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 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

 

[TheAutumnWind]

Turn off caps lock please.

Does it always turn over when you turn the key and its simply not firing sometimes?

 

[YUKONJOSEPPI]

Yes when I turn the key it will always crank. It is 50/50 if the problem will happen. Half the time it starts normal with no problem. There are times when cranking that you can tell it is sputtering and trying to start. This is rare. The normal is

-turn key cranks but does not start .
-turn key off
-try to start again and start every time

I took it to the dealer twice they told me there is something wrong with the fuse box. Couldn’t tell me the exact problem they just said they saw corrosion. This was not helpful.

I tested pin 86 and it is giving me a Variety of voltages with the key off. 0.20v - 2.23v. Strange .


Sent from my iPhone using Tapatalk

 

[OR VietVet]

I would look for a leaking injector bleeding off residual fuel pressure.

 

[YUKONJOSEPPI]

They are all brand new injectors. But I know that doesn’t mean one isn’t bad. What’s the best way to check for that?


Sent from my iPhone using Tapatalk

 

[OR VietVet]

Sorry, I missed the new injectors but you can still get a bad one that is new. You said this, "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)". You are losing pressure and now you have to find out why. You can remove the fuel rail and have the injectors mounted in the rail and then turn the key on and see if you see the pressure build and if any injectors are leaking. Don't crank the engine but just turn the key on.

 

[Doubeleive]

I would suspect a leak in the fuel rail, especially if pressure is not holding, I believe there is 3 places for o-rings and there not cheap only the dealer has them. nobody else sells the right size. I would inspect the fuel rail closely at those 0-ring locations use some soap and water spray while cycling the key for fuel pressure leak. just my .02 cents I had a problem with my 00 and bad o-rings in the fuel rail. you might even be able to see a fuel leak if you look close with a flashlight. again just something to check for.

 

[YUKONJOSEPPI]

Thanks for the input. I’ll have to plan to do in the next week or two. The interesting thing is I would think that even if I did have a small leak if I cycled the key three times and pressurize the system three times and then try to start it should start. But I will tell you I’ve tried that and the times when it decides it’s not gonna start even after three cycles of the key off And on it still will not start.

I went to the junkyard and got a Fuse box from under the hood of another 06 6.0. This is what the dealer said was wrong. I cleaned all the connections and put electric grease On every connection. Obviously did not fix the problem but I was at the junkyard anyway to get roof racks and some internal parts so it only cost me 20 bucks. Now I have more than $20 worth of fuses.

I got a code reader that does relearns and gives you live info. I was going to do a throttle position sensor relearn and a crank sensor relearn since I’ve been told you should do them when you put a new one on.

Then I was going to hook it up to the live info and see if it shows anything weird.


Sent from my iPhone using Tapatalk

 

[ks03]

Watching for the security light when it happens?

 

[Doubeleive]

Watching for the security light when it happens?

if it was the security system he would be having to do the 10 minute relearn, and it would start and die within a second