No start 99 gmc yukon!!!!!

[Mustang2xvt]

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?

[Mustang2xvt]

Nobody....? Really need help!

[Moose Monkey]

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

[95 S_Trucker]

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.

[Mustang2xvt]

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.

[Moose Monkey]

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.

[Mustang2xvt]

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

[BR3W CITY]

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

[Mustang2xvt]

Originally Posted by BR3W CITY

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

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

[Moose Monkey]

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

[Mustang2xvt]

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?

[Mustang2xvt]

Btw... Wanted thank everyone for the help!

[Moose Monkey]

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