1980 280zx Fuel Pump Issues

A forum for owners of S30 and S130 Datsun Z's... 240Z, 260Z, 280Z and 280ZX!
tkbailey
Posts: 7
Joined: Sun Aug 30, 2015 8:49 pm
Car: 1980 Datsun 280ZX Black Gold

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I just acquired a nice 1980 280zx black gold. Been sitting in a garage for about a decade. Anyway, I changed oil and battery and replaced fuel in tank. Once I turned the key on, I could hear the fuel pump whizzing away.

Came back the next day and the fuel pump doesn't spin up when ignition is in the on position. I replaced the fuel pump, which didn't help, so I reading the service manual. It looks like a simple circuit. When the ignition is on, it should activate relay 2, and then relay 1, and then pass power to the pump.

I get 0 volts at the fuel pump, so, I'm trying to check relay 1. If I have done my research correctly, it is behind the glove box to the right, 3rd relay back. Anyway, I look at the relay shown in the service manual versus the one in my car and the pins are different.

So, I decided to move on and check relay 2. Relay 2, if I understand correctly, is the 2nd relay from the front of the car, and closest to the side of the car. What's weird about this relay is the manual shows the relay being twice as big as the other relays...which isn't the case in my car. All the relays in the engine compartment are the same size/configuration, and the inhibitor relay seems to be missing (which I guess wouldn't make a difference in this situation).

Am I completely on the wrong track here? I think I find the correct relay 1, and the pins are different than the service manual so I'm not even sure how to test.

Maybe some pictures will help:
diagram relay 1:
Image

actual relay 1:
Image

diagram relay 2 location:
Image

actual relay 2 location:
Image

diagram relay 2:
Image

actual relay 2:
Image
Image


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djwarner
Posts: 407
Joined: Sat Jan 23, 2010 6:07 pm
Car: 1971 240Z Series I
2006 350Z
Location: Central Florida

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You don't say that you actually cranked the engine. There is a check valve that keeps the fuel galley pressurized. The sound may be different because it is pushing against pressure.

If you are worried about starting an engine before it is ready, without pressure it wouldn't start anyway.

You may actually have a malfunction, but it is worth a try.

tkbailey
Posts: 7
Joined: Sun Aug 30, 2015 8:49 pm
Car: 1980 Datsun 280ZX Black Gold

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Sorry, I thought when the car was in the on position the fuel pump should run. I have a fuel pressure gauge hooked up and even while cranking it doesn't move off zero.

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evildky
Posts: 14713
Joined: Sat Jan 31, 2004 9:23 pm
Car: 71 240ZT, 87 300ZXN/A-T, 06 350Z GT, Tundra TRD RW
Location: Louisville, KY
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Check your afm. If the afm is bad, disconnected or the flapper door gets stuck it won't let the ecu turn on the fuel pump.

tkbailey
Posts: 7
Joined: Sun Aug 30, 2015 8:49 pm
Car: 1980 Datsun 280ZX Black Gold

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I'll check it out. But, the AFM doesn't seem connected to the fuel pump circuit, so I don't see how it can prohibit the fuel pump from turning on.

tkbailey
Posts: 7
Joined: Sun Aug 30, 2015 8:49 pm
Car: 1980 Datsun 280ZX Black Gold

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In the pic above of relay 2, I pulled the bottom left relay and turned the key on. Was able to get the fuel pump to build pressure. Decided to crank and the car started. Put the relay back in and disconnected the oil pressure switch and the fuel pump also turns on in the on position.

I think I had my oil a little low when I changed it, which might have prevented the fuel pump from activating (or the sensor is faulty). Anyway, I topped up the oil and things seem to be working better. Still have a little work on the clutch and stuff before I try to drive this thing.

It does seem that the 1980 service manual is wrong. The fuel pump relay 2 has been replaced with two relays that are all the same. I think they went this route in 1981 and this new feature must have slipped into these cars.

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evildky
Posts: 14713
Joined: Sat Jan 31, 2004 9:23 pm
Car: 71 240ZT, 87 300ZXN/A-T, 06 350Z GT, Tundra TRD RW
Location: Louisville, KY
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There is no oil pressure switch, only the oil pressure sender that sends a signal only to the oil pressure gauge. The afm sends a signal to the ecu which can prevent the ecu from turning on the fuel pump. the ecu receives no signal from the oil pressure sender. Glad you got it working but I assure you it has nothing to do with the oil pressure sender.

tkbailey
Posts: 7
Joined: Sun Aug 30, 2015 8:49 pm
Car: 1980 Datsun 280ZX Black Gold

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Sorry, the manual completely disagrees with you:

1. There is a oil pressure switch
2. It feeds directly into fuel relay 2
3. The AFM is not mentioned anywhere in the fuel pump operation diagram

Image

Image

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evildky
Posts: 14713
Joined: Sat Jan 31, 2004 9:23 pm
Car: 71 240ZT, 87 300ZXN/A-T, 06 350Z GT, Tundra TRD RW
Location: Louisville, KY
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The early S130 apparently has less in common with the late s30 and late s130's than I would have imagined. Of all the L6 engines i have dealt with I have never seen a single one with an oil pressure switch. Where is it located? A "T" with the sender? You do have an oil pressure gauge right? (Maybe some models did not get the gauge and got a switch instead?) I have never seen this on any 240, 280, or 280 zx turbo or n/a, every one I have owned did have an oil pressure gauge. If it has a gauge and a switch I'd like to know where, a pic would be great. As for the power circuit, I never messed with the n/a injection system but the turbo's fuel pump gets turned on by the ecu, which it won't do if the afm is stuck wide open (found that out the hard way).

tkbailey
Posts: 7
Joined: Sun Aug 30, 2015 8:49 pm
Car: 1980 Datsun 280ZX Black Gold

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Oil pressure switch is near the bottom of the passenger side of the engine. Not sure if there is a separate pressure sender, but there is a pressure gauge. I do wish this was a turbo model as I would be more inclined to keep it long term.

I imagine turbo cars are more sensitive to fuel issues as low pressure can cause damage.

This is a weird car as you can see from my original post as some things don't quite line up with the schematics. I think Nissan probably implemented some of the 1981 relay features in some of the 1980 cars to eliminate the variety of relays within the car. They all seem to have the same part number, which makes testing a different relay a lot easier.

Thanks everyone for your help.

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evildky
Posts: 14713
Joined: Sat Jan 31, 2004 9:23 pm
Car: 71 240ZT, 87 300ZXN/A-T, 06 350Z GT, Tundra TRD RW
Location: Louisville, KY
Contact:

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Does you car have an oil pressure gauge? The sender is located on the passanger side just forward of the oil filter, on the turbo there is a "T" that screws in the block moving the sender out and the oil port from the turbo comes out the side of the "T".

Stock compression and boost are both quite low while the fuel mix tends to be quite rich, never heard of a stock turbo car having any issues due to leaning out. Modified, the HG tends to blow out when you get knock.


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