Dead ’03 FJR - Intake air pressure sensor?

[QuikSilver]

Dead ’03 FJR - Intake air pressure sensor? Adv diagnostic help and wisdom requested

Symptoms and diagnosis:

My ’03 FJR (42,000 miles) suddenly would not start yesterday with no previous warning or symptoms. Fault Code #16 is displayed, which the manual claims the symptom is “A stuck throttle position sensor is detected”.

The shop manual further states that the “fail-safe” action by the ECU is “Fixes the throttle position sensor to fully open”. The manual also claims that the FJR should be “Able to start and Able to drive” under this fail-safe action.

The troubleshooting section of the manual says to check out three sensors and look for clogged or pinched lines.

Only the “Intake Air Pressure” Sensor (Diag Code 03) has strange readings. The readings bounce around rather erratically and quickly with 3, 7, and 11 being the numbers that are displayed most often when the engine is cranked with the throttle closed and the fuel pump disconnected. When the throttle is opened, the readings go to zero. The spec is 10 – 200 (mm Hg). This sensor sounds like the culprit. I suspect either the sensor is defective or it isn’t seeing enough vacuum. Next step is to put a little vacuum pump on the input line.. I also notice that there is a “Pressure regulator” connected to this throttle body vacuum line and it is connected to the bottom of the gas tank.

The urgency is that I plan on leaving for a 17 day MC trip this Friday, Aug 17.

Questions:

Anyone else seen a problem like this? If so what was the solution? Clogged line? Bad sensor? Something else?

Anybody understand the purpose of the Pressure Regulator line that connects to the gas tank? Could it be a contributor to the problem?

Other background information:

The throttle position sensor (Diag Code 01) checks out fine (smooth 15-100 read-out as the throttle is opened).

The atmospheric pressure sensor (Diag Code 02) correctly reads out the atmospheric pressure (613 mbar which is correct for 6200 feet elevation). I do not see a hose on the input to this sensor which is under the seat and the crossbar. (Is this normal?)

Getting spark with plug electrodes lying against frame. Plenty of fuel being injected into engine. Engine cranks hard but there is no indication of combustion. Just a raw fuel smell I suspect the reason that the FJR will not start is that it is getting way too much fuel as the “fail-safe” action by the ECU is “Fixes the throttle position sensor to fully open”. To me, this means “full throttle” and thus lots of fuel. Don’t quite understand how this correlates with the “Able to start and Able to drive” comments in the manual.

New battery also installed yesterday. I let the cylinders breathe overnight with the plugs removed as I was suspicious they could be fuel fouled with all of the cranking I did yesterday. New plugs installed this morning and they were very wet after one second of cranking.

Thanks in advance for any help.

Regards,

QuikSilver

Ride Hard! You can rest when you die!

 

[QuikSilver]

Only the “Intake Air Pressure” Sensor (Diag Code 03) has strange readings. The readings bounce around rather erratically and quickly with 3, 7, and 11 being the numbers that are displayed most often when the engine is cranked with the throttle closed and the fuel pump disconnected. When the throttle is opened, the readings go to zero. The spec is 10 – 200 (mm Hg). This sensor sounds like the culprit. I suspect either the sensor is defective or it isn’t seeing enough vacuum. Next step is to put a little vacuum pump on the input line.. I also notice that there is a “Pressure regulator” connected to this throttle body vacuum line and it is connected to the bottom of the gas tank.

Update: Intake air pressure sensor output is roughly linear with vacuum and 8" of vacuum gives an output of 200 which agrees with the spec.

This implies a vacuum leak of some sort. The lines look pretty good though. That brass colored "pressure regulator" and all the lines and connections that hook it up to the fuel tank are still suspicious to me.

QuikSilver

 

[ionbeam]

The pressure sensor under the seat is the same as the one on the intake, you could swap the two. The sensor under the seat has no hose and is a PITA to get at. Your test with the vacuum pump should have ruled out the Air Intake Sensor though.

It is possible that you have a vacuum leak. I'm sure you have checked all the hoses carefully? Hmmm, you have a vacuum pump -- I see an opportunity to test the hoses here

I don't recall reading about anyone with a totally failed Fuel Pressure Regulator.

Suspect #1 is the Throttle Position Sensor, a proven bad character. Try holding the throttle wide open and crank the engine in short ~3-4 second bursts with the throttle wide open. Usually the bike will start within 2-3 tries. It is proven that the throttle position sensor can be bad and still pass the diAG 01 15-100 test. Take mine for instance... First I had a no start, then an episode of cruddy running followed by an engine drop out at 2.5k rpm and sometimes at idle but only when hot. New TPS, no more problems. A couple of weeks ago I detailed in this Forum the troubleshooting of my TPS using a Digital Multi Meter Velcroed to my dash.

 

[Constant Mesh]

In my '04 FJR Owner's Manual on page 1-6 you can see the vacuum hose diagram (#3) for the intake air pressure sensor and the fuel pressure regulator. The intake vacuums of the throttle bodies are teed together with the intake pressure sensor and the fuel pressure regulator.

The atmospheric pressure sensor has no hose connection to the engine. Its input is open to the atmosphere.

I believe both of these pressure sensors are identical. You can verify this by disconnecting the vacuum hose from the intake pressure sensor. With this hose disconnected both sensors should have identical readings -- the atmospheric pressure.

If both are identical or nearly so then there may be a break in the intake vacuum hose system or possibly a plugged hose.

The fuel pressure regulator has three connections:

The fuel connection to the fuel rail,

the intake vacuum hose connection, and finally

the fuel return hose to the tank.

If the fuel pressure at the regulator is too high it returns fuel to the tank to lower the pressure. The vacuum air line adjusts the setpoint of the regulator as the throttle is operated when the engine is running.

You need to check the vacuum line system thoroughly to verify there are no leaks and/or possibly a plugged line to the pressure sensor.

 

[mech 1 twa]

TPS is most likely the problem. Thats what coded.

Engine is now flooded, cylinders full of fuel. New plugs will foul pretty quickly.

Compression is low from cyl. being washed down with fuel.

Try removing plugs and drying them. Then add a small amount of engine oil in each plug hole. Not a lot of oil

just enough to coat area inside a little. This will restore compression. Crank engine a few seconds to spread it around. Half a capfull from oil bottle top not much, or serious damage could happen.

Put plugs back in and see if it will start. If it does might smoke a litte.

Good luck.

 

[Rogue]

Whats the latest?

 

[QuikSilver]

Whats the latest?

First of all – thanks to everyone for their quick response, insights, and assistance in helping me with this matter. This is an incredible forum with many knowledgeable individuals willing to take the time to share what they know.

I now refer to last weekend as “The 40 hour oil change”. That was the elapsed time between when I tried to start the FJR to change the oil at 7:30 AM on Saturday and when the oil was finally changed. I probably invested 16 hours in trouble shooting and chasing parts, a few wild geese, and fishing for red herring.

I’ll try to provide a succinct summary hoping that it will save someone from a similar fiasco.

The bottom line is I think that the low terminal voltage of the 4-year-old OEM battery voltage was the primary source of the problem. It had been reading about 11.6 V (Passport 8500 meter) when not kept on the battery tender. The FJR had not been on the “Tender” or ridden for about two weeks. I now suspect that the voltage was too low to give adequate spark even though the engine was spinning very freely. I had seen this symptom a few months ago and gave it some throttle while cranking and it eventually started. Not so this time. I gave it quite a bit of throttle while cranking and that is when EC 16 (“A stuck throttle position sensor is detected”). The shop manual states that the “fail-safe” action by the ECU is “Fixes the throttle position sensor to fully open”. I believed that once this occurred it was like trying to start the vehicle with the throttle wide open. There was a very strong scent of raw fuel in the air. I raised the tank and pulled the plugs. They were definitely soaked with fuel. Sticking my finger down the spark plug holes while cranking showed copious amounts of raw fuel (way too much) being injected with the throttle closed. Lying the spark plugs against the frame showed spark on each plug, although some of the wet plugs showed rather feeble sparks. The battery terminal voltage while cranking was ~ 9 Volts.

I really thought all I needed to do was let the fuel evaporate for a few hours and get a new OEM battery and the problem would be resolved. That is what I did, but it did not fix the problem. Then I decided to let the cylinders dry out overnight with the plugs removed and start fresh in the morning with some new plugs. No luck in the AM with no throttle or full throttle. EC 16 was still present and the plugs were soaked with fuel. I was unable to reset the EC 16 code using the kill switch in diAg 62 mode as suggested in the shop manual. My thought was that until I could reset that code, the engine would remain flooded. Note: All of the cranking was done with the fuel tank elevated with a 11” long 2X4. This is much longer than the 7” 2X4 I use during TB synch. More about this later as I now think the steep angle of the tank could have been a contributing factor. This long 2x4 sure made it easier to remove the plugs and make sure the caps were on correctly about a half-dozen different times. When I started these experiments my fuel light had just come on so I added a gallon of fuel to bring the tank up to an estimated 2.6 gallons (my reserve indicator comes on with about 5.1 gallons left).

With a new battery and fresh plugs in place, I started chasing down the performance of the three sensors that the shop manual referred to as possible culprits. The TPS and the atmospheric pressure sensors checked out just fine. BTW, I replaced the TPS sensor about 6,000 miles ago (thanks for the insight in diagnosing that problem IonBeam).

As it turns out, the Intake pressure sensor showed essentially no vacuum. But, when I pumped on the sensor input with a hand vacuum pump, the sensor output was linear with vacuum and right on with the spec. I disconnected the TPS and cranked the engine and got an EC 15 code in addition to the EC 16 code. After this occurred, I was able to erase both codes in diAg 62. Finally EC 16 was gone!!! Knowing what I know now (but didn’t know then) if I would have put everything back together with dry plugs and I bet she would have started.

Instead, I was intent on chasing the “no intake vacuum” symptom. So I decided to remove the sensor, plug the line, and apply hand vacuum to the atmospheric pressure sensor just as I started to crank it with diAg 03 displayed, thinking if I could just fool the ECU and get her started, I could get all of the fuel dried out and everything would be back to normal. At the instant I added vacuum to the disconnected intake pressure sensor, EC 12 showed up, which the manual indicates means “no normal signals are received from the crankshaft position sensor” . Oh boy, here we go!!! Another potential problem!!!! I could not erase this code using the diAg 62 procedure.

Frustrated, I took a couple hours off to let the cylinders dry out in the hot sun with the plugs removed. I went out and bought a very nice stainless steel, 41” wide, 66” tall, 17 shelf toolbox at Costco. I told my wife that I bought it with the money I saved by not taking the FJR to the dealer to solve this problem. At least I did one thing fun this weekend.

When I returned, Code 12 was gone, but the engine would not start. At this point, I had gone back to using the old plugs that had 5000 miles on them and looked very good.

Since I wasn’t getting any vacuum reading from the intake pressure sensor or with my vacuum gauge attached to the vacuum manifold while cranking, I pulled off the fairly complicated rubber hose vacuum manifold. It held a solid vacuum with all of the lines plugged with pegboard hooks. I also checked the brass colored pressure regulator that is attached between the vacuum manifold and the gas tank. No vacuum leak here either. When I hooked everything back up, Code 12 was gone, but the engine would not start.

I then retried applying vacuum to intake pressure sensor with hand pump while cranking in diAg 03 mode. Code 12 reappeared!! This time I could clear the code using diAg 62. I repeated the experiment and got the same result. As crazy as it seems, I saw this as progress.

I then pulled the plugs. They were now as dry as a bone. Put finger in spark plug hole while cranking with closed throttle. No fuel observed. Crank with throttle wide open. A small amount of fuel was present. Hmmmm….

So here we are, 36 hours into the process and no measurable progress had been made. I removed the plugs (again), and let the cylinders “breathe” for an hour during dinner”.

My gut feel was that for the last try I would put the new, dried, plugs back in, put everything back to the normal rideable condition (tank down, T-Bar in place, etc …) and crank her one more time. Voila!! She ran a little rough for the first several seconds but finally returned to normal in about 15 seconds, and as if nothing had ever happened. I did the only thing I could, I warmed her up and changed the oil.

Since then she has run fine and has started easily on six cold start occasions. No error codes, no nothing except a fine running motor.

A few mysteries still remain:

Why couldn’t I reset the EC 16, which I believe I induced by giving it wide open throttle while cranking it the very first time. The code was observed and retained in memory even when the battery was removed. I could only reset it after EC 15 showed up when I disconnected the TPS.

Where did the no intake vacuum condition come from? Is this related to having the tank at about 60 degrees above horizontal?

Where did the EC12 condition come from when I used the vacuum pump on the intake pressure sensor? Why couldn’t I reset EC12 on demand? Why did it disappear from memory twice on its own accord?

I am still suspicious that the ECU could be a culprit as it would not allow me to reliably erase codes, especially EC16 and EC12.

Note: The starter motor sure cranks hard with a very low battery. Unfortunately it appears that the CDU stops producing spark before the injectors stop injecting fuel.

BTW - I realize that this is not a self-consistent story. It doesn’t quite all add up. Also, I don’t think I am completely out of the woods.

If it happened all over again and I saw EC 16 when I knew I had a marginal battery, I would go get a new battery, disconnect the TPS (so that I could reset EC 15 and EC 16 at the same time), not remove the plugs, return the tank to its normal position, and crank it. If it wouldn’t start, I would put in new plugs, lower the tank, and crank again.

So there we go. The 40 Hour oil change. I leave for a 17 day MC trip with my wife on her Hayabusa on Friday. Say a prayer for me. At least it didn’t happen on a 36 degree morning in Breckenridge, Colorado where I will be next weekend!

Regards,

QuikSilver

Ride Hard! You can rest when you die!

 

[Afast03nNJ]

You sure did some good diagnostics there. I think the culprit was a low battery which caused a weak spark, which then caused a flooded engine condition. The rest was just the ECU getting totally confused while you attempted to get it started. Good long cranks with a nice charged battery while holding the throttle wide open should get it started if that every happens again. Most ECU's are programmed to read a flooded engine condition if the throttle is held wide open during cranking. It will not dump tons of fuel under those circumstances.

 

[james1300]

So what was your out come?

 

[QuikSilver]

So what was your out come?

Just completed an absolutely fabulous 16 day sport touring trip with my wife on her Hayabusa in an attempt to ride every twisty road in Colorado. The FJR performed flawlessly with absolutely no hint of any problem.

Thanks to everyone for their insight and advice. My short summary is to beware of a marginal battery before starting a long trip away from home.

Regards,

QuikSilver

Ride Hard! You can rest when you die!!