Hi guys,
i have a 2001 xr2 blazer. I've had it for about 6 months. Lately I've been having an issue with an inconsistent start. The fuel pump went out so I replaced it. I tested the fuel pressure and I'm getting about 58 psi from the tank.
I put a new coil on it and I'm getting spark to the plugs. Relays are working.
Sometimes it'll start and sometimes it won't. I've taken it to two local mechanics and it starts everytime they try and start it so they can't help. There are no codes showing.
Any thoughts on what I can check next before I spend thousands of dollars at the dealership mechanic? I've been told to check vacuum lines and they are all connected....worn but connected.
Not sure if it would a timing issue or ECM issue. Any help would be appreciated
Tito Perez

 

Make sure you have a good strong battery #1, new cap and rotor (acdelco) only would may help

 

Won't turn over or turns over and won't run?

George

 

turns over but doesn't start.

 

When it won't start is it cold or hot or both?

George

 

usually it won't start after sitting over night

 

Intermittent failures are tough so you have to make some educated guesses. Since it might be things that happen when the engine is cold, you can start there. While cold:

1) I would check fuel pressure starting pressure and leak down. Getting set up when cold with the gauge taped to the windshield might catch a pressure issue. Check pressure as soon as it wont start.

2) When it won't start try putting the pedal to the floor to clear out the possibility of flooding from leaking injectors. A more advanced test of injector condition is a balance test with a pulse tester and a pressure gauge.

3) Crank it it with the ignition disabled. If the cranking has a wobbly cadence you might have a compression problem. If you want even better information a compression test might be valuable.

4) An intake manifold vacuum leak can be worse when cold and get better when warm. You can do the water bottle test when cold to look for leaks. Also as soon as the system goes closed loop, you can look at idle and 2500 rpm fuel trims. If they get better at 2500 rpm you may have a vacuum leak.

5) You may have spark but is it strong enough. You can use a gap tester. Check spark as soon as it won't start.

6) Inspect the distr cap for carbon traces.

Unfortunately you have no codes and it won't stay broken long enough to catch most computer or ignition problems but maybe some of this will help. If you are desperate then of course intelligent guessing and part swapping is an option but that can get out of hand.

George

 

Could be the beginning of a passlock issue

 

Ok...I replaced the cap and rotor. Cap had the #4 input plug burned out and the #2 wire had a break in. I put in a new cap and new rotor and it fired right up. Keeping fingers crossed. Thanks for all the input and advice.
Tito