Wife woke me up at 5:30 to take her to work. Seems the Blazer wouldn't start - crank, no cylinders firing. Snowing heavily here, 10 degrees, and the Blazer is only 4WD vehicle we have with a parking garage sticker for her hospital. Typically this vehicle starts first turn of the engine - amazingly well - never depress the pedal, just turn the key and it's running immediately.

Dropped her off in my Avalanche and waited for daylight, and for the auto parts stores to open. Borrowed a fuel pressure gauge from O-Reileys down the street. Hooked it up and found normal pressure during pulse and cranking (with oil pressure). Held pressure with key off. Got out the OBD2 adapter and checked for RPM while cranking. Got 130 RPM. Hooked up an old spark plug with opened up gap to the end of an old wire, plugged it directly into the coil, and grounded the spark plug against engine with vice grips. Nice spark when cranking. So I thought it could be flooded for some reason and thought I'll try the clear flood mode before digging into the distributor.

Held pedal to the floor and cranked for 15-20 sec. A few times I felt a cylinder fire but no start and it wasn't getting better. Turned the key off and then immediately tried again with zero throttle. Fired immediately and idled smooth.

It all seems a little strange the way it started and had a smooth idle, but engine seemed to have been cleared from being flooded. Last year we had same experience one time (cold weather), but I managed to get it started for her. Anyone ever seen anything like this? Difficult to diagnose when it's a one time a year thing.

 

High Humidity causing something to fritz? though it had spark when you cranked it the second time i wonder if a connection to the ICM or coil - or the components themselves, are compromised in some way.

 

I feel like a tech student getting a pop quiz.

As you said, damn near impossible to diagnose when it won’t stay broke. A few thoughts come to mind.

Did you pay attention to the security light to see if the passlock sensor got wonky and the fuel injectors we’re disabled? It usually starts for a few seconds first but ...

Depressing the pedal activated clear flood mode but also exercised the TPS so maybe it was wonky in the cold.

It was flooded as you suspect but then why. You held fuel pressure Si probably not a leaking injector.

Any one of several other sensors may have been hosed which affected fuel delivery like ect, map, etc

as you said the distributor. Did you check for spark at any of the plug ends of the ignition wires?

 

Could be possible. Seems to be cold-related. Thanks for the input.

 

No pop quiz here! I'm a believer that there are few brand new problems, and that this has been seen before in a Blazer! Why I ask.

No I need didnt pay attention to the security light, although I probably should have. In hind sight, I would rationalize that any problems there would cut off fuel, not flood engine - but who knows! Maybe it really wasnt flooded. Wife did say that for her it started (zero throttle) and ran rough for just a few sec (zero throttle) and then died and would not start again. Another possibility.

I did check the ECT and Intake air temp sensors for normal temps and they were. Also happened to notice the TPS read zero degrees in one of the gauges shown.

You know..... The MAP sensor could be a good possibility. Glad you mentioned it. I remember that Cadillac back in 1981 had trouble with water freezing in a loop of vacuum line to the MAP sensor and blocking flow and causing flooding. Used to drag them in a lot for that the first winter The cure per the TSB was replacement and relocation of the MAP sensor with no loop in the hose. They made a parts kit to do that. The moisture was supposedly getting into the hose during the 8-6-4 mode changes (yes, Cadillac had active fuel management back in 1981).

Never checked for spark on downside of distributor, but haven't had any problems since replacing the distributor and adjusting CMP retard. Checked it yesterday after it started and its still at -0.5. New Delco cap/rotor last fall. Really didnt feel like digging along side the engine yesterday in the heavy snow and my good coat! That would have been next, but it started.

This morning I went out and started it for her. Cracked right off like normal.

Now I'm kinda suspecting the MAP sensor and a very cold 3-day weekend without running may have caused the start/die and then flood. Really is very close to what I've seen before on the old Cadillacs - I had forgotten....

But nothing more to do right now. Thanks to both of you for your input. It helped me clarify some things in my mind.

 

A couple of the other usual suspects could be the IAT sensor or idle control valve.

George