Hey guys I really need some input here.

I have a 1999 blazer LS that has a few problems that I've been working on since I bought it (mostly minor things that can be ignored).

Over last couple of days I replaced the bank 3 O2 sensor and yesterday I did an oil change. I drove it around last night and it was just fine. I planned to change spark plugs since I got some misfires (like when going up hills on highways and what not) but did not do it yet, although they were working fine for city driving.

HOWEVER, today I was driving my blazer just fine for about ten minutes then it all went to sh*t. Everything appears normal before I started driving (I checked the gauges just to make sure my oil change was all good). While on a main road, I lost throttle and the engine powered down, then stalled off. I couldnt get the engine to turn over and it was obvious that I was low on battery power. Tow truck brought it back home. No shops were open.

While at home, tow truck driver boosted me with a battery pack and I got the engine running again. NOTE: while it was running, I tried hitting the gas while idling and the voltage definitely went up a bit showing that the alternator was working somewhat, but then it went back down to about 10V. About five minutes later of idling, it all powered down again and engine shut off. We had the hood open and it was obvious that it was losing power before this happened.

Again, the console showed that there was only like 7V getting through instead of the normal 14V (centre). By all accounts we thought the previously rebuilt alternator was dying, and it looked worn down a bit, so I made the decision and we bought a new AC Delco alternator and installed it. Tried boosting the blazer (with another car this time) to get enough juice, which was bumping it up to 10V, to get the engine going but just couldnt do it. So unfortunately, I couldnt get it running to see what the voltage was while running, or to see if the new alternator would help.

The AC Delco battery was put in new about 11 months ago and never gave me problems. Testing the battery with everything turned off shows me around 10V getting through. So I just dont know if maybe there is something wrong with this battery or some wiring, or something else entirely.

Could bad spark plugs cause such an energy-drain issue after you do a new oil change?

Or maybe the new O2 sensor (bank 3, after cat) kicked in after driving for a day and decided to shut everything down?

My engine light also came on intermittently (never blinking) through this ordeal, but my scan tool insisted that there were no codes I'm just at a loss here and I need this thing working so I can go to work.

 

I don't have a clue on that one, but please put a post on here when you find out what the heck's causing that. I'm curious to know. I'm sure you tried cleaning your battery terminals and battery cables. I use sandpaper to get all the corrosion off them.

 

I'd disconnect the battery cables and hook up jumpers to JUST THE BATTERY. If it shows 14 volts or so from the other vehicle, let it sit a while then check the voltage of JUST the battery with the jumpers not connected. If the voltage drops a lot you prolly have a bad cell in the battery

 

A mechanic buddy was in town and he determined that it was definitely the fuel pump. We cut a hole in the back of the Blazer's floor and replaced it instead of dropping the tank, and now it runs MUCH better.

I'm kinda pissed that this wasn't obvious before buying a new alternator. Somehow it managed to fire up and run for about 5 min after the tow truck driver boosted me after we towed it home, and he said he heard the fuel pumping while we were looking for the issues. Maybe just the towing of the Blazer on that angle was enough to shift the gas in such a way that it somehow primed the gas lines... I really wish it could've just gave me a computer code for this.

On a further note, I did have a fuel filter clog up and kill my throttle back in November. Shop replaced it back then. Apparently replacing a bad fuel filter with a new one can do damage to the fuel pump because of the change in pressure. One main difference I have noticed with the new fuel pump is that my engine cranks over immediately, as opposed to that cranking sound that reminds me of hacking out cigarette tar out of my lungs every morning lol.

 

Glad you got it going. I'm wondering, what did you use to cut the hole in the floor above the pump? A cutting wheel attached to a drill? A dremel tool? A torch? How did you be sure that sparks falling from the cutting process did not ignite anything? I understand that if there are no fuel leaks in that area, it's unlikely that a fire could happen. but still, wasn't it kinda scary? And what do you use to cover the hole now? Thanks, Mike... Also, you know ,there's new guidelines for disposing of your old fuel pump properly (see attached image)

 

My buddy who took out the fuel pump is a heavy duty mechanic, and we're all small town people. I definitely wouldn't say that using an edge grinder for this job is by the book procedure, but real life isn't a Michael Bay movie either.

As for how did we reinstall the square we cut out of the floor? Duct tape. Works pretty good.