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Davo
Davo, Master technician
Category: Car
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Experience:  ASE Master Technician/Advanced Automotive Diagnostic Technician
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1998 Chevy: light came..in it doe to vibration)and..my truck..driven

Customer Question

I have a 2000 Chevy C1500 pick-up , 4.8L w/automatic transmission(w/OD) ---- 87000 miles -- religiously maintained and have passed emissions 3 years in a row with flying colors --------for a long time the fuel gauge was very erratic - acting properly at times and not at other times - I suspected a faulty float assembly -------coincidentally my son's pick-up - a 1998 Chevy pick-up had fuel pump problems --- we replaced the fuel pump and all worked fine - thinking that maybe his float assembly would work on mine - I lowered my tank and removed the fuel pump ----- the float assemblies were not the same so I reinstalled mine and reinstalled the tank ----- no problems - no "service engine soon" lights- still a faulty fuel gauge - I purchased a new float assembly from the Chevrolet dealer - removed the fuel tank once again and replaced the float assembly w/o removing any connections from the fuel pump other than the ones required to replace the float assembly - the replacement was identical to the original one - I also replaced the O-ring where the fuel pump goes into the tank - - and then reinstalled the fuel pump and fuel tank - all worked fine - the fuel gauge worked properly - after a few miles the "service engine soon" light came on - I had the code checked - it showed an emission leak - a P400(?) code which indicated a general leak ------ I had the code reset - drove approx 60 miles - removed the tank and the fuel pump once again and methodically inspected all connections for breakage, kinks, misconnections, etc. One of the polyethylene hoses leading into the fuel pump had been bent at one time but was not in a kinked position --- as a precaution - I wrapped a metal screw with duct tape (to prevent metal rubbing the polyethylene hose and rubbing a hole in it doe to vibration)and then attached the screw alongside the "kinked" area of the hose with duct tape - thus making a "splint" - I triple checked all other connections and found no other problems ---- after reinstalling the tank I was able to drive approx 340 miles with the light off - a total of 400 miles with the light off ----- I had one technician suggest that I may have cracked the check valve inside of the vent hose when I first replaced the float assembly - my truck does not have the 4" vent hose w/check valve that he suggested so that was not the problem---------all connections are tight, unobstructed and properly installed- any clues -----------the truck runs great even with this light on so there is not another problem somewhere else - the light first came on when the correct float assembly was changed - the codes were reset - the light stayed off for approx 100 miles (i.e.- the drive cycle required by the computer) - the codes were reset again - truck was driven approx 60 miles --------- tank lowered , insppected and reinstalled - and the light reamined off for approx 340 miles - a total of 400 miles with the light off - well past theXXXXXcycle and diagnostic code shows only a general problem
Submitted: 11 years ago.
Category: Car
Expert:  Davo replied 11 years ago.
 You may have a leak at the seal you replaced between the tank and pump module.If you didn't crack any of the plastic pipes on the pump assembly and didn't damage the fuel tank pressure sensor or connector.You have a leak that you induced the problem is in something you touched.The code number is XXXXX P0440 or P0442 and both are evap leaks.I suggest dropping the tank again and putting the old seal back in if you still have it.The time to set this code varies by certain conditions and mileage isn't one of them.Make sure the fill and vent hoses are tight also.Please hit the ACCEPT button if this answers your question.Don't close the question if you have more questions about this problem.   
Customer: replied 11 years ago.
Reply to Davo/diablo666's Post: where is the vent hose located -there is a smal (1/4"ID) hose just behind the fill cap assembly but it has a cap on it -and serves no apparent purpose - also wheere is the fuel pressure sensor -------------- I really don't want to drop thius tank again until I am 100% positive where the problem is at --- I do not have the old O-ring and the new one seats in quite well - I can tell this by the amount of force required to drive the lock ring into its proper locking position - not a great deal of force but sufficient enough that you can tell that there is a good tight fit ------dewll on my problem some more and see if you can theorize another propblem area - I have "theorized" intil I am blue - thanks
Expert:  Davo replied 11 years ago.
 Before we continue get the code read again and post the number.For all I know the person that read the code told you the wrong description of the code number.I'm guessing at the code number from your description and it may lead us in a big circle.
Customer: replied 11 years ago.
Reply to Davo/diablo666's Post: the code number was P0440 - but please anser regarding the vent hose
Expert:  Davo replied 11 years ago.
 The hose you are seeing up there is the rear axle vent hose.The fuel tank pressure sensor is on the top of the tank on top of the fuel pump module.The tank is vented during filling through the vent valve.
Expert:  Davo replied 11 years ago.
 I must ask for an accept on this question to continue any further in helping diagnose the problem.  
Customer: replied 11 years ago.
Reply to Davo/diablo666's Post: I very dearly want to accept your answer and have no problem paying you for it - however we have talked some and you don't seem sure of what my problem is - and I want to be 100% sure before I drop the tank a 4th time - I know the problem is in the area we have talked about but I find no visible signs of any damage - kinks, breaks, misconnections - I have thought about replacing all the hoses leading into the fuel pump assembly but I am not sure that this would resolve the problem - is there any way of testing anything oris there anything that someone could visually see - again the problem did not start until I removed the fuel pump assembly a 2nd time -- and after the 3rd time I was able to drive over 300 miles before the light came back on - as I originally said this is a vey vexing problem and I don't want to spend hundreds of dollars for someone to look over what I have already seen - ty for understanding

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