1995 4.3 Vortec starts then dies
 

Let me start by saying this, I've been browsing this website for a while now trying to find the culprit of my issue. I've officially run out of ideas and now am going to just post what I've done so I can get specific help at this point. I've been chasing my problem for a while now on a wild goose chase, trying to figure out what the actual cause is. I got my Blazer knowing that it was not properly working at the time, thinking it would be an easy solution. The person I bought it from said that it was driving fine up till one day it died trying to pull out of his drive way, and that he replaced the fuel pump thinking that was the issue. I bought it from him, and have done multiple things since then trying to figure it out. First things first, it does not have a check engine light come on when it IS running. Originally, it ran from a cold start at idle anywhere from 5-10 minutes, then died from a stuttering idle, if I revved it at anypoint during that time, it would not rev above 2800, and would proceed to stutter out and die. So I replaced the fuel filter, and it had no affect. Then I replaced the distributor cap and rotor, still no affect. At this point my friend and I were wondering if it was ignition related instead and decided to check the spark plugs, wires, and the ignition coil. So we replaced the spark plugs, and the spark plug wires (one wire was shot, and all the plugs were fouled) so we replaced the wires and plugs, didn't need to replace the coil because now they were producing a blue spark and was good to go. After that the issue seems to have changed slightly, now it'll start up, and die after about 10 seconds, whether I rev it or not, then it will not start up for almost an entire day. So, thinking maybe the previous owner screwed up, I replaced the fuel pump assembly as a whole, and blew out the fuel lines, and it has not changed it's issue as of today. I know one thing to do is to check the fuel pressure, as I've seen lots of posts saying it's possibly the fuel pressure regulator, but I cannot find the correct connector for the TBI. If anyone has a link to the CORRECT one, that would be fantastic, but at this point I'm clueless as to what would be next.

We can get your truck running right but it may take some work. Problems like this can have many causes so proper diagnosis will narrow down what to fix and is nearly free. Parts swapping works only if you get lucky or have an extremely obvious problem. With generalized bad performance we see thread after thread with a big list of what’s been replaced so far with no change and asking for help.

a couple of things first. Any parts replacements/fixes need to be verified before moving on. In the ideal world, you diagnose and confirm the cause, fix it and confirm it’s fixed before moving on. Example: truck runs like crap, you have misfire codes, ignition is weak, diagnosis indicates the coil and the coil replacement produces a fix with confirmed strong spark.

These trucks are notorious for fuel system problems and are very sensitive to improper system pressure. Also, non OEM replacement fuel pumps are famous for poor performance or early failure. Your fuel system pressure needs to be tested per the sticky before you move on. What brand of fuel pump did you use? What does the system pressure look like when the truck runs like crap?

What about the brand on the ignition components? Do you have 1” of strong blue spark at the plugs? What does it look like when truck starts to run like crap?

regardless of CEL status, do you have any codes?

Have you checked compression recently?

Does your scanner show live data with fuel trims? If so what are the short term and long term trims, both banks, with polarity, at idle and 2500 rpm?

you may very well get parts swapping suggestions from other members. If that’s your thing, no problem. If however you want to use proper diagnosis, well get you right.


George

As far as the ignition components, I went with ACdelco, I confirmed that the gap was correct on all the plugs, and made sure that there was a strong blue spark coming from both the Ignition coil, and all the spark plugs that I could see at the time.

The fuel pump assembly was Spectra Premium. There was a little bit of a difference between the assembly that was in the tank versus the one I put in, right above the pump on the old assembly there was what seemed to be a diaphragm that I believe was leaking, and the new assembly just has piece of tubing in its place.

Since the Blazer is a 1995, it does not have OBD2, and I unfortunately do not have access to a scanner that will read OBD1, and from some videos I've watched, you can use a wire to get the dash to flash a code using the check engine light, however (as far as I can tell) it has an OBD2 connection, So I haven't been able to check that

And like I stated before, I have not been able to find a correct connection to test the TBI pressure, and would love to have a link to the correct pressure tester. The local auto parts store will only lend a full kit pressure tester if a give them a $200 deposit, which is ridiculous.

What does the spark look like when it starts to stumble?

can you take the cap off and take a photo of the fuel rail connector, I’m not familiar with the system on an older truck like yours? If it’s just the std shader port then I show the fittings that I used in post #43 in the fuel pressure testing sticky. If not I’ll look at the photo and help you figure out what type of fitting you have.

George

These are the best pictures I could get of the valve, it's towards the back of the engine bay, and pretty hard to reach for a short guy like me.
https://cimg8.ibsrv.net/gimg/blazerf...b91626dd7.jpeg
https://cimg6.ibsrv.net/gimg/blazerf...a090ac87f.jpeg
To me they look like standard Schrader Valves, but all kits I found in town didn't have a connector for it.
Also, the spark stays the same, definitely not an issue there.

That looks like the garden variety fuel fitting found on all of my chevys and most of my vehicles. It’s a Schrader port and the common size is a 4AN which is 7/16-20 threaded and a 37 degree (JIC) flared end. There are other sizes and I am not familiar with every year of the Blazer but you can find which threaded nut of a known size fits those threads and confirm the port size with this article:


https://fuelab.com/understanding-fue...apered-thread/

George

Cool, thank you! I'll have to take a look at it at a later point. I have to work a couple 12 hour shifts.