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Discussion Starter · #1 ·
Hey everyone, I’m sure this question has been asked a million times, I’ve read through many of them and haven’t been able to completely solve my problem. I’m not electrical savvy on automobiles so please bare with me. I parked my Z about 6 months ago running fine, no problems. Now it won’t start. When I turn the key in the on position I do not hear the fuel pump. The car will start however with starting fluid. I’ve ran a pair of jumper cables from my battery directly to my fuel pump wires, and immediately the fuel pump kicks on and the car will start and run perfectly, that is until I unplug the cables from the battery. So I know that my fuel pump works fine, and so obviously the pump is not getting power, correct? There is a set of bullet connectors under the passenger seat and from my understanding they run to the fuel pump, using a tester, I see that they have power to them when cranking the car. I’ve checked my fuses, fusible links, and I’ve pushed the afm flap and did not hear the fuel pump kick on. My oil pressure seems fine. Like I said when I inject starter fluid, the car runs great. I’ve read many times that the fuel pump relays rarely go bad, my car only has 93k original miles so I wouldn’t think the relays would be bad anyway. I just don’t know what could’ve happed in the last 6 months that would cause this sitting in a garage.

Thanks all for the tips, I could really use them
 

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When I turn the key in the on position I do not hear the fuel pump. The car will start however with starting fluid.

I’ve pushed the afm flap and did not hear the fuel pump kick on.

Seems like you've managed to work around not quite understanding how the fuel pump gets power. It's described in the Engine Fuel chapter of the FSM if you want to get up to speed.

I had the fuel pump relay contact switch in my 1976 AFM get dirty once. Take the black cover off and check it. The fuel pump will only "kick on" if the key is on when you open the flap.
 

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Discussion Starter · #3 ·
I should have clarified, but yes I have moved the afm flap with the key in the on position and still nothing happened. You are referring to the black cover of the afm correct? Mine is still factory sealed with the original glue so I’ve been hesitant to remove it
 

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Yes, that black cover. It's just pressed on, no clips or latches. Cut the sealant and pry it off.

BUT. The other way to test it is at the fuel pump relay plug. Which is up under the dash by the hood latch lever. Probably easier to remove the black cover.

You can see the tiny little contacts that supply the circuit to the fuel pump relay. A little metal arm that moves with the AFM flap.
They're small because they don't pass much current. With a multimeter or circuit tester you can probe the base of the two legs of the switch to see if the contacts are making contact. a tiny piece of dust or a small hair can stop them from closing. Move the flap and you'll see how it works.

There are pictures on atlanticz.ca. Do not do any of these adjustments! Just look at the pictures. http://www.atlanticz.ca/zclub/techtips/afm/index.html
 

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You can see the tiny little contacts that supply the circuit to the fuel pump relay. A little metal arm that moves with the AFM flap.
They're small because they don't pass much current. With a multimeter or circuit tester you can probe the base of the two legs of the switch to see if the contacts are making contact. a tiny piece of dust or a small hair can stop them from closing. Move the flap and you'll see how it works.
l
My '76 used to shut off on hard cornering intermittently. Found these tiny little contacts were reading about 15-20 ohms when closed. Should have been reading zero, or close to it. I cleaned the contacts by polishing them with a thin piece of cardboard. That was 15 years ago, have not had an issue since!
 

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Discussion Starter · #6 ·
Well I’m back after 6 months of discouragement. I tried all of the above suggestions without any luck. I know I have power to the connectors under my passenger seat, I tested the connectors with a tester. I’ve cleaned my afm connectors and oil sensor connectors. I really don’t know where else to check. Thanks!
 

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There is a set of bullet connectors under the passenger seat and from my understanding they run to the fuel pump, using a tester, I see that they have power to them when cranking the car.
If the connector has power there when you crank the engine then everything in front of that is working, at least for Start. Does the engine start then die immediately or does it not even pop?

Here's another test that will tell you something. If the connector by the seat has power when you turn the key to Start then it should have power if you remove the small yellow wire from the starter solenoid and turn the key to Start. That is actually Nissan's official factory test method, described in the Service Manual. Much easier to hear the pump with the starter not engaged.

Try that. If there is power at the connector but the pump does not run then the problem is between that connector and the fuel pump. You've been working on the wrong end of the car.
 

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Discussion Starter · #8 ·
If the connector has power there when you crank the engine then everything in front of that is working, at least for Start. Does the engine start then die immediately or does it not even pop?

Here's another test that will tell you something. If the connector by the seat has power when you turn the key to Start then it should have power if you remove the small yellow wire from the starter solenoid and turn the key to Start. That is actually Nissan's official factory test method, described in the Service Manual. Much easier to hear the pump with the starter not engaged.

Try that. If there is power at the connector but the pump does not run then the problem is between that connector and the fuel pump. You've been working on the wrong end of the car.

Thank you! I’ll try these suggestions when I get home. Could it possibly be the ignition switch? I had a friend tell me since the pump isn’t priming it could be the ignition switch
 

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Thank you! I’ll try these suggestions when I get home. Could it possibly be the ignition switch? I had a friend tell me since the pump isn’t priming it could be the ignition switch
The pump does not prime. There is no priming. The pump only gets power when the key is at Start OR if the engine is running (which causes the AFM flap to open).

There are many people out there who will give you advice even though they don't know what they're talking about. Your best option is to download the 1977 FSM and read the Engine Fuel chapter. It describes everything in great detail.

https://www.classiczcars.com/files/category/13-280z/
 

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Discussion Starter · #10 ·
Well I followed the Instructions in the FSM, it had me test the ecu for either “battery” or “continuity” and my ecu passed all the tests. I followed all the instructions until it kept telling me to retest. Now retracing my steps with a multimeter, it seems that I’m not getting power under my passenger seat when the key in is the “on” position. With the car running I get power there, I know because I blew a test light checking. With the key in the on position I checked the fuel pump wires with a multimeter. And it shows the slightest amount of power. Connected to the spare battery however it starts pumping. On a new note, I replaced my oil pressure switch, when I turn the key on the oil pressure jumps sky high way past 90. When I use the spare battery to force the car to run, the pressure corrects itself a bit but slowly falls to zero.
 

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it seems that I’m not getting power under my passenger seat when the key in is the “on” position.

With the car running I get power there, I know because I blew a test light checking.

With the key in the on position I checked the fuel pump wires with a multimeter.
You're making progress. There should not be power "under the passenger seat" with the key on. That would be power to the pump and as discussed above the pump only gets power at Start or with the engine running. You have to remember that.

If you get power at the fuel pump wires under the seat then the pump should have power. Unless you're measuring the wrong wires.

Again, there is no power at the pump with the key on.

It might be that your fuel pump relay is bad.
 

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it seems that I’m not getting power under my passenger seat when the key in is the “on” position.

With the car running I get power there, I know because I blew a test light checking.

With the key in the on position I checked the fuel pump wires with a multimeter.
You're making progress. There should not be power "under the passenger seat" with the key on. That would be power to the pump and as discussed above the pump only gets power at Start or with the engine running. You have to remember that.

If you get power at the fuel pump wires under the seat then the pump should have power. Unless you're measuring the wrong wires.

Again, there is no power at the pump with the key on unless the engine is running or the AFM flap is open.

It might be that your fuel pump relay is bad. A good way to check the relay is to turn the key on then open the AFM flap. The pump should get power then. Because the AFM flap is open.
 

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Discussion Starter · #13 ·
Okay well I know the pump will not run with key on while I push the AFM flap. So probably a bad relay? If so where’s the relay? Under the passenger seat? Or under the steering wheel? I read in the fsm that the one under the steering wheel should “click” when you turn the key on, mine does.
 

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The relay locations are shown in the Body Electrical chapter. 77 should have a combined relay, with the EFI relay and the fuel pump relay in the same 2 inch long rectangular housing. The EFI relay clicks when you turn the key on.

There is a test procedure in the FSM for the relay. But once you know how it works it's easier to test on the car. Could be something as simple as a bad wire.
 

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Could the relay still be bad even if it clicks?
Going to spitball here and say if the inside of the relay is corroded (rust on the terminal the relay's click is clicking on) then the power that is attempting to go to the fuel pump wouldn't be transmitted (even with the click).
 

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Power to the pump

Well I followed the Instructions in the FSM, it had me test the ecu for either “battery” or “continuity” and my ecu passed all the tests. I followed all the instructions until it kept telling me to retest. Now retracing my steps with a multimeter, it seems that I’m not getting power under my passenger seat when the key in is the “on” position. With the car running I get power there, I know because I blew a test light checking. With the key in the on position I checked the fuel pump wires with a multimeter. And it shows the slightest amount of power. Connected to the spare battery however it starts pumping. On a new note, I replaced my oil pressure switch, when I turn the key on the oil pressure jumps sky high way past 90. When I use the spare battery to force the car to run, the pressure corrects itself a bit but slowly falls to zero.
Checking the green wired barrel connector behind the passenger seat, that connector should only have power with the key in the START position or with the engine running. Just having the key on when the engine isn't running doesn't put power to that connector. Unplugging the starter energizer lead like someone else mentioned is a good way to make the tests easier. The oil pressure switch only affects power to the pump on the 78 and newer cars, the 75-77 depend on the switch in the air flow meter. Using the FSM injection tests at the ecu connector you should be able to find out when the power is and isn't working correctly to the pump. If you want to guess, try replacing the main efi relay. I have them in stock for 125.00 new and 65.00 for used ones and they fit all 75-77 z's. Remember that the 78 and newer cars use different wiring and relays compared to the 75-77 z's.

Z man of Washington
 

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Discussion Starter · #19 ·
If I’m getting power under the passenger seat when the car is running, then my problem has to be between the passenger seat and the fuel pump correct?
 

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Not necessarily, but let's backtrack for a minute.

The place to check for juice to the pump is at pos. pole on the pump itself. Power here should eliminate consideration of the pump relay.

The next check (again, with power to the pump) would be to ground the pump's neg. pole to the chassis. No run, dead pump.

If it runs thus grounded, the issue is downstream on the black wire's way to the system ground.

Or not. Two cents worth does not guarantee success...
 
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