2006 Yukon Denali "wont start"

[nwngunner]

I have a 2006 yukon xl denali with the 6.0l engine. Recently the head gasket went and the engine smoke its self. We had a new engine put in it. It was running perfect. Then at about the 300 mile mark it developed an oil leak at the rear main seal. The cover plate had a crack in it and started leaking.

We took it in for warranty work. During which point in time it sat for a few weeks. My mechanic dropped the transmission and put the new cover plate on. At that point in time the starter decided to take a dump. Almost 200k on the body. So while it was on the rack he put a starter in it.

We go to get the vehicle and it will not start. Would crank and fire then die. Told me mass air flow sensor. The thing ran perfect three weeks before. I was able to get the truck home from the shop after the mass air flow sensor was put in. I drove it for 15 or 20 miles and it ran like a top. Now that it is home it wont run. At this point I have replaced the mass air flow, the coolant temp sensor, and the throttle body "entire thing not just the sensor"

I pulled a plug and it looked to be running rich "only 300 miles on new plugs" which is why i replaced the throttle body. How ever for ***** and giggles at this point, when I put my hand over the throttle body "with intake tube off" it would start and run for 15 or 20 secs.

I went and got a good fuel pressure tester, at pump cycle it shows 62#. I know I shouldn't have done it, but I can get it to fire and run off of a bit of ether. I know its getting spark, its getting fuel to at least the rail. What do I do next? Is there a signal wire to the injectors telling them to open? How do I test that the injectors are opening? When the ignition sits on the fuel pump will hold about #50 to #55 and then slowly loose pressure. I tried a different relay with out any luck. I am at a loss here, I am fairly decent on older engines never delt with injector issues before.

At first "when we first got it home" I had a flooding issues. The oil smelled a bit like gas, then again that might just be from the rings seating yet.

Any help that any one can give me would be great.

 

[Doubeleive]

have you checked the neutral safety switch?, when you turn they key to run is the security light flashing? any codes?

 

[nwngunner]

The security light is not on. The wife left the key on for ten minutes to clear that still no difference. Would the neutral safety keep power from going to injectors to prevent them from opening?

 

[Doubeleive]

if the switch was in the incorrect position or faulty the symptoms would be just like as if the starter was dead it wouldn't even try to turn over

 

[Doubeleive]

If you don't have a tech2 or snap on scanner or one that's pretty high end to troubleshoot with then, I would maybe check the ground wire on the injector harness if you are leaning towards the injectors not getting power, that problem has came up before, the ground can break inside the harness, the fix is to just make a new ground and / or replace the harness, there generally not to cheap though around $200, just something to check anyway

 

[nwngunner]

Thanks for the assistance. The wife and I just went back out to work on it some more. So we got it to start and actually run. We put an additional five gallons of gas in it, along with I took and force fed it gas through the intake. "Even more stupid I know" I also put a can of seafoam in it. I am wondering if from sitting if the injectors are getting sticky or if i had some bad gas.

So the damn thing runs, at fist it would only run for 30 secs. Now it will actually sit and run. We let it idle until the engine came up to operating temp. So its running, we can shut it off and it will start right back up. While its running its holding @62 pounds on the fuel rail. While it was running i had no pressure loss. I still find it odd that it looses pressure while it is sitting not running with the key in the run position.

I had pulled one plug before we got it started and the plug was dry as a bone. Couldnt tell that it even had fuel on it, but it was grey in color. Different then any plug I have ever seen.

 

[nwngunner]

Well it started again last night, then this morning it fired at first crank reved for a few secs then died. Wont refire again. At a complete and total loss, its getting towed back to our mechanic.