75 280z fuel problems

[bahelion89]

So, I've been doing electrical troubleshooting on my 1975 280z. The afm hasn't been messed with, and the fuel pump is good(i ran a jumper and it runs good). i had an issue with my starter not getting enough juice but fixed that issue with a relay.

the motor was swapped with another L28e(previous owner) and has 40,000 miles. the car also has a 5spd swap and a 6-2-1 header. it had been messed with electrically but i turned everything back to stock.

Now to my issue,

when i turn the key to the on position i get the fuel relay click as well as my belt interlock click(aka put seat belt on or no start) i then turn the key and the starter cranks but no fuel. i have disconnected my starter and tried listening to hear the fuel pump but nothing.

the fuel injection manual says that if the fuel relay clicks then to check the 35 pin connector for the following leads:

Results:

1) Lead 10: 12.25V
2) Lead 1: 11.52V
3) a) Lead 5: 1.4ohms
Lead 16: 1.7ohms
c) Lead 17: 1.6ohms
d) Lead 35: 1.4ohms
4) a) Lead 14: 12.2V
Lead 15: 12.2V
c) Lead 30: 12.2V
d) Lead 31: 12.2V
e) Lead 32: 12.2V
f) Lead 33: 12.16V

are these the correct readings?

if so i still have zero power to my fuel pump..

i have been cleaning a bunch of my connections and using electrical grease afterwards. i also have no power to my tail lights. i have cleaned the 2 connectorson the passenger side several times and still getting nothing. I'm stumped.

i will be following the entire trouble shooting section of "no engine start" later

also do you have any idea how to delete the belt interlock unit?

Thanks for your help!

 

[Tony D]

.

Edited December 17, 2013 by Tony D

[9rider]

Check if you really have power to the pump. 

There is 2 relays on pass side for the pump.

Key on position won't give the pump on unless you move the flap of AFM ( fuel pump contact point inside the pump).

Check cold start valve. 

Install a fuel pressure gauge. 

Read more in this forum if all thing above don't work out.

Good luck.

[bahelion89]

2 relays on the passenger side?

 

as far as i know i have the one dual relay that controls just about everything and it is loacted on the drivers side.

 

if there is other relays neither my efi bible or fsm give me any info on them.

[9rider]

The dual relay on driver side control the blinker and hazard light. 

[bahelion89]

you apparently have never had to look at the electrical in your car. the dual relay is a crucial part of the fuel system, not blinkers. read the fuel injection manual.

[9rider]

This is weird, the blinker in my driver side is for the blinker and hazard light. My Z is 76 280z. I wonder if there is a difference. 

 

Edited: My mistake, I mistake with ignition control unit which is on the pass side. Yes, the dual relay on the driver side for the fuel pump.

Edited December 18, 2013 by 9rider

[superlen]

BA,

 

When you turn the key to "on" and here the click. The following should happen:

 

1) Coil/Contact #1 in the Fuel Pump Relay (as you noted, there are two in there) turns on. That's the click you hear.

2) That should route +12V to your dropping resistor (via pin 43),  +12V to a series switch inside the AFM via pin 39 (this is the switch that makes contact when air is flowing), & +12V to the ECU via pin 10.

 

-- At this point if you push the AFM vane open manually, that internal switch should route +12V back to the relay on pin 36 & you should here another "click" & the pump should come on. Note: the wire coming back to pin36 also runs out pin20 to the ECU, but don't worry about it at all. The ECU does absolutely nothing with this signal & in fact it's not even connected inside the box. The ECU does nothing to control the fuel pump. It's all in that relay and the AFM switch.

 

-- The second relay should also come on if the key is in the "start" condition. You usually can't hear that click though as the starter/engine noise hides it. If you pull the wire going to the starter solenoid, you can turn the key to start (the starter of course won't engage) but you should hear the relay click. I read again your post and you tried this but didn't hear the second click.  (Check that pin 73 has +12V ALL the time even if key is off - its fed by a fusible link that lots of times gets really gunky and corroded so there's a good place to start).

 

3) Now, assuming you hear the second "click". That should route power from pin 73 (+12 from the battery via fusible link) to pin 74 (the actual wire going to the fuel pump)

 

Hope this is helpful.

 

Lenny

Edited December 18, 2013 by superlen

[9rider]

^ good post.