I have a 2005 Chevy Blazer and it's been running just fine until today. I turned the key and it sounded like it would turn over but just didn't. Had the battery and starter tested and both were fine. No weird noises, no usual signs of a faulty alternator. Spark plugs, cables, cap and rotor were all recently replaced. So was the fuel filter. I plan on checking the ignition switch tomorrow but I'm at a total loss here.

 

This is a shot in the dark, but I discovered that my starter relay was responsible for an intermittent no crank situation.

Because it is so easy to try, you might try swapping the starter relay for another identical one to see if that helps.

 

It was not relay. Could low transmission fluid be a potential cause as well? I just noticed a small leak where the cooling line connects to the radiator and then checked the level. It seems to be low...

 

I don't think low trans fluid could cause this unless the torque converter was locked up wjich seems super unlikely to me.

I believe there is a "sticky" thread that outlines the troubleshooting procedure for no-start conditions.

I know others here have more experience than I do with this issue.

 

I can help you with this. Lets start with three voltage measurements. The resting battery voltage at the battery terminals. That voltage at key on and that voltage at a crank attempt.

George

 

Blazer had extended crank for last 3 months.
Had ice and rain and temps under 20f for a few days straight. Went to start 01 blazer. Crank no start with some what of a small stutter at the end.
Checked fuel pressure, checked spark at coil and spark plug, performed injector leak test on each cylinder, checked crank position power with test light and watched rpm signal in scan tool. Showed 160 rpm.
Checked ignition module signal with vantage and coil primary. Primary ignition wave form looked ok except for a quick drop down to ground.
Removed distributor cap and saw that points were corroded and checking continuity with dmm found I could not get continuity from any point to it's corresponding wire out put. Only from coil to center of distributor cap. Sanded points down to show shiny metal and took sand paper to rotor tip. Replaced distributor cap and she runs great.
I had replaced distributor cap only a year and a half ago so it wasn't I first suspect but just because I had spark to my spark plug didn't mean I had good spark.
Another tip I'd suggest when checking powers, grounds and signal voltage koeo is to have vehicle hooked to jumper cables to another vehicle to maintain charged system and to check the simplest things first
No money spent just time for this one.

 

If it's not cranking well. Send 12 volts to starter solenoid signal or command wire ( small wire) . If it doesn't crank with good battery, battery to starter wires and secure connections, solenoid or starter is prob bad.
hit bottom side of starter with hammer while cranking again
If it fires up replace starter, brushes going bad

If it does crank, command side is the problem.
use jumper wire at starter relay ports place between load side hot and ground. If it cranks continuity from control/signal wire is good.
Get dmm and confirm load and command side power and ground on relay port.
Only one side should be hot out of the four. That will be the load side. ( Look at picture on relay to confirm.
Get jumper wire or pin and place in control side hot and black lead to ground. Crank engine. Of no voltage present on command side, source back to PCM, back probe positive lead and black to ground.
no 12v signal means PCM not commanding crank.
Security issue with passlock, failing pcm, faulty wiring.

IF 12v is present, when cranking check continuity between PCM and fuzebox.
if you can access class 3 scan tool and look out for u and b codes. Or no communication intermittent or permanent. Also check signal voltage at iat, maf, crank sensor and cam sensor koeo. Crank and cam should be 12v
Maf and iat should be 5. Anything else key on engine off possible resistance from bad sensor, bad wiring or bad PCM. Unplug each sensor until good signal voltage is present again.
Bad PCM or going bad will have erratic and intermittent signal voltages


Confirm it's not mechanical problem of engine by turning crank on harmonic balancer bolt ( preferably with belt removed to rule out other belt driven accessories) If you can turn it by hand your good, replace starter.

 

Hello everyone! Did some more troubleshooting and turns out my fuel pump died. Had it replaced and it's running again. I had hoped the slight shuddering/misfire I've been feeling would go away with a new pump but it's still there and I have no idea why. I know it's not the spark plugs as I had replaced all of that already but the mechanic suggested a bad coil or even something as simple as a bad o2 sensor...