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mw1871
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Feb 4, 2009, 5:55 PM
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2002 chevy fuel problem
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My son has a 2002 Chevy Blazer with a 4.3 V6. We have been chasing a driveability problem for some time now and discovered that the fuel pressure drops to 0 when the pump shuts off. At pressure we are at 60 psi. With 160,000 miles we feel the pressure regulator, with its reputation for failure, would be a good investment. My question is along with the regulator and plenum gaskets, are there any other parts I am likely to need to perform this task. Also, how much time should I expect to need ( barring any mishaps) ? Thank you for any and all responses.
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Loren Champlain Sr
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Feb 4, 2009, 6:00 PM
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Re: 2002 chevy fuel problem
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The fuel pressure regulator does just that, regulates how much pressure goes to the injectors under a given load.
If the fuel pressure is bleeding off, there are several possibilities. 1) Check valve in the fuel pump allowing pressure to return, 2) Injector(s) leaking fuel into intake, 3) Fuel feed lines (under plenum).
Loren
SW Washington
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mw1871
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Feb 4, 2009, 6:53 PM
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Re: 2002 chevy fuel problem
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In your opinion, do you feel a pressure regulator is a waste of time or am I possibly on the right track? The diagnostic charts say to install shut off valves in the pressure and return lines to aid in diagnosing. I am not having any luck in finding any nor am I in trying to find parts to fabricate my own.
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Loren Champlain Sr
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Feb 4, 2009, 6:58 PM
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Re: 2002 chevy fuel problem
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Yes, the fuel pressure regulator won't do it. You'll need to hook up a pressure guage, first, to confirm that it is losing pressure after shut down, then start chasing as to where the pressure is going.
Loren
SW Washington
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mw1871
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Feb 4, 2009, 7:14 PM
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Re: 2002 chevy fuel problem
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Do you have any suggestions on how to isolate the fuel lines. I have had suggestions to actualy pinch the plastic lines but I am scared that they will either crimp closed or crack.
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Loren Champlain Sr
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Feb 4, 2009, 7:17 PM
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Re: 2002 chevy fuel problem
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No, don't crimp the plastic lines. You can crimp the rubber return line, though. Should be back, by the firewall.
Loren
SW Washington
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mw1871
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Feb 4, 2009, 7:29 PM
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Re: 2002 chevy fuel problem
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I will try to find the rubber line and give that a try. However that will only isolate fuel returning from that point. But that will at least fill a puzzle piece, I dont know if it will solve the puzzle. I wont see the car until this weekend at the earliest. Thank you for all the input and I will post my findings.
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mw1871
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Feb 7, 2009, 1:35 PM
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Re: 2002 chevy fuel problem
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As promised, here is the latest update. I was able to craft a couple of shutoff valves and resumed troubleshooting. I traced the fuel pressure bleed down to the fuel pump. With a new fuel pump installed the pressure is now holding steady when the pump shuts off. Now some of the driveability is improved but the vehicle still feels as it has a sputter or miss. A compression test is showing uniform readings. The plugs show no sign of gas or oil fouling. Cap, rotor, and wires have been replaced. We did a resistance check on the injectors and they are all within 3 ohms. The manual gives various readings depending on temp and they are right on. We took these readings at the ecm so that any wiring problem would show. My gut feeling is a fuel delivery issue. The ecm is not throwing any codes. We traced the ecm grounds and they are clean and tight. Any thoughts?
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Loren Champlain Sr
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Feb 7, 2009, 1:46 PM
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Re: 2002 chevy fuel problem
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If you have absolutely ruled out a secondary misfire, it could still be dirty, or clogged injectors. A gas analyzer would be a big help in diagnosing.. If you have a secondary misfire, it will show up in HCs. If you have a misfire from a lack of fuel, you won't see the high HCs as there is no unburned fuel. Not sure if I explained that correctly?
If this is the case, doing an injection cleaning may help. If you've never had this done, you can look at it as a needed maintenance. And, you'll see an improvement in performance and fuel economy. The machine we use is called a Motor Vac. Most shops will have one.
Loren
SW Washington
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