Have a 1999 4.3 liter Blazer that has had the fuel pump replaced 3 times in 4 months. The last time the fuel pump stopped working we beat on the tank and it started. Now we have no power to the fuel pump. We have checked relays, we have oil pressure, and we have hot wired the pump and it ran. The truck will still not run. Any suggestions????

 

Have you changed the fuel filter?

 

We have no voltage to the pump with the key is on. yes they replaced the filter when the fuel pump was changed the first time. the tank also apprears to be clean

 

Have you probed the relay sockets for voltage to the coil? Might eliminate that possibility.

Hope this helps!

Regards,

Thomas

 

I had lots of problems getting a fuel pump replaced then getting it to run, now I know it sounds obvious, but the pump relay will go in wrong ! Its worth double checking its fitted correctly before chasing around in circles ! Also if your sure relay is working OK, you could just run a new feed to the pump.
Also there is something different in the wiring of the fuel pump/sender unit depending on where you buy it from. I didn't see mine before it was fitted so can't say what ! But now my fuel gauge reads OK, until I put the lights on, then it goes to empty ! But hey, at least its running (after a fashion) which it hadn't been for weeks !
o

 

The fuel pump relay should not matter which way it is installed. That is by design.

to the OP, where did you hot wire the pump at? Did you try jumpering it at the relay? If so, then the rest of the wiring from the relay to the pump should be fine.

 

A couple of things I would check. (The fuel pump drove me crazy too)
You say you have oil pressure. Do you have voltage on the other side of the O/P sender? (Could be a wiring problem in that circuit)
When you "hot wired" the pump did you use the test plug in the engine compartment?
If you want to check your relay, (I know on my 94) the one next to it on the firewall is the same relay. If you swap them, you can test it that way. Really don't know about a 99 though.
Do you have a wiring diagram to chase down the wires? They're worth their weight in gold for troubleshooting. I have a factory book that saved ne a bunch of time and coin.
I know it may be obvious, but did you check for a blown fuse?
How is the ground wire? I believe it's bolted to the rear frame member above the license plate light. You might try to clean it.
These are some suggestions. My fuel pump was intermittant and am familiar with the "beating on the tank" method.

 

Try this.... Take a pair of needle nose pliers and twist the terminals on the relay very slightly, might be the terminals got hot in the fuse block and opened. Also, at some point while replacing pumps, did you ever replace the harness connector that plugs into the fuel pump?

 

I'd have thought that too, the relay had been replaced by a different one (siemens) rather than the original, which may have been missing a key pin but it certainly fits in wrong and right ! It will go both ways around as the contacts are at opposing corners, but it can go in one row of contacts out.

 

Well obviously if you do not put it into the proper location, it won't have a prayer in working. But there is no orientation required for the relay.