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Mattt

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  1. Mattt
    I have a question on the L59 5.3 flex fuel engine fuel/intake system. Up thru 2004 the L59 has a return fuel line that returns to the fuel tank. The 2005-06 has no return line back to the fuel tank but instead has a different fuel pump that apparently regulates fuel to the rail. I have a 2004 truck equipped with the L59 engine (with return line). Is it possible to swap the fuel pump to the later style, abandon the fuel return line, and run the 04 like an 05-06 L59 5.3? The reason I ask about doing this is I want to swap to the 2007+ NNBS or TBSS intake manifold and that system also has no fuel return line either. I have found most people use a particular Corvette fuel filter with the built in pressure regulator and fuel return line fitting when swapping to the newer intake manifold on an older GMT800 truck. I was looking at this option as an alternative. How much of a difference in how the fuel system/intake/fuel pump module work on an L59 from is there between this cross over when GM did away with the fuel return line to the fuel tank? Is the only difference the fuel pump? Is the flex fuel sensor the same or different? Thank you very much in advance for any and all insight.
  2. Mattt
    Sorry for not following up after the helpful replies. I may try replacing the sending unit, but still can't get a solid line of sight on it. I guess replacement is just done by feel since I know where it is located and the harness apparently clips on. I will also have to take a look at the back of the valve cover gaskets as there is no obvious leak from the front, side or top of them. Thanks again.
  3. Mattt
    Thanks for the suggestions. I will check those out. Also, good idea on the vinyl flooring scrap to keep the garage clean. That oil pressure sensor is almost impossible to see back there. Is the crankshaft sensor just as difficult to access in the truck?
  4. Mattt
    Have this oil leak that recently started dripping with a vengeance. This is on a high mileage 2004 5.3 in a Tahoe. The engine will be coming out soon for a refresh or replacement, but this oil leak is making a big mess wherever I park, so I'd like to address it before it the garage floor stain is permanent. With the engine running, I can see the drip come from above and somewhat to the rear of the starter, near the bell housing, but not quite on the bell housing. It is coming from higher up in an area that I can't view. Want to take a stab at where this leak is originating from? Is that location for a leak a tell tale sign of one common leak that 5.3's suffer from? I have attempted to look at the oil pressure sending unit, as I read they leak, but I can't get my eyes on it at the back of the intake manifold up against the firewall. Is there a trick to getting eyes on that sending unit?
  5. Mattt
    It's time for an update with my 2001 Silverado 4.8 problem. After 13 months, the Secondary Air System I/M Readiness test has FINALLY completed and run. Last month I broke down and had the A/C repaired as driving around with no A/C was getting old. A/C had leaked refrigerant at the charging port. ~$230 later and I have functioning A/C. I gave the truck a few weeks of driving with A/C on, and plugged in to check the Sec Air Sys I/M. As of last week, it was still showing Incomplete. Fast forward to yesterday....I plugged in again and the Sec Air Sys I/M Readiness test has FINALLY completed and gone to "OK." Quick like today, first thing this morning....I went and had the smog check completed and ran to AAA so I finally have tags for the first time in over a year. I am making a leap here......but I DO think that the A/C being functional is one small part of the Secondary Air System running it's self test and flipping the I/M Readiness Status to OK. I spoke to a friend that is a GM Tech and he told me there is a lot of strange code in the factory program that can make even a seasoned tech scratch their head when diagnosing problems. He wasn't certain that the A/C was linked to Sec Air Sys, but said there is a strong possibility that it was.
  6. Mattt
    Ok, thanks. I was hoping there was more than that, like a cut/paste or image from an actual GM technical document. You know the old, if it's posted on the 'net then it must be true.......
  7. Mattt
    Thanks for posting that et888. Can I ask where you ran across that piece of info that states to run the A/C as part of the drive cycle requirement to get the Secondary Air System to run? I ask that because I've floated that idea for almost a year and every tech or auto shop person thought I was nuts for suggesting that. My truck currently does not an A/C that actually cools. I can turn the A/C on at the dash, but the compressor doesn't turn on. About 18 months ago I noticed the effectiveness of the A/C was going away, so I suspect a small leak somewhere. I have not had it looked at, and in my experience finding a small A/C leak can get expensive quickly and since this truck isn't worth much being 15 years old, fixing the A/C has not been high on the priority list. Any suggestions or info where you found the A/C info related to drive cycles would be appreciated. Good luck and keep us posted if that takes care of it for you.
  8. Mattt
    Yeah, I'm almost a year out, as of May, and still hasn't cleared and ran the Sec Air System I/M ready test. It is stuck in INC. There is another thread with relevant info to the this problem....no solution has revealed itself yet, short of taking the vehicle into a dealer or independent shop and opening up your bank account wide for exploratory "diagnosis." Other thread: http://www.tahoeyukonforum.com/threads/trying-to-pass-smog-in-cali.76752/page-6
  9. Mattt
    Months later.....Secondary Air system still has not run and gone to OK in I/M readiness. I checked the engine operating temp and it runs just above ~200*, 203, 205. One thing I did notice when viewing Live Data with engine running is that Secondary Air system result shows "Atmos." I'm not sure what that is telling me, but would like to know.
  10. Mattt
    Moving this back up in hopes someone has a solution. I have driven my truck many hundred miles, probably thousands of miles and still Sec Air System is INC. As an example, yesterday I drove 100 miles in mixed traffic in the city. My driving ranged from 70mph full speed freeway to bumper to bumper traffic, street driving typical, idling, stop and start at least 5 times. Still INC....this has been going on since May and still will not clear that test. I've disconnected the battery and all other tests run and clear...except Sec Air System. Help! Thanks in advance.
  11. Mattt
    Williamsauls, Thank you for replying back. Would you say it ran the test due to one drive that was longer, more miles?.....Or would you say it was just the sheer number of miles you racked up on the odometer over time? I found the info that no I/M monitors can be incomplete now...and that is really stupid and short sighted if you ask me. Now my truck will NOT be smog checked for who knows how many months until this test runs. It's already been since May. This ridiculous rule put in place by unelected Jack booted thugs who are living high off the hog of CA Taxpayers, CARB(California Air Resources Board), courtesy of one party screwed up rule in this formerly great state...but I digress. I guess I'll just keep driving and hope it runs the test at some point. Thanks again.
  12. Mattt
    Add one more 2001 Silverado with a 4.8 to the list of incomplete I/M Readiness tests, the Sec Air System as "inc." I've gone round and round with this truck since May and this problem. No matter what is done, the Sec Air System will not complete. The truck has 150k on the odo, runs great, no stored codes. What is the definitive word....can you pass a CA Smog check in 2015 with one I/M showing incomplete? Can it be the Sec Air System showing Incomplete? One more twist to my story....this truck does not have functioning A/C right now and has not for over a year. The A/C light on the controls lights up, the fan turns on, it just does not blow cold. I suspect a refrigerant leak, but have not had it checked. I know some drive cycles say to have the A/C on during a particular procedure.....is there any way possible that lack of A/C working would prevent the ECM from trying the Sec Air System test? Seems unlikely, but figured I'd throw that in there. I'm hoping someone before me has figured out the solution to this puzzle and would not mind sharing it. Thanks in advance.
  13. Mattt
    I'll check the FPR tomorrow. Thanks for that easy check. Fuel check valve....where is it located? Fuel filter was new when the pump went in about 6 months ago. I know it could be plugged already....only way to check that is replace it. Might be an easy....what if..... Thanks again for the suggestions.
  14. Mattt
    2001 Suburban w/ 5.3....I replaced the fuel pump a few months back, just the pump not the complete module. I bought the pump in an ACDelco box off Ebay and the part # comes up as a ACDelco-Mexico part # BGV00250 Recently the Sub has been hard starting after sitting for a while. I put a pressure gauge on the schraeder valve and my fuel pressure is low....like 40 psi. At least once on a cold crank, key on, engine off it only primed(~2 sec) to 30 psi. It always starts but generally not without a long crank or cycling the key on-off-on-off-on which is giving me a longer prime. I didn't replace the regulator when the new fuel pump went in. I'm trying to avoid just throwing parts at this problem and looking for a little help which way to go. I have little faith in the Ebay pump now but I'm not sure that is the problem. The problem could just as easily be the regulator. Is there a way to discern what is causing the low pressure....regulator or pump? Thank you in advance.

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