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Brae

Fuel pump and Relay problem

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    I'm having a problem with my 1976 280z. The fuel pump works when I connect a battery to it, and I've checked for continuity on the relay and thats fine aswell, but when I dont have a dedicated 12v, it wont work.

    When I try to start the car, it cranks but there is no click from the relay, and the fuel pump doesnt make a sound.

    I've tried using the fuel injection bible for this problem (the relay not clicking). When I perform the continuity check for the 2nd step on page 55, I ONLY get continuity when the NEGATIVE is connected to 20 on the control unit and the positive is grounded. After performing this step I tried the one on page 56 but could not get continuity either way. I've checked the fuel pump/wiring/air regulator, and they all seem fine.

    Also when I used a battery for the fuel pump while cranking, it still wouldnt start but fuel was going past the filter. Does anyone know how I can fix this, or if me putting a switch to bypass the relay to make a fuel pump switch would solve the problem I'm having? Thanks in advance.

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    i checked the fuel pump shut off switch and both the input and output have continuity, also i checked the air regulator wires for continuity and the one wire nearest the driver side (i believe #48) does not have continuity. Since that goes to the relay and then the fuel pump, would that be the reason my relay isnt clicking and im not hearing anything from the fuel pump? If that's the case, how do i change/fix that wire.

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    i checked the AFM and did all 3 of the steps for resistance, but noticed for 1 (3b) that it was around 185 ohms and then whenever i had a friend press open the flap, it would increase. I thought it was supposed to decrease when you press it in? On the other 2 resistance checks i had 181.5 ohms so the AFM seems fine from what i understand (and the switch is working). I have a few wires that i have no clue where they go (about 3), perhaps they could be another reason but they did not seem to fit anywhere, other then the black one on the afm that is under the top left bolt, but i dont know where i connect the other part of it to. I'll take pics tomorrow

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    follow the wiring from battery to pump and measure 12v as you go at all connectors. Don't worry about other efi components at this time: "work the problem".

    Just turn key to on and connect afm switch (move flap up) to ensure power to pump path is in a running mode before you start your hunt.

    Here is a wiring diagram:http://www.atlanticz.ca/zclub/techtips/wiringdiagrams/76_280z_wiring.pdf

    Edited by Blue

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    ... and remember that there are also a couple of enormous connectors on the main wiring harness, just on the inside of the passenger firewall. They can get a bit crusty, to the point that the large(ish) current demands of the fuel pump can cause arcing and burning of the contact (which lies in the path between the fuel pump relay and the fuel pump). Of course your relay would still click, even if that contact were bad.

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    So I did every test under the No start category of the FSM, including the voltage checks and what i've found is this.

    1(6) water temperature sensor (13-ground) has no continuity

    1(8) Air regulator and fuel pump (34-ground) has no continuity

    2(2) Power line circuit is (10-ground) is only reading .04 volts

    2(3) injector and dropping resistor terminal steps

    A(cylinder 4, 14-ground),

    B(cylinder 1, 15-ground),

    C(cylinder 5, 30-ground),

    D(cylinder 6, 31-ground),

    E(cylinder 3, 32-ground),

    F(cylinder 2, 33-ground) all are reading .04 volts

    3(2) Air regulator - It didn't say to do this one, but it was only reading .05 volts at "start"

    The line before the relay, after air regulator is the one that is the problem from what i can tell from the checks for the fuel pump not working, what should I do now, follow that wire and change it out? Lost please give tips.

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    Well, my philosophy is that you should fix problems as you find them, even if they don't have anything to do with what you're trying to diagnose (i.e. your fuel pump not operating). It sounds to me like you have a lot of corroded connections. After decades in very hostile conditions underneath the hood, the electrical connectors deteriorate quite a lot. You'll probably find they're severely corroded. You may even find that the plastic connector bodies are very frail and crumbly. You can replace MOST of them with Bosch-type injector connectors, which you can buy from a vendor named f0rest on eBay:

    http://cgi.ebay.com/ebaymotors/injector-connector-kit-6pc-datsun-280z-280zx-300zx-/290452375892?pt=Motors_Car_Truck_Parts_Accessories&hash=item43a04f8954

    The throttle position sensor connector can be grabbed off of several other models of wrecking yard cars. The AFM connector can just be cleaned up. (It doesn't get as much engine heat). You should simply spend time going through electrical connectors -- cleaning (DeOxit, lemon juice, WD-40), lubricating, and replacing if necessary. Add a bit of silicone dielectric grease when you re-make your connections. After you've examined and serviced every connector you can find, then take your measurements again.

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    If you did these tests with the key at On, it looks like your Fuel Injection harness fusible link is blown, disconnected or has a corroded connection. It is the single green wire, that looks like some sort of extension with a connector on each end, connected to a white wire directly from the battery positive terminal. If it is in its original spot, it may be attached to the side of the relay box with a long plastic peg. OR, your FI and Fuel Pump relay is bad. It is combined for the 1976 model, attached up above the hood release handle. A silver box, about 1 x 1 x 2".

    With the key On you should have battery voltage at the dropping resistors, they are fed directly by the EFI/Pump relay, which is on the circuit with the FI fusible link. There are some good diagrams on pages EF-25 and more in the FSM.

    EDIT - Blue covered the relay in Posts #3, 4 and 5. That's the one. His diagram shows where the link is also. It's green.

    Edited by Zed Head

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    Just bought the connectors, thanks for the link. Zed head, i just put 4 brand new fusible links in just the other week, is there something else is could be? Ill check the fusible link again but I'm pretty sure its good. I'm Leaning towards it being the relay as my friend said he couldnt get his relay to work either on both of his Z's so he just made a switch for the fuel pump. If I cant get the relay to work I'll have to resort to the switch since the added security is nice. This week I'll try to fix all the connectors and if i find something else/fix it then I'll let you know, wish me luck :P

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    The 5th fusible link (For the EFI System) is at the +pos battery lead where it connects to the battery post. It can come unplugged easily.

    It is labeled "EFI Power connector" by the fool who made this drawing:

    eficonnections.jpg

    Edited by Blue

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    Here is an expensive replacement - http://www.thezstore.com/page/TZS/PROD/11-3470

    I don't think that the diode and resistor measurements are critical, from my limited understanding. They are there mainly to stop electrical spikes in the circuits when the contacts open and close (I believe it might be referred to as "flyback" - http://en.wikipedia.org/wiki/Flyback_diode)

    Here's another link with some recommended diodes for a similar purpose - http://www.bcae1.com/relays.htm

    More info - http://www.rvsafetysystems.com/Relay%20data%20sheet.pdf

    If you're thinking about trying to make your own, you probably know this anyway, but just in case. Looks interesting, if you get it to work.

    You might find a stock Datsun replacement on EBay also.

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    Thank you Zed Head for the links. I have the engine running with two normal relays with one diode on the starter side. Problem is its running rich so I want to rule out the relay before i look into other components.

    Will update you on the outcome.

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    I installed the injector connectors and no difference, but i took a look at that "5th" fusible link and i took pictures hoping it will help, im not sure which one it is because theres 2 wires that connect, but im guessing the one where the guy tried to tie it together with tape (its also very wobbly/loose; might be broke?) might be the reason for these problems im having. Just looking for some confirmation that it's the wire you are talking about. post-25082-14150816355799_thumb.jpg Would this alone cause the symptoms that i've listed?

    post-25082-14150816355011_thumb.jpg

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    You picture doesn't show where those wires connect. One of those red wires supplies your EFI harness (injectors ECU and relays), the other is a ground and connects to the negative post.

    The one from the positive terminal should have a green fusible link. If you can't get a link, consider an inline fuse holder. The green link is estimated at 40 amps.

    I would first determine which of those is the ground and which feeds the EFI harness, fix them up right,then continue testing. I don't think that you can test the circuits right until you get power to the relays.

    Edited by Zed Head

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    post-25082-14150816358596_thumb.jpg The white wire connects to a fusible link then it goes to the relay on this pic. I dont see the other red wire on this diagram Edited by Brae

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    are you saying that my positive one having 3 wires coming out is wrong? Should i move the black one that turns to red with no fusible link on it to the negative side

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    I think, but am not sure, that one of those red wires is a dedicated ground wire for the EFI harness. The other is the power wire. If that is true, then you don't have a complete circuit for some of the components of the EFI harness.

    I think that you can confirm which is which by finding one of the components that is fed by the white wire in your wiring diagram and testing continuity back to the one of the red wires.

    But, yes, I think that you should have one red to positive and the other to negative. I just looked at my 76 to be sure. I wouldn't connect anything until I knew which red wire was which. From what I've read, it's not uncommon to be fooled by the red ground wire.

    Edit - I just looked at Saridout's wiring harness diagram and the red ground wire is shown leading from the battery negative. It should be also connected to body ground so you should have had a direct short if you connected your battery cables with those wires connected like that. Unless it's already been damaged in the past. According to the diagram, the red ground wire also connects to Pins 16, 17 and 35 at the ECU connector, and one of the legs of the water temperature sensor circuit.

    Don't guess and connect. My harness has some charred wires from POs' wiring work.

    2nd Edit - actually it's shown in your copied wiring diagram also. A wire from the negative through a connector and on to 16, 17 and 35, etc. Both "R" for red.

    Edited by Zed Head

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    ah ok, well the one with fusible link stays on positive, the other one ill take out and put it on the negative. Now it's starting to all make sense why lots of things arent working. since there was a direct short im assuming the fusible link is fried haha. I hope the other wire is fine.

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    i bought the car like this so when i plugged it in i never noticed anything weird, so it must of been fried before

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    so i changed the wire and fuse to an inline maxi fuse one, and these are my results for the FSM tests of the engine not starting. for continuity i wrote down the # and also set it to make noise if continuity existed.

    1 (3a) AFM continuity from 6-8 181.6, no noise

    (B) AFM continuity from 7-8 188.7, no noise

    © AFM continuity from 8-9 101.5, no noise

    1 (5) Fuel pump contact 10-20 004.2, noise

    1 (6) Water temperature sensor 13-body no continuity

    1 (7) Electronic fuel injection relay 20-body only made noise at "On"

    1 (8) Air regulator and fuel pump 34-body only made noise at "Start"

    1 (9a) Ground circuit 5-body 001.5, noise

    (B) Ground circuit 16-body 000.7, noise

    © Ground circuit 17-body 000.9, noise

    (d) Ground circuit 35-body 000.8, noise

    2(1) Revolution trigger signal 11.72 volts

    2(2) Power line circuit 11.83 volts

    2(3) Injector and dropping resister 11.81-11.83 volts for all 6 checks

    3(1) Starter signal 11.64 volts

    3(2) Air regulator 11.63 volts

    3(3) Cold start valve and thermotime switch 11.74 volts

    From what I see it seems that only 1(6) is the problem, but i could be wrong, am i reading this information incorrectly? please do let me know :). on the + side, almost everything that was wrong with it before is fixed other than 1(6)

    Edited by Brae

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    No continuity will make the engine run very rich once it starts. It tells the ECU that the engine is very cold and needs lots of extra gas.

    Have you tried to start it again yet? If everything except the WTS is correct, it should start, run really rich for a little while then choke out and die in a cloud of blue smoke. If it won't start, check that the injectors are firing (although many cars will start on gas from the CSV, if it's working). The ECU grounds the injectors when it receives the "break" from the blue wire from the coil negative. Check for continuity between coil negative an Pin 1 with the key off. Or use a test light or test bulb to be sure the injectors are firing.

    Edit - forgot one thing - the tachometer circuit with its resistor has to be hooked up for the ECU to work correctly. It's on the blue wire from the coil negative also. If your tach isn't connected the ECU won't fire the injectors.

    Edited by Zed Head

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