1977 280z no power on fuel pump

[240zadmire]

Hi

 

car is early 1977 280z

I recently put back the car after take it out for painting interior, engine bay.

When turn ignition to on I hear no sound on the fuel pump.

what I did:

- connect direct power from battery to the 2 wire on the passenger side and hear fuel pump.  Which means pump is good.  Check continuity from the wire to the relay connector is good.

- check the continuity base on the fuel injector bible on pin 20 against ground, no continuity.

- ignition coil and spark plugs has electrical.

 

funny thing is that both the pins of the cold start valve are positive.  I connect positive pin from the voltmeter to battery and the negative to any pin has 12 volts.

 

what did I do wrong? Some wire definitely messup

 

thanks

 

 

 

 

 

[Yarb]

There are three areas you can check. The FSM has the diagnostic checks for the fuel pump circuit. Involves the afm, oil pressure switch and alternator. Chances are when the engine bay was refurbished there is an open circuit at one of those areas. The FSM will lead you through the diagnostics. 

[SteveJ]

Actually there is no oil pressure switch for 75-77.

What @240zadmire doesn't say is whether or not he moved the AFM flap. When the key is in the ON position, the fuel pump doesn't run when the flap is closed.

[Dave WM]

don't worry about the cold start. Its powered only during "start" and pretty sure its activated by grounding (like the other injectors). You should get a FSM and read the entire fuel injection chapter, read it again... its very through with lots of good info, but will take some time to get thru it.

[Dave WM]

5 hours ago, 240zadmire said:

 

 

"funny thing is that both the pins of the cold start valve are positive.  I connect positive pin from the voltmeter to battery and the negative to any pin has 12 volts."

 

 

 

 

 

 

 

 

 

The above does not sound right at all as far as how your are testing things. You would want to confirm voltage is getting to the CSV by connecting a positive meter lead to the CSV harness and the neg lead to the chassis ground. Nothing to the battery positive. Next you would turn the key to start, look to see if 12 is there only during start. If not try the other side of the harness and test again. This is with the injector unplugged from the harness. Also consider the CSV does not generally activate unless its under 70f or colder. It frequently fails to fire due to the thermotime switch going open from corrosion. Lastly a properly working system will only fire on "start" for a limited number of seconds before it disables itself to avoid flooding (thermo/time).

[Zed Head]

9 hours ago, 240zadmire said:

When turn ignition to on I hear no sound on the fuel pump.

As everyone is saying, this is correct.  The pump does not get power when the key is on. 

Here's the pump test from the FSM.

[240zadmire]

@Zed Head and all,

 

Just before I left for work,  I did the below:

I move the AFM flap all the way to the left and check pin 20.  Set voltmeter to continuity test and got something like 572.  Not sure what that mean.

Look at the circuit diagrams, seem like CSV and Thermotimer are connected in parallel.  I traced the circuit between the CSV and Thermotimer, one pin on CSV and the other on thermotimer and seem to have continuity.  repeat the same steps for the other pin and also got the continuity.

 

I did replace all the fuel injection connectors as they wore out.  I was very careful about which pin for which side.  I also did replace the connector for the thermotimer and the coolant temperature.

I did not replace the CSV and Auxiliary connectors as I ran out of connector.  I was very careful about the which wire goes to which.  Hopefully I didn't screw up somewhere by connect positive to negative wires. 

I will check again when I get back home.

Thank you all for the help.

will keep everyone posted.

 

regards

 

[Dave WM]

since you have had it, did the car ever run?

[240zadmire]

@Dave WM

 

History of the car was that it sat for 10+ years.  Was running very before it sat there, previous owner stated.  Bought and able to get it working and confirmed still very rough on idle.  Replace all vacuum hoses and clean up all electric connectors where possible.  Seem to fix it.  However, after a drive when put back in neutral at stop light, high rpm stayed for at least 20 seconds before idle normal. 
 

long story short, few rust here and there, paint faded... pull the engine to fix the rust.... and we all know, one thing led to another, couple of years gone by, all rust spots fixed and paint inside out.... put the car back to where it rightfully... and now I’m trouble shooting it.

 

must be some ground/wire broken somewhere.  I don’t know. 
 

regards

[Zed Head]

Does the engine run now?  You haven't really described what you're trying to do.  Just your incorrect (no offense) thoughts about the fuel pump.

[Dave WM]

you are going to need to systematically address each issue. start with getting the pump running, for this the FSM would be best.

But to jump the gun, you need to get a fuel pressure gauge installed, then pull the starter solenoid wire, turn the key to start, while in start the pump should run. if it does note the fuel pressure, should be around 36 psi. This will at least test to see if the pump can run in the most basic mode (start) and that it can produce the required pressure.

Next up will be to confirm a spark, for this you will need to replace the solenoid wire, pull the center coil wire, get it close to the chassis ground and crank the engine, this will confirm a spark.

Then you will need to confirm the plug firing order. reattach the coil wire, and see if the engine can run on some starting fluid sprayed into the TB, if it runs at all then you will need to see what the pump needs to run, some need AFM input from a micro switch, others need oil pressure, and some may need input from the alternator. All this is so the pump will NOT run if the key is in "ON" but the engine is not actually running, its a safety thing to keep gas from pumping into the engine bay, possibly fueling an engine fire. Its not something you want to bypass.

So its going to be up to you to determine what system your setup uses. It may have be altered at some point in the life of the car. Typically you could just look at the AFM and see if it has 5 or 7 leads. If 7 then its AFM controlled, if 5 then the AFM is not controlling it so something else is (does the oil sending unit have to connections or just one).

Anyway once the fuel pump is behaving as it should then you need to start looking at fuel control, that would be the ECU and injectors. What you don't want to do is load up the parts cannon and fire, all that does is introduce possible errors in the replacement of parts. there is a process that needs to be followed to sort this out.

[240zadmire]

Hi all,

apologies if I miss state the current situation.

 

- the car crank up

- there sparks on each spark plug

- direct wire connect to fuel pump, the pump spin

- fusible links have continuity 

- starter works hence sparks on spark plugs

- turn the key to on, a noise coming out from AFM

 

connect voltmeter to fuel pump while turning the key to start got zero volt.  That’s why I start from to trouble shoot why there is no power to the fuel pump.

i will keep digging from the manual to find info.  
 

I’ll be honest, tracing wire diagrams and the symbols like relay is pretty tough for me.  The answer is all there.  It just doesn’t make much sense to me is all.  I’ll keep looking but if you have more info, please help.

@Zed Head I’m not offended that easy.  If I don’t know, I don’t know.  Remember you help me the other day with the brake could not hold pressure!? It’s only easy if someone point it out what you did wrong.  It would take me days if not weeks to figure it out.  But once you explained, made perfect sense and I thank you for that.  I learned something.

 

regards