99 blazer with 4.3 will not start. no codes. changed maf sensor and
map sensor. still nothing. checked fuel pressure -58 no start and 52
running. changed fuel filter still nothing. squirt carb cleaner in throttle and starts right up and runs fine, drives fine. can start back up for couple hours and is fine. Next morning will not start. Any help would be greatly appreciated. a couple weeks ago changed coolant temp sensor.
Could it be fuel pump? even though pressure is there.

Thanks!!

 

First and foremost you seem to be missing one of the things engines need to run. you have fuel, and you have compression, but how good is your spark? Pull spark plugs, look at your spark plug wires, and your distributor. Do any of them need changed? Next check your coils sometimes they don't die right away they just kinda faid into death leaving you scratching your head and swearing (this happened to me) Generaly if you can get a vehicle to start it's not a sensor, also you said that it will start up after you originally start it, this to me points to your distributor cap and rotor, cause after it runs it dries out or makes better connection somehow under there. But this is just my speculation.

 

Thanks! Will check that out today. A neighbor also said to check the fuel pressure relay. Not sure what to check there?

 

If you have fuel pressure I wouldn't worry too much about it. This sounds alot like just simple spark problems. My dad's dodge 2500 had the same problem and we changed every sensor you did thinking it was that, well it was just the coil lol. Also it was the fact that it was -20F outside which the truck did not like at all.

 

still no luck. Checked plug-has spark. Coil checked out good with ohm check. Still will not start. Fuel pressure 58 ign. On,
50 running. Just took a little squirt of carb cleaner and started right up. Ran for half hour and pressure stayed at 50.
Any idea's?


also forgot to mention replaced dist. Cap and rotor.

 

What kind of fuel are you using? Some of the fuels with higher alchohol content are not that easy to fire cold. Is it possible that you might have filled up with E85 or something on accident?

 

No, its regular unleaded. Been getting it at the same station for years.

 

what does the coolant temp sensor say when its cold. Does then comp think its warm and isn't supplying ample fuel to start properly. I have seen bad coolant temp sensors cause start up problems before.

other thing to check would be tps, if the comp is seeing a WOT it will shut off fuel thinking its in flood mode.


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• Check the Engine Coolant Temperature (ECT) sensor with the scan tool. Compare the engine coolant temperature with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees greater or less than the ambient air temperature on a cold engine, check for a high resistance in the coolant sensor circuit.
borrowed from gm's SI

 

the coolant temp sensor is fine. I check it in the morning and it is right on. I also check it as the car is running and the temp goes up as it should. I replaced the sensor two weeks ago. I will check the tps tomorrow.

 

Sorry you did say you changed the coolant temp sensor, I missed that the first time I read your first post.