No start 99 gmc yukon!!!!!
 

Have a 99 5.7 gmc Yukon... Was running fine, shut it off then the next morning tried starting it up and nothing. Turns/cranks wants to start but nothing, checked it for codes and have none. The fuel pump, plug wires, distributor, cap and rotor were replaced maybe 6 months ago. Holds fuel pressure( key on jumps to 60 psi then drops to 55psi when the relay clicks on and stays there), the pump and relay come on, have spark at all plug wires.


Thought the timing chain had jump but everything is at tdc. I swapped out the spark plugs, starter, crank sensor, battery and did a compression test this morning with cold engine(since it will not start) and here are the numbers
#1 150 #2 150
#3 170 #4 110
#5 85. #6 90
#7 150 #8 75

Would these low of numbers cause it not to start?

Re: No start 99 gmc yukon!!!!!
 

Nobody....? Really need help!

Re: No start 99 gmc yukon!!!!!
 

Just saw post. Have 03 pickup, numbers good enough to run. Ran fine before?

Re: No start 99 gmc yukon!!!!!
 

Ask a mod to move this to the 88-98 section(gmt400).

Check for spark at all the cylinders. Most likely it's a cap/rotor problem, since you have fuel pressure and compression.

Re: No start 99 gmc yukon!!!!!
 

Sorry... Newbie here and I didn't realize I posted this the wrong forum. And yes it was running fine, shut it off and it didn't want to start the next morning. And it's just been collecting dust since. I will try a new cap / rotor, hopefully that's my problem.

Re: No start 99 gmc yukon!!!!!
 

Any luck? Spark a little funny on them sometimes. Had one the air gap to wide on pickup , wouldn't fire to fuel fouled plugs, but was still nicely arc. Only ran first start with new plugs. Will drive you nuts.

Re: No start 99 gmc yukon!!!!!
 

Ok... Swapped out the cap/ rotor and still will not start, to say I was disappointed would be an understatement....

Re: No start 99 gmc yukon!!!!!
 

6&8 either are leaking compression through a valve, or have worn their rings out. Thats a very large discrepancy between individual compression tests.

Re: No start 99 gmc yukon!!!!!
 

Wouldn't this have cause a misfire code prior to it not wanting to start?

Re: No start 99 gmc yukon!!!!!
 

Just for giggles, unplug some main pieces and see what codes come up

Re: No start 99 gmc yukon!!!!!
 

On the urging of my neighbor, I bit the bullet and bought another cap/rotor. Wouldn't you know it the sucker fired right up! But now it vibrates alot espcially when you put it in drive. Ran it for codes and none came up, maybe a misfire?

Re: No start 99 gmc yukon!!!!!
 

Btw... Wanted thank everyone for the help!

Re: No start 99 gmc yukon!!!!!
 

That's great now recheck fire order , just for giggles