I have a 89 Iroc. 5.7 TPI. Just purchased. Has some problems and I don't know where to start working first.
1. Not getting voltage to the fuel pump;
New relay. Wire into relay is hot. ECM wire is giving the 2 sec voltage. Ground wire is grounded. Wire leaving relay is hot.
2. Not getting voltage at the plug just before the fuel tank.
3. Vats is working correctly only part of the time. About half the time it will allow you to turn the engine, the other half the security light will not go off.
Any ideas? Can the vats affect the voltage to the pump? Would a new key and ignition possibly fix the vats prob?
I've never worked on 3rd gens. I'm used to a 2nd gen with no brain of its own.

 

And no fuses are blown. Any ideas? I need them if you have any!

 

No, VATS does not affect the fuel pump.
You say you get 12V on the FP wire coming out of the relay when the ECM tries to prime the pump. Good troubleshooting.

I would check connector C313, it's located under the car, above the differential, on the fwd wall. Unplug it and check voltage there. If no voltage, you have a problem with the tan/white wire somewhere between the relay and the C313. If you find voltage there, clean the connector, plug it back in and see if the pump starts working again. The connector is known for causing trouble after all these years in service.
If you still don't get any fuel, you can probe the wire on the pump side of the connector (when plugged in). If you have voltage there, the problem is on the tank/pump side.
Also make sure you have a good ground on the black wire at the same connector.

Let us know what you find.
Lou

 

check both circuits of the relay..the coil side and the power side to pump..if ur getting power side voltage to the pump (backprobe relay) and ur not getting power to the pump..then somewhere in between is the problem...check whole wire

 

Thank you! That helps me know to worry about my vats problem later. So the plug is known to cause problems. Ill check that. Maybe unplug and give it a good cleaning. I'm sure I will have a lot more questions as I go.

 

Well, I think I was wrong about the wire leaving the relay having voltage. Checked again tonight. Has power coming in, has the 2 second ecm voltage, has a ground, brand new relay,,but no voltage leaving relay...does this add up?

 

Ok, good to know.
When you turn the key on and you see voltage from the ECM, does the relay click? You might have to put your hand on it.
Either way, whether it clicks or not, it seems like your problem might be a bad connection. The connectors tend to heat up and start melting or deforming and can break the contact. You can bend the relay tabs just a hair one direction or the other and that usually helps restore the contact.

Let us know what you find.
Lou

 

Unplug the relay and jumper the two thick wires in the relay connector to see if the pump runs
That will confirm the wiring to pump and pump itself are fine

 

Ok thanks, I will check it out soon as I can and I'll let you know what I find.

Thanks!

 

BTW, I'm pretty sure the relay clicks with the ECM voltage, I know that I am hearing a click from somewhere. I will make sure its the relay.

 

the relay can click but you can still have a poor connection..just because it clicks doesnt mean its good...use a T-Pin on the power wire (Tan and white wire) that feed ur pump on the relay side and backprobe it..if the relay is energized and you do not get power there then inspect the relay wires make sure they are good at the electrical connector..if those are good then replace the relay..or look under the relay itself there is a plastic tang..pull that out and the whole relay case should slide off..see if the connection is dirty and then sandpaper it and see if it works..

I have a relay video and how they work if you have any relay question.. look me up on youtube..search for KLOWNY1969

 

Thanks, I will check that relay video out