1975 280 starts for 2 seconds and shuts off???

[jlenownnab]

Hello,

I'm not having any luck finding a close enough scenario due to other members modifications, etc...so I'm starting this.

This is a car I took everything out of-the engine bay, removed the suspension, drive train, gas tank, etc. - last winter and freshened it all up.

This car has been great for the last year. The only flaw has been sometimes when I turn the key it clicks once and does nothing. When I try starting it a second time it fires right up. So, being winter I thought I would do a few things on the list to better my car. 

1st. I wanted to send my combo switch and turn signal off to Dave and have that rebuilt. It came back, I installed it along with the upgraded turn signal flasher per Dave's advice. It was a little bit tricky getting it seated properly so the horn worked, but I finally got it working.

I did not try and start the car when completed, but I did turn the key to the on position and checked turn signals, wipers and lights. All were working nicely.

2nd. I decided to pull my coil out for media blasting and paint. I started to undo the negative side of my battery and decided not to because the terminal was in bad shape. After the coil was painted I was carrying it over to the car for installation and dropped it. The coil has a slight dent in bottom edge. After installing it I tried to start the car, the starter kept turning it over but no fire, no gas smell either.

3rd. I purchased a new coil from O' Rileys. I installed it and tried to start the car and after a couple long sessions of turning the key over it finally started. Not convinced that was the problem, I re-installed the coil I dropped and the car fired right up. I drove the car around the block and it ran perfect.

4th. I replaced the starter in hopes that the starter on the car maybe had a dead spot or was just starting to go bad, causing the car not to always start on the first try. When finished with that, the car would not start again. I remembered I started undoing the negative terminal on the battery while removing coil so I went back to there. ( Although, all I did with it originally was work it a little with my hand, no tools.)  After wiggling the negative terminal, the car fired right up (the horn stopped working now).

5th. I was Unable to tighten the negative terminal so I decided to buy a new one from Motorsport Z. I installed the new negative cable/terminal and once again it won't start. The car turns the starter fast and sounds great. But, it will only run for two seconds and it shuts off. If I try to depress the accelerator to keep it running, it dies immediately. Also, the tachometer jumps around when the key is in the on position with the car not running. I do have a jump box hooked up to the battery.

While trying to start the car I do not smell gas in the engine bay. The AFM is new, the grounds are good,. I tried upping the idle, no help.

 I come to you great fellow Z owners to help me get her on the road again.

Thanks, Stewart

 

 

[Zed Head]

Sorry, I ran out of time to read what you wrote before Google stuck an ad on your page.  But I notice that you mentioned a "dead spot" as a reason to buy a new starter, and didn't really describe what you meant by "won't start".  Might be a clue there.  People have had iffy ignition switches.  I had one in a 1978 car.  Fixed it by recrimping the S connection.

Describe how it doesn't start.  Does it make noise, or does the engine just spin and nothing happens?

The tachometer needle jumping around suggests a bad electrical connection, or electrical nose from your jump box.  Maybe disconnect the jump box and see if the tach needle still jumps around.

[jlenownnab]

Hey Zed, the tach does not jump when the battery pack is unhooked.

[Zed Head]

I wouldn't worry about the tach needle then.

If you're in a hurry you might break your post in to small pieces and repost.  Can't read it 'cause of the ads.

[JSM]

I clicked the ad, said I saw it already, it went blank, but text was still covered, then refreshed and it went away. 

[JSM]

Intermittent like that can be the key switch. The electrical component  behind the key itself. Very easy to change. 

Edited March 15, 2018 by JSM

[jlenownnab]

I'm not sure why members are having trouble reading my post? The intermittent click is on the back burner for a minute. For whatever reason the car only runs for 2 seconds then shuts off? New AFM, recent tune up, checked connections/grounds, checked for vacuum leaks?? Car ran great last week. After trying to start it repeatedly, I don't smell has?? Not flooding.

[Zed Head]

16 minutes ago, jlenownnab said:

I'm not sure why members are having trouble reading my post? The intermittent click is on the back burner for a minute. For whatever reason the car only runs for 2 seconds then shuts off? New AFM, recent tune up, checked connections/grounds, checked for vacuum leaks?? Car ran great last week. After trying to start it repeatedly, I don't smell has?? Not flooding.

The ads are showing up where there are large blocks of text.  Like your first post.  It's not you, it's Google Adsense.

Your problem is very typical of the fuel pump contact switch in the AFM not closing.  Usually this is due to low air flow through the AFM.  Are all of the hoses properly connected to the intake system?  PCV hoses and all others?  Are you using a 1975 AFM?  A 1978 AFM might not have the switch adjusted properly or might not have it at all.  Open up the new AFM and check the fuel pump contact switch.  You can bend the rod with a pair of pliers to make it close at lower or higher air flow.  Move the vane and you'll see how the very small contact points open and close.  They control power to the fuel pump relay.

[jlenownnab]

I bought the AFM last year, it is for a 75. I will check hoses and open AFM if I have to. It seems odd that one day it runs great and the next it doesn't. 

[Zed Head]

I had a brand new Motorsport Auto AFM have a problem with the contact switch.  Left me stranded, until I rigged up a bypass wire using a PO's leftover bypass wire.  A hair or a piece of lint or something must have got stuck between the contacts.  I used a match book striker to clean up the contacts and have been golden ever since.  Although, I've had several other AFM's in there in between.  It happens.  Might be why Nissan got rid of it in 1978.

You can check the AFM contact by turning the key to Run/On and opening the vane.  You should hear the pump run and/or the relay under the steering wheel click.  Easy check.

Edited March 15, 2018 by Zed Head

[jlenownnab]

Sounds good, thanks. Will do this morning.

[jlenownnab]

I want to let everyone know what I found, never know if it will help someone. I did all the recommendations from responses except open AFM. I wanted to verify fuel pump was getting power before anything further. Long story short.... when I replaced the negative cable on the battery I went ahead and unhooked the positive also. I then removed the battery for some cleaning. Unknown to me, when I put the battery back in and hooked everything up, a connector was slightly separated on positive cable. Ends up the fuel injection wiring runs to the positive and negative side of the battery. So happy to have it running again.