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Usain_Boat

Car stalled in driveway and now no power to fuel pump

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This afternoon I was trying to drive my car to get alignment, I know so many things to do, and when shifting from reverse to first my car stalled and would not fire up after. I started testing things and found that I have no power to my fuel pump. It definitely works still since it ran when I shorted it on a battery, and I have ground to its plug. The problem is the positive terminal has no voltage. I then tested all the fuel pump relays according to the FSM and all pass along with continuity from the positive terminal at the pump to the fuel pump relay. Also, I have reseated my oil pump plug and Have tested for voltage when the ignition is in "Start" and not just "On". Some troubleshooting tips would be much appreciated since I have already tried to look through the FSM and wiring diagram.

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Some reading but hopefully you'll get the "light bulb". :beer:

http://atlanticz.ca/zclub/techtips/EFI&fuel.htm

Thanks again, and again and again... to @240260280

Fuel Pump Checks

Author: 79-280-ZX (---.sympatico.ca)
Date:   Sep 27, 6:48am

Pumping from one can to another with no restriction (i.e. no FPR) should result in zero PSI on the outlet line but the pump should push at least one litre in 30 seconds.

If you hook up can 1->pump->FP gauge->FPR->can 2 then you should see 37 PSI pressure and still get ~ 1 litre in 30 seconds out of the return port of the FPR.

If you do not get 1 litre in 30 seconds the pump is probably toast.

If you use a 2 litre coke bottle and you see air bubbles coming out of the return hose with this set up the pump is sucking air.

If you do not see air bubbles with the can to can method but you do when hooked up to the fuel tank then suspect a hole / leak in the tank pickup tube or the pickup tube is above the level of fuel in the tank.


Wayne Monteath
Masham, Quebec.
1979 280ZX 2+2
1981 280ZX 2+2

 

 

Fuel Pump Control Circuit Information

Author: 79-280-ZX (---.sympatico.ca)
Date:   Jul 1, 9:34am

Well we have some confusion here. This question comes up at least once a week and gets as many wrong answers as correct ones. So, here in one basket, is the correct answers for all years from 75 to 83.

The fuel pump control for the 75 - 77 N/A.

When the engine is not running the flap in the AFM is closed and the fuel pump control switch in the AFM is OPEN. When the key is turned from "OFF" to "RUN" there is no continuity through the fuel pump switch in the AFM and the fuel pump should not run. When the key is turned to "START" the engine turns over AND the fuel pump relay closes which starts the fuel pump. As air is sucked past the flap in the AFM it opens and the FUEL PUMP contacts in the AFM close. When the engine starts the air flow through the AFM keeps the fuel pump running because the switch is closed. If the engine stops / stalls the flap in the AFM closes and the fuel pump control switch in the AFM opens thereby shutting off the fuel pump.

The fuel pump control for the 78 - 81 N/A.

When the engine is not running the oil pressure switch is closed and the transistor at the 'L' terminal of the alternator is "closed" and BOTH idiot lights for ALT and OIL are ON. When the key is turned to ON the idiot lights are on and the fuel pump is OFF. The fuel pump only "starts" when the key is turned to Start. These years used three relays to control the fuel pump. If the engine stops / stalls the loss of BOTH ALT and OIL signals simultaneously shuts off the fuel pump.

The fuel pump control for the 82 - 83 N/A.

For 82 - 83 N/A models the fuel pump starts and runs for ~ 5 seconds when the key is turned from "off" to "on" and then shuts the fuel pump "off" until the key is further turned to "start" at which time the fuel pump starts up again.

The ECU uses pin 13 to control the fuel pump operation since it does not have a FPCM. When the ignition switch is turned from "off" to "on" the main EFI relay closes and supplies battery voltage to pin 27 of the ECU. The ECU then supplies battery voltage to pin 13 of the ECU to close the Fuel Pump Relay for ~ 5 seconds. When the ignition switch is further advanced to the "start" position the "start" signal is sent to pin 26 of the ECU which in turn allows the ECU to provide battery voltage to pin 13 thus starting the fuel pump again.

The ECU also monitors the Ignition Coil Trigger on pin 18 coming from the '-' ignition coil terminal. If the engine stops / stalls or the engine speed drops below 50 RPM the ECU removes battery voltage from pin 13 which causes the Fuel Pump relay to open and stop the fuel pump.

The fuel pump control for the 81 - 83 Turbo models.

For all 81 - 83 Turbo models the fuel pump starts and runs for ~ 5 seconds when the key is turned from "off" to "on" and then shuts the fuel pump "off" until the key is further turned to "start" at which time the fuel pump starts up again. The 81 Turbo ECCS used pin 16 to control the fuel pump operation since it did not have a FPCM. All 82 - 83 Turbo models used a Fuel Pump Control Modulator in conjunction with the ECCS to control the fuel pump operation. If the engine stops / stalls the loss of the ignition signal stops the fuel pump under control of the ECCS and / or the FPCM.


Wayne Monteath
Masham, Quebec.
1979 280ZX 2+2
1981 280ZX 2+2

Post Edited (Sep 18, 1:17am)

More excellent info from Wayne Monteath

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Could be a bad relay.  If you can grab a new one at a cheap price, I'd swap it out.

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I just posted this trick in another post.  Disconnect the oil pressure switch and turn the key to Start.  That should cause the pump to get power.  If it does or doesn't, both will be clues.   You might have a bad switch so reseating the plug won't help.  Make sure that the wires to the switch aren't shorted to ground either.  That would be like having the switch closed.  

Also, check your fusible links. 

image.png

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I have checked a few more things. Unplugging the oil pressure sending unit a cranking as Zed Head suggested does not get power to the fuel pump. Also, I checked while cranking today and neither the fuel pump relay nor the fuel pump control relay has power while cranking and do not "click" as they did when I tested them off of the car. And for the Oil Pressure sending unit's harness the connection marked in red is shorted to ground, is this normal?

 

Also, I have checked my fusible links and they have continuity. That's all that I should be testing for correct?

 

 

WireToGround.png

Edited by Usain_Boat

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1 hour ago, Usain_Boat said:

 Also, I checked while cranking today and neither the fuel pump relay nor the fuel pump control relay has power while cranking and do not "click" as they did when I tested them off of the car.

Also, I have checked my fusible links and they have continuity. That's all that I should be testing for correct?

Measure voltage with the key on, on both sides of the links.  Follow the power path.  If the relays don't click it means they're not getting power.

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Ok, It's fixed! I had a suspicion it was the plugs under the dash in the passenger footwell so I took them apart and reseated them. I also found some corrosion on a plug coolant spilt on while replacing the heater valve so some combination of reseating and cleaning plugs got it running again. While I'm here, what is the best way to clean all the body plugs since you can't really fit sandpaper in the plug?

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Good detective work!

For cleaning contacts, ideally a small file or blade for burnishing.  You can also do this:

 

1. soak whole connector in bowl of vinegar.

2. rinse by soaking in bowl of water.

3. blow out with compressed air.

4. flush with electrical contact cleaner.

5. make and break the connection 3 or 4 times.

6. apply dialectic grease.

7. connect

 

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Thanks for the vinegar tip. Cleaned the contacts in the plugs and now it runs and I even have low beams. I've just lost brake lights, blinkers, and reverse lights now...

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Ok, its been a while but I now have turn signals back. One of the wires going to the reverse switch had broken off and was grounding out and blowing the flasher fuse. I replaced the switch since the wires were so stiff but now I don't have reverse lights. Both the old and new switch look the same and thread in but neither will turn the reverse lights on (I resoldered the old switch just to test). I know the circuit works because eliminating the switch by shorting the connector turns on the lights. My concern now is that the transmission is not hitting the switch. I have replaced the original 4 speed with a 280zx 5 speed but as far as I know the reverse switch is the same. 

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Try to actuate the switch while it's not in th he tranny and see if the lights work

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17 hours ago, Patcon said:

Try to actuate the switch while it's not in th he tranny and see if the lights work

I just took it out and pressed the switch and it turns on the reverse lights. What is the next step?

 

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Put the switch back in, without wires, put the car in reverse and check for continuity across the switch contacts.

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On 6/23/2019 at 2:46 PM, SteveJ said:

Put the switch back in, without wires, put the car in reverse and check for continuity across the switch contacts.

Just tested, there is no continuity when the switch is unplugged and the transmission is in reverse.

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2 hours ago, Usain_Boat said:

Just tested, there is no continuity when the switch is unplugged and the transmission is in reverse.

That means that it is likely that the switch is not being actuated. 

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10 hours ago, Usain_Boat said:

Ok, that's what I think as well how can I fix it?

There is either a problem with the lever that trips the switch or you need a switch with a longer plunger. Can you shine a flashlight into the transmission for a look?

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I took a video and everything in the trans seemed to be working so I removed the O-ring that came with the switch and cleaned the bulb connections in the rear and now it works like it is supposed to. I'm honestly not sure why it wouldn't work before. 

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