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ECU failure??? Or something else???


kubagsx
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Hi

 

It is my first post here :)

 

My XX worked not very well last time. 20 000 miles done. Year 2002.

 

Fuel consumption was horrible. I could do only 90 miles on a tank driving very calmly!

 

I checked all the sensors and noticed that the voltage, which is delivered to the IAT sensor (is in the airbox) and to the engine coolant temperature sensor is only 0,44V ! Haynes manual says, that in both cases it should be between 4,5 - 5,5V.

 

It is possible that bikes consumes so much fuel because of it. Manual also states that when low voltage is present, the ECU can be damaged. 

 

What should I do now? Maybe the manual is wrong and you had similar issue? What is the reason of it?

 

Thank you in advance!

J.

Edited by kubagsx
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Guest Kubagsx

Hi. Voltage at the battery is 12.9V. When the key is turn off, the Voltage at the sensor is 0. When I turn on the key, Voltage appears and is only 0,44V.

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First thing I'd check is the fuel pressure regulator, pull the hose off and see if there's gas in it.  The 4.5-5.5 is probably with the engine running so if you're checking with the engine off that would explain it.  Even if you're checking correctly, I doubt that being .1v below the minimum spec would cause that much of a problem.  If either of those sensors is reporting super low it would make it run rich and unless it's a totally open circuit the computer probably would't know that it's faulty.  Low voltage to the sensors would probably make it run rich, but I don't think .1 is enough to make such a dramatic difference.  If your bike has an O2 sensor that 'should' correct a rich mixture, and if it's faulty it could cause the rich mixture.

 

I'd avoid riding it 'till the problem is corrected.

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Shit, I misread the voltages and thought I saw that you were getting 4.4.  .44 is way off and if the sensors work as I think they do, that would cause a super rich mixture.  Verify that you're testing correctly and try testing at the ecu to know if it's the ecu or a wiring problem causing the low voltage.

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Hi

 

The problem with voltage was in the connectors. Some were seized. Cleaned them and voltage is ok now.

 

I have ordered the fuel pressure regulator. Thx

 

I don't have O2 sensor, while I installed power commander with O2 sensor eliminator.

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  • 2 weeks later...

The FPR vent lines should be bone-dry; any residual fuel--even moisture--is a sign of a compromised FPR diaphragm, a pinhole would do it. This is one of the few weak spots in the XX. The original (FPR) design predates the proliferation of alcohol-laced unleaded fuel, which is thought to contribute to weakening/compromising the diaphragm; anecdotal reports, while falling short of empirical evidence, seem to support this conclusion. Fortunately, the fix (replace the FPR) is relatively inexpensive and easy to do (on the right end of the fuel rail).  

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3 hours ago, ironmike said:

The FPR vent lines should be bone-dry; any residual fuel--even moisture--is a sign of a compromised FPR diaphragm, a pinhole would do it. This is one of the few weak spots in the XX. The original (FPR) design predates the proliferation of alcohol-laced unleaded fuel, which is thought to contribute to weakening/compromising the diaphragm; anecdotal reports, while falling short of empirical evidence, seem to support this conclusion. Fortunately, the fix (replace the FPR) is relatively inexpensive and easy to do (on the right end of the fuel rail).  

 

7 minutes ago, superhawk996 said:

You don't wanna fuck it off.  The gas all goes to #3 cylinder and can lead to a really bad time.

What is an average lifespan of FPR?

How quick FPR failure can lead to ruin the cylinder wall?

Edited by kubagsx
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It doesn't ruin the cylinder wall, it hydrolocks the engine.  As in, the ENTIRE engine fills up with the contents of the gas tank.  Been there, done that, got the t-shirt and the stains on the ceiling when I had to pull the spark plugs and pump the fuel out.  That was quite the geyser.

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37 minutes ago, Furbird said:

It doesn't ruin the cylinder wall, it hydrolocks the engine.  As in, the ENTIRE engine fills up with the contents of the gas tank.  Been there, done that, got the t-shirt and the stains on the ceiling when I had to pull the spark plugs and pump the fuel out.  That was quite the geyser.

It's worse when a plug fires and jams a piston into a slug of gas that's in the cylinder. It bends the connecting rod.

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5 hours ago, kubagsx said:

 

What is an average lifespan of FPR?

Somewhere between 5 seconds and 500 years.  There's really no way to say, but if yours is factory it is absolutely suspect.  This is a thing that seems somewhat particular to 'Birds, but it happens to all vehicles.

5 hours ago, kubagsx said:

How quick FPR failure can lead to ruin the cylinder wall?

Any excess gas is bad since it washes the oil off the walls/rings/pistons and dilutes the oil with something that doesn't lubricate for shit so everything suffers to some extent.  The quick catastrophic potential is a hydrolock on startup which will possibly bend a rod and could break a piston.

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5 hours ago, XXitanium said:

It's worse when a plug fires and jams a piston into a slug of gas that's in the cylinder. It bends the connecting rod.

I'm pretty sure the gas won't ignite.  I think the damage happens from starter torque and momentum of the other parts.  The same damage happens when an engine is cranked with too much water or oil in a cylinder.

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40 minutes ago, XXitanium said:

I don't THINK the starter has enough juice to bend a rod.

Probably not without some amount of momentum build up, but it has happened with many engines that had water or oil in the cylinders so it's not a fuel ignition issue.  If a cylinder is full and already on the compression stroke the starter probably can't bend a rod, but fluid usually gets in through an open valve so there's going to be some amount of spin/momentum before the compression happens.  It's a relatively common issue when someone does injector work on 7.3 diesels, some of the cylinders fill with oil and if they're not purged they're fucked.

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