2001 4X4 Blazer Not Starting
 

Started running rough and then after I filled up (of course at $3+/gallon) it won't start at all. The codes it is shooting are P0128 (coolant temp below thermostat) & P0420 (Catalyst Efficiency Below Threshold Bank 1). It will crank and crank, but never actually starts. I cleared the codes and it started for a second and then shut off.

I've done some researching here and found some info on the codes. The odds are that I'm going to drop it off to a mechanic, but from my understanding the P0420 code is probably a bad O2 sensor and/or Catalytic Converter.

So, I guess my questions are - Does it make sense to try to do the O2 sensor myself 1st, or is it harder than I'm probably expecting? Because I'm quite certain that a shop is going to tell me it's the more expensive option, if not both.

Also, is it logical to think that the codes are related, or does the fact that I have these 2 specific codes lead anyone to a more specific conclusion? Such as, "Oh, if you get those codes together then it's probably...."

I appreciate all of your help. I'm at my wit's end with this thing. I've put more money in to keeping it running than I did to buy the piece of crap.

Well from my experience of working on cars. If its got a full tank of gas and wont start its probably the fuel pump. They usually go bad after you've run low on gas then stopped to fill up and it wont start. Just a guess as you haven't tested anything yet. Oh and O2 wont cause a car not to run and i dont think that a coolant sensor will either.

This is a good place to start

98+ No-Start - Engine Cranks OK
96+ Fuel System Diagnosis

Thanks for the help. I didn't think that an O2 sensor would cause it to not start at all either. The bad news is that I just looked up the fuel pump to get an idea of how much it costs and it's over $300.

I will never in my life buy another Chevy Blazer. Maybe I just ended up with a lemon, but it has DESTROYED my faith in the Chevy name. This car has been a complete money pit.

You bought a 9 year old vehicle... Don't let one bad experience deter you.

And test things out first. The pump might not be the culprit.

Seeing as how you have already thrown in the towel, you let us know if you actually want to figure out what's wrong with your truck. No use wasting everyone's time if this is a lost cause.

I've got so much money in to it at this point that I need to figure it out. I really do appreciate the help and I'm truly hoping to get it fixed. I actually bought it 5 years ago and it has been an unbelievable headache since the 2nd week I owned it.

Just a head's up...I had my girlfriend turn the key while I listened and I did hear the fuel pump buzz. I'm guessing that means that it's probably not the fuel pump?

I have seen people screw up a perfectly good vehicle in less than a year.

Hearing the pump and having the pump deliver the required 55+ psi of pressure are two different things. I'd go through the two links posted above and let us know what the results are.

Yes just cuz something buzzes dont mean its working properly and can still be your problem.

Yes, check and see what pressure your fuel plump is holding. As feverously stated, it has to be 55 pounds, if not, the engine will not start. You will need a fuel pressure gage set to test the pressure such as this. @ $17.99

I might add, many times if your fuel pump will not hold 55 + pounds, you can start it by spraying carburetor & or starting fluid into your intake. For about 2 months, maybe more, mine would not start when cold unless I sprayed starting fluid in the intake. I got tired of that and replace the fuel pump and all is well.

@JustJerry - Thanks for the info! I read through the links originally posted and most of that seems out of the scope of my tools/mechanical ability.

I really appreciate all of the help, but my vehicle knowledge is limited.

I guess my next step is to see if I can get it started with carb/starting fluid and testing the fuel pressure. If that's my problem then I'll work on getting it changed out. I found a "how to" video for that exact car.

I guess my final question here is this: What's your opinion on buying a used fuel pump vs new? Brand new at AZ is $300+ and I can probably get one at a junk yard significantly cheaper.

It takes a fair amount of work to swap out a fuel pump. The question you have to ask is whether you want to do it again if you get a faulty pump from the junkyard. The chances are VERY high that you would be doing it again shortly unless you get lucky.

With all of the somewhat fragile connections to the tank, the more you drop it, the more likely you are to break something else.

IMO, spend the money on a new AC Delco or Delphi fuel pump assembly and do the job right the first time.