LB7 issue. Undercarriage of truck is soaked with diesel fuel.

[CareyK]

LB7 issue. Undercarriage of truck is soaked with diesel fuel.


I require some suggestions for an issue I have just encountered today. I have a 2002 GMC Sierra crew cab with the Duramax LB7 engine. I did a trip today (120 miles) and the truck used a 1/2 a tank of fuel! When I fueled the truck up I noticed diesel fuel on my back bumper! I then looked under the truck and in shock I saw that underneath the truck it is completely soaked in diesel fuel??
The truck has a "rough" idle, sort of like a miss to it. The truck at idle always ran smooth. Do I have injector and or injector pump issues? Any suggestions will be greatly appreciated. This is the first time that I am posting on this site but have been a member for a number of years now. A great site by the way.

Cheers,
CareyK

[DmaxMaverick]

Check your engine oil level. You'll probably find it's overfilled. This is normally caused by a failed injector(s), which dumps fuel into the crankcase, forcing the excess out of the crankcase vent (pipe that extends below the front area of the engine). When you drain the "oil", you'll likely drain 18 or so quarts, so be prepared for it (5 gallon+ container). Do not drive it until the injectors are replaced, and clean up the fuel covering the undercarriage before it dissolves the entire frame coating (which is essentially a hard wax).

[CareyK]

Thanks DMax Maverick. I really appreciate your input. I checked the oil and it is on the full mark but I didn't check to see if it is actually higher than full! But the oil on the dipstick looked too clean to me since I changed the oil about two weeks ago. The oil on the dipstick wasn't dark at all so it probably is full of diesel.
I can't do anything further for another week since I just flew into site today, where I work at a remote site. This is quite a disheartening situation.
It looks like I will have to get the truck towed to a GM dealership. If one injector is bad, it sounds like all will have to be replaced. Doesn't pay to do just one. Also the truck does have 270,000 kms on it (I was hoping for a whole lot more). Hopefully the engine is still Ok!

Thanks again,
CareyK

[CareyK]

Check your engine oil level. You'll probably find it's overfilled. This is normally caused by a failed injector(s), which dumps fuel into the crankcase, forcing the excess out of the crankcase vent (pipe that extends below the front area of the engine). When you drain the "oil", you'll likely drain 18 or so quarts, so be prepared for it (5 gallon+ container). Do not drive it until the injectors are replaced, and clean up the fuel covering the undercarriage before it dissolves the entire frame coating (which is essentially a hard wax).

If I am going to replace all the injectors, what else should be replaced. In reading past threads on this site, something was mentioned about replacing the tubes that go to the injectors. Also I read somewhere on this site that there are washers that rust and these too should be replaced.

Any help will be appreciated.

CareyK

2002 GMC Sierra Crew Cab 2500HD (270,000 Kms)

[Kennedy]

We do thermostats and replace the coolant while inside. You'll want a set of the return line banjo seals and I highly recommend replacing all 8 high pressure supply lines to avoid contaminating the new injectors.

[DmaxMaverick]

There's still a lot of factors to consider. It may not be a bad injector. Internal fuel leaks are just as often a broken fuel return line, or leaky banjo seal. You'll have to consider all the factors and decide the best course.

The engine blocks are extremely durable, and I've not heard of any being damaged from (short period) fuel in the crankcase. The rough idle and "miss" is likely due to the crankcase being full of fluid (hard running, with the crank submerged, and little/no air cushion under the pistons). What I suggest, and do, is perform a "sacrificial" oil change, so you can run it long enough to get some diagnostic data before beginning repairs. You can't realistically run it once the tear-down begins, so it's best to do it up front. This will give an opportunity to measure the injector performance, return rates, fuel pressure control, etc., which makes the decisions a little easier once the source of the leak is determined. If you can't do any of that yourself, it'll cost you the dealer's rate for a full diagnostic, but I highly recommend it. It may save you a bunch of cash later. Replacing injectors, assuming they may be bad, is a crap shoot.

As John said, it is almost always best to replace the high pressure injector supply lines. Unless they come out looking pristine, and you have a means of ultra-high level cleaning (ultrasonic, etc.), just replace them and put that worry to bed. There are other sources for new OEM lines (much less than dealer price), so you may want to get a head start on that once it is determined they will come off, before repairs begin. The same applies to other necessary high cost parts that may be needed. You can often save more than 1000 bucks by shopping around, and still have the same parts the dealer will use. Steer clear of aftermarket branded parts. OEM only.

[CareyK]

There's still a lot of factors to consider. It may not be a bad injector. Internal fuel leaks are just as often a broken fuel return line, or leaky banjo seal. You'll have to consider all the factors and decide the best course.

The engine blocks are extremely durable, and I've not heard of any being damaged from (short period) fuel in the crankcase. The rough idle and "miss" is likely due to the crankcase being full of fluid (hard running, with the crank submerged, and little/no air cushion under the pistons). What I suggest, and do, is perform a "sacrificial" oil change, so you can run it long enough to get some diagnostic data before beginning repairs. You can't realistically run it once the tear-down begins, so it's best to do it up front. This will give an opportunity to measure the injector performance, return rates, fuel pressure control, etc., which makes the decisions a little easier once the source of the leak is determined. If you can't do any of that yourself, it'll cost you the dealer's rate for a full diagnostic, but I highly recommend it. It may save you a bunch of cash later. Replacing injectors, assuming they may be bad, is a crap shoot.

As John said, it is almost always best to replace the high pressure injector supply lines. Unless they come out looking pristine, and you have a means of ultra-high level cleaning (ultrasonic, etc.), just replace them and put that worry to bed. There are other sources for new OEM lines (much less than dealer price), so you may want to get a head start on that once it is determined they will come off, before repairs begin. The same applies to other necessary high cost parts that may be needed. You can often save more than 1000 bucks by shopping around, and still have the same parts the dealer will use. Steer clear of aftermarket branded parts. OEM only.

Thanks for all your great support. One thing I have noticed (lately) is that the truck periodically had a rough idle (the odd day for the last 4 months) and when I changed the oil a few weeks ago, there was only 9 quarts that came out (no diesel fuel). When I did my 120 mile drive yesterday, I noticed near the end of the drive (the last 1/2 hour) my oil pressure was a little lower than usual at idle (at a stop sign). Usually at idle my gauge is sitting at 1/4 deflection (from 0), but now it is only half of that, just an oberservation. Having said that, I believe this is due to the oil being thinned out with the diesel fuel.
That I would pass this info along.
Once again, thank you very much for your professional support. I appreciate it very much.
Should I take the chance and drive the truck 5 miles to the dealership or just get it towed(common sense dictates towing though!).

CareyK
2002 GMC Sierra Crew Cab 2500HD

[DmaxMaverick]

It's my pleasure. That's why we're here.

Yeah, the mess, miss, and low oil pressure is a pretty good indicator.

If it were me, I'd change the oil, do whatever diagnostics you can, then drive it to the dealer. 5 miles won't hurt anything on a "fresh" change. Easy on the throttle to keep the fuel pressure/volume to a minimum. Just don't linger too much anywhere with the engine running. Save a sample of your old oil for the dealer, to show what "was" in there. The oil will probably cost you a lot less than a tow truck, even if you don't do any diagnostics. Just use "cheap" oil, as it'll get another change after the repairs are done (it must, so make sure they do it!).

[mmiddle]

Please read my post titled "LB7 Guru's Please Help". Learn my lesson the easy way. You will thank me later.
I tried to save a few bucks and it cost me 5 months of down time and a LOT of work and hassle.

[leolkfrm]

for what it is worth I also had leaking underneath...had to replace all fuel lines and return cooler as the had rotted out!...I caught it early so not too bad of a mess, $1000 dollar repair at a local shop that I trust....

[CareyK]

Please read my post titled "LB7 Guru's Please Help". Learn my lesson the easy way. You will thank me later.
I tried to save a few bucks and it cost me 5 months of down time and a LOT of work and hassle.

I agree. It's best to replace all applicable parts. My truck is now at the GM dealership. New (remanufactured Bosch injectors from GM, $300 each. New high pressure lines as suggested by John Kennedy. New seals, gaskets, etc.) Cost estimate by service manager is $5000 (CDN), includes labor. Ouch. But that's the reality of owning a diesel. Warranty is for one year, parts and labor, unlimited mileage. Only time will tell how will this repair will be. An interesting note, their parts man said they cannot get NEW LB7 injectors any more, just remanufactured injectors from GM!