Fuel pump and relais?

[Sjoost]

Hi all,

 

In my attempt to get my 280z (1976model) running I ended up at the fuel pump. There I found it was leaking from the terminals. I decided to replace it with a Bosch 0580464070. Figured that should work. Made some modifications and changed the terminals (possibly i mix them when i cut them off to put new terminals on). I figured I measure the one making ground. Thought that other would be Positive. Connected them, and pump did not work when cranking (start position of ignition ). Dit a continuity measurement on the 2 terminals and to my surprise my multi meter made a sound (this is not in start position btw). Suddenly it seemed that both were making continuity with ground? Is this normal?

I measured the voltage when cracking (start position) and that gave around 9volts. 

Took out the pump and connected to the battery directly, and it would run. So pump works. Measured the relais (below the steering-wheel) as per the FSM, and it worked.

 

I'm lost, what can this be, why is the pump not working? 

 

Anyone have a clue?

 

Greetings, joost

[SleeperZ]

You will not get reliable measurements from a multi meter if the component you are measuring is connected.  That said, a fuel pump will have a fairly low DC resistance, and a continuity measurement will probably register as a short.  So measure resistance with the pump wires disconnected.

 

9 volts is probably too low to power the pump.  I would expect you to measure battery voltage (at least 12V) at the pump when the key is held in the START position, especially with the pump disconnected.  If you measure battery voltage with the pump disconnected and 9V with the pump connected, you have bad wiring.  Measure resistance from the negative to ground, it should be less than 1 ohm.  if you can, measure the positive to the relay or ignition switch, it should be less than 1 ohm as well.

 

I am not very familiar with how these cars are wired anymore, but if you can measure the wires and the connections in the circuit you will find the problem.

Edited October 24, 2018 by SleeperZ

[NewZed]

2 hours ago, Sjoost said:

Connected them, and pump did not work when cranking (start position of ignition ). Dit a continuity measurement on the 2 terminals and to my surprise my multi meter made a sound (this is not in start position btw). Suddenly it seemed that both were making continuity with ground? Is this normal?

I measured the voltage when cracking (start position) and that gave around 9volts. 

Took out the pump and connected to the battery directly, and it would run. So pump works. Measured the relais (below the steering-wheel) as per the FSM, and it worked.

 

 

If you measured 9 volts on one of the wires that is about right (actually it's low but it should still run your pump), with the voltage drop from the starter.  You tested the pump and it works.  That leaves the ground.  

 

Edit 2 - rethinking the 9 volts.  That's pretty low even with the starter draw.  Seems like the battery needs charging before further testing.

 

It's not really clear why you were measuring continuity when all you needed was voltage and ground.

 

If you disconnect the yellow wire at the starter solenoid you can get power to the pump  without the engine turning over.  The fuel pump will get power at Start but the starter won't.  Makes it easier for testing.  You can hear the fuel pump.

Edited October 24, 2018 by NewZed
had starter instead of pump

[jhm]

If the wiring is original (i.e. not modified by a previous owner), the black lead for the fuel pump should be ground.  Don't remember for sure what color the positive lead is.....possibly white or yellow?

 

Poor grounds are very typically the source of electrical issues with these old cars.  Check your ground wire for good ground, as NewZed suggested.

[Sjoost]

Thx NewZed and jhm for feedback. 

 

Gives me some things to work on. I also found manual online on the complete injection system and that one also suggested to remove the start motor lead, so the engine does not crack.  It also has many checks from the control unit. The 9volts could also be bit more, like more towards 10, but for sure I will recharge my battery first (I measure 12.5 there, so should be fine, but will try it anyway). I would expect pump to run slower at lower voltage, or am i mistaken there?

 

I did not really notice difference in colour of the wires but i will also recheck and make sure I have the black connected as ground to the larger loop terminal of the fuel pump.

 

I will also do a recheck on the relais as per EF54 - EF56

 

Any tricks to keep the starter in "start" position. I'm working on the car mostly alone....

 

Thx guys, I'll keep you posted.

 

btw, is there any high resolution diagram of the wires and colors somewhere. I only have very bad versions of the 1976 model.

 

joost

 

 

Edited October 24, 2018 by Sjoost

[jhm]

Yes, pump will run slower/weaker with less voltage.  Once the engine is running, the alternator will  be charging the system at 13.5 - 14 volts; which will obviously be plenty sufficient for the fuel pump.  Good luck with it.

[NewZed]

14 minutes ago, Sjoost said:

 

Any tricks to keep the starter in "start" position. I'm working on the car mostly alone....

 

 

Since yours is a 1976 model you can also prop open the AFM vane with the key on.  Use something inside the AFM or take the black cover off of the side and move the damper weight.  That will send power to the pump also.

[Sjoost]

Ok i will also give that a try. Btw, i am missing the hose between the airflow meter and the throttle chamber. Presume that that can not be the reason for my pump not running right?

[NewZed]

That will stop the pump from running once the engine starts.  The engine will start then die, over and over, because there is no air keeping the AFM vane open.  But the AFM switch is bypassed during Start, as shown in the wiring diagram.

 

You need that hose to keep the engine running.

 

But, since the hose is off it will be easy to stick a screwdriver in to keep the vane open.  This should keep the pump running and allow the engine to stay running if you get it started.  But it will only idle and maybe rise a few RPM before it leans out and starts backfiring or dies if you open the throttle.  Unless you manipulate the AFM vane by hand at the same time to pretend it's measuring air flow.

Edited October 24, 2018 by NewZed

[Sjoost]

Exactly NewZed, what i thought.

 

For now getting the engine running and run for short time is fine, until i get a good hose. Indeed i will set the vane open, to keep the pump normally running in "on" mode.

 

For now, i first need to get some pressure in the fuel line by getting the pump working on "start".

 

I'll keep you posted.

 

Thx so far.

[Sjoost]

(Well still working on this issue, Thisis were i stand:

1. I retested the fuel pump/fuel injection relais (I actually have 2 in my car, one mounted and one was just hanging there, so previous owner might have had some issue here too). I checked all the terminal points as instructed in EF-54 onward. 

2. In addition to those instructions I also tested all the connections (85- 88y) on the relais including the functioning of the diodes. All perfect.

3. From "the fuel injection handbook"  tested all the circuits on the Control Unit connector. There I had 2 failures only. 'The fuel pump relais circuit. and the "air regulator and fuel pump circuit". On both i was not getting continuity from pin 20 and 34 to ground (I did also connect the terminals of the air regulator to rule out that one in the circuit. 

4. Air flap open and close, all worked, but no power to my fuel pump, no matter what setting my ignitions in.

5. I again looked into the continuity of the 2 terminal wires on the fuel pump (disconnected pump) and found that both were giving continuity with ground!!!. And with each other.

6. Removing one of the 2 connectors on the relais, did indeed change that to one ground and one not. Having the right side of the connectors in the relais (to the pump side), and other one out, I found that from one side 88c on the relais was giving continuity with positive terminal at pump, but the connector going onto the 88c was giving continuity with the negative!

 

I'm bit lost, but it seems there is some ground leak , but no idea how to find it.

 

In contradiction to what i said before, I am not getting any voltage on the pump terminals, no matter what setting the ignition key is in.

 

Before I also had some strange issue with headlight not working and horn.

 

Any help is welcome here, for some next steps to take )I did short wire "S" and "R" on the ignition connector, but that should not be an issue i think, looking at the schematics.

 

Hope to hear!!

 

Joost

[NewZed]

2 hours ago, Sjoost said:

 

3. From "the fuel injection handbook"  tested all the circuits on the Control Unit connector. There I had 2 failures only. 'The fuel pump relais circuit. and the "air regulator and fuel pump circuit". On both i was not getting continuity from pin 20 and 34 to ground (I did also connect the terminals of the air regulator to rule out that one in the circuit. 

4. Air flap open and close, all worked, but no power to my fuel pump, no matter what setting my ignitions in.

5. I again looked into the continuity of the 2 terminal wires on the fuel pump (disconnected pump) and found that both were giving continuity with ground!!!. And with each other.

 

I'm bit lost, but it seems there is some ground leak , but no idea how to find it.

 

In contradiction to what i said before, I am not getting any voltage on the pump terminals, no matter what setting the ignition key is in.

 

 

Your continuity tests might be confusing you.  Better to measure resistance.  And study the wiring diagram.

 

If you look at the diagram I posted  before you can see that Pin 34 is the ground circuit for the air regulator.  And it's on the same circuit as the power supply for the pump.  So if you measure continuity you are measuring back through the air regulator to ground.  The pump ground wire is also connected to ground.  So they are connected, circuit-wise, but only via a common ground and common power supply.  The pump and air regulator are branches on the same circuit.  If you measured resistance instead of continuity you'd probably get about 60 ohms,that's about what the air regulator heating element is.  If you don't get 60 ohms then you might have a wire that has shorted directly to ground.  It might also have destroyed your relay, or blown the fusible link.  I would take a few more measurements, check your fusible links, and look for a wire with broken insulation.

 

[Sjoost]

Hi NewZed,

 

I have been measuring for few hours. I checked the resistance on the air regulator and got around 60ohm. Just to be sure, I connected the two terminals on the air regulator after that. Figured since Relais seems ok, if the relais also gets the feeds as above. Checked the signals  from the ignition to 76 (being 86a in on relais), and 71, (being 86c on relais)., and 70 (relais in 88z). 76, and 70 were fine and giving battery voltage. But measurement on 71 was 0 volts on "on", actually jumping bit up upon switching ignition but not a real voltage signal. If 86c does not get power, the pump would never work. Tried a few time more,  and suddenly I did get 12volts on 71. So i put relais in again, but still no 12volts on my pump terminals. Took out the relais again, and no 12volts on 71 again. Tried a few times more, and waited for some time while in on, and i heard another click..... and suddenly 12 volts... how..?? Seat belt light is on, and goes off after few seconds (have the seat belt in the lock). But then I found out that when "Floor Temp" light is on, I get 12 volts on 71, but when "Floor light" is off, i get nothing.....  I really don't know why most of the time it does not turn on, and randomly, really like  out of 20, it is on and i have 12 volts on 71 (86c), and i bet that when that is the case with the relais in, I would get 12volts on fuel pump terminals.

 

I did not check the system around the floor temp, but figure i give you this update, as you might recognize something here straight away..

 

Hope to hear some new clues......

 

cheers Joost

[NewZed]

 

2 hours ago, Sjoost said:

But measurement on 71 was 0 volts on "on", actually jumping bit up upon switching ignition but not a real voltage signal.

 

...suddenly I did get 12volts on 71. .... no 12volts on 71 again...... and suddenly 12 volts... how..?? Seat belt light is on, and goes off after few seconds (have the seat belt in the lock).

 

Hope to hear some new clues......

 

 

That sounds more like a bad ignition switch.  It's not uncommon.  Pin 71 gets its power directly from the switch.  The pins in the electrical switch can get loose and have sporadic and weak contact.  I had one, it was the Start pin, and it took me quite a while to figure out.  

 

You might remove the switch and check it, along with its wiring.  The hardest part is removing one of the little screws that has a one-way head on it.  Theft protection.

 

Here is a link to a very nice color diagram.  By a member there called Saridout.

 

https://www.classiczcars.com/files/category/1-wiring-diagrams/

 

Here's a picture of the part, and its source link.  It's behind the key.   I had to restake the copper on the back to fix mine.  https://zcardepot.com/all-products/electrical/ignition-switch

 

[Sjoost]

NewZed,

 

I already checked the switch, before i read your post. From BE-28 i checked all and especially "B" and "IG" since those are the 2 active on " start" and "on", which are needed for fuel pump relais. Both had power in both settings. 

 

Therefore, I checked the working of the "floor Temp" sensor" and found in EC-17 that that system is also interacting with the fuel pump relais and grounding all over.

 

I removed the passengers seat, and removed the relais (btw what is the thing next to the floor temp relais, on the left and is it normal that 2 pins missing in the connector?)

 

Did the relais check as per EC-21 and found that terminals , and found error as no continuity exists between 5 and 6, and this should be present. Other continuity was okay. Did not bother yet to connect 12volts to check other functions. 

 

What do you think, could this be the issue? From the schematic I concluded that this could be reason, but i' m not sure. For sure I need to find a new relais, or is it common to remove the floor temp system?

 

Cheers,

 

Joost

 

 

Edited October 28, 2018 by Sjoost

[NewZed]

2 hours ago, Sjoost said:

I already checked the switch, before i read your post. From BE-28 i checked all and especially "B" and "IG" since those are the 2 active on " start" and "on", which are needed for fuel pump relais. Both had power in both settings. 

 

The other things connected to the power source can cause a voltage drop, but they won't cause zero voltage, like you reported the first time at the relay.  That has to be a broken circuit.  Not sure that the floor temp lamp or sensor would be involved in a zero reading.

 

Your ignition switch tests don't say if you wiggled the wires or the connector, or the key.  You said the problem was sporadic, sometimes there, sometimes not.  Those are are the worst kinds of problems because you have to reproduce whatever causes the randomness.  So you tested once but can't confirm much from that single test.

 

I'm not sure how you're doing your measurements but you might start measuring with the connectors connected.  Through the back of the plug.  Then if you get a zero at the relay you can go back to the switch and see if it's zero, or the other side of the relay.

 

And don't overlook the connectors themselves.  I had a T plug at an alternator that looked fine but was not making electrical contact.  I've also had my starter solenoid wire do that (almost bought a new starter but wiggled some wires first).  When you get an odd result wiggle connectors while your meter is still connected.  Tap the relay to see if the solenoid is stuck.  Good luck, I've spent some time figuring things like this out and you have to think outside the box when you're getting weird results.

[Sjoost]

Still struggling here, just an update, maybe you guys see some points I'm missing.

- Restrued the Floor Temp relays and all seemed fine in the end. Reinstalled it.

- Been wiggeling with wires

- Found that my short-wiring on the ignition of the "S" and "R" wires causes 12volts to run back trough the "S" system in the "on" position, causing both coils in the relais to be closed in "on" position. Fixed this, and found that when removing both terminals from the Fuel relais, Floor Temp light would also work.

 

So no I put in one of the 2 connectors in the fuel pump relais. I installed only the right side (88d, 86a, 88y,85,86c & 88z).

 

This resulted into the double click of the relais. First click in "on" and second click in "start". In both cases  12volts on my fuel pump!!!, and floor temp light "ready" burning at "start" and switching off in "on". So that seems all fine

 

BUT

- once i put in the connector in the left side (88c, 86,88a,86b,88b) all turns bad. Then i put ignition in "on' position, or start position, floor TEMP light does not light up, and I get no 12 volts on the fuel pump.

- When I remove the (88c, 86,88a,86b,88b) side again, still things do not work. 

- However, after waiting for 5 minutes, all works again, with the left terminals installed. 

// considering that it seems something is "loading" or "unloading" I was wondering if there could be some coil or condensor which is malfunctioning. Also considering that when i connect the (88c, 86,88a,86b,88b), on the fuel pump terminals I get continuity with 0 resistance....

 

Anyone have any clue why connecting the left side of the above diagram give the issue here. Could it be something with the dropping resistor?

 

Hope to hear from you...

 

Edited October 31, 2018 by Sjoost

[Sjoost]

YEH!!!

 

I got it solved!

- I had short linked to ignition black blue and black yellow, as my "s" on ignition was not getting switched. From the measurements I noticed that via the ignition coil, 12volts is also active back from the black-blue in the "on" setting. Due to the short link, the pump/injection relais switched both relais at the same time, causing a mess in that control circuit. 

- I fixed the ignition switch first, and got that sort of solved (bad chinees replica)

- Now still no power in the pump, with the strange things as described before

- I started pulling plugs again, and then I also noticed the seat belt warning light was off. I disconnected the seat belt (which i had locked months ago to avoid the beep), and tried again. Suddenly I got the beep-beep sound again.

- Tried it the ignition again , and it worked!!! I think the seat belt relais was stuck and causing some leak, and that together with the bad switching on the relais from the bad ignition switch, and my short link.

 

Now I got my fuel pump working, and engine running (after an explosion in my improvised air intake hose, due to starter fluid). Engine starts nice, but drops after 5 seconds. Think my fuel level is too low. Man...! lots of fuel is needed to be put into that tank before the outflow nozzle is reached from totally empty. 

 

Thx for all the help, and I' m sure I will need some more soon:-)

 

Joost

[NewZed]

4 hours ago, Sjoost said:

Now I got my fuel pump working, and engine running (after an explosion in my improvised air intake hose, due to starter fluid). Engine starts nice, but drops after 5 seconds. Think my fuel level is too low.

 

Now that your relays are right, be aware that 1976 uses a fuel pump relay contact switch in the AFM, and a separate Start power circuit.  Starting then dying quickly is a common sign of the AFM switch not staying closed, due to low air flow.  The engine's intake system, including the crankcase (the PCV system is connected to the intake system), needs to be sealed so that all air entering the engine passes through the AFM.  Any leak, like a missing oil fill cap, will cause the AFM vane to stay closed and the switch to open, killing pump power.  It's a safety feature.

 

[Sjoost]

Since I am missing the hose between the AFM and engine, I did improvise a tube there, which I think is not fully air tight. 

Also, I am really doubting if the vacuum system is correctly working. What I have understood that this should work correctly in order to have the AFM switch open too. 

For sure the AFM switch to the pump is working.

My car also has an Airco, so I get mixed up with all the vacuum hoses (of which some are missing). Anyone know which are essential for the engine to run correctly? 

 

Cheers, Joost