EDIT: Sorry for the long first post. Just trying to give all the details.

Ok, so I'm basically looking for some insight on a problem I had last week and any input is appreciated. I'll try to explain the specifics best I can and should mention I'm not the mechanic type and just trying to save some money as I've been laid off for awhile.

I have a 2000 Blazer ZR2. Just over a week ago I had a crank but no start condition. The gas gauge has been bouncing for quite some time so from what I've seen on this forum the sending unit in the fuel pump is bad and I pretty much assumed it was the fuel pump had finally gone. I had it towed home as I wanted to check it all over before I got a $900 bill put in it. I both swapped the fuel pump relay for another and tested it using a DMM and a 9 volt battery, it tested fine. After going through a 100 or so pages on here I decided to try the rubber mallet trick to see if it would run. I had no help on this so I used a fused wire from the battery to the bypass in the under hood fuse box. The pump did not run initially, but after a quck slap of the hand directly under the pump it would "run" (very rough and gurgly) long enough for me to jump in and start it. It ran fine, no problems and I could start it with one slap every time. After more reading I went to check grounds, however I couldn't find the one coming from the tank. Some suggest a strap from the tank to the frame (couldn't find one) others say it goes to the pack above the bumper, then to the frame corner. If that's the case, it's in the loom and I didn't go so far as to pull all the wires out. It seems the strap on the corner frame goes into another loom on the rail (where I assume they must all meet up).

Being low on cash, I somehow convinced myself I could replace the pump myself but wanted to rule out anything else possible before I spent the money and dropped the tank. I saw mentions of the fuel pump pressure switch and decided to take a look at it. I took off the distributor cap to get at it and I then noticed some black stuff in the little pocket beneath the distributor itself. After deciding it wasn't a dead mouse I realized it was some lining from the hood which has been torn up since I bought the Blazer about 8 years ago. I went to pull it out and it kept coming. It ended up being a big ball of the stuff complete with a peanut shell and pieces of it or others. Yes a peanut shell, so it seems a squirrel had packed it for the winter. So anyhow, I couldn't get the connector off the pressure switch and was getting frustrated at this point and decided to put it back together and go after the grounds by the tank one last time. So I went to see if I could get it started after replacing the cap just to make sure and when I turned the key I could hear the fuel pump run nice and smooth (no jumper wire) as I can only assume it should sound and it started right up. Turn it off, hear it wind down. Tried it several times and it primes, starts, and runs smooth, no problems.

Any thoughts on this? I didn't see any exposed wires but I'm going to take another look since it's so hard to see the switch under the distributor and could easily have missed something. My (uneducated) guess is the liner was shorting something out (possibly the pressure switch since they're on the same fuse) and the pump wasn't getting enough power to run properly. Or when putting it back together I inadvertantly tightened something that was previously loose, although I previously checked as many connections as I could find. It has been starting and running without problems for 4 days now but for piece of mind would still like to locate the exact cause.

A few things to note as well. Using the jumper wire, the pump still needed a slap to "run" as rough as it did. The driver side speaker in the dash rarely ever worked. It would kick in for a minute or two from time to time but seems to have worked ever since. Also, in a YouTube vid (by robinsonauto) he pulls the pump relay and the truck stalls. After testing it to be bad he replaces a new one and the truck keeps running. When I pull the pump relay, the truck stalls. Definitely replace?

 

I honestly think the pump is bad. If you can get it running by smacking the bottom of the tank with a hammer, that is a tell tale sign that the fuel pump is really on its last legs. That, and the gauge being off. Remember, when you replace the pump, AcDelco or Delphi only!!!!!!! You'll kick yourself using any other brand. Happens way too often.

On a side note, if you pull the pump relay, it cuts the power to the pump and will stall the truck. That's what it was designed to do! Works the exact same way as pulling a fuse/circuit to a room in your house. The power to that room will go out.

Just my $.02

Edit: Could have been a short somewhere in the line like you mentioned, lets hope! Dropping the tank is not a fun task!

 

AHMEN to the using any other brand, i did a regreted it within a year! these trucks are oddly picky when not using AcDelco products.