multimeter. If you have a good connection from that try wiggling the wires a little. If you still have a good connection I would suspect the relay even though swapping it resulted in the same conditions. You could try and borrow one from someone for a quick test.

You made a mention that you have done a lot of farkles and though in the back of your mind that one of these could be the source. While it is possible, I would have to know how you wired them and if anything interfaced with the headlamp circuits. Such as driving/fog lights I think I saw that you have PIAAs or some form of aux light on your bike. Depending on how that is wired it may be a bad tap that is causing your light issues. Are they wired so that they only work or don't work based on if the high beam is on or off? If so where was that connection made?

Over the years I have been known to do some pretty complex wiring jobs on vehicles. You should see all the stuff I have done to my truck over the years.
 
You know Erik, the more I think about this the more I tend to rule out the ground issue. By all means check continuity from the relay socket to ground but I suspect on the ground side will be fine. I would imagine if it were a ground issue the problem would be the opposite based on how the circuit is designed. You would think that if you lost ground on the relay (left) side and you were on high beams the left would cut out not stay on all the time. It wouldn't drop to low but go out all together. But as you said a funny ground issue can cause all kinds of strange things.

I would like to know more about how you operate your driving lights because I suspect that you have a bad connection there. Try pulling the fuse for your driving lights and see if the problem goes away. I don't know if Rich helped you with wiring them but if he did maybe he know how they are wired if you don't recall for sure.
 
You mentioned the OEM bulbs work fine. I thought I came across a post that you made last year that said that while the OEM bulbs would work the left side was slow to go back to low beam. It was like the right would drop right away but there was a second or so delay before the left would go back to low.
 
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