contact cleaning?

[chaseincats]

41 minutes ago, Zed Head said:

Did you block the CSV?  Not really clear what "both hoses" means either.  Also, not clear what the problem is.  You mentioned a labored start, and a start up time/stutter, and a lower fast idle, but what would you like to be better?  You probably mentioned it in another thread, it seems like you've described it before.  Can't remember what car you have either.

I think that, generally, raw fuel in the intake manifold or cylinders will cause the engine to start up faster.  That's what the CSV is for, to squirt a load of raw fuel in to the manifold.  Might be that you have a weak spark problem instead.  Not sure.  Anyway, give fresh description of the problem and something might show.

Sounds good @Zed Head, see below:

Car: 1978 280z stock L28 motor

Problem:

• Long crank times after sitting overnight (>7 seconds of cranking before it will run).
• After starting, it can be restarted on the 1st or 2nd crank even if the car was only running for a second or two (the car doesn't need to warm up to achieve the 1st/2nd crank start).
• After sitting for a few hours/overnight the car reverts to the >7 second cranking time before a start

 

Done so far:

• Checked for low/slow fuel pressure - the fuel pressure gauge shot up to 38ish lbs almost immediately, so the fuel pump is good
• Installed brand new NGK plugs and wires (they were old anyway) - this didn't fix the problem.  (ignore the previous posts about capping hoses, that theory is busted).

The CSV is new and worked great in the winter, but is not being triggered now because of the warm weather. 

 

Observation:

• I noticed that by spraying contact cleaner into the fuel injector power connector after sanding them a bit (the connector that comes off of the positive battery cable), the car starts up on the first or second crank regardless of how long it had been sitting - however I need to keep doing this every few days or it reverts to the 7-10 second crank.
• I also tried the Ox-Gard recommended above which worked for a few days, but I am back to the 7-10 second crank until I clean and re-spray the contact cleaner on those connectors.

 

any ideas?

Edited May 30, 2019 by chaseincats

[Zed Head]

25 minutes ago, chaseincats said:

Observation:

• I noticed that by spraying contact cleaner into the fuel injector power connector after sanding them a bit (the connector that comes off of the positive battery cable), the car starts up on the first or second crank regardless of how long it had been sitting - however I need to keep doing this every few days or it reverts to the 7-10 second crank.

Are you positive that this is real?  Seems odd. 

Still not clear how exactly you blocked off the supply and return lines to the fuel rail.  Your problem really sounds like either an FPR that leaks down quickly or a bad check valve in the fuel pump.  Pretty common and slow starts in the morning are the symptom.  If you didn't get a good seal on your supply and return lines they could still be leaking.

In short, sounds like a fuel pressure leak-down problem.

[chaseincats]

It definitely is odd but it's been so consistent that I haven't ignored it.

I got vice grips and temporarily clamped the hoses that connect to the fuel rail on the supply and return side (didn't block off the metal lines specifically).

I spliced in an in-line check valve between the fuel filter and the rail a while back but that didn't change the starting issue (that should have been in the original post).

 

I'm not sure if somebody wired my car differently, but unlike other 280s, when I turn my key to 'on' not 'start' my fuel pump primes (I did this when I was testing the fuel pressure with the gauge).  Whenever I start the car, I usually turn it to 'on' for about 5 seconds to pressurize the rail but this doesn't affect the cranking issue which leads me to believe that its not a fuel rail pressure issue.

 

[Zed Head]

10 hours ago, chaseincats said:

I'm not sure if somebody wired my car differently, but unlike other 280s, when I turn my key to 'on' not 'start' my fuel pump primes (I did this when I was testing the fuel pressure with the gauge).  Whenever I start the car, I usually turn it to 'on' for about 5 seconds to pressurize the rail but this doesn't affect the cranking issue which leads me to believe that its not a fuel rail pressure issue.

"Primes" usually means that it activates for a few seconds then turns off.  

Kind of sounding like you might have some fuel pump relay problems.  The pump should not get any power until you turn the key to Start or the engine is running.  Relay testing is shown in the FSM.

[chaseincats]

8 minutes ago, Zed Head said:

"Primes" usually means that it activates for a few seconds then turns off.  

Kind of sounding like you might have some fuel pump relay problems.  The pump should not get any power until you turn the key to Start or the engine is running.  Relay testing is shown in the FSM.

Right - it turns on until the fuel pressure gauge gets to 38 then shut off after a few seconds.  If it's working (tried this a few times over the course of a few days and pressurized perfectly/within a second or 2 each time), why would the relay be a problem?

[Zed Head]

6 minutes ago, chaseincats said:

Right - it turns on until the fuel pressure gauge gets to 38 then shut off after a few seconds.  If it's working (tried this a few times over the course of a few days and pressurized perfectly/within a second or 2 each time), why would the relay be a problem?

Because it's doing something it's not supposed to be doing, even if it seems like a good thing.  1978 cars did not come with the priming function.  It's not working correctly, therefore it might have other problems too.

[Zed Head]

[chaseincats]

1 minute ago, Zed Head said:

Ah, so you're saying that its pressurizing in on where it should be - so maybe its not/or delaying pushing fuel through at 'start'?

[Zed Head]

No, I'm saying that it's not working correctly.  It might be shutting power off when you turn the key to Start.  I'm saying it's screwed up and wrong.

Edit - to be blunt and clear...(smiley face here).

Edited May 30, 2019 by Zed Head

[chaseincats]

44 minutes ago, Zed Head said:

No, I'm saying that it's not working correctly.  It might be shutting power off when you turn the key to Start.  I'm saying it's screwed up and wrong.

Edit - to be blunt and clear...(smiley face here).

lol fair enough.  Why would it start the car up immediately after it starts once.  I'd have thought that if its electrical it would have a sluggish start each time, no?

 

Edit - ive been looking through the FSM and your chart and am a bit confused - it says 3 out of the 4 situations where the key is in 'on' have the pump being actuated without putting the key to 'start.'  Am I missing something here (I'm not the best at electrical)?

Edited May 30, 2019 by chaseincats

[Zed Head]

The other three happen when the engine is running.  Either oil pressure or alternator current need to be present.  It is a confusing chart, because Nissan doesn't really describe that oil pressure causes the switch to open.  

[chaseincats]

18 minutes ago, Zed Head said:

The other three happen when the engine is running.  Either oil pressure or alternator current need to be present.  It is a confusing chart, because Nissan doesn't really describe that oil pressure causes the switch to open.  

I just got off the phone with my old Z mechanic (he exclusively does old Zs).  He was saying that depending on which AFM you have, some s30s turn the pump on when the key is in 'on' like mine is doing (with the car off).  I am assuming that he is referring to the 1978 air flow meter since only '78's afm had the fuel pump pin removed from the AFM by Datsun (I dont recall why).

 

Edit - it seems that 1978 came with two AFMs depending on when it was made.  earlier 1978 models share the universal 280z afm (7 pins) but some 1978 models share the 1979 280zx 5 pin model.  weird

Edited May 30, 2019 by chaseincats