2006 YUKON DENALI XL (6.0L)

[joey corasaniti]

HELLO ALL

I HAVE A INTERESTING PROBLEM ON MY 2006 YUKON DENALI XL (6.0L)

THE TRUCK HAS A INTERMITTENT START PROBLEM

THERE IS NO RHYME OR REASON WHEN IT START OR DOES NOT START.

WHEN IT DOES NOT START ON THE FIRST TIME IT ALWAYS START ON THE SECOND TIME.

LET ME TELL TELL YOU WHAT I HAVE DONE TO TRY AND FIX IT

PARTS REPLACE

(FUEL STUFF)

-FUEL PUMP TWICE. ONE MOGG AND ONE FROM THE DEALER. THE DEALER TOLD ME THAT THE NEW FUEL PUMP I PUT IN WAS BAD.

- NYLON FUEL LINE

-STEEL FUEL LINE CONNECTS TO THE RAIL. ( POINTS OF INTEREST THERE IS NO FUEL FILTER, OR FUEL REGULATOR ON THE RAIL.)

-INJECTORS

(ENGINE STUFF)

-CRANK POSITION SENSOR (THERE IS ONLY ONE CONFIRMED WITH THE DEALER)

-CAM POSITION SENSOR (DID NOT DO A RELEARN)

-OIL PRESSURE SENSOR

-MASS AIR SENSOR

-MAP SENSOR

-VAPOR CANISTER PURGE SENSOR (TOP OF INTAKE)

-ACELERATOR POSITION SENSOR

-IGNITON SWITCH (DID THE RELEARN FOR PASSLOCK)

-ALTERNATOR

-STARTER

-PCM FLASHED TO THE VIN

-BODY CONTROL MODULE FLASHED TO THE VIN (DID RELEARN FOR PASSLOCK

-FUEL TANK PRESSURE SENSOR

-FUEL RELAY SWAPP

-FUEL FUEL SWAPP

WHAT I HAVE DIAGNOSED

THE FUEL RELAY HAS 4 PINS

86 30
87 85

86 GET 1 VOLT LESS THE BATTERY VOLTAGE WHEN TURNING KEY
30 GET 12 VOLTS ALL THE TIME
87 HAVE TO RECHECK BUT I BELIEVE NORMAL 12 VOLTS
85 I BELIEVE WAS GROUND

I ADDED NEW GROUNDS TO THE FRAME, CHASSIS AND ENGINE. I CLEANED ALL THE GROUNDS ON THE FRAME AND ENGINE GROUNDS ACCEPT FOR ONE. THE MAIN GROUND OFF THE BATTERY THAT GOES TO THE ENGINE BLOCK.


WHEN I GO TO START THE TRUCK AND IT DOES NOT START I HAVE THESE TESTER HOOKED UP

- FUEL GAUGE (50-55 PSI)
-SPARK TESTER (GETTING SPARK)
-NOID TESTER (INJECTORS FIRING I CHECKED 2 DIFFERENT ONES

IF I CYCLE THE KEY 3 TIMES AND TRY IT STILL WILL NOT START

I WILL TELL YOU THE PRESSURE DOES NOT HOLD AT 50-55 IF I CYCLE THE KEY AND LET IT SIT. ITS LIKE THE CHECK VALVE IS BAD. BUT HOW CAN THAT BE TWO BRAND NEW FUEL PUMPS (ENTIRE HOUSING)

WHAT CAN I CHECK. SHOULD I BUY A 300-400 COMPUTER AND USE REAL TIME MONITORING TO FIGURE SOMETHING OUT.

THANKS FOR EVERYONES HELP.

JOE

[Doug_Scott]

First, put your wallet away, and stop throwing money at it. It never seems tp work.

 

An engine only needs 4 things to run.  Fuel, ignition, timing, and compression.  Timing should be part of ignition though. 

 

Are you saying that occasionally the engine will just turn over and make no attempt to actually fire?  How long are you cranking the engine when it doesn't start? 

 

When it doesn't start, do you just let the key go, then just turn the key to the start position, or do you turn the key back to the off position? 

 

Your truck may have a fuel filter mounted to the frame, or it may be part of the fuel pump. 

 

Have you tried cranking the engine longer before giving up? Check the battery voltage while enging is cranking over.  You should take the negative cable off the engine so you can get a good look at end of the cable for any white powder under the plastic insulation. The white powder is essentially aluminum rust. 

[Jsdirt]

Rule #1 - stay the hell out of dealership service departments unless you're under warranty! Good Lord - that wasn't a parts cannon. That was a parts nuclear warhead!

 

If you're getting fuel pressure, there's no need to check the relay for it. The bleed down could be due to 1 or more injectors stuck open. Pull the dipstick - is the level higher than normal, and does it smell like fuel? Any smoke out the tailpipe when you're cranking? What is the fuel pressure reading while cranking?

 

How does the engine sound when cranking? Is it a steady cadence, or does it sound like it's wavering up and down in RPM?