78 280z fuel injection conundrum

[geekin]

hi guys,

im having a problem getting my z to stay on. I can start it but it shuts off immediately. its a California model 280z. all of the emissions stuff and cold start have been removed by po. seems like the fuel pump dosent stay on after start. the fuel pump works and I have a g3 fuel filter in line with fuel rail. if I use the cold start plug on the harness the car stays on longer but dies cause its not meant to keep car running.

a little brief history of stuff I've done:

efi relay crapped out so replaced it with 2 relays and worked fine for awhile.

a bad battery killed my alternator and found out po did a alternator upgrade after going through a couple alternators.

then recently after a couple months of driving had a coolant leak while driving and car shut off. not sure if they were related but after car shut off and I popped the hood I could see coolant spraying from the little nipple above the alternator.

haven't been able to get it running since. I have used the fsm to test components and everything seems to be in order. my questions is what keeps the pump running after the car is started? isn't it the fuel pump control relay? I pulled it and opened it and it looks really clean. also my relay has 6 pins unlike the 5 pin connector that I've been seeing all over the forums so im unsure how to test it. when I get home ill take some pictures of what it all looks like. any suggestions of what I should check would be helpful. this  is my first build and im lucky for it to be my dream car. thanks for the help

[siteunseen]

You may have a bad fusible link.

Straight wire the pump to the battery and tape the wires up on the door and see if you can drive it,

[geekin]

last time I checked them they seemed fine. they did have water in the pots a couple weeks ago though but that happened before and it still worked fine. ill wire up the pump and see if it works. what would be the fix if it works? also am I correct in thinking that the afm doesn't have the pump shut off in the 78, that its all done by the fuel pump control relay and that you need the oil pressure switch signal and the signal that says the car is on to get the pump to stay on?

[JSM]

So when you say doesn't run, you know it's not getting fuel?  If you spray ether into the TB boot will the car try and run? Just trying to confirm it is a fuel pump issue.

You've checked to make sure your injectors are pulsing correct?

Edited February 13, 2017 by JSM

[siteunseen]

Here's a quick read from Blue's Tech Tips    http://atlanticz.ca/zclub/techtips/

The fuel pump control for the 78 - 81 N/A.

When the engine is not running the oil pressure switch is closed and the transistor at the 'L' terminal of the alternator is "closed" and BOTH idiot lights for ALT and OIL are ON. When the key is turned to ON the idiot lights are on and the fuel pump is OFF. The fuel pump only "starts" when the key is turned to Start. These years used three relays to control the fuel pump. If the engine stops / stalls the loss of BOTH ALT and OIL signals simultaneously shuts off the fuel pump.
 

[geekin]

so when you use the cold start plug essentially it dumps fuel in to get car started. when I do that if I rev it it stays on a little longer as well. isnt it like using ether? when I turn the key to the acc position you can hear the pump in the back and you can see the fluid in the g3 filter move. I also disconnected the hose at the filter to make sure I was getting fuel pressure when pump is on and I am. but after I start it the fuel pressure is gone. the fuel gauge on the dash goes back to empty. there is a full tank of gas as well.

[geekin]

I know the alternator is working because when I do the cold start/ start it charges the battery for those few sec. so am I correct in thinking my oil pressure switch is faulty? could be cause it was in the spray area of the coolant leak. I also did check the oil and its right bellow the full line on the dip stick. but when I get home today ill wire the pump to the battery and see if I can get it running that way. also if I wanted to bypass the oil pressure switch how would I?

[siteunseen]

Straight wiring will bypass the oil switch.

Have you hooked in a fuel pressure gauge yet?  That will show a lot and is a WHOLE lot safer than straight wiring.  I did the straight wire and drove my car with the wires looped through the passenger's window for a quick yank if things went bad.  Also had a fire extinguisher out of my Dad's boat riding in the passenger's seat.

You can get a gauge at Lowes in the swimming pool section.  They have them there for the pool pumps, for cheap too.

$9.95

Edited February 13, 2017 by siteunseen

[JSM]

16 minutes ago, siteunseen said:

Straight wiring will bypass the oil switch.

Have you hooked in a fuel pressure gauge yet?  That will show a lot and is a WHOLE lot safer than straight wiring.  I did the straight wire and drove my car with the wires looped through the passenger's window for a quick yank if things went bad.  Also had a fire extinguisher out of my Dad's boat riding in the passenger's seat.

You can get a gauge at Lowes in the swimming pool section.  They have them there for the pool pumps, for cheap too.

$9.95

 

I think you have some kind of electrical gremlins going on.  I would definitely start with fusible links first.    Your fuel gauge going to empty is weird too.  I would pop all your fuses and clean each end with steel wool and re-install as well.

Otherwise start tracing through the schematic and check each component.

http://www.atlanticz.ca/zclub/techtips/wiringdiagrams/78_280Z_wiring.pdf

This is my opinion, but skip that pool gauge.  I went to my local Napa and for $20 they had an oil filled one that was pretty nice.  I've also seen the smaller ones at autozone.  I had the harbor freight kit and was running their gauge on car for awhile until it died, Junk.

I would for kicks unhook the fuel pump wires from the car and see if it runs ok jumping it with a battery.

Edited February 13, 2017 by JSM

[geekin]

I have a toggle switch that I can wire it to. so just disconnect the pump and wire it to the battery? what is the purpose of the gauge and where do I put it? before or after the filter or on the fuel rail? the fuel gauge fills when I put car in acc but after I start it goes to empty. Im assuming that's loss of fuel pressure from pump shutting off.

 

[JSM]

I would skip the gauge for now, but it would go after the fuel filter going into the rail.  Just to ensure your getting proper fuel pressure to the engine.

The gauge going empty is another problem.  Thinking on this more have you changed the switch on the back of the key?  I'm wondering if it is worn and shutting everything off once you apply start (bad contact inside.) If it is killing your gauge it may be killing other things needing to be on like your fuel pump!

I think there is a check for that too in the FSM.  I would check this first.

Bypassing the fuel pump is simple way to see if the car would run with it running stand alone.  Finding the wiring issue is second.  At least to me it would be.

Edited February 13, 2017 by JSM

[geekin]

yup so long as I can get it working I can figure out whats not working. ill wire up the pump first then check the ignition. I haven't messed with the ignition at all. changed to a removable steering wheel setup but the ignition was left alone. still have to fix the horn though. the contact plate wasn't working well with removable steering mount. every time I turned the horn would go off hahahaaa