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Buell Forum » 1125R Superbike Board » Archive through September 11, 2015 » Fuel pressure drops in Diagnostic mode « Previous Next »

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Panshovevo
Posted on Saturday, August 22, 2015 - 08:26 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

'09 1125CR, built May of '09.
6.1 firmware in IC.
8500 +- miles.

Low fuel warning light was working when I bought the bike in May of this year, quit working normally in July.

Checked for trouble codes after running out of fuel.
U0001 Comm Error and P0087 Low fuel rail pressure showed after the fact, even though the check engine light was not indicating stored codes.

Low fuel warning light now comes on when coolant temp reaches 155 degrees, and goes off when coolant reaches 173. If coolant temp fluctuates, like 172-175 at night, light will come back on when it drops to 172 and go back off at 173, and repeat.

During diagnostic mode checks, fuel pressure will sometimes fluctuate, sometimes drop to 40 KPA and sit there. Activating the stop/run switch (to the off position) will usually make the fuel pump kick for a second and raise the fuel pressure.

When the engine is started while in Diagnostic mode, the fuel pressure goes to 410-420 and stays in that area. It has been running fine on the road, other than being a little fussy at low throttle settings, especially when the fuel is less than half full and it's hot from running in traffic in 90+ temps. Topping off the tank with cool fuel makes a dramatic difference for a while.

When the engine is stopped with the off/run switch, the pressure will fluctuate in the low hundred KPA range for a bit, then usually drop to 40 KPA and stay there.

Briefly grounding the wire that goes from the pump to the ECM will start the pump and drive the fuel pressure to 575 KPA until the ground is broken.
Then the pressure drifts back to 40 KPA.

The Comm Error checks in the Electrical manual indicate the IC is bad.

I've been trying to find the ECM ground, but haven't thus far.

I checked the resistance of the thermistor. It shows 2.3K Ohms with fuel in the tank, at ambient temp of around 90 degrees. No trouble codes related to it, though.

Open to suggestions...

All connections I have checked so far have been good.

(Message edited by Panshovevo on August 22, 2015)

(Message edited by Panshovevo on August 22, 2015)

(Message edited by Panshovevo on August 22, 2015)
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Panshovevo
Posted on Saturday, August 22, 2015 - 08:40 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Some things are not following what the manual says should be happening.
For example, the check engine light should be staying on for 8 seconds after the key switch is turned on when codes are stored. It doesn't. It turns off after 4 seconds.

The Comm Error, once stored, should be changing to Theft Error after the switch is cycled. It isn't.
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Panshovevo
Posted on Saturday, August 22, 2015 - 12:28 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Finally got to the ECM ground by pulling the left side radiator and fan housing.

Clean and tight, damnit...
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Panshovevo
Posted on Saturday, August 22, 2015 - 04:16 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I added a separate ground wire from the cylinder head ECM ground point directly to the ground side of the battery, pulled the headlight assembly and checked the front frame ground, and put it back together far enough to run it and check for coolant leaks.

Everything is as before with the exception of the low fuel warning light is not coming back on when the coolant temp drops after hitting 175 and turning off.

I intentionally cooled the motor by shutting it off, letting the fans run until they stopped, starting it and circulating the coolant until the temp stopped dropping, and repeating until I got it down to 165 degrees. No low fuel light yet.

We'll see what happens when I ride it tonight.
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Panshovevo
Posted on Saturday, August 22, 2015 - 10:57 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

No low fuel warning light tonight, and it's running better enough that the wife noticed from the rear seat.
Much smoother power delivery at low throttle settings, especially in the lower rpm range.

Can't say why, or what made the difference.

Possibilities are the added ground wire, or maybe one of many connectors that got separated and inspected is making a little better contact than before.
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Panshovevo
Posted on Sunday, August 23, 2015 - 08:03 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Rode the '76 shovel today, as I was tired, and didn't feel up to riding the Buell with the wife on the back. Keep hoping she'll get over her issues with riding herself on the road, but it may never happen...
She's had her motorcycle endorsement for 25 years.
She re-took the MSF course a few months ago, and we got her a little 250 Suzuki to practice on, but I can't get her out on public roads. She has put several hundred miles on it riding around the community.

At any rate, I did fire the Buell up in the shop, and warm it up.
The low fuel light came on at about 175 and stayed on until about 195...topped off the tank last night.

I ordered a Buelltooth and an Android tablet today. Maybe it will help figure this thing out.
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Panshovevo
Posted on Tuesday, August 25, 2015 - 07:50 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Low fuel warning light is still coming on when warming up from ambient temps. It comes on later than before and stays on to a higher temperature.

Comes on around 175 degrees now, as compared to 155 before, and stays on until around 190 degrees.

Haven't ridden it at night with a start from ambient temp. If the above numbers hold true, the light will be staying on, as the temp doesn't reach 190 degrees on night rides in my experience.

I also noticed that now sometimes I have to hit the starter button twice to get it to fire.

First push of the button it spins fine, just no start. Release the button, hit it again, and it fires immediately. The battery is a Shorei lithium iron, I believe, in good condition.

I really wish I could install a fuel pressure gauge to check the accuracy of the fuel pressure sensor, or at least figure out a way of testing the sensor. May look into that further today. I imagine I could use air to test it, if I could figure out the thread, and make a test rig. I've seen similar sensors used on some automotive injection systems, an automotive shop may have a test rig.

As I said before, when doing a diagnostic check, the fuel pressure is not where it should be when the engine isn't running, but sticking a thin probe in the fuel pump ground wire and touching it to ground starts the fuel pump and drives the pressure to where it should be.
This makes me suspect that the ECM is not providing a good ground to the pump unless the engine is running.

Although I've never seen Comm Error displayed on the IC at any time other than reviewing stored codes, it is there.

I'm leaning toward replacing the IC first, as it has the 6.1 firmware. Checked with Al at American Sport Bike yesterday. He can get one, but it's going to take 2 1/2 weeks to get to him, then shipped to me.

I have no problem spending the money to replace whatever it needs, but don't like taking the "shotgun" approach of replacing everything it might be...

Any thoughts? I'm wide open to suggestion.
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Froggy
Posted on Tuesday, August 25, 2015 - 11:52 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

I wouldn't worry about the Comm error, especially since it is a historic code. It is stupidly easy to get that message to appear, it can happen if the battery was a hair too weak during cranking.

I would only focus on your fuel pump issues. I'll check mine out later and see if the pressure drops like you mention, I know my LFL goes on and off when it wants (not temperature sensitive)
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Panshovevo
Posted on Tuesday, August 25, 2015 - 12:42 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Thanks Froggy, I would appreciate that.
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Zac4mac
Posted on Tuesday, August 25, 2015 - 10:29 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

John
Your fuel pump is on the way out.
A weak pump will maintain the 420 kPa required for idle fine but drops off as RPM increase.
The drop at key-on, engine-off is the telltale. Spec is ~520kPa, steady.

As an aside, my 1125(Loretta) has been doing this on and off for a year or two now.
I have a used pump assembly but haven't used it yet.
The next time Loretta's engine fires, it will be 1190cc and all will start from scratch.

I still have to figure out how to add the shower heads...

Oh yeah, Frank is spot-on about the comm error, don't worry about it.
Also, I've never heard of or seen a comm error morph into a theft error but I don't use the alarm mode.

Z
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Panshovevo
Posted on Wednesday, August 26, 2015 - 09:03 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Z, any idea of what might be failing in the fuel pump to cause this?

As I said above, when I'm checking pressure in Diagnostic mode with the engine off and the pressure has drifted down, I stick a thin probe in the wire that runs from the fuel pump to the ECM and ground it, the pump runs and the pressure shoots up to 550 KPA.

I'm wondering if there is a check valve in the pump that is leaking, or if the ECM isn't signaling the pump to turn back on.

The manual says to check it with a pressure gauge at ignition on, at idle, and at 4000 rpm. I haven't checked at 4000 rpm yet, but can do that today.

Incidentally, I pulled the fuel pressure sensor again yesterday to measure the thread, it appears to be a standard SAE o-ring coupling thread.
I may stop by a local hydraulic shop and see if they can put together an adaptor that will allow me to mount a pressure gauge with the pressure sensor so I can check the pressure while riding it.

(Message edited by Panshovevo on August 26, 2015)
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Panshovevo
Posted on Wednesday, August 26, 2015 - 11:34 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

FWIW, the fuel pressure hits 550 KPA when started, then settles at 410-420, even when revved and held at 4500 rpm with no load.

Short of road testing with a pressure gauge teed into the line, there is no way of testing it under load that I'm aware of,as the IC exits Diagnostic Mode when the speed sensor registers anything other than zero.

This tells me it would pass the pressure test shown in the manual.
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Shawns
Posted on Wednesday, August 26, 2015 - 11:47 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only) Ban Poster IP (Custodian/Admin only)

Mine does the same thing. I am also experiencing power loss at 5k+. I thought my fuel pump was restricted, maybe its on its way out. I maintain 60psi at 4k so the manual says it's still good. I checked mine with ECMSPY in stands.
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