2001 LB7 Continued Diagnosis of Idle Smoke - Chevy and GMC Duramax Diesel Forum
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Old 04-28-2010, 02:01 PM   eBay Motors  #1 (permalink)
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2001 LB7 Continued Diagnosis of Idle Smoke

My Duramax LB7 has been smoking white smoke at idle, constant flow every time I stop the truck. You can almost feel the Idle not being very smooth on the truck as if the Fuel Pressure Regulator was not working properly. Now a few weeks ago I had thrown the FPR Code p0089 (while it was smoking at idle). So I began to look into the issue, got a lot of feedback off the forum here. heres what Ive done.

-Checked and replaced Air Filter so thats brand new
-Put a brand new Oil filter and oil change
-Put a brand new Fuel Filter in
-Continuously checking the oil for any sign of diesel within it. None, no smell, or sign of it when checking the dipstick after letting the truck rest.
-Paid very close attention to temperature of truck while driving 200 mile trips and all. Never even broke 200 degrees. Obviously looking for any signs of a bad head gasket.

Then I Looked up some diesel shops or mechanics to get my injectors tested and had my truck hooked up to a computer. Went with Ben from BT Diesel Works, out in Old Saybrook, CT as recommended by a bunch of guys on this forum. He hooked up to computer and found injectors looked good and was convinced it was the Fuel Pressure Regulator, because when at Idle, the idle levels would not stay consistent and ran super high and it showed a spike in the chart on his computer. Plus the combination of that and the Check Engine code pointed to the FPR. so i went ahead and changed it and put a brand new Bosch FPR in.

Started it up, still smokes at idle same amount and same rough idle as if its not staying at a constant level.

What do I do now. where do i go. thoughts suggestions. i need to solve this, obviously without hurting the truck while driving it on a day to day basis?

Also after I changed the FPR was there something I was supposed to reset on the computer or any other tricks to that process other then simply replacing the part?
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Old 04-28-2010, 02:05 PM   eBay Motors  #2 (permalink)
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put some two stroke oil in your fuel, worked for me...
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Old 04-28-2010, 02:09 PM   eBay Motors  #3 (permalink)
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How much two stroke oil and what did you use. like chain saw stuff, or the kind you used to put into your dirt bike fuel. any recommended brand?

What does the 2-stroke oil do if you dont mind explaining just bit?
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Old 04-28-2010, 02:13 PM   eBay Motors  #4 (permalink)
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I didnt want to replace my fuel pressure regulator so I ready so thread on here about people putting some two stroke oil in their fuel to lube injectors and fuel system as a temporary fix.

I ride sleds so I had some arctic cat apv oil (45.95/gallon RIPOFF) laying around so i just said screw it and poured a moderate ammount in. About the same ammount that is recommended for a standard fuel addititive.
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Old 04-28-2010, 02:17 PM   eBay Motors  #5 (permalink)
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I 2nd the two stroke oil suggestion. The white smoke wouldnt indicate a bad FPR, the rolling idle could. Does it sound loud at idle...and what I mean is the injector "knack knack knack knack knack.." Is it louder than other LB7s you have heard? If your FRP sensor is bad, it could be adding too much pressure at idle which makes the injectors loud and starts to F up a smooth idle. My 03 is quiet at 35kpa idle rail pressure, my 01 is loud and has a rough idle, if I turn my rail pressure down, it quiets up and smooths out.

And someone else chime in here, a cracked injector wouldnt neccesarily show a bad balance rate. White smoke says your getting too much fuel at idle... so either leaky injector (cracked, bad seat, whatever) or FPR sensor.

My guesses.

Start with the bottle of 2 stroke.
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Old 04-28-2010, 02:18 PM   eBay Motors  #6 (permalink)
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well along with that I have some Ski-doo 2 stroke oil, ill run some through it and see what happens. and try the 2 stroke oil first.

Daschae, as far as your comments. the FPR is brand new just put it in on sunday. I dont know if my LB7 is loud in comparison to any others but I will take a look at the rail pressure. And so far last resort is possible cracked injector or bad injector I will keep that in mind. And I completely agree with too much fuel at idle. I guess were all just trying to figure out where its coming from.

Out of curiosity I'm going to try the 2 stroke oil, but i do run diesel clean additive every fuel tank. but if the oil works then it works. hahha.

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Old 04-28-2010, 07:23 PM   eBay Motors  #7 (permalink)
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subscribed....and bump for you phatfox77
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Old 04-28-2010, 10:00 PM   eBay Motors  #8 (permalink)
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My cousin's LB7 had a bad wire going to the FPR.

I think it sounds like injectors though.....My 2001 started loping at idle worse and worse along with white smoke......I swapped all the injectors and it has been running like a champ!
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Old 04-29-2010, 06:59 AM   eBay Motors  #9 (permalink)
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Andrew I sent you a PM regarding this.

For the people who are suggesting the two stroke oil...the reason you run 2-stroke oil is to free up a sticking regulator, if you read, you'll see he just replaced the regulator with a brand new one...so why would it be sticking?

The injectors all looked good, there were not any other codes, and the regulator command current (mA) and duty cycle (%) seemed right on what normal values should be...I am really surprised/confused a new pressure regulator did not fix it, all of the other LB7's that ive worked on that had these symptoms was for a bad regulator. Considering the miles, it was about time for it to go out anyways. Desired rail would not follow actual rail at idle, etc...

As I said in the PM, could also be wires going to the pressure regulator, but not REALLY likely in my opinion. Early 03-04 6.0 powerstrokes had an issue with this. Ive had to replace ICP (injection control pressure) sensors on early 6.0's because what happens is the sensor leaks oil into the connector, and the crap in the oil seeps into the wires and changes the wires resistance enough to not give a proper feedback signal to the ECM/FICM. But like I said, thats on 6.0 PSD's...Im not sure how oil or anything else would contaminate the connector on a duramax pressure regulator.

Andrew and anthony- the next step would be to check for good connections on everything, and trace the wires from the ECM connectors all the way to the pressure regulator with a multimeter to make sure there isnt anything causing resistance in the wire. Give me a call or let me know if you want me to email the wiring diagrams to you so you can trace them out to make sure the wires have perfect continuity/0 ohms.

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Old 04-29-2010, 07:04 AM   eBay Motors  #10 (permalink)
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So here is What Ben At Diesel works Said in regards to this post and he is the one who ran all the tests on my truck.

Ben's Responce:

Hmmm very strange. I cant see it being a CP3 issue because when we commanded 23,000psi at idle, it was able to sustain it. If the CP3 was bad it wouldnt have held 23,000psi.

Does it still throw any codes? Other than a fuel filter, I cant really see what else would be causing the issue. There isnt any electric fuel pump or anything on it, just the mechanical gear pump on the back of the CP3; thats what sucks the fuel all the way from the tank. Provided there arent any blockages in the line or anything, but then again at wide open throttle, we would see a drop in pressure if the fuel lines were blocked.

Bad ECM is possible I guess, but very rare. I wish we had updated with the latest dealer updates when you guys were here....not that that would have fixed it, but at least then we could 100% cross the ECM off the list of other potential problem spots besides the regulator. When he pulled the connector off the regulator, was there any oil or anything in it? Did the terminals on the connector look clean and dry?

As far as the injectors, they all looked fine, no fuel in the oil or anything so there shouldnt be any leaks or anything that could make the pressure do funny things.

Theres no computer reset or anything, every other LB7 ive had with those symptoms, cleared right up with a replaced fuel pressure regulator.
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