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Jeepers92

Fuel Pump Relays rewire

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I'm a bit out of my element now on this 1978 280z s30. 

I believe both of the fuel pump relays are bad. Unfortunately when I ordered the new ones, they don't have the same pin structure so I have to rewire them. I'm simply not sure which wire goes where though I ventured some guesses. 

Could someone take a look at what I've posted in this PDF can correct anything and tell me which wire goes to which? There is a 4 pin and a 5 pin. 

https://www.docdroid.net/4M0eepL/fuel-relays.pdf

Thanks. 

fuel relays.pdf

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What did you base your guesses on?  The wiring diagram is in the Engine Fuel chapter of the FSM.  There are also test procedures for the relays.  Might be that yours aren't really bad.

Any chance you could post a picture?  Not a fan of clicking strange links.  Never heard of docdroid.

https://www.classiczcars.com/files/category/13-280z/

image.png

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Worst case is to run a bypass to a toggle in the car to bypass the relay. That seems unsafe because you have to remember to turn it off and I dont know what else the relay controls. However I have to get to work and the shop estimate is well out of range so I have to figure it out myself. I hope I uploaded those correctly. Like I said. Best guesses. 

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Relays just need straight forward logic.  They can be tedious though, for sure.  Guessing is bad where electricity is concerned.

You didn't say if you confirmed that either of the two relays were bad even though you copied from the test section, so it looks like you've made your decision.  Wire up the new relays and run the tests.  If they pass you guessed correctly.  Good luck. 

image.png

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I did follow that testing and determined both were bad, The problem i'm having is which wire goes where. Don't know electricity so i'm not sure which wire from the car goes to which on the new relay, the pins are in a different configuration with different numbers. That's the translation I need. 

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1 minute ago, SteveJ said:

Send me a PM this weekend. I will help you out.

It sounded like this might be a needed daily driver ASAP

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The Nissan fuel pump control relay is an odd one, with two solenoid switches in it.  The 5 pin that you showed won't work directly as a replacement, since it only has one solenoid.

If your relays are still installed on the car you might try unplugging your oil pressure switch and turning the key On.  The fuel pump might run then if the oil pressure switch side of the the relay is intact.  The pump will lose power when you turn the key off, so it will only be dangerous in a car accident.  Might get you by.

It seems odd that both relays would be bad, unless the car has been under water.  Any chance that you wrote down the results of your tests?  There might be a simple short term solution based on test results.

The fuel pump relay itself is a common 4 pin relay, easy to replace.

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Thanks for the help, I got the relays working as they should, unfortunately didn't fix the issues. 

Anyone know where the ignition relay is on the 78 280z? I pulled the bracket down above the fuse box on the passenger side. None of the numbers on the relay correspond to the ignition relay.  

under dash relay pics.jpg

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There might be more numbers once you remove it.  Yours looks in great condition though.

image.png

 

Here's mine.

image.png

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On 1/14/2019 at 10:30 AM, Jeepers92 said:

I'm a bit out of my element now on this 1978 280z s30. 

I believe both of the fuel pump relays are bad.

Describe the actual problem and somebody can probably get you on the right path.  CO has a 78, I think, and he knows some specific 78 stuff.  He loves looking at those relay diagrams and will explain the fuel pump control scheme in great detail.

And SteveJ and others just generally know Z electrics.  But you gotta give some clues.

Edited by Zed Head

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Thanks Zed. 

Here is the long story. 

 

The original problem is that the car would run for awhile until it reached operating temperature, maybe a 10 minutes later. At that point it would die. 

There would be no electricity in the car. dash wouldn't work at all. jumping battery does nothing. No lights come on. 

Once it dies if you have the key on accessories the headlights will stay on, the defogger will stay on, the hazards will work and the fan will work for the heater, as well as the electric antennae . 

The oil gauge, fuel guage, volts guage do not work. 

The battery is in great shape, brand new and the voltage is where it is supposed to be. At least unless I've been cranking on it awhile. 

Originally when you turn the key on and off without trying to start it, the fuel pump would not come on after the car had died. 

Once you let it cool off, then when you turn it on, the fuel pump would come on and you could start the car. 

At first it would drain the battery and we checked the air flow sensor and for a parasitic draw but those checked out fine. 

Continuity checks on the harness appeared to be according to the FSM.

Once the car died we started checking individual pieces like the fuel relays, they appear to check out fine. 

We ended unchanging the starter and the alternator because they are original very old. Those work and check out fine.  

The other thing we did was check the fuel pump. We ran the car til it died, then put direct hot and ground wires to it to make sure it would turn back on, and it did.

I bypassed the fuel relays, directly ran the fuel pump from the battery to a switch so I can manually turn it on and off, wanted to make sure that the pump wasn't bad though continuity came up fine. After the car dies I can flip the switch and the fuel pump comes on, but no power to the dash.as i said before.

I forgot to mention that we did also change the ignition switch

I also put on a clear fuel filter so I can see the gas is going through. 

 I did some more testing just to see what changes happened when you try to turn the car over.  

Once it dies if you have the key on accessories the headlights will stay on, the defogger will stay on, the hazards will work and the fan will work for the heater, as well as the electric antennae . 

The oil gauge, fuel guage, volts guage do not work. 

The batter starts out at 11.31v. 

when I turn the pump on with the switch, drops to 11.10. 

if you crank the car with the pump off drops to 9.6 

if you crank the car with the pump on battery goes down to 9.5

Never noticed but when you turn the key to the accessories there is a click behind the glove box, I assume that is normal. I checked all fuses in the kick panel too to make sure they work and are the appropriate sizes. 

I've done some forum searching and there were some mentions due to the specific gauges not working that maybe the ignition module isn't working right. I can't find one in the FSM. I found reference to ignition coil, which I tested and it's fine.

I finally found the ignition relay after searching the FSMs

At this point I'm thinking I need to test this ignition relay, however I can't find anything in the FSM that will tell me which pin is which nor what readings I should get.

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55 minutes ago, Jeepers92 said:

The batter starts out at 11.31v. 

Your voltage numbers are way off, for starters.  Could be that there is a drain somewhere.  Start with a fully charged battery, over 12.6 volts with nothing connected, and see if voltage drops when you connect the cables.  11.3 volts shouldn't even crank the engine.  Something is wrong.  You might just have a failing battery. 

https://ussolarinstitute.com/glossary/battery-state-charge/

image.png

 

 

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Sounds like a fusible link issue to me. Pop the hood now and remove the plastic covers off the fusible links. Don't wait until the problem occurs. Remove the covers now.

Then the next time the problem does happen, pop the hood again and wiggle the fusible links around and see what happens? Start with the thickest one (probably black in color).

The reason for removing the covers now is because sometimes they are a little difficult to get off and you don't want to knock the fusible links by accident. You want to be able to isolate what wiggling (if any) has an effect. And if you bump a fusible link while removing a cover, you won't be able to isolate the issue.

Of course, if you pop the covers and everything under there is loose or green or bubbly and burned smelling... Then you might just assume that's where the issue is and start working on it without definitive identification.

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Another clue to a draw is a spark when you attach the battery cables.  Only the clock should draw current and it creates a tiny tiny spark.

Just offering basic from-the-start troubleshooting ideas.  Your story jumps around a lot.

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Thanks Cap, I'll give that a try, we did find one that was bad previously. it was obviously burned through. 

When we put the cables on the battery there is a spark. Can't tell about the radio though, the guy we got it from took his out. 
Haven't prioritized getting one yet. 

Does anyone have anything showing how to properly test the ignition relay that's under the passenger side kick panel? 

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Here's one diagram.  It's a pretty simple relay.  Looks like you can check at least one side at the fuse panel.  I didn't look for the other side but it's probably in the same chapter.

image.png

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Well let me back up just a little bit and clarify something... You said in your list of symptoms the following:

On ‎1‎/‎21‎/‎2019 at 12:16 AM, Jeepers92 said:

Once it dies if you have the key on accessories, the defogger will stay on, and the fan will work for the heater, as well as the electric antennae . 

The oil gauge, fuel guage, volts guage do not work. 

Never noticed but when you turn the key to the accessories there is a click behind the glove box, I assume that is normal. I checked all fuses in the kick panel too to make sure they work and are the appropriate sizes. 

So the statement that I want to clarify is about the voltage gauge.... So what you're saying is that when the problem is occurring, the needle on the voltage gauge is swung all the way to the left at like 4 volts? Like the battery is not connected at all. Is that correct?

If so, then there is most likely a problem with an intermittent connection with the black (largest) fusible link.

As for checking the ignition relay... There are two sections to it. One section sends power to a bunch of fuses when the key is turned to the ACC position, and the other section sends power to a bunch of fuses when the key is turned to the next click in the ON position. The click you're hearing when you turn the key to ACC is the first side of the ignition relay, and based on the fact that your heater fan, defroster, and antenna work, that side is working correctly.

The other side of the ignition relay (the side that is engaged with the key in the ON position) powers (among other things), the turn signals. So with the key in the ON position, the turn signals should work. Check for that next time the problem occurs and let us know what you find?

The above is a non-meter required way to check the function of the ignition relay. If, however you have a meter and want to test the relay a little more directly... Measure the voltages on the fuses, You should see the bottom three on the forward column (closest to the firewall) go hot when the key is turned to ACC. Those three, I believe are labeled AIR CON, WIPER, and RADIO.

Then on the next click to ON, you should see the two above that go hot. I believe they are labeled FLASHER and FUEL GAUGE.

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Not to discredit any of the above advise, but from what I have experienced, 80% of the issues arise due to the 'vintage wiring connections' available at the time of production.

First picture shows an unmolested harness from the fusible links to the main harness. The circled area is the highlight of my post.

20190123_162149.jpg

Unwrapping the harness gave an abundance of gritty, sand type substance. My best guess is that the harness from the fusible link acted as a 'funnel' for atmosphere & water to weep into the harness. Pic #2... As you can see, I have unwrapped more of the 'upper left' harness, which, in reality, feeds from the alternator.

20190123_162636.jpg

Now, once in that hornet's nest, I discovered why I was having so many electrical issues that I couldn't chase down but to the fusible links, changing them never helped. Pic #3 shows a close up of the factory 'crimp' connection, which is now non-existent.

20190123_162645.jpg

Well, I guess I got a bit of camera shake on that last one, but you can still see the remaining amount of gritty/sand substance left on that part of the harness. The electrical 'connection' was relying on the pressure of the wrapping tape, and, whatever else obtained access..... like gritty sand... as in intermittent...

I have since upgraded my fusible links from the factory to the Caddy Catera Maxi-Fuse setup.  In the OEM configuration, the 3-way (front) connector had 3-80A fuses, so I was assured the assembly could handle whatever the Z could throw at it...

I was able to salvage enough red wire from the donor to route into the cabin of the Z, and the blue holder shown below is a direct feed from my alternator (internally regulated)

100_5762.jpg

 

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Captain Obvious  

I did check as you said. the blinkers do not come on ,I'm guessing that means that the other side of the relay is bad, I'll need to find a way to replace it. 

One of the fusible links is bad as well. I'll need to find a place to replace those. I was wondering about an old school temp fix. remember in the day those fuse links that were in car stereo's fuse in the middle good wiring? 

Do those work interim or is that just a bad idea? Put a 20 or 30 amp fuse in it? 

wal280z I have not had time yet to check the wires, I most certainly will be doing that Saturday when I can get out in the sunlight. Thank you. I'll let you know how that goes. 

 

Thanks again for the help, I'll report back on Sunday. 

 

 

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Well I'm not yet ready to condemn the ignition relay. That blinker test was just a quick and dirty way to do a rough test. If the blinkers DID work, then you can be pretty sure that the relay is working. But if the blinkers did NOT work, then there's a number of things that could cause that, including (but not limited to) a bad ignition relay.

In fact, the same (largest) black fusible link that would cause the voltmeter to read zero (or four) would also cause the blinkers to not work as well. (It would also cause the dome light, map light, brake lights, horn, etc. to all fail.)

So, which fusible link was it that you found to be bad? What color was it and what position on the car?

And you never answered... When the problem is occurring, does the volt gauge read all the way to the left (like 4V)?

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Well if the volts go all the way to the left, then there's a problem with the fusible links, or (hopefully not) something more serious going on with the wiring as Wayne mentioned. For the meantime though, I want to believe that the wiring inside the harness is OK at this point.

So the last thing you said "red closest to the windshield" leaves me a little puzzled and makes it necessary to drop back again and do some verification about the link positions. Here's a pic I whipped up showing the correct fusible link positions and their basic functions. This pic is from my 1977 car and I have personally verified that it is correct for 77:
77-78links.jpg

I have indicated with the title of the pic that it applies to both 1977 and 78, but full disclosure... Even though I believe they are the same, I have never personally verified that 78 is the same as 77. So first thing to do would be to verify that your links are the same as mine and here's an easy way.

One of the links goes to the headlights and nothing else. Nothing. Turn your headlights on and (after verifying that they are on) disconnect the link I have labeled "headlights".

If the headlights go out, your 78 is the same as my 77. If the headlights don't go out then 77 and 78 are different.

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20 hours ago, Jeepers92 said:

wal280z I have not had time yet to check the wires, I most certainly will be doing that Saturday when I can get out in the sunlight. Thank you. I'll let you know how that goes. 

Thanks again for the help, I'll report back on Sunday.

@Jeepers92 - a small suggestion for you - after replacing the fusible link as Captain Obvious mentioned, if that cures your issue, that's great. But, before unwrapping your harness, give it a slight twist (reference my first picture) leading from that 4-way intersection of wires about 4" towards the alternator, and about 4" up to the fusible links. Those are the two areas where the wires are spliced. No need to open Pandora's box unless you absolutely have to.... Usually, if the key is left on in the ignition, you will HEAR all sorts of relays clapping once they get a good 12V feed....

Edited by wal280z

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