2006 Yukon Denali xl (6.0L) intermittent start

[YUKONJOSEPPI]

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 ENGINEGROUNDS 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

There are no engine codes. Idle’s a little rough and the light dim sometimes. Runs great lots of power no issues driving


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

 

[SnowDrifter]

Holy parts cannon batman

Confirm for me; crank no start?

Have you hooked up a mechanical fuel gauge to your fuel rail? What's fuel pressure while cranking? What about key off engine off? Does it hold steady or bleed down?

 

[OR VietVet]

Why does this thread keep repeating?

https://www.tahoeyukonforum.com/threads/2006-yukon-denali-xl-6-0l-intermittent-start.115700/

 

[YUKONJOSEPPI]

So I got a better fuel gauge then I was using to make sure it was 100% correct.I know with the key in the off position it does not bleed fuel pressure. With the key in the on position it does slowly.


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[YUKONJOSEPPI]

I was going to try today hooking the gauge up turning the key on and pulling the fuel relay to see what happens.


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[YUKONJOSEPPI]

The pressure when cranking is 55 psi


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[avalonandl]

I would point to a couple of possible issues. ECM or ignition module. Also connection points for these.

 

[YUKONJOSEPPI]

Is there a difference between the ignition switch in the ignition module? When I put the new PCM in I looked at all the connection points and from what I could see they all look good.


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[rockola1971]

I would point to a couple of possible issues. ECM or ignition module. Also connection points for these.

ECM? This aint a 1994 model, a 2006 model has a PCM. Ignition module? You do realize the PCM is the "ignition module" in Gen 3 and 4 models, right? The PCM controls ignition time and dwell and fires the ignition coils directly.

 

[rockola1971]

Cranks but no start and then crank over a second time and it starts is a stereotypical symptom of a bad fuel pump check valve which is located in the fuel pump module assembly.

 

[YUKONJOSEPPI]

I Agree with you about the check valve. It just seems so crazy that I would get too bad fuel pump’s in a row.

The first one was a After market And the one that’s in there now is from the dealer.

I’m not sure if it’s possible to even check that or diagnose it what do you think


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[OR VietVet]

You can attach a fuel pressure gauge and when you shut it off you can monitor the gauge to see how much the pressure drops.