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Thread: Rebuilt 6.2 Lost Power After 600 Miles

  1. #1
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    Default Rebuilt 6.2 Lost Power After 600 Miles

    I refreshed a 6.2 / GM4 turbo, complete rebuild, pistons, bearings, heads, injectors, IP (mechanical), glow plugs. 500 miles around town break-in no problems, took a short road trip (100 miles) lost power, limped last 10 miles, couldn't get over 50 mph, lots of blue smoke. Trailered home, pulled turbo, exhaust manifold, glow plugs (#6 burned) compression tested @ 400lbs each cylinder. Leak down test on #6 good. Pulled injectors and sent them back for testing figuring #6 was leaking. Heard back on the injectors and they were all good. Chatting with injector rebuilder and he said sounds like the IP is over fueling and maybe advance piston is worn and I tell him he rebuilt the pump 600 miles ago then he thought the timing was off. I have a Kent Moore Tach and Time and set the timing @ 4 degrees advance, jumping the cold advance brings the timing to 6 degrees advance. Timing was done at 1300 RPM. I checked the timing tonight and it might be closer to 3.5 degrees now, along with a garage full of blue smoke. Still think IP is over fueling but I can't say for sure.
    Opinions?
    Thanks!
    97 Tahoe / 11 AMG 6.5 Banks Sidewinder, DSG Gears, Heath Diesel Cooling
    04 F-250 Cummins Powered

  2. #2
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    If it's idling, it's not overfueling. Check the basics. Air and fuel supply. Check the oil level and condition. Also check that the wastegate is actually doing what it should. If it's stuck open, power goes away and it smokes. It won't cause smoke at idle, though. Sounds more like a bad IP than anything. Forget the advance plunger and the HPCA, for now. They don't add that much advance, and if it is too advanced, you'd hear it, and it probably wouldn't start.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  3. #3
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    https://photos.app.goo.gl/9YdBZMYDui8naMSZA
    Video at idle with turbo removed.
    Motor starts very quickly with 5 second glow plug cycle when cold, no glow plug when warm. Oil looks good and was changed after break-in.
    97 Tahoe / 11 AMG 6.5 Banks Sidewinder, DSG Gears, Heath Diesel Cooling
    04 F-250 Cummins Powered

  4. #4
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    Rule #1 when you have a performance problem: Change the fuel filter...
    The Constitution needs to be re-read, not re-written!

    If you can't handle Dr. Seuss, how will you handle real life?

    Current oil burners: MB GLK250 BlueTEC
    New ride: MB GLS450 - most stately
    Gone but not forgotten: '87 F350 7.3, '93 C2500 6.5, '95 K2500 6.5, '06 K2500HD 6.6, '90 MB 350SDL, Kubota 7510

  5. #5
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    As John said....FUEL FILTER

    Also could have a failing lift pump...

    With the engine idling....open the water drain up front (If it has one) and fuel should come out and engine not stall. If the engine stalls...lift pump is not working

    If the lift pump has died or is not working the IP simply can't pull enough fuel on it's own.

    Check the filter first and make sure its not clogged up.
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  6. #6
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    After running 100% homebrew in another 6.2 I know all about performance related clogged fuel filters...lol! Started with a new fuel filter at engine break-in, while checking for obstructed return line I ran the overflow into a cup and was surprised at the amount of fuel returned after running 20 seconds. The lift pump isn't that old and I have ash tray mounted tattle-tell light wired to it so I know when it is powered. Drove 250 miles return home trip with no power to the lift pump thanks to a bad oil pressure sender, amazed it ran with just vacuum from the DB2 but helps running with a full tank.
    I'll look for a flow specification and check the filter.
    97 Tahoe / 11 AMG 6.5 Banks Sidewinder, DSG Gears, Heath Diesel Cooling
    04 F-250 Cummins Powered

  7. #7
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    On top of what was already said. I would put an in line fuel pressure gauge after the filter to confirm you are getting fuel to the IP and see what your pressure is. If pressures are good and #6 is over fueling… I would try a different injector for #6 and if problem continues, IP for sure.

    You should be getting a safe 3-7 psi on your fuel pressure.

    You could also try advancing or retarding the IP timing while running to see if that fixes your problem. I’ve had a few ips that needed to be fully advanced to get the motor running right.

    If you like, you could mail me your injectors and I can do a free pop pressure test on them.
    Last edited by 2INSANE; 11-26-2021 at 09:05.

  8. #8
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    Quote Originally Posted by Robyn View Post
    As John said....FUEL FILTER

    Also could have a failing lift pump...

    With the engine idling....open the water drain up front (If it has one) and fuel should come out and engine not stall. If the engine stalls...lift pump is not working

    If the lift pump has died or is not working the IP simply can't pull enough fuel on it's own.

    Check the filter first and make sure its not clogged up.
    The older I get the more I seem to overlook the simple solutions. Lift pump was putting out 25% of specified volume with and without the filter. The last one purchased was in 2017. After installing new pump and pressure gauge its drivable. Will play with timing to see if I reduce the hazy smoke.
    97 Tahoe / 11 AMG 6.5 Banks Sidewinder, DSG Gears, Heath Diesel Cooling
    04 F-250 Cummins Powered

  9. #9
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    Quote Originally Posted by 2INSANE View Post
    On top of what was already said. I would put an in line fuel pressure gauge after the filter to confirm you are getting fuel to the IP and see what your pressure is. If pressures are good and #6 is over fueling… I would try a different injector for #6 and if problem continues, IP for sure.

    You should be getting a safe 3-7 psi on your fuel pressure.

    You could also try advancing or retarding the IP timing while running to see if that fixes your problem. I’ve had a few ips that needed to be fully advanced to get the motor running right.

    If you like, you could mail me your injectors and I can do a free pop pressure test on them.
    Installed a pressure gauge after the filter and it's at a steady 6 lbs. Thanks for the pop test offer, I sent the injectors back to the rebuilder (Accurate Diesel) and he said they all tested fine. That doesn't explain why #6 glow plug was burned down after 600 miles. Still concern about the diesel rich smoke coming from this, luck for me I don't need to drive this. In fact planning on giving this to grandkids for first vehicle and that is 7 years in future!
    97 Tahoe / 11 AMG 6.5 Banks Sidewinder, DSG Gears, Heath Diesel Cooling
    04 F-250 Cummins Powered

  10. #10
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    Quote Originally Posted by garysleeman View Post
    Installed a pressure gauge after the filter and it's at a steady 6 lbs. Thanks for the pop test offer, I sent the injectors back to the rebuilder (Accurate Diesel) and he said they all tested fine. That doesn't explain why #6 glow plug was burned down after 600 miles. Still concern about the diesel rich smoke coming from this, luck for me I don't need to drive this. In fact planning on giving this to grandkids for first vehicle and that is 7 years in future!
    Did you try playing with the IP timing while motor is running? Simply loosing the 3 15mm nuts and turn it driver or passenger and use a bar of some sort to turn it.

    If that does not work…

    I am thinking the problem is your IP. I’ve had a handful of IP’s that were rebuilt from great companies that were junk. 6 psi fuel pressure after filter is great!

  11. #11
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    Gray smoke with strong fuel smell is usually retarded timing. If you advance it, and it either becomes too noisy (Diesel rattle) to clear up the smoke, or doesn't help much or at all, the IP is suspect. (Too) retarded timing effectively lowers the compression ratio, causing late, incomplete combustion and unburnt fuel exiting the exhaust (smokes off in the hot pipe). It's simple to test retarded timing on a warm engine by powering the HPCA (apply 12V to the spade, after the engine is up to operating temp), which advances the timing a few degrees. Diesel rattle should increase and smoke should clear. It is also important to test it to ensure it works. If it is either stuck advanced, or doesn't engage, damage can occur if it suddenly decides to work. The burned glow plug could simply have been a bad plug. I've seen more than a few over the years, of all brands. A bad IP (uneven timing) can also burn individual plugs (as well as damage cylinders/pistons). With your compression test values, it's unlikely any permanent damage is done. Running the engine for an extended period with a failed lift pump can damage the IP, as well.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  12. #12
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    Upon further IP diagnostics found depressing the advance arm does not change how the engine runs. With only 600 miles on the pump will be sending it back for repair.
    97 Tahoe / 11 AMG 6.5 Banks Sidewinder, DSG Gears, Heath Diesel Cooling
    04 F-250 Cummins Powered

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    Quote Originally Posted by garysleeman View Post
    Upon further IP diagnostics found depressing the advance arm does not change how the engine runs. With only 600 miles on the pump will be sending it back for repair.
    Like!

  14. #14
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    That tells a big story....

    Was the outfit that worked on the IP a certified stanadyne shop ????

    I bought a "Rebuilt" IP once off ebay....I needed a core.....
    The price was not bad ....the local stanadyne shop up in Portland did not have one...

    The pump was sold as "Rebuilt" Haaaaaa...It was a good core though.
    The head was usable....they had to oversize the CCA bore and sleeve it....

    Waaaaay too much junk out there being sold as rebuilt.

    The one I got was clean, had new seals and gaskets and looked fine....until it was apart and you started checking stuff......

    It came back from the shop in top shape and ran a long time.

    Cleaned up and resealed....a far cry from overhauled.

    The shop runs all pumps on there test machine and checks the operation completely against factory specs....
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

  15. #15
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    I've used Accurate Diesel for DB2 rebuilds and injectors for GM and Ford diesels for close to 20 years, only had one injector that went south after a 1200 mile trip. I had a conversation today with them about this pump and he is not convinced there is a problem with the pump, thinks the issue is timing. He wanted to know far apart the timing marks were on the pump and front cover. The pump line was close to 5/16" left (looking from the front of the motor) of the front cover mark. He said the timing was severely retarded and I should align the timing marks. I moved the pump mark 1/8" left of the cover mark and the motor sounded better and timing with my Tach-N-Time was advanced 8-9 degrees. Next I moved the pump very close to aligning the marks and the timing was 13-14 degrees advanced. Motor was clacking away now and depressing the advance piston when the motor was being timed (1300 rpm) did nothing.
    This was a junkyard motor from a 92 truck with an 1988 block casting date. I didn't take note or don't remember the timing marks location before tearing the motor apart. I don't see a circle stamped in the pump but I do in the front cover. Good chance pump isn't original to the engine. This is the forth 6.2 I've had and I don't think any of them had useful timing marks on them.
    The possibility that the pump driven gear could be misaligned by a tooth was also discussed, I took photos during motor assembly to verify the timing chain crank and cam gear alignment and drive and driven gears for the IP alignment. I looked at the photos last night and they were right on the money.
    I could dial back on the timing a bit and run it there, seemed to not be running rich, looked like roll coal when I stomped on it with the timing advanced 14 degrees. Or send the IP back to be checked out, it is still under warranty.
    97 Tahoe / 11 AMG 6.5 Banks Sidewinder, DSG Gears, Heath Diesel Cooling
    04 F-250 Cummins Powered

  16. #16
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    It is the pump man! I’ve had the same bull**** excuse from Badger diesel about the chain or gear drive not installed right. Blah blah blah they don’t want to pay for their **** up. It is as simple as that. Get your money back and find a different company. Penscoladiesel served me well. They are cheaper too.

  17. #17
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    Quote Originally Posted by 2INSANE View Post
    It is the pump man! I’ve had the same bull**** excuse from Badger diesel about the chain or gear drive not installed right. Blah blah blah they don’t want to pay for their **** up. It is as simple as that. Get your money back and find a different company. Penscoladiesel served me well. They are cheaper too.
    Not so fast. If he had mentioned the scribes that far off, the first thing I would have suggested is advance the timing (a lot) and toss whatever timing device he was using. The Kent-Moore is a better set, but is also inconsistent, engine to engine, and they fail often. I do better timing by ear. Let's see how it goes with some advanced timing.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  18. #18
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    Quote Originally Posted by DmaxMaverick View Post
    Not so fast. If he had mentioned the scribes that far off, the first thing I would have suggested is advance the timing (a lot) and toss whatever timing device he was using. The Kent-Moore is a better set, but is also inconsistent, engine to engine, and they fail often. I do better timing by ear. Let's see how it goes with some advanced timing.
    Good idea Dmax. A Little more tinkering with the timing would not hurt and does not take long.

    He did say that the advance piston did nothing when pressed which indicates a stuck piston or not properly built IP. At idle a properly built IP should make the motor run more like poop when depressing the advance piston from my experience.

    I once had an IP that needed to be advanced fully to the driver side, 1/2” from the mark, where the ip casing was against the 3 bolts. It ran better but was over fueling which caused the motor to overheat after 5 miles at 88 degrees outside temperature. I paid $800 for that POS IP and the company would not honor the warranty because they claimed it was the Geardrive timing causing the problem which was bull crap when they were over 1500 miles away.

  19. #19
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    Quote Originally Posted by 2INSANE View Post
    Good idea Dmax. A Little more tinkering with the timing would not hurt and does not take long.

    He did say that the advance piston did nothing when pressed which indicates a stuck piston or not properly built IP. At idle a properly built IP should make the motor run more like poop when depressing the advance piston from my experience.

    I once had an IP that needed to be advanced fully to the driver side, 1/2” from the mark, where the ip casing was against the 3 bolts. It ran better but was over fueling which caused the motor to overheat after 5 miles at 88 degrees outside temperature. I paid $800 for that POS IP and the company would not honor the warranty because they claimed it was the Geardrive timing causing the problem which was bull crap when they were over 1500 miles away.
    This is a primary reason I suggest powering the HPCA on a warm engine. It will first verify that it's working. Secondly, will allow an internal timing advance at will. If it is not working, or is stuck advanced, it would explain why near-aligning the scribes is too advanced. Depressing the advance plunger at idle is less advance than the HPCA, but should offer some audible difference, but may not in every case. That is, unless the timing is extremely retarded. The timing "sweet spot" is narrow, but the range of retarded timing "flat" range is quite wide. Using the throttle advance as a measure is very unreliable in all but a nearly well-timed engine. I would suggest using it as a measure for too-advanced timing at idle. The scribe range between too retarded and too advanced is less than 1/4". The throttle advance is within that range, while the HPCA is wider. Hard cold starts are also a good indicator, in that, flooring the throttle for a cold start can help in extreme cold not only because it increases fuel volume, but bumps the advance a bit if the HPCA isn't already adjusted to max. Usually, an engine that requires throttle input to start cold can use more external advance.

    Also note, as I said before, a healthy DB2 pump will run without a lift pump (albeit, maybe poorly), but extended running without supply pressure can damage the IP's internal transfer pump. If it's unable to develop internal case pressure, the internal advance won't work.
    1985 Blazer 6.2
    2001 GMC 2500HD D/A
    dmaxmaverick@thedieselpage.com

  20. #20
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    Maverick is referring to the electric IP advance.

    The two electrical connections on the IP.

    One is for the shut off (More accurately the turn on) solenoid .

    The other connection is the COLD ADVANCE

    In stock trim.....DEPENDING ON THE APPLICATION and year of the rig...The cold advance is powered by a 12 volt supply from the ignition that routes through a temperature switch in the rear side of the RH head.

    This keeps power to the Advance until the engine is up to about 110 F or so (Some reasonable heat in the engine)

    To test the advance.....With a cold engine....Check for voltage at the cold advance terminal on the IP WITH THE KEY ON.

    Depending on the set up....there can also be a fast idle solenoid in series with the cold advance.

    To check the advance when the engine is warm....Rig up a wire from the battery that you can momentarily jump to the cold advance terminal on the IP.

    The engine "Cackle" should increase noticeably when active.

    The arm on the side of the IP simply advances the timing a small amount as the throttle is opened.

    The DB2 pumps are all mechanical as far as the injection timing goes......The mechanical arm is sort of like the fly weights in a distributor.....Well sort of....

    You have spoken of the term "Rich" A diesel has a finite air source...WIDE OPEN ALL THE TIME.....
    Fuel delivery rate equals engine speed.

    Now....THIS SAID

    When you mash the throttle hard and ROLL COAL under load.....the engine is restrained as far as the speed it can reach due to load.

    Anything more than a slight grey haze out the exhaust is wasted fuel and excess exhaust temperature.

    A small (Short duration) puff of black smoke that clears quickly is pretty normal....A cloud that pours out like water out of a hose....NOT SO MUCH.

    Coal rolling.....Yeah it looks cool ....is wasting fuel, does not make any extra power and is hard on the engine....especially if you are pulling hard on a grade and run the exhaust temps off into the ozones (1000F at the manifold outlet to the head pipe is pretty much a good place to call it ENOUGH....

    BLUE/WHITE smoke is unburned fuel that is being pumped out the exhaust.

    Retarded timing is one of the culprits.....The other can be a dribbling injector that allows a bit of fuel to get loose during the last vestiges of the power stroke and into the start of the exhaust stroke.....

    Poor injectors with low pop pressures and leaks internally are the reason.

    A good injector should "POP" (Open) at around 2000 psi and spray a nice cone/mist pattern.....An injector that displays DRIBBLING, PEEING A STREAM or other strange anomalies are junk.....Proper operation is a quick POP....SPRAY and then closed.....
    Last edited by Robyn; 12-02-2021 at 08:19.
    (1) 1995 Suburban 2500 4x4
    (1) 1997 Astro
    (1) 2007 Chevy Avalanche
    THIS IS BOW TIE COUNTRY

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