Well my car has told me it's 16 years old with 210k miles on it several times in the last week :-(

I need some information about the fuel pump wireing.

The wires going into the relay have melted off the insulation for a inch on 2 of the wires. My manual doesn't have the wireing diagram for my car. What color wire is what on a 1989 formula firebird 305 TBI?

Also which wires have fuesable links in them and where they run through the car would be nice. I really do not want to have to take all the wires out of the split tubes to trace it.

Once I have all this checked out and rewired, I will check to make sure the fuel pump isn't the cause, but I may go ahead and replace it, its orginal to the car. I just hate having to drop the tank, and I've got to drain it, I filled up about 20 min before it died.

I've searched but the ones that had the diagram posted, the picture is missing.

 

Hope this helps.

 

Thanks, It helps a little. I actually have it running now.

Where is the fues holder on the wire that goes to the battery.

I can't seem to find it. I may just run a new wire from the battery to the relay, but really would prefer to keep my wireing intact and not spliced all up.

 

Look all the way to the left on that diagram, it says fuse holder. Actually, there is more involved with that fuse because it is in a dashed square box. It is on the red hot wire though. Just follow it.

 

That fuse holder is located in the general vicinity of the battery. It is just an in-line fuse holder with a 20 AMP fuse in it.

 

Thanks I finally found it after tracing the wire back. I've got the wire fixed and the fues replaced. Now I still have a problem.

The wire running from the relay to the fuel pump, with the car off this test to ground. If I crank the car it test to +12. I am assuming it is the oil pressure switch that does this. Is this normal, the reason I ask is if I drive the car for a few min, it will not crank again. I have to unplug the relay and plug it back up again to get it to crank. Tracing the diagram this shouldn't happen correct?

There is still something wrong with it, its either a short to ground or the oil pressure switch.

Also if you crank the car, you can unplug the relay and it keeps running. Looking at the diagram, this should happen correct. I never realized this.

Thanks for the help, I hate tracing down wireing issues.

 

bench test the relay.

 

The relay works, its brand new, and I've tested it

 

Some more information I found.

with the relay unpluged, and the ignition on, I get +12v on the green (signal) wire. When I plug up the relay the green wire goes instantly to 0v.

What tells the computer to run the fuel pump or not?

I've got the good ole rigging in place right now with a switch inside to turn on and off the fuel pump, but really would prefer not to keep it like this.

 

vats?

 

Not likely. VATS will disable the starter and the fuel injectors only. Turning the key to the "ON" position will still cause the relay to run the fuel pump to prime the system. Have you checked the ground wire for it at the back of the right cylinder head along with the braided ground strap going to the firewall.

 

It's not vats,

The ground wire at the relay is showing good ground. I'm kinda lost on this. I will check the wire at the cylinder head tommorow. I may end up having to do what I've nerver done before and take it to a mechanic.

The fact that the hot wire going to the fuel pump when the car is off is showing continuity to ground, but with the car running is not showing any continuity to ground seems strange to me, I may go ahead and replace the oil pressure switch, but its only a couple years old.

Looking at the diagram the oil pressure switch shouldn't go to ground under 0 oil pressure. I guess I could un plug the oil pressure switch and see what response I get from that.

 

Looking at that schematic you will notice that until that circuit in the oil pressure switch/sending unit closes (as when the key is turned to the run position), it is open and therefore no power going through it. If you pull the connector to it and put a digital multimeter to the orange wire and ground you will find battery voltage there. If you do the same thing to the brown wire on that connector you will find nothing. And that circuit won't close until the distributor starts spinning the oil pump and that unit sees pressure building.

 

well it's not just showing 0 voltage. If I put my multimeter on resistance put probe on the block and one on the brown wire it is giving me tone, which means the brown wire is grounded with the car off. That means when the computer tries to prime the fuel pump it the relay is sending voltage to both ground and the fuel pump.

When I crank the car, and its running, If I probe between the block and the brown wire I do not get a tone, which means the brown wire is no longer grounded.

Is the oil pressure switch supose to switch between ground and +12 or just off and +12?

 

If you will look at that schematic again, you will notice that there are only two ground symbols (point) in it. One is at the the fuel pump which is grounded to the car frame behind the rear seats. The second one is the ECM at pin "B2" and it grounds to the engine cylinder head and creates the ground for the fuel pump relay through pin "B" of the relay. So therefore the oil pressure switch would be grounded through the fuel pump relay. Secondly, if you are going to check something for voltage, you do not set the meter for checking resistance. Also it is not a good idea to check certain items on the car for resistance, most notably of these is items that are connected to the ECM.

 

I know how to test for voltage, and the computer was unpluged when I was testing for resistance, except when I was testing it when it was running.

Brown wire = the one that splits form the relay and runs to the oilpressure switch, the other split runs to the fuel pump + 12 the other split runs to B2 on the computer

with the meter set to 20 voltage range on dc the car running the brown wire at the relay test to +12 volts dc.

With the meter set to check for resitance, the brown (b2) wire is not showing any ground.

With the meter set to 20 voltage range on dc the car off the brown wire at the relay test to 0 volts dc.

With the meter set to ristance the car off but with the switch set to run the brown wire test to ground.

with the meter set to ristance the car off and the switch off the brown wire test to ground.

If the brown wire never had voltage running through it I wouldn't do a resitance check, but since it does it will not hurt it to do so, I am more at home working on computer electronics than car wireing. The computer voltage monitor (b2) will not be harmed by a resistance test since it is designed to receive a 12 volt dc current with more ampreage behind it than my multimeters resistance test will provide.

The question is should the oil pressure provide these results?

Second the green wire (a1) coming from the computer to the relay, to engage the relay, shows 12 volts when the relay is unpluged car off but the switch set to run position. But as soon as I plug up the relay the geen wire goes to 0 voltage. Something is telling the computer to remove the power when I plug up the relay. Either that or the relay is drawing to much ampreage to engage and the computer is protecting its self by turning off the voltage. I guess I should do a bench test and do a ampreage test to see how many amps it takes to engage the relay.