Results 1 to 31 of 31

Thread: Fuel Pump gets no power

  1. #1
    Registered User zewald's Avatar
    Member ID
    CZCC-23817
    Join Date
    Mar 2011
    Location
    North Hills, CA
    Age
    32
    Posts
    14

    Default Fuel Pump gets no power

    Hey guys, i have a 75 280z, and it's taken me about 2 months of spinning my wheels to finally get on here and ask about this problem. I've looked at everything i can think of in the car. my fuel pump will not pump gas into the engine, it's not getting any power. i've checked the connections, and gone through as much of the harness as i can get to at the moment. and i haven't been able to find any problems, i replaced the pump to no avail. (i tested the old one and it definitely was faulty anyway) but i was wondering what else i should check to find the problem. this car has been my dream car for a long time, and i really want to get the thing up and running. any help would be appreciated.

  2. #2
    Brianz1973 BrianL1987's Avatar
    Member ID
    CZCC-20905
    Join Date
    Feb 2010
    Location
    Lodi CA -USA
    Age
    54
    Posts
    92

    Default

    I'm no expert on 280's but, have you check with test light to see if it is 12v or, ground that is faulty? If you've already checked the basic: fuse box & (in-line fuse?) I would just run new wire to solid power source. FYI- Mine was wired to coil by PO & figured out that it was robbing power from coil at higher rpms.

  3. #3
    Registered User zewald's Avatar
    Member ID
    CZCC-23817
    Join Date
    Mar 2011
    Location
    North Hills, CA
    Age
    32
    Posts
    14

    Default

    i don't have a test light. where could i find one? and the problem is that even when cranking the engine, the fuel pump gets no power. i've checked all the grounds and gotten rid of all the corrosion i could find, so i just don't know what to do next.

  4. #4
    Low Budget/High Value
    Member ID
    CZCC-20342
    Join Date
    Oct 2009
    Location
    Washington County, OR
    Posts
    3,629

    Default

    If you don't have a test light or a voltmeter, then how do you know the pump is not getting power? When you say "no power" do you mean "no noise" from the pump? Or have you checked with a voltmeter?

    Most auto parts or hardware stores will have a test light for sale.

    Do you get spark? Will the engine start on starting fluid? If no spark, check your EFI harness fusible links.

  5. #5
    Registered User zewald's Avatar
    Member ID
    CZCC-23817
    Join Date
    Mar 2011
    Location
    North Hills, CA
    Age
    32
    Posts
    14

    Default

    i checked with a volt meter. and the engine does spark, it's run for as long as 30 seconds on starter fluid. where is the fusible link for the fuel pump? i've checked the fuse box and replaced blown fuses, tested the fuel relay, the control unit, and will check the AFM tomorrow. thanks for replying by the way. both Zed Head and BrianL1987

  6. #6
    Registered User cozye's Avatar
    Member ID
    CZCC-22603
    Join Date
    Sep 2010
    Location
    La Grange, KY
    Age
    50
    Posts
    747

    Default

    trace back through with a voltmeter using the FSM wiring schematic (if you don't have this it's available for download). There are two relays, fuel control relay and a fuel pump relay (at least on the 77-78 there are two). The AFM switch mentioned is a an easy test as well. Go back until you hit a 12v signal and you will know where the problem is.
    1978 280z 4sp

  7. #7
    Registered User zewald's Avatar
    Member ID
    CZCC-23817
    Join Date
    Mar 2011
    Location
    North Hills, CA
    Age
    32
    Posts
    14

    Default

    that's great man, thanks. hope it works. with gas prices the way they are, i need to start driving the thing so i get better gas mileage than in my truck, haha.
    Last edited by zewald; 03-07-2011 at 07:14 PM.

  8. #8
    Low Budget/High Value
    Member ID
    CZCC-20342
    Join Date
    Oct 2009
    Location
    Washington County, OR
    Posts
    3,629

    Default

    I'm not sure what you know but the fuel pump only runs when the starter is engaged and when the AFM pump contact switch is made, for 1975. It doesn't run when the key is at On, unless air is flowing through the AFM.

    So one way to check the power lines to your pump is to disconnect the small wire from the starter and turn the key to Start. The engine won't crank but the fuel pump wire will get power if it is connected and working correctly. If you do that and find that the pump runs, then you can move on to why the injectors aren't opening.

    Maybe you've already done this. Some people expect the pump to run when they turn the key to On.

    Another way to check is to take the air intake hose off of the AFM or take the side cover off and rotate the vane while the key is at On. This will get the relay to feed power to the line also.

    Fuel pump power runs through the fuel injection relay. I don't see a fuse on the diagrams but there might be one.

  9. #9
    Registered User cozye's Avatar
    Member ID
    CZCC-22603
    Join Date
    Sep 2010
    Location
    La Grange, KY
    Age
    50
    Posts
    747

    Default

    Good advice Zed.

    Zewald, if you are expecting good gas mileage, don't get your hopes up too much. 19-20 mpg seems to be about the average for an EFI 280z.
    1978 280z 4sp

  10. #10
    Low Budget/High Value
    Member ID
    CZCC-20342
    Join Date
    Oct 2009
    Location
    Washington County, OR
    Posts
    3,629

    Default

    Thanks cozye, I was writing while you were posting so didn't see yours.

    And 19-20 mpg is about exactly what I get in my 76. Seems to go up a little in warm weather and down in the cold.

    By the way, the 75 and 76 (maybe 77) have a combined fuel pump and fuel injection relay. Both relays in one long housing, up above the hood release handle in the cabin. The fuel pump relay takes its signal from the AFM to turn the pump power on. They are expensive.

  11. #11
    Registered User olzed's Avatar
    Member ID
    CZCC-20649
    Join Date
    Dec 2009
    Location
    Auckland. New Zealand.
    Age
    76
    Posts
    1,069

    Default

    Speaking of gas prices, we are currently paying $2.16 per litre for the cheapest stuff in NZ, and it's expected to go higher. Thats over $8 a gallon at a guess. The sooner that the problems are sorted in the Arab countries the better.

    Sorry to hijack.

    Brian.

  12. #12
    Z geek at large FastWoman's Avatar
    Member ID
    CZCC-19635
    Join Date
    Jul 2009
    Location
    Hampton Roads, VA
    Posts
    2,787

    Default

    I feel your pain, Brian! I'm starting to think, "Geesh, what have I gotten myself into?" I wonder whether our machines would be capable of 30mpg with more modern EFI systems -- like the Megasquirt.

    Zewald, do everything Zed said! Great advice! Instead of listening for the pump to run, you might watch for fuel pressure -- e.g. with a gauge on the fuel line. Some pumps are only barely audible. (I can barely hear mine. It's a soft, low, rumbling.) If you have a fairly new fuel line somewhere (e.g. between the fuel filter and the fuel rail, you can just squeeze it with your fingers and feel it get firm when it becomes pressurized.

    Beyond that, just trace out all your wiring with a schematic diagram. Don't forget to check each and every connector for signs of charring. The pump draws a lot of current, and the contact in my big wire harness connectors had gone bad, charring the contacts and melting part of one of the connectors.
    Last edited by FastWoman; 03-08-2011 at 09:02 AM.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

  13. #13
    Registered User zewald's Avatar
    Member ID
    CZCC-23817
    Join Date
    Mar 2011
    Location
    North Hills, CA
    Age
    32
    Posts
    14

    Default

    19-20 is great guys, remember, i said i have a truck. haha. i get 16 on average. any savings helps.

    I've tried depressing the flap of the AFM, but nothing happens. actually, i have the fuel line disconnected from the intake manifold, because i just want to see if the pump will fill the line and make it overflow (into an empty coke bottle) does that have anything to do with it? will it not pump if the manifold isn't registering fuel or air movement?

    Zed, yes, i've done that, and thanks for all the info. the pump doesn't run. i'm getting very discouraged.

    BTW, at O'reilley auto, the combined relay is around $140 but at nissan genuine parts, it's only about $80 at least that's what my research has found: just a quick fyi. I've checked the relay and it clicks just fine, how would a faulty fuel tank sensor effect anything? i think mine might be faulty.

  14. #14
    Low Budget/High Value
    Member ID
    CZCC-20342
    Join Date
    Oct 2009
    Location
    Washington County, OR
    Posts
    3,629

    Default

    The EFI fusible link is a green wire with a connector on each end, that is in-line from a tap off of the positive terminal of the battery, in the engine bay. Check it for power on the output side, it's hard to tell if they're bad.

    It looks like the coil and ignition module are on a separate circuit so maybe the car will run on starter fluid with the EFI fusible link blown.

    Back to what cozye suggested. Page EF-4 in the FSM shows that the injectors, the fuel pump and the air regulator all get power from the EFI/Fuel pump combo relay. I would turn the key to On and see if I had power to the injectors, then open the flap, key still On, and see if I had power to the air regulator plug (the air regulator has a heater inside that turns on when the engine is running), I think that pump might be on the same circuit (according to the big wiring diagram). If you don't have power on the output side of the relay (injectors, air regulator and pump wire), but do have power in, then maybe the relay is bad. If you stare at the diagram long enough you can figure out how to jump it to get power to the fuel pump wire, just for a test (I did it to install a cutoff and priming switch for my pump).

    Page EF-54 has the procedure for checking the combo relay. Not too difficult if you can reverse things in your head to figure out what pins you're looking at. You can at least check all of the pins on the connector for power to see if you have input power to the relay.

    If you browse through the Engine Fuel section of the FSM you might get some more ideas.
    Last edited by Zed Head; 03-08-2011 at 07:35 PM.

  15. #15
    Registered User tlorber's Avatar
    Member ID
    CZCC-20299
    Join Date
    Oct 2009
    Location
    Los Angeles
    Age
    55
    Posts
    1,190

    Default

    Have you tried hooking 12v directly to the pump? Just to see if it will push fuel through?
    My car is a '73 which doesn't have all the cut-offs but it sounds like the later Z's have a series of sensors that tell whether the motor is running. If you can jumper around these to provide a "yes" condition to all, and then one by one remove the jumpers you may be able to eliminate the problem.

    Where in North Hills are you located? I spend a fair amount of time in Van Nuys.

  16. #16
    Registered User zewald's Avatar
    Member ID
    CZCC-23817
    Join Date
    Mar 2011
    Location
    North Hills, CA
    Age
    32
    Posts
    14

    Default

    right next to CSUN. off the 405

  17. #17
    Registered User zewald's Avatar
    Member ID
    CZCC-23817
    Join Date
    Mar 2011
    Location
    North Hills, CA
    Age
    32
    Posts
    14

    Default

    you guys, and girls of course, thanks fast woman, have been great, thank you. i think friday is the next day i'll have enough time to do anything, so i'll let you know how it goes.
    Last edited by zewald; 03-08-2011 at 09:05 PM.

  18. #18
    Z geek at large FastWoman's Avatar
    Member ID
    CZCC-19635
    Join Date
    Jul 2009
    Location
    Hampton Roads, VA
    Posts
    2,787

    Default

    You're welcome! Tlorber has a good point. I've read on this list where someone had a steel fuel line clogged with crud. It's not a common problem, but it could certainly happen.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

  19. #19
    Registered User zewald's Avatar
    Member ID
    CZCC-23817
    Join Date
    Mar 2011
    Location
    North Hills, CA
    Age
    32
    Posts
    14

    Default

    ya, checked that too, i sent compressed air through the whole line.

  20. #20
    Z geek at large FastWoman's Avatar
    Member ID
    CZCC-19635
    Join Date
    Jul 2009
    Location
    Hampton Roads, VA
    Posts
    2,787

    Default

    Or maybe crud from the tank could have clogged or jammed your fuel pump?

    Check your fuel pump for electrical conductivity. If you don't have any (infinite resistance), then that's your problem. Then try jumpering some power directly to it to see if it runs.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

  21. #21
    Registered User zewald's Avatar
    Member ID
    CZCC-23817
    Join Date
    Mar 2011
    Location
    North Hills, CA
    Age
    32
    Posts
    14

    Default

    ok, so after checking every circuit that runs through the control unit, it looks like everything but the air flow regulator circuit is good. also, i took the fuel pump relay off and tested continuity (based on the FSM) and that seems to be shot. I was under the assumption that it was functioning regularly because when i turned the ignition to "start" it clicked once. apparently it should click repeatedly? i'll see if i can get a mechanic friend of mine to get me a good deal on one, and keep you guys posted.

    also, at pick a part i found a throttle valve switch and a motorized antenna, i'm happy about that.

    hope the relay and air flow regulator fix my problem. thanks for all the ideas guys.

    on a side note, when i turn the car ON, my catalyzer lamp comes on, should that happen? i'm actually still confused on what that actually indicates.

  22. #22
    Z geek at large FastWoman's Avatar
    Member ID
    CZCC-19635
    Join Date
    Jul 2009
    Location
    Hampton Roads, VA
    Posts
    2,787

    Default

    I don't remember the way the '75 is wired. It was long ago that I owned one. My '78 has two relays in that circuit. One is the fuel pump control relay, which shuts down the fuel pump if the engine dies. It's a rather complicated relay that could only be replaced with an OEM part. The other is the actual fuel pump relay (which is controlled by the fuel pump control relay). It's a very simple relay that could be replaced with a Bosch-style SPST relay, available at any auto parts store for maybe $5. (You'd have to change connectors.) I'm hoping it's the simpler type that's giving you headaches.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

  23. #23
    Registered User zewald's Avatar
    Member ID
    CZCC-23817
    Join Date
    Mar 2011
    Location
    North Hills, CA
    Age
    32
    Posts
    14

    Default

    Alright, after installing the new throttle valve switch, replacing the contacts on the cold start valve and the air flow regulator, and fixing some broken wires...

    IT WORKS!!!

    you guys have been great, and honestly, even with help from my step dad (who used to work as a mechanic) i would not have been able to figure it out. Thank you SOO much.

    the car is running, and after about 10 seconds of holding my breath, waiting for it to start clanking and shaking and blow up, it didn't. the engine sounds great. i think that's about it on this thread for me. i'll probably transfer over to the "what i did today" forum. hope to see you there
    thanks again

  24. #24
    Registered User
    Member ID
    CZCC-21882
    Join Date
    Jun 2010
    Location
    LA
    Posts
    14

    Default

    Could any of you guys point me to the direction of the fuel pump relay and the starter relay for a '78 280z, I have the same issue with the pump not getting power. thanks in advance!

  25. #25
    Z geek at large FastWoman's Avatar
    Member ID
    CZCC-19635
    Join Date
    Jul 2009
    Location
    Hampton Roads, VA
    Posts
    2,787

    Default

    Zewald, that's great! I'm happy you're running again!

    Knarf, the fuel pump relay and the fuel pump CONTROL relay (two different relays, both controlling the fuel pump) are located inside of that black steel box on the inside of the passenger side fender -- the same steel box that the two fusible link assemblies are mounted to. You can get inside the black box by removing the black plastic cover on the backside.

    The starter doesn't have a separate solenoid. It's just part of the starter.

    If you haven't found it yet, you can download a free factory service manual for the '78 Z. Better still, if you look for it, you can find a used paper one on Ebay or Amazon for $80. It's a lot easier to use than a file on a computer. Something like this, except for a 280Z, not a B210:

    http://cgi.ebay.com/1978-Datsun-B210...item5197e36a8f
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

  26. #26
    Registered User
    Member ID
    CZCC-21882
    Join Date
    Jun 2010
    Location
    LA
    Posts
    14

    Default

    Thanks for the fast reply, fastwoman! Is there a way to test these relays to see if they're functioning properly? I'm considering the possibility that this could be a wire issue as well.

  27. #27
    Low Budget/High Value
    Member ID
    CZCC-20342
    Join Date
    Oct 2009
    Location
    Washington County, OR
    Posts
    3,629

    Default

    The 1978 FSM is well-copied, in to chapters, and easy to get through, if you want to dig a little deeper on your own - http://www.xenons30.com/reference.html

  28. #28
    Registered User
    Member ID
    CZCC-21882
    Join Date
    Jun 2010
    Location
    LA
    Posts
    14

    Default

    Thank you zed, I'm downloading it now. I hope I can get it starting without going to a mechanic.

  29. #29
    Registered User
    Member ID
    CZCC-21882
    Join Date
    Jun 2010
    Location
    LA
    Posts
    14

    Default

    For anyone who might know, I don't know if its of any significance but the "fasten seat belts" light and the buzzing sound when I turn the key isn't going off anymore, is that any indication to the problem with the fuel pump or related in anyway?

  30. #30
    Low Budget/High Value
    Member ID
    CZCC-20342
    Join Date
    Oct 2009
    Location
    Washington County, OR
    Posts
    3,629

    Default

    That would be an odd coincidence. I would check to see if anything else doesn't work, radio, headlights, brake lights, etc. Or just go direct to your fusible links. You might have one blown.

    The Body Electrical chapter should have the wiring for the buzzer and warning light. Each chapter usually has a nice small wiring diagram for the topic, easier to use than trying to follow the big "whole car" diagram.

  31. #31
    Z geek at large FastWoman's Avatar
    Member ID
    CZCC-19635
    Join Date
    Jul 2009
    Location
    Hampton Roads, VA
    Posts
    2,787

    Default

    Knarf, work backwards from the fuel pump. Does it get power but not run? If it doesn't get power, do you at least have power at the connector at the firewall? If not there, do you have power at the fuel pump relay? If not, is the relay tripping? Do you have power to the relay? Etc., etc. There's no "usual" failure point. You just have to trace the circuit down until you find the problem.
    My last three sports cars while I still owned all three:

    2001 BMW Z3 Roadster 3.0i soft/hard top (sold)
    1966 Ford Mustang Coupe (sold)
    1978 Datsun 280Z (enjoying very much )

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. 1976 280z fuel pump relay and power
    By SmokeyRoach in forum Electrical (S30)
    Replies: 13
    Last Post: 04-16-2011, 01:56 PM
  2. electric fuel pump on 240z 260z?
    By Bpaccaud in forum Body and Paint (S30)
    Replies: 2
    Last Post: 03-19-2003, 02:28 AM
  3. Fuel Pump for L26
    By mattymatmat in forum Engine and Drivetrain (S30)
    Replies: 5
    Last Post: 04-05-2002, 09:59 PM
  4. Electric Fuel Pump Diagnosis
    By Mike in forum Engine and Drivetrain (S30)
    Replies: 17
    Last Post: 01-25-2002, 01:19 PM
  5. Fuel pump has no power
    By Phacade in forum Engine and Drivetrain (S30)
    Replies: 0
    Last Post: 08-13-2000, 09:01 AM

Tags for this Thread

Bookmarks

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •