91 Blazer w/ TPI, fuel issues.

[85 Jimmy]

Right now my pump does not cycle with the key in the run position or when cranking.
I checked power to the pump, no power.
I checked power to the relay, there is only power to one wire and it's when the pump should normally cycle on.
Shouldn't there be a constant power to the relay?
If so where should I start looking to find the issue?
I've also checked the fuses and they're all good.
I'm using a harness from street and performance and a 1227727 ECM

 

[dyeager535]

Did you get a wiring diagram for that harness?

Unless someone else has the exact same one, going to be hard to say where that power should come from.

I would expect constant 12V to the relay from the battery. I'd expect at least two small wires on the relay connector, and two large ones...the two large ones should be battery 12V and then the feed side to the pump. Two small ones would be the "trigger" wire for the relay (ECM fed?) and ground.

 

[85 Jimmy]

I'll try to get a picture of the connector up before I leave for work in 10 minutes...

 

[85 Jimmy]

No diagram, but I'm pretty sure this is how it goes. It's been awhile since I messed with it b/c I got tired of dicking with it. I'll have to check to make sure this is right tomorrow before I go to work.

Brown=power to the pump
Black=ground
Green=power when pump should get power
Orange=nothing

 

[85 Jimmy]

I may have brown and green mixed up though. It's been a minute...

 

[dyeager535]

That's the standard GM TPI fuel pump relay from the looks of it.

My *guess*, without seeing the wiring diagram, is that something between the battery and that relay is messed up...fusible link, fuse, bad connection, something.

 

[eagle mark]

Orange=nothing

and there's your sign!

The green comes from ECM to turn on relay. But without power in Orange it has no power to send to Brown pump.

 

[Keitha]

and there's your sign!

The green comes from ECM to turn on relay. But without power in Orange it has no power to send to Brown pump.

Exactly: A relay is just a switch - you need 4 wires - Power in from battery, power out to device, ground, and a trigger (low current 12v source). The trigger is the ECM sending a low current signal to the relay to connect the circut between the 12v in and the device (fuel pump).

 

[85 Jimmy]

So from the factory where does the orange, or constant power to the relay come from? Maybe I can find a wiring diagram on google.

 

[eagle mark]

With an aftermarket harness that may not help. What does the aftermarket harness use for fuses and power wires?

Really need to trace that orange wire back to power source is the only fool proof way to find why it has no power?

 

[85 Jimmy]

The harness has 3 fuses, 1 for each injector bank and I can't remember what the other 1 is used for. Then it has 1 power wire that has a fusible link in it. The 3 fuses get power and you can read codes (there are none) and all 3 fuses are good. I'd imagine that if the fusible link was bad nothing in the system would get power. I'll have to trace it this weekend, if it's not raining like it has been for the last week.

 

[eagle mark]

A stock 7727 harness, the fuel pump relay power is tied into the fuseable link wire... but it also supplies power to ECM, so the other fuse you don't know what it goes to may be ECM power.

Anyway, somewhere there is your issue.