Hi folks,
My son has been using my old X to commute to local university. Today he drove off as usual but when he tried to start truck to come home he got a slight crank but then it shuts off or dies. The engine will start to crank over but gets about a quarter turn and stops. All electrical accessories work, battery gauge is in normal 13V indication. New starter 4 weeks ago replaced battery at same time (Wal-Mart warranty exchange). Is a 6.8L Gas with 370,000 miles. Consistant service. Oil coolant good. I replaced starter solinoid by battery today did same thing.
Theft light is flashing when key goes in ignition (weird) goes off as you try to turn it over. Have tried putting it in neutral and park to start. 1/4 tank of gas feul pump replaced two years ago. Last time starting problem about three years ago was solenoid replaced crank sensor at time from bogus forum diagnosis. thats about all the info I have. Hooked up OBDII no codes being thrown.
Thanks in advance
BB

 

Have you tried a jump start? Your battery could read the right voltage even though the alternator is not charging.

 

That is a good point. My son said he tried to jump it before I arrived but it did not do anything. That being said if it had a bad solenoid it may not have been successful. I plan to swing by campus in the morning and pull the battery for a test to make sure it hasn't dropped a cell as we have only recently hit 100 degrees and it is not uncommon in the first spike of texas heat or the first freeze for batteries to crap out especially in cranking amperage.
If the battery is good I could pull the Alt and take it up to texas alt and generator and have it tested, too.
But it is acting suspiciously like the security or ecm is interrupting the cranking like it is in a safe mode. Unfortunately I am comparing it to the 2002 Range Rover we also have. I also a year ago had a Cadillac Catera that had the timing belt slip and wreck the valves and it would turn over and not start so I am coming at this from my own level of paranoia as I do not have time to rebuild an engine right now.
Thank you for the input
BB

 

I will walk out to
Mine right now and see how the theft light acts on start up

 

In mine as soon as the key is in the one position theft light goes solid then off and stays off while cranking and once started.

 

Do you have a different key? Maybe if the key is not sending the right signal anymore that is causing the anti theft to activate.

 

That's a normal PATS prove out so PATS is ruled out.

This is a failure to properly crank. Might be a weak battery, corroded cables or connection, weak starter, an accessory driven by the serpentine belt, or even an internal engine concern.

Check battery voltage, no load, partial load (headlights), heavy load (starter engaged).

If battery tests good, check for excessive voltage drop in the battery and starter cables when attempting to crank.

Remove the serpentine belt and see if it will crank. If so, an accessory is bound up.

To check for an internal engine problem, put a big ratchet on crank bolt and see if it can be rotated through two compete revolutions.

 

Thank you all

ProjectSHO89 I appreciate the breakdown. My battery checked low and WalMart charged it picked it up and it is trying to crank now but still stops and starting ceases. Had my son crank it and the belt tensioner is bottoming out and the belt slacks about 2" over ALT pulley as cranking ceases or seizes as the case may be.
I will attempt to remove the belt as the a/c compressor is shot and is on the todo list this month. Its pulley may very well be seized. Would this stop cranking? Is there a clip to remove and allow it to free wheel or is there a smaller belt that can be purchased to bypass a/c and get us through the next couple of weekends till I can do the needed a/c repairs?
I am also going to take a breaker bar and see if I can get the motor to turn over. I will take the tools to pull a valve cover if it doesn't turn and see if I have a broken timing chain.
I had also looked up vapor lock will see if releasing the gas cap changes anything and I'm sure it wont hurt to change the fuel filter given the milage.
I will also try the second key but correct me if I am wrong it should not even attempt to crank if the chip issue is a problem. I have also ruled out the neutral safety switch because the starter is engaging.
It will be a pain in the backside but I will pull the starter and run it to o'riellys and see if it tests a dud. Not unheard of that a rebuild fails after 6 weeks.
open to any other ideas.
Thanks again to all!!!

 

Ya I miss read the OP. The key shouldn't allow it to start cranking and then stop. My bad. I think ProjectSHO89 is on the right track. I have had cars that the alternator locked up and the engine would not turn over.

 

Sounds like you are on to the problem with the AC compressor. Try removing the belt completely and see if it starts then.

 

Thanks for all the Sage advice guys. ProjectSHO89 had the right advice. I released the gas cap just incase vapor lock as we have had our first 100 degree days. Nothing. Cranked the engine two full cycles and pulley moved as normal But and thats my big butt! the belt stayed put. Reached up and tried to move A/C pulley frozen. Removed belt, cranked right over and started with slight hesitation, I don't know if computer picks up on this and halts cranking as previously had happened. Had a fuel smell like it was flooded after I shut it down.
Final question. Is there a known belt size to temporarily bypass A/C to get truck home till new compressor a/c kit arrives?

Thanks to all your input solved it and saved a lot of headache on a very packed week.

Cheers,
BB