This spring I picked up a 2001 RWD LS Blazer for my girlfriend that needed a new fuel pump and fuel lines. We replaced those and the Blazer ran just fine until about a week and a half ago when it suddenly wouldn't start. Just overnight it decided it wasn't going to start and it was basically stuck in a clearing in the middle of the woods. My girlfriend drained the battery trying to start it so I charged her battery from my car as well as hooked up a brand new battery for my Mercedes that I had sitting on a charger in the basement.

I confirmed it had fuel pressure, I made sure the throttle body was still fully functional and that there were no blockages in the intake, and I made sure it had spark. It didn't start and stumble, it didn't even change the sound it made when it was starting. It wasn't flooded, it sounded like it was cranking normally, it just wouldn't start. I hit it with a spray of starter fluid and it fired right up. It runs and drives normally, it revs exactly how I'd expect it to, normally it doesn't have any issues whatsoever after it's started.



Here's how it behaves now:

First start of the day requires starting fluid, it won't do anything other than endlessly crank.

If it's parked for an hour or less it might start just as expected, it might take two to five tries, or it might need starting fluid.

If it's parked for one to three hours it's almost guaranteed to start normally. I haven't had it not start but I have had it stumble and catch still on the first try.

If it's parked for more than three hours it requires starting fluid.

Occasionally it will just die at a stop sign. No stumble, no flickering of the gauge cluster, no additional lights, just die as though I shut it off. It needs a quick spray of starting fluid to start back up. This has happened three times.



It'll rev normally, it'll drive normally, nothing engine related comes up on a code reader, it just seems normal once it's started. It'll run fine for a couple hours and at least 130 miles at a time and I bet it would run longer but we haven't had a further trip since it's started. The ONLY thing that I found in the engine bay that was a little off was some rodent damage on insulation to two wires going to the fuel injector spider but when I trimmed some of the insulation off before the damage on the wire and tested the pin after the resistance was identical to one of the wires that had no rodent damage. I'm still going to replace those sections of wire and put new sleeving on them but they don't seem to be functionally damaged. It has been driven ~1,100 miles since this started and has consistently behaved how I described it above.

Any ideas?

Quick edit: I forgot some details. I have basically zero maintenance history on this Blazer other than it got the entire AC system replaced in 2016 or 2017, it got new tires in 2019, the fuel lines rotted out in early fall 2020 and it sat in my mom's driveway abandoned by the family member that owned it (pissing my mom off in the process) until they sold it to me in May of this year. Fuel pressure at the rail is ~60psi when primed before the engine runs.

 

Just having fuel pressure on this system is not good enough. I suggest that you perform the fuel pressure and leak down test in the sticky. The lower voltage during cranking probably drops marginal pressure below the cutoff and when it starts and the voltage shoots up your back online.

Whats the pressure when you crank and wont start?


Georg

 

The pressure when primed is around 60psi, when it's cranking it drops to 50-55. There's no leakdown. I thought I added that to the OP, my bad!

 

So its still 60 psi at the rail 10 min after key on?

George

 

A little over ten minutes, yeah. It might have dropped one or two PSI, I just remember being surprised that it basically didn't leak down at all.

 

That’s good. This says that you are either:

losing too much fuel pump or injector voltage during cranking

injectors are marginal

fuel pump is marginal at lower voltages

George

 

Gotcha, I'll start by repairing the injector breakout and monitor voltage/current then!

 

I didn't end up having a chance to repair the injector harness yet, however we took it an another drive to my hometown today. It started having some major issues on the highway then we hit several points where it wouldn't start. Over the course of about an hour it went from running fine to running absolutely God awful, started dying as soon as throttle was taken off, then after parked for a couple hours we couldn't get it started again. Checked fuel pressure again and it would hit 55 inconsistently at prime, when it would no longer start at all it would randomly prime anywhere from 30-45 PSI. I got a new fuel pump in and it's fine now.

 

Glad your fixed up, thanks for the report.

George