Ok, I think I'm getting somewhere now. EFI experts out there please advise

[rcb280z]

Ok, so in my "How weird is this" post Im trying to understand why my fuel pump is energized with the key in the "on" and "start" position. It's a 5/77 280. The fuel pump shut off is different in the 8/77-78 models. I don't have much time to spend on the Z these days so what little free time I have is dedicated to finding this problem. When I test connectors 39 and 36 (AFM still hooked to 7 pin connector) for the fuel cut off I get 7.19ohms with contacts open and closed. I should mention that I am connecting my ohm meter to the 39 and 36 connectors inside the AFM. Just behind the black cover. I should get no reading when the contacts are broken. I even physically made and broke the contacts between these 2 connectors and still the same reading. So I'm thinking It's in the EFI relay. Maybe a set of contacts have fused together. Any thoughts? That could be what is slowly draining my battery. I drive it maybe once a month or every 2 months. I've been accused of speaking in broken sentences, hopefully that doesn't happen when I type. Thanks for any help.

[FastWoman]

The first thing to do is to measure across 39 and 36 with the AFM unplugged. Then measure across the plug end. That will tell you where you're getting conductivity.

It sounds like your contacts aren't actually closing, or else you'd get a zero'ish reading. Perhaps a switch part is bent? What happens if you gently nudge the contact with the tip of a pen?

[rcb280z]

Fastwomen, As a matter of fact I just finished those exact tests. I'm getting that same 7.19 ohm reading on the AFM plug. I get nothing on the AFM until i plug the connector back in. I tested the AFM while I had it out of the car and it tested right so I'm guessing EFI relay. I will have to test that next I guess. I know enough to keep my Z in good running condition since 1985 but when it comes to electrical (even with FSM in front of me) I'm lost. I have pretty much read all your post's and plan on trying that yogurt cup test some day for something to do. It sounds interesting. Hope you can continue to follow my progress on this issue and continue to offer your knowledge. It may take me a few days to get to anything else right now unless I happen to get a few extra minutes tomorrow. Thanks.

[rcb280z]

UPDATE:

I tried to remove the EFI relay from under the dash on the drivers side but couldn't get to the top screw! I have stubby screwdrivers I just can't get to it. It doesn't help to have extra large hands in this case. Anyway, with the EFI relay unplugged I decided to turn the key to the "on" position and the fuel pump came on! How is that possible if the relay is un-plugged? Back to the drawing board. This is why you want to test things before you just start throwing parts at it. I'm going to start going through the FSM again. This time I'm going to look at ignition circuit. Maybe I'm missing something there. Ideas anyone? Fastwomen? Thanks.

Bob

[rcb280z]

UPDATE

I honestly don't have a clue now! The only thing I haven't tested is the ignition switch itself. I thought it was the EFI relay but when I unplug it the fuel pump still runs. Now I'm getting discouraged. There was another post that had the oposite problem from mine and I'm not sure the outcome. I will keep searching.

[cygnusx1]

Whats the history of the car? Previous owner rewiring? With the pump running, you may be able to isolate the source circuit by pulling fuses/fusible links/connectors one by one.

[rcb280z]

Dave, I had an electrical fire in the "engine bay" harness 8 yrs ago. Found an exact match harness that was in excellent shape and it was easy. Didn't have to splice anything in anywhere. I have owned the car since 1985 so no rewiring that I know of. It probably would have shown itself already, I think. So you are saying while the pump is running to start pulling fuses/fusible links/connectors one at a time and replacing what I pull if it doesn't have any effect correct? Thanks.

[cygnusx1]

Correct. Additionally you can trace the wire from the fuel pump, from connector to connector. 77 uses the AFM contacts, and 78 uses an oil pressure switch to failsafe the fuel pump to the OFF position. Does your oil pressure sender have two wires on it, or is there an oil pressure switch on the block? If so, you have an oil-switched setup.

Edited January 10, 2012 by cygnusx1

[rcb280z]

my oil pressure sender is on the block with one wire connected to it. but aren't they all this way except for 78 and on?

[rcb280z]

Ok Dave, I did forget about something. I have that CRS disease lately it seems. The only rewire I can think of now was the parking light and headlight harness upgrade I did. I purchased the harnesses from Dave, Zs-ondabrain. I am very pleased with the product. I didn't have to splice it in anywhere. It was a direct plug into existing connectors deal. I know it can't be from that. I honestly don't know how long it has been this way. The only reason I started looking into it is because I saw in post's here and other sites that the fuel pump is not supposed to run in the "on" position if the engine is not running. That threw up a red flag because mine does run in the "on" position when the engine is off. Hope you will continue to help me diagnose this. I would appreciate it.

[Zed Head]

Are you sure that you unplugged the right relay? Since you have the AFM switch, and the one wire oil pressure sender, the relay should be a 1x1x2" silver box, with two connectors and 11 pins.

[rcb280z]

Zed Head, yes that is the correct one. It is the one to the drivers left leg and up. Two connectors, the top one is white the bottom one black. Does it seen strange that I can unplug those two connectors and the fuel pump still runs?