2003 CHEVY SILVERADRO 5.3 T ENGINE WON'T START

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ronnie310
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Joined: Tue Apr 15, 2014 12:51 pm

2003 CHEVY SILVERADRO 5.3 T ENGINE WON'T START

Unread post by ronnie310 » Wed Jul 06, 2016 4:36 pm

TRUCK HAS 156,000 MILES ON IT HAS BEEN SERVICED REGULAR. IT CUT OFF WHILE DRIVING. IT WOULD CRANK BUT CUT OFF IMMEDIATELY. AFTER IT SET ABOUT 4 HRS IT CRANKED BUT RAN ONLY A FEW MIN. IT HAS NO CODES IN SYSTEM. FUEL PUMP COMES ON. FUEL PRESSURE GOES TO 60 PSI AND PUMP CUTS OFF. WITH PUMP AND KEY OFF FUEL PRESSURE IS ABOUT 52 PSI. FUEL FILER CHANGED. THANKS FOR THE GREAT HELP YOU GIVEN IN THE PAST.

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carriedi
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Re: 2003 CHEVY SILVERADRO 5.3 T ENGINE WON'T START

Unread post by carriedi » Wed Jul 06, 2016 9:24 pm

If you have good fuel pressure you need to check for spark and injector pulse. If you have something that can tell you that you have no codes, will it let you see the crank and cam sensors? See if the computer sees the engine turning over. If you have spark but no fuel injection pulse it could be the anti-theft. Does the security light blink?

If your engine died while driving that would indicate something other than the security. If the security system sees a fault while the engine is running it will set a code and turn on the light but it won't kill the engine and it won't go into theft mode because it is programmed allow starting if it gets a key fault while running. (it knows you had to have a good key to get it running so loosing a key signal while running means a circuit problem. it defaults to let you start engine) But if you clear the memory and you have a bad key circuit, you will no longer be able to start the engine. Now the memory doesn't see a key fault with the engine running. That code is gone, you cleared it. Now, it only sees that the key circuit is wrong when starting so... no go.

so, it always will crank, right? Does it start and die or does it never start?
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ronnie310
Posts: 7
Joined: Tue Apr 15, 2014 12:51 pm

Re: 2003 CHEVY SILVERADRO 5.3 T ENGINE WON'T START

Unread post by ronnie310 » Thu Jul 07, 2016 2:24 pm

carriedi wrote:
> If you have good fuel pressure you need to check for spark and injector
> pulse. If you have something that can tell you that you have no codes,
> will it let you see the crank and cam sensors? See if the computer sees
> the engine turning over. If you have spark but no fuel injection pulse it
> could be the anti-theft. Does the security light blink?
>
> If your engine died while driving that would indicate something other than
> the security. If the security system sees a fault while the engine is
> running it will set a code and turn on the light but it won't kill the
> engine and it won't go into theft mode because it is programmed allow
> starting if it gets a key fault while running. (it knows you had to have a
> good key to get it running so loosing a key signal while running means a
> circuit problem. it defaults to let you start engine) But if you clear
> the memory and you have a bad key circuit, you will no longer be able to
> start the engine. Now the memory doesn't see a key fault with the engine
> running. That code is gone, you cleared it. Now, it only sees that the
> key circuit is wrong when starting so... no go.
>
> so, it always will crank, right? Does it start and die or does it never
> start?
SECURITY LIGHT BLINKS NO CODES.
TRUCK CRANKED THIS MORNING AFTER SETTING OVER NIGHT , RAN PERFECT FOR APPROX 90 SECONDS. CHECK PUMP POWER WITH TEST LIGHT, HAS POWER WHEN KEY IS TURNED ON FOR APPROX 10 TO 15 SECONDS THEN POWER GOES OFF. I THINK THAT IS CORRECT, FUEL PRESSURE BUILDS UP AND PUMP CUTS OFF. I THEN TOOK FUEL LINE OFF GOING INTO FUEL FILTER AND CONNECTED LINE TO A HOSE AND RAN IT INTO A CONTAINER. FUEL PUMP CAME ON AND PUMPED FUEL INTO CONTAINER FOR APPROX 10 TO 15 SEC AND PUMP CUT OFF. POWER TO PUMP CUT OFF WITH LINE DISCONNECTED SAME AS IF IT WERE HOOKED UP AND BUILDING PRESSURE. WHY IS POWER DROPPING WITH OUT BUILDING PRESSURE? PUMP STOPS BECAUSE POWER TO PUMP CUTS OFF. COULD FUEL REGULATOR VALVE BE THE PROBLEM? IT SEEMS TO BE WORKING OK ACCORDING TO FUEL PRESSURE GAUGE.

ronnie310
Posts: 7
Joined: Tue Apr 15, 2014 12:51 pm

Re: 2003 CHEVY SILVERADRO 5.3 T ENGINE WON'T START

Unread post by ronnie310 » Thu Jul 07, 2016 6:55 pm

ronnie310 wrote: SECURITY LIGHT BLINKS NO CODES CHECKED POWER TO FUEL PUMP WITH TEST LIGHT, POWER COMES ON FOR APPROX 10 SECONDS WHEN KEY TURNED ON AND FUEL PRESSURE COMES UP, POWER DROPS AND PUMP GOES OFF. DISCONNECTED FUEL LINE FROM TANK TO FILTER, RAN LINE INTO A CONTAINER. TURNED KEY ON PUMP CAME ON AND RAN APPROX 10 SEC. POWER DROPPED AND PUMP WENT OFF. SHOULD PUMP CUT OFF WITH OUT BUILDING PRESSURE. CHANGED FUEL REGULATOR MADE ON DIFFERENCE. TRUCK CRANKED THIS MORNING AFTER SETTING OVER NIGHT, AND RAN PERFECT FOR APPROX 90 SECONDS, THEN CUT OFF, WILL NOT START NOW.
> carriedi wrote:
> > If you have good fuel pressure you need to check for spark and injector
> > pulse. If you have something that can tell you that you have no codes,
> > will it let you see the crank and cam sensors? See if the computer sees
> > the engine turning over. If you have spark but no fuel injection pulse it
> > could be the anti-theft. Does the security light blink?
> >
> > If your engine died while driving that would indicate something other than
> > the security. If the security system sees a fault while the engine is
> > running it will set a code and turn on the light but it won't kill the
> > engine and it won't go into theft mode because it is programmed allow
> > starting if it gets a key fault while running. (it knows you had to have a
> > good key to get it running so loosing a key signal while running means a
> > circuit problem. it defaults to let you start engine) But if you clear
> > the memory and you have a bad key circuit, you will no longer be able to
> > start the engine. Now the memory doesn't see a key fault with the engine
> > running. That code is gone, you cleared it. Now, it only sees that the
> > key circuit is wrong when starting so... no go.
> >
> > so, it always will crank, right? Does it start and die or does it never
> > start?
> SECURITY LIGHT BLINKS NO CODES.
> TRUCK CRANKED THIS MORNING AFTER SETTING OVER NIGHT , RAN PERFECT FOR APPROX 90
> SECONDS. CHECK PUMP POWER WITH TEST LIGHT, HAS POWER WHEN KEY IS TURNED ON FOR APPROX
> 10 TO 15 SECONDS THEN POWER GOES OFF. I THINK THAT IS CORRECT, FUEL PRESSURE BUILDS
> UP AND PUMP CUTS OFF. I THEN TOOK FUEL LINE OFF GOING INTO FUEL FILTER AND CONNECTED
> LINE TO A HOSE AND RAN IT INTO A CONTAINER. FUEL PUMP CAME ON AND PUMPED FUEL INTO
> CONTAINER FOR APPROX 10 TO 15 SEC AND PUMP CUT OFF. POWER TO PUMP CUT OFF WITH LINE
> DISCONNECTED SAME AS IF IT WERE HOOKED UP AND BUILDING PRESSURE. WHY IS POWER
> DROPPING WITH OUT BUILDING PRESSURE? PUMP STOPS BECAUSE POWER TO PUMP CUTS OFF.
> COULD FUEL REGULATOR VALVE BE THE PROBLEM? IT SEEMS TO BE WORKING OK ACCORDING TO
> FUEL PRESSURE GAUGE.

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carriedi
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Re: 2003 CHEVY SILVERADRO 5.3 T ENGINE WON'T START

Unread post by carriedi » Fri Jul 08, 2016 12:01 am

it is unusual for the fuel pump to run for 10 seconds on a key cycle. The fuel pump does not turn off after it builds up pressure, it stop running when the computer says to shut off. A key cycle should turn the fuel pump on for two seconds. the amount of fuel or the build up of fuel pressure will depend on the integrity of your fuel pump. A good functioning pump should be able to pressure up the system to full spec within the two second prime.

The security light should not be flashing. If the light flashes then the security in not seeing the correct key and will shut down the injector pulse. The codes you need to look for are in the BCM (body control module) and should be "C" codes. If you are using a code reader to look for codes, most code readers read engine codes "P" codes and they don't see other modules.

Like most newer cars, your key does no turn on the starter relay like it used to. your key tells the computer that you want to start the engine. Then the computer turns on the starter relay in the underhood relay/fuse box. When the starter won't crank the engine check the starter relay and feel it with your hand while someone tries to start the engine. If you don't feel the relay click then the relay is not getting a signal to pull the contact down. So either the computer is not sending the signal or the relay is not doing it's job.

There are three things that may be happening. The anti-theft is not working, the starter relay is not working or the ignition switch is not working. (there could be other possibilities but these three are the first things to look at.

you will need a scanner that can access the BCM and Passlock data, a good wiring diagram for the PCM and for the starting system, and a good dvom to check the circuits with.
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