I have a 75 280z. I had a fine day driving around yesterday. Decided to take a ride today after work. All was fine till I got home and turned the car off. Engine shut off but the fuel pump stayed on. I had to disconnect the battery to turn it off. Let it sit for a few minutes, connected the battery and pump is on all the time with no key in the ignition. Worried about flooding, I just left the battery disconnected. What could be the problem?

Fuel pump relay stuck ?

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Pat & Regina
Current Inventory
73 240Z Gray (in fostercare)
74 260Z White project car (back on the road)
74 260Z Brown triple webers
75 280 Z stroker
82 280ZX
91 300ZXTT
12 370Z Black

Where are the relays located ? Is there more than one for the fuel system ?

Ok it seems like it was the fuel pump relay. I didn't have to replace it . I located the relay just near the engine hood release lever. The relay is silver with 2 connections. With the battery disconnected, I removed the 2 connections to the relay then inspected them. They seemed clean(not burned). Reconnected them and connected the battery. Then put the ignition to the on position. I then heard a sound for about a second. I'm guessing it was the sound of the fuel system pressurizing. Then it went off. I then started the car, let it run for about 5 minutes, then turned the car off. I was happy to hear that the pump went off as well. I then repeated the process to make sure it wasnt just a tease. All seems to be ok.

Thanks for directing me in the right direction.

Personally, I would start trying to find a replacement for that relay....this time it was just an inconvenience, next time it may fail and strand you right in the middle of a pack of zombies. You may think this is unlikely, but I've seen at least four movies where cars run perfectly until zombies surround it, and then they simply refuse to start. Forewarned is forearmed!

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71 on a rotisserie, two more in pieces in my shed...and a 69 1600 waiting for me to get to it

Mark, you need to widen your movie selections!

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Phil
1981 280zxt - Now in the care my son!
2014 370Z Sports Touring Roadster

Yeah your right. I should find a spare/replacement. You never know. Zombies are drawn to stranded cars. Very common problem.

Thanks

Hi George,
You may want to clean your air flow meter. In the 1975-76 cars only, this problem can be caused by ANY stickiness in the air flap's ability to open and close fully. I think you will find the inside of the AFM is quite dirty.

On the 1975-76 280-Zs, the fuel pump and relay(s) rely on a mechanical switch contact located inside the black cover of the AFM.

When the AFM is at rest with the engine shut off, the AFM flap returns to "full rest", opening the switch (shutting off current flowing from the main EFI relay located on the driver's side underdash area between the column and the side wall of the car).

This main EFI relay is easy to spot as it has an unpainted aluminum housing and is twice the length of a single relay. There are two square plastic multiconnect connectors.

The two relays located near the battery are not the main EFI relay in the 1975-76 cars.

I suspect the fuel pump run-on problem has not been fixed and will return in the future. If this should happen again in the future, a quick test to see if the problem is inside the AFM, is to merely disconnect the AFM and see it the pump shuts off.

Cleaning the AFM is as simple as removing it from the car and then spray cleaning the interior hollow, air flap door etc with "Brakleener" which is a trichlorinated cleaner for brake parts.

Be sure to remove the idle speed adjustment screw prior to cleaning (this is the large aluminum "screw" with a single blade screwdriver slot in it.)

Be careful not to damage the rubber O-ring on the idle screw, and relubricate the screw threads with a white lithium grease prior to reinstallation.

Do NOT use carb cleaner to clean your AFM. It can and will damage internal components.

When you have the AFM off of the car, note the number of connector pins in the electrical connection. The 1975-76 AFM's have seven pins, while the 1977 and later Z and ZX's have only five.

This is because the fuel pump and relay control switch(s) is not located in the AFM after 1976. (It is oil pressure and alternator sensing circuit controlled)

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Kim Blough

See? This is why this Club is so valuable to our members ~ experience gets shared among us and saves us time, money and headaches.

Without having made the mistake ourselves, who would have thought that using brake cleaner on the AFM is safer than using carb cleaner on it? Thanks for that!

Frank

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1970 240Z

If you squirt brake cleaner in a zombie's eyes, they make funny noises. Then you can set them on fire and watch em flop around. Brake cleaner is great stuff!

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71 on a rotisserie, two more in pieces in my shed...and a 69 1600 waiting for me to get to it

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1970 240Z

Fuel switch sticking in AFM.

personally i find that there is never a full can of brake cleaner around when those pesky zombies show up, so i just bludgeon them with my tire iron or whatever is handy