QuestionQUESTION: I have a 2000 Chev Silverado, 4.8 Liter V8,automatic trans. We live in Texas and the heat is getting pretty intense. Don't know if that has a bearing on anything or not.
In Feb 2012 I installed a new fuel pump. Worked beautifully until yesterday, it started, I backed a foot then it died. I cannot hear the fuel pump kicking in when I turn the key on now. I am wondering about a possible issue between the turning of the key and the pump getting the "message" to kick in. What is the route of that "message".
Also, recently the throttle body wa.s cleaned. Could that have done something
ANSWER: HI JENNIFER. CLEANING THE THROTTLE BODY WOULD HAVE NO BEARING ON THIS AT ALL. JUST BECAUSE YOU DO NOT HAER THE PUMP TURNING ON DOES NOT MEAN THE PUMP IS NOT GETTING POWER TO IT..TO ANSWER YOUR QUESTIONS, WHEN YOU TURN THE KEY ON AND CRANK THE ENG THE IGNITION SWITCH SENDS POWER THROUGH TO THE PCM. THE PCM SENDS POWER TO THE FUEL PUMP RELAY OR GROUNDS THE RELAY TO ENERGIZE THE RELAY TO SEND POWER TO THE PUMP IN THE TANK..SO I WOULD CK THE FUSES REAL CAREFULL,IF OK REMOVE THE FUEL PUMP RELAY IN THE FUSE BOX IN ENG BAY AREA [MARKED ON COVER] AND SWITCH IT WITH ANOTHER RELAY OF THE SAME SHAPE AND SIZE. SEE IF IT WILL START..IF IT WILL NOT START,YOUR NEXT MOVE IS TO GET UNDER THE TRUCK AND FIND THE WIRE HARNESS THAT GOES IN TO THE TANK,UNPLUG THIS AND GRAB YOUR SELF A 12 VOLT TEST LIGHT AND CK FOR POWER ON ONE OF THESE WIRES [,I THINK IT IS THE LITE GREY WIRE] WHILE SOMONE IS CRANKING THE ENG OVER. YOU WANT 12 VOLTS ON THIS WIRE WHILE ENG IS CRANKING OVER AND WHEN YOU TURN THE KEY OFF THERE SHOULD HAVE POWER ON THIS WIRE FOR 2 TO 3 SECONDS [AFTER TURNING THE KEY OFF.] IF SO THE WIRING IS ALL OK TO THIS POINT..I WOULD SUSPECT A [FAULTY FUEL PUMP] AT THIS POINT. DID YOU REPLACE THIS WITH A GM PUMP ??? IF YOU DID NOT THEN I AM NOT SURPRISED IT HAS NOT LASTED LONG,,AFTER MARKET PUMPS DO LAST LONG..I DONT KNOW WHY,, BUT THAT IS HOW IT IS..JUST TO MAKE SURE THAT THIS DOES HAVE AFUEL PROBLEM AND NOT A IGNITION PROBLEM,SPRAY A LITTLE STARTING FLUID DOWN THE THROTTLE BORE AND CRANK IT OVER,IT SHOULD STRAT RIGHT UP..IF NOT YOU AY HAVE NO SPARK.IF YOU HAVE FUEL PRESSURE GAUGE YOU COULD CK FOR, PRESSURE AT THE MAIN LINE CK PORT..BUT THIS INFO SHOULD KEEP YOU BUSY FOR AWHILE. IF YOU NEED MORE INFO DONT BE SHY. GET BACK TO ME..THANK YOU ,,,TOM..IF YOU ARE FINSHED WITH ME,, PLEASE RATE MY ANSWER.
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QUESTION: Tom, thank you for the above answer, it has been helpful. We thought we had it repaired but now it is acting up again (fuel pump). We have purchased a new pigtail for the fuel pump, installed it and the truck ran fine for a few days. So here we are again...
We put the test light on the grey wire on the harness (it is the correct power wire) and it lights up, but goes out within 2-3 seconds. The seat belt signal has not stopped beeping before the light goes out on the test light. We have moved the relays around in the fuse box, but nothing changes. What could cause the signal to stop, especially so quickly.
Also, you mention above the "PCM". What exactly does that stand for? I am just guessing at it's meaning.
ANSWER: HI JENNIFER, [PCM] SORRY ABOUT THAT, TECH LINGO [POWER CONTROL MODULE]OR COMPUTER. THE SYSTEM SOUNDS LIKE IT IS WORKING CORRECT, WHILE CRANKING THE ENGINE OVER THE GREY WIRE WILL STAY HOT ALL THE TIME THE ENG IS CRANKING,AFTER YOU TURN THE KEY OFF THE WIRE SHOULD REMAIN HOT FOR 2 TO 4 SECONDS. THIS PRIMES THE FUEL RAIL FOR A INSTANT START UP. ARE YOU SAYING THAT WHILE YOU ARE CRANKING THE ENG YOU LOOSE POWER AT THE PUMP. [GREY WIRE]IF THIS IS THE CASE IT SOUNDS LIKE THE CIRCUIT IS OVERLAODING. WIRE PROBLEMS OR GROUND ISSUES MAYBE ?? HAVE YOU CHECKED FUEL PRESSURE? OR IS THERE ANY FUEL AT THE CK VALVE BY THE FUEL RAIL IN ENG COMPARTMENT ??/ I BET NO FUEL UP THERE. IF THERE IS POWER LIKE I SAID ABOVE WHILE ENG IS CRANKING THIS SOUNDS LIKE A BAD FUEL PUMP, I ALSO ASKED YOU IS THIS A GM FUEL PUMP OR AFTERMARKET. AFTERMARKET PUMPS HAVE A HIGH FAILURE RATE...LET ME KNOW,,,, HERE TO HELP..
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QUESTION: I was correct on PCM.
Fuel pump is aftermarket. Fuel pressure has not been checked since we replaced the pigtail. Prior it was low.
And yes, I am saying that power is lost (at the pump) while trying to crank the motor. My husband did have to repair a stray ground wire. He did not get a new "eye", he just wrapped the wire around the bolt and cranked down on it. Do we need a fancy "eye"?
Thank you again for your time and assistance.
AnswerHI JENNIFER,YOU HAVE TO MAKE SURE THAT ALL CONNECTIONS ARE CLEAN TIGHT AND SEALED..WATER LOVES WIRES. RUN 12 VOLTS TO THE GREY WIRE AT THE PUMP WHERE YOU PUT THE NEW PIG TAIL IN,, SEE IF THE ENG STARTS. IF IT DOES, WE KNOW THE PUMP IS GOOD. WIRING OR COMPUTER IS THE ISSUE.....GET BACK TO ME !!!
