Which wires would I check to diagnosis the no fuel pressure using the key but pressures up using the "G" terminal. I checked the wires going from the Oil Sending unit in back of the Distributor all the way to the firewall. They look fine with no cracks or frays. The oil sending unit looks ok. No oil leaks or cracks and the connections are tight. Do all the wires go to the ECM and if so should I follow them all the way to the ECM? Is there a way to test the Sending Unit with a voltmeter to see if its getting or giving a signal? This problem is giving me an ulcer.
1) I checked the fuse on the side of the dash and it looked good
2) I replaced the Fuel pump relay (ok waste of money)
3) Engerized the Fuel pump with the "g" terminal(pressured up)
4) I changed the distributor cap (old one had cracked)
5) checked the connections on the Oil sending unit. connections good
6) I did the pinch test on the return and feed lines. Pinching the return did not hold pressure. Pinching feed line caused the Fuel pressure to surge to 56 psi, then it went down to the mid 20 as it did with the return line.
7) I lifted the fuel injectors out of the manifold and pressurized the system. I noticed no leaks coming from the injectors.
8) I replaced the Fuel pressure Regulator with a Holly unit because i was getting fuel in the vacuum line.
9) I scattered holy water on the engine. nothing happened.

What would be the next step.

 

How would I trace a wire to see if it is grounded in regards to the Fuel system? Would I start with the Oil Pressure Sending wires at the back of the engine and follow them through the firewall towards the ECM. Im still not get any power to the Fuel Pump when I use the key, only through the "G" terminal. Is there some way of using a Volt meter to test any connections that might affect the Fuel pump energizing? Is it possible I zapped the ECM when I was energizing the Fuel Pump? I'm totally lost in fixing this problem. All the wires I've checked so far look fine.

 

oops, thought my original post didnt make it on. sorry for the duplicate

 

Oops, i think i misread the schematic.

 

I checked the A1 Terminal on Fuel Pump Relay and the test light stays on whether the cars ignition is on or off. As a side note I just decided to touch other parts of the car for fun and I found the hood release cable that goes from inside the car to the latch release on drivers side has some power in it. The test light lit up because there is a small tear in the protective coating where i could stick the test light. I dont think this is normal. Mmmmm more confusing for me. I am going to drop the panel under the drivers side dash right now and check for wires touching the release cable. If i see no wires touching the hood release cable what else do you think it could be?

 

When i tested the connection on A1 at the Fuel Pump Relay I disconnected it and tested it that way. Should I have kept it connected and tapped into the wire?

 

correction.....when I touch the test light to most metal surfaces the test light goes on (headers, brakelines, Oil sending unit) Something is energizing the car!!!

 

i am too stupid to own a corvette. I made a mistake with the test light. I had the test light ground on the positive terminal. Thats why everything had power. Ok, I put the ground on the right one and checked A1 again on the Fuel relay green wire. I have no power to the A1 terminal when I turn the ignition on. I have disconnected the relay from the input cable and tested it that way. Should I have kept it connected and tapped into the wire?

 

I edited that post shortly after making when i realized i misread the schematic. It comes from A1 on ecm but is terminal "C" on fuel pump relay. Not a 100% sure, but it does look like the ecm sends power through "C" to energize coil in relay.

 

So you think I should put a tester light on "C" on the fuel pump relay to see if it lights up for a few seconds when I turn the key to the on position? I see the wire is Green/white still, its just on "C" instead of "A"

 

Terminal "C" (ckt# 465) of the fuel pump relay should be energized whenever the ignition is "ON". When the ECM wants to run the fuel pump it grounds circuit# 450 (terminal "B"). Where is your Factory Service Manual (FSM)???

RACE ON!!!

 

My FSM wont be here for another 7 days. I hope it comes the wiring diagrams! So, if I put a test light on "C" it should light up when i turn the key to the on position?

 

I thought it should operate the same way, but i see no ECM connection to terminal "B", just grounded.

 

Im sorry to show my ignorance but I want to make sure I do this right. When I get home I will unplug the fuel relay harness out of its socket and put a test light into "C". I will then turn the car to the "on" position and see if the light goes on. If it does my fuel relay is getting energized. If not, then i light the car on fire and collect the insurance. Just kidding. I love my car.

 

I hate over sized pictures (graphics). When they are a part of a post I have to pan and scan just to read the message. In this case, your size is perfect, but I can't read any of the print on the schematic. Can you crop out whatever, if anything that doesn't apply to the discussion? Or with no further dialog, just blow it up a little. Here is what *I* am using for reference.

The more I look at this, I may have been wrong in my previous post. It may be the 12 volt relay drive on circuit# 465 that runs the pump and circuit# 450 may be (looks like) a permanent ground. That detail would be easy enough for someone with a DVOM to check out and verify.

RACE ON!!!

 

Better pic

 

Plan 1 sounds good
Scrap plan 2

 

I just went through the same thing.....turned out to be the oil pressure switch on the back of the block......

 

Obviously our diagrams are for different years. Thank you for your revision. Mine was scanned from the FSM directly, and not the electrical supplement. Yours makes it clear that circuit# 450 at terminal "B" goes directly to ground. Mine shows it grounded through the ECM, and I though that left it unclear. Even with both of your diagrams combined, one cannot tell where circuit 465 originates. Because of what *I* have, I am willing to accept it comes from a 12 volt driver inside of the ECM.

RACE ON!!!

 

I would test mine but i have just started my teardown. I'm curious now, i hope he tests input "C" and gets back to us.