I bought an '88 S10 Blazer (Vin Z) from my buddy about a week ago. It has been sitting since February. He says he was driving it and it just died. He thought he might of ran out of fuel so he put about 5 gallons in it but it still didn't fire up. He's not mechanically inclined at all so he sold it to me for practically nothing.

Over the past week I have been messing with it. It will fire right up with a shot of starting fluid but immediately die. My initial thought was the fuel pump. I have replaced the relay but had no change. I tried applying 12 volts to the pump test connector but it didn't come on. I have checked all the fuses and checked the codes and found nothing. I pulled the relay and did a voltage check from the orange wire to the grey wire and it has 12 volts on it.

I took some pictures also:


I replaced the relay on the right (grey one). That should be the FP relay, correct? Also notice the blue/pink wire on the brake booster? It doesn't connect to anything.


Another shot of the blue/pink wire and the red wire that connects to the terminal block on the passenger side firewall. What are these for? I read a post on here that the FP gets power from these? They run down the firewall, under the truck, and all the way back by the fuel tank.


The terminal block where the red wire (the red one with the inline fuse) connects.


This is the rear-most crossmember right behind the fuel tank. Notice the connector with the tan and pink wires. According to my wiring schematics, those connect to the FP. I measured the voltage from the tan wire to ground and got 0.11 volts but only when the ignition was turned on. I also cleaned the ground wire and reattached it to the crossmember. Also notice the same red and blue/pink wire from the engine compartment. I traced it all the way back to the rear passenger side.


And here is where that red and blue/pink wire stops. It was tucked on top of the fuel tank. Where is this supposed to go?


Another shot of the big gauge ground wire where is attaches to the rear crossmember. It looks to me that its pinched between the tank and crossmember? Its so tight I can't move it.


I really don't want to drop the tank unless the pump is the issue. The FP relay gets 12 volts but the connector by the tank does not. The pump does not run when the relay is bypassed. I put 2 more gallons of gas in just to make sure there is some in there. The oil pressure gauge registers about 30-40 PSI when the engine runs for a couple of seconds. I'm stumped... Sorry for the super long post. I really appreciate any help you could throw my way!

 

1. The Pink/Blue wire looks like something that someone has added. Your Blazer is a little older than mine but I think the junction block on the firewall should have two wires coming from the bottom screw if you don't have a tow package and three if you do. The red wire going to the back of your truck could be part of the tow package. I haven't taken a good look at the wire bundle on a tow package so I don't know what it looks like at the back of the truck. Those are a couple things you should investigate.

2. That sounds like a fuel pump issue to me. When you disconnect the wires to the fuel pump do you have 12V to ground? If not, check the continuity of the wire from the prime connection back to the fuel pump connection. There could be a break in the wire between the firewall and the back of the truck. If the wiring checks out OK then you will need to drop the tank and pull the pump.

 

The weird thing is that I'm not getting a whole lot of voltage (0.11v) at the fuel pump connector with the ignition on. I measured that from the pink wire to the frame. With the ignition off there is zero.

Where is the fuel pump prime connector located? Is there anywhere else I can detect power (that's accessible LOL) on the fuel pump circuit? Here is a snippet from the pre-1992 engine controls schematic:


I also broke down and bought a Delphi fuel pump anyway. It was $160 shipped from Amazon (with 2 day shipping!) and includes the hanger assembly, float, sock and pump. I figure I'll have to pull the tank anyways, I might as well replace it. The previous owner ran it out of fuel a few times and the truck has 187k miles, so I figured why not...

 

I don't know where the prime connector is on your truck. On mine, a '94, it's coming out of the wire loom directly behind the transmission dipstick. You have a different injection system (TBI) than I do (CPI) so I don't know if it's the same on yours.

There's nothing wrong with changing the fuel pump on a truck with so many miles on it. I'd go ahead and do the job if you plan on keeping the truck for any length of time.