280Z Difficulty starting

[Marios280Z]

Hi all, new guy here. I will take this opportunity to introduce myself and my car.

 

About me

My name is Mario, I live in Cedar Rapids, IA. I'm in my low 30s (for those who care), I like to work on cars, but I don't have a whole lot of detailed experience, however I'm very willing to learn. In early April igot the car (I wasn't necessarily looking for one, it found me). I've knew about 2X0Z for a while (my father in-law has two of 240Z sitting in his backyard rusting away ) but when this deal came I could not refuse.

 

About the car

1978 280Z, 59,XXX miles when I got it. Original, survival (I have all the original paper work including signed contract from the dealer and window sticker). Never saw snow, rarely  any rain. Previous owner had it for over 25 years and drove it maybe a 1000 miles a year. Always garaged. Few things he did to car: lower suspension with Tokico springs and adjustable shocks, big brake kit upfront, SS brake lines,cold air intake, newer spark plug wires, 2.5" exhaust form MSA, including down pipe and all the way to turbo muffler. Other than that all was stock, including all the engine gaskets! 

 

What I did when I got the car

Replaced the fluids: engine oil and filter, rear diff, MT oil, coolant. replaced the spark plugs with with the stock NGK ones, replaced fuel filter, distributor cap and the rotor, replaced battery cables, installed new 16x8, 0 ofset XXR513 black/silver wheels that came with the purchase.

 

The issue

I have hard time starting the car after it sits for a while (for example a day at work). The car did not have this issue when I first got it, but slowly it developed it. One point to mention is that it started BEFORE I did any part replacement under the hood. Here is the link to a youtube video of wha the car does. Sometimes it is more sever, sometimes it is less sever:

One additional point to mention is that the RPMs are typically low for "cool start". I would expect the RPMs to sit around 900-1000 when the engine is warming up and slowly come down to 700-800 rpms. It's as if the engine does not recognize the "cool start" and perhaps does not go into fuel enrichment period.The starting issue is there regardless of the outside temperature. It could be 85 or 60 degrees, still acts the same. Based on what I noticed this morning when I sarted the engine I'm thinking it has something to do with the air delivery. Right after I started the car (RPMs were hovering around 700) I went in and unplugged the vac hose between intake manifold and fuel pressure regulator. As soon as I unplugged it at the FPR and left it opened (therefore providing more air to the system), the engine reved up to around 800-900rpm. When I plugged the vac hose with my finger engine would drop rpms. After few minutes of running, this drop and rise of rpms was much lesser, if any at all.

 

Here is what I did for troubleshooting so far

I do have EFI bible and the Service Manual and  I actually have performed quite a bit troubleshooting in the cold start department: replaced water temp sensor as well as water temp sensor connector, cleaned thermotime switch and replaced its electrical connector. I performed continuity/resistance/voltage tests as described in Service Manual at the ECU for water temp sensor, themotime switch, Cold Start Valve, and Auxiliary Air Recirculating valve. All checked out OK, unless I misinterpreted the results. I pulled out CSV, cleaned it externally and cleaned its electrical connector. I pulled the AAR valve and made sure that the internal flap was moving freely. I took out Air Flow Meter and made sure the flap was moving freely. I wiped it inside. Having AFM out gave me inside look at the throttle body, so I sprayed some electrical connector cleaner and wiped it clean (there was actually quite a bit black gunk that came out)...the starting problem persists.The fuel pressure is not maintained in my system. I installed inline fuel pressure gauge right after the fuel filter. The pressure drops to 0 after few hours of car being off. However, before I crank the car I prime the fuel pump by turning ignition to ON/OFF position 4-5 times, until I see that pressure gauge reads around 31 psi. Even then I still get the problem. ...I started to run out of ideas.

 

​What else can it be? One of the comments in my youtube video says it could be a vapor lock. If so, what could cause this vapor lock?

 

Beside this starting issue I believe car drives well (I say believe, because I have never driven a Z so I don't have a benchmark to compare to). It feels like it pulls all the way through the RPM range. The only other thing I have noticed is that when I drive it harder I get slight afterfire when up shifting 1-->2 and 2-->3 gear.

 

Help...

Edited August 5, 2015 by Marios280Z

[Zed Head]

What I did when I got the car

Replaced the fluids: engine oil and filter, rear diff, MT oil, coolant. replaced the spark plugs with with the stock NGK ones, replaced fuel filter, distributor cap and the rotor, replaced battery cables, installed new 16x8, 0 ofset XXR513 black/silver wheels that came with the purchase.

 

The issue

I have hard time starting the car after it sits for a while (for example a day at work). The car did not have this issue when I first got it, but slowly it developed it. One point to mention is that it started BEFORE I did any part replacement under the hood. 

 

One additional point to mention is that the RPMs are typically low for "cool start". I would expect the RPMs to sit around 900-1000 when the engine is warming up and slowly come down to 700-800 rpms.

 

Right after I started the car (RPMs were hovering around 700) I went in and unplugged the vac hose between intake manifold and fuel pressure regulator. As soon as I unplugged it at the FPR and left it opened (therefore providing more air to the system), the engine reved up to around 800-900rpm. When I plugged the vac hose with my finger engine would drop rpms. After few minutes of running, this drop and rise of rpms was much lesser, if any at all.

 

The pressure drops to 0 after few hours of car being off. However, before I crank the car I prime the fuel pump by turning ignition to ON/OFF position 4-5 times, until I see that pressure gauge reads around 31 psi.

 

 The only other thing I have noticed is that when I drive it harder I get slight afterfire when up shifting 1-->2 and 2-->3 gear.

 

Help...

In the video the RPM went to 1000 after it started and it didn't sound too bad.  Doesn't fit your description.  It does sound like you might have a starter problem though.  It seems to be letting go before the engine starts.  Oddly, a 1978 parts car that I had would do the same thing.  You had to keep trying until it would catch.

 

The RPM increase with a small vacuum leak is normal.  

 

Your fuel pressure readings seem low but it's not clear what you're doing.  I don't know why the pump would get power just from turning the key ON/OFF.  The pump shouldn't run unless you hit Start, or the engine is actually running.

 

Get the engine running, and take the hose off of the FPR again.  Then read the fuel pressure.  That will tell you about your fuel pump and FRP.  Or take off the small wire from the starter solenoid and turn the key to Start.  That will run the pump, but not the starter.

 

One last thing - you said that you confirmed that the AAR flap was moving freely but you didn't say that it was open when cold, and closed when the engine is warmed up.  If it doesn't move, then there's no idle speed increase when cold.  Basically, it's not doing anything.  You can apply 12 volts directly to the two pins if you want to verify it's closing.  It only takes about a minute.

[Marios280Z]

In the video the RPM went to 1000 after it started and it didn't sound too bad.  Doesn't fit your description.  It does sound like you might have a starter problem though.  It seems to be letting go before the engine starts.  Oddly, a 1978 parts car that I had would do the same thing.  You had to keep trying until it would catch.

 

ZedHed, you are right, in that video the RPM went to 1000. That's becuase I had my idle screw artificaly set to high so thtat during the start engin would run at higher RPM. That in turn casued increased RPM during idle once the engine warmed up. I have another vidoe over here that shows lower RPM:

 

 

That's interesting theory about the starter. I don't have a problem starting it at any other times. Perhaps I just let go before the engine catches because I feel like I'm dragging the starter.

 

Regarding fuel pressure. When I unplug the vacume hose, the pressure goes up to around 38-39 psi. I have found on one of the forums few people saying that 31/32 with the vac hose ON and 38-39 without the vac hose at idle is normal. Service manula talks about 36psi...

Every time I turn key to ON, the fuel pressure increased by around 8-10psi, that's why I do it few times to get up to around 32. I have unplugged the starter and turn the ignition key to start, at which point I could actually hear the pump running.

 

What I did with AAR is I removed it and put in in the fridge for few minutes. When I pulled it out the flap was 3/4 way open. Not sure if it will ever fully open from what I saw in a AAR fix DIY found on atlanticzcar website. I have not warmed it up to see if it would actually close the flap.  I can try and do that.

 

Any other suggestions?

[Zed Head]

ZedHed, you are right, in that video the RPM went to 1000. That's becuase I had my idle screw artificaly set to high so thtat during the start engin would run at higher RPM. That in turn casued increased RPM during idle once the engine warmed up. I have another vidoe over here that shows lower RPM:

 

What I did with AAR is I removed it and put in in the fridge for few minutes. When I pulled it out the flap was 3/4 way open. Not sure if it will ever fully open from what I saw in a AAR fix DIY found on atlanticzcar website. I have not warmed it up to see if it would actually close the flap.  I can try and do that.

 

Any other suggestions?

IF we redefine your issue from "difficulty starting" to "low idle after starting" or "high idle after short warmup" then the problem is most likely the AAR.  IT's supposed to be almost completely open at normal cold engine temperatures, like anywhere from 30 - 90 degrees F, then close slowly as it warms up.  It actually has an electric heater inside to make sure it closes within a short amount of time.

 

I would pull the hose from the AAR and see where it's at engine cold.  If it's closed already, you have a problem.  They can be adjusted.  Maybe someone messed with yours already.

[Marios280Z]

Well,let's revisit the AAR. I installed bypass to AAR.See picture.will report tomorrow if it works.

[Zed Head]

Numbered my edits

 

3.  Actually, I'm not sure what will happen with that setup.  Looks like the AAR is directly to air.  You'll get a lot of unfiltered air if it's open, might get the high RPM.  Or you'll get nothing if it's closed.  The loop on the throttle body to the big hose probably has no affect.

 

2.  Moved to front!~ - BUT.  Your picture shows that you completely bypassed the throttle blade.  The engine might go to sky-high RPM right away.  Don't start it like that.

 

 

1.  Aacck...

 

The AAR can't be bypassed without having the idle speed problems.  All cars, even carb'ed cars, have devices to increase idle speed for a minute or two until the combustion chambers get warm enough to work right.

 

Your idle speed with the bypass can either be set to have a very low idle RPM that needs throttle pedal action to stay running, or it can be set with a good cold idle that gets too high after it warms up.

 

If nothing changes though, you'll know the AAR wasn't working.

Edited August 6, 2015 by Zed Head

[Zed Head]

Did that hose nipple on the big hose have a plug on it or was it open to air?  It should be plugged, I believe.

 

Anyway, I think that your problem is a simple one, don't do anything crazy like adjust the AFM or change timing or what you showed in that picture.

[Zed Head]

I looked in the FSM and see what you did in your picture and where your hose ends are.  Sorry, I couldn't tell what you were doing.  My mistake.  Haven't looked at AAR connections for a while.

 

 

All that "bypass" will do is confirm that your AAR was never opening or closing,  Not moving at all.  All you've done is open the passage permanently.  You'll be stuck with an idle that's too low, then gets right, or just right then gets too high.  Best to fix the AAR.

 

Sorry for the mess of posts.

[Marios280Z]

I'm not sure where your concern is coming from Zed Head. Right now it is isolated (air wise) from the engine. When the AAR is operating correctly during inital start up and is wide open, than it acts exactly like the hose I connected. The one end of the hose is connected before the throttle body to pick up the air, just like the AAR assembly does. Then istead of flowing through the assembly: the rubber hose--->metal pipe--->again to a short rubber hose---> to AAR valve---> to another short rubber hose--->to the emettal niple---> into the intake manifold PASSED the throttle body, I simply connected the two points prior to throttle body and passed the throttle body with just a continues hose. I was NOT going to drive it this way. I was going to ONLY start in the mornig to see how it would go. There is no signal to the ECU from the AAR at all, as you know.It's a dumb air passage with heating element to close it when things get warm.

"2.  Moved to front!~ - BUT.  Your picture shows that you completely bypassed the throttle blade.  The engine might go to sky-high RPM right away.  Don't start it like that." That's exactly what the AAR does, it bypasses the throttle blade. From the EFI Bible:

"You know that idle speed can be raised by simply bypassing throttle plate. During warm up, we do exactly that by using an air valve, called an Auxillary Air Regulator.(...)When the engine is cold the valve is open;so when the engine starts, ari can bypass the throttle plate and go through the valve."

 

I'm not sure what you mean by: "Did that hose nipple on the big hose have a plug on it or was it open to air?  It should be plugged, I believe."

[Marios280Z]

Ha, you must have posted your last message as I was writing my response No biggy.  I will let you know tomorrow if bypassing AAR helped to start the engine right up.

 

Does anybody have any other idea what may be happening here? looks like we have a lot of audience Zed Hed,but nobody is pitching in

[Zed Head]

It's early.  

 

I would put more in to your description of "difficult starting".  Do you mean that you have to try two times?  Or that it idles poorly for 1/2 second?  The sputters, before it dies?  Because really, it seems to start pretty quickly.  How does it start when it's warmed up?  Is this only a cold start problem?  The more details on the actual problem, the better.

 

 

If you want to mimic what the AAR would do, open the idle screw up so that when it starts the RPM sit at 1200 RPM, engine cold.  You can do this in one shot, the engine won't heat up that fast.  Start it, adjust the idle screw, turn it off, restart.  See if it starts the way it used to.  If it starts fine, but the idle never drops, then it's not a starting issue, it's an AAR issue.

[Marios280Z]

It's early.  

 

I would put more in to your description of "difficult starting".  Do you mean that you have to try two times?  Or that it idles poorly for 1/2 second?  The sputters, before it dies?  Because really, it seems to start pretty quickly.  How does it start when it's warmed up?  Is this only a cold start problem?  The more details on the actual problem, the better.

Yes, the fact that I have to try 2,3, sometimes 4 times before the engine catches, the fact that it sputters before it dies, and the low idle on start up.  I will take a video of how it starts when it is warm (with a touch of a key). I'm also concerned that if I don't get to the bottom of this I will have a heck of a time starting it when the temps start dropping to 40s and 30s (note,  I will not be driving it in the winter). Also, one time I have started it cold (with the typical trouble, so it took me couple of tries), and about 2-3 seconds after it finly started I turned it off. Then attempted to start it again and the enging started right up...Not sure if it was just a fluke or what. Next time I encounter the difficulty I will repeat this test to see if it will start right up or not.

 

Another point  I should mentioneis the CSV test I performed. I pulled the CSV out of the intake manifold and put it in the jar. I had my wife crank the engine (when cold). There was no drop of fuel coming out of the CSV. Granted, it was about 85 degrees outside, so I don't know how valid the test was. I think the FSM talks about the upper temp limit for the thermotime switch being 70 degrees. At that point I also checked the wire continuity between the CSV connector and the thermotime switch and it was OK. On the other hand I  had peopl tell me that they have entirly removed the CSV from their Z cars and never had problems starting even in cooler temps.

 

You have a good point with that idle screw. But for tomorrow morning I will try with the AAR bypass.