280Z Difficulty starting

[siteunseen]

Is the new fuel filter's arrow pointing toward the engine?  If it was starting right up before you did the things you mentioned it has to be something simple.  Are the thermo time plug and the coolant sensor plugs reversed at the thermostat housing or possibly the bullet connections?  Just guessing this morning, you seem to know what you are doing so I apologize for sounding pretentious. 

[Marios280Z]

Is the new fuel filter's arrow pointing toward the engine?  If it was starting right up before you did the things you mentioned it has to be something simple.  Are the thermo time plug and the coolant sensor plugs reversed at the thermostat housing or possibly the bullet connections?  Just guessing this morning, you seem to know what you are doing so I apologize for sounding pretentious. 

 No offense taken at all. I have thought about switching the thermotime switch and water temp sensor connectors. I believe they are OK a the bullet connector. They are color coded at that point, but  I will double check that with continuity check. The starting issue began before I did almost any work under the hood, however I cannot recall is it started before or after install of new fuel filter. When I installed it I paid attention to the IN/OUT marking on it, but I will go back and double  check my work.

 

This morning (car sitting outside over night, the temps were around 60 degrees this AM) I recorded a video of a start up with the AAR bypass, as I mentioned in the previous post. As expected with the extra injection of air the RPMs went up almost to 2000rpm. I then immediately turn the engine off and attempted to start it again (in the past when I did that once the car fired right up). Unfortunately this time the trouble was still there. This test proved that the AAR is NOT the root cause of the issue, however it also proved that my AAR may not be operating 100% correctly since I get low idle RPM when engine is not warm - I'm guessing that AAR is not opening all the way.BTW, I have removed the AAR bypass before I drove to work. Here is the video:

 

 

Let's get to the bottom of this guys...

[Zed Head]

 

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.

 

 

That last video was informative.  Did you "prime" the fuel system like you describe above or just try it with zero fuel pressure?  That would make a difference.

 

You're getting closer.  Working on these EFI systems is best done by being rigorous, detailed, and repeatable.  For example, my question about fuel pressure.  Can't tell if the latest video is different from the other ones.

 

Another thing to look at is the TVS (aka TPS).  It's the switch on the throttle body that tells the ECU the engine is at idle, so it can add a little fuel.  And are you starting with your foot off the gas pedal or are you pressing it?  These engines start best with no pressure on the pedal.  When the AAR is working correctly.

 

Also, the fact that you can run the fuel pump with the key alone (which you never explained, above) could indicate a wring issue.  Maybe your ACC circuit is enabled at Start and the voltage drop is weakening the spark.  Could be that the ballast resistor is incorrectly wired, with Start passing through the resistor.  Weak spark plus lean mixture = hard starting.

 

Lots of little things to look at, but any one or combination could be a contributor.  You didn't get the quick fix so it's time to open up the Engine Fuel chapter and start testing components.  Make a list of what's not right and post it (like the fuel pressure issue and the way power is supplied) and somebody might see something.

 

Here's a sample of what you'll find in the FSM.

[siteunseen]

I've thought that maybe your throttle plate is crudded up around the bottom and not letting any air pass by like it should, it affects idle.    

 

It may not help your current problem but cleaning all the electrical connections is always helpful.  You already know about atlanticz's tech tips so look at this, http://atlanticz.ca/zclub/techtips/electricalconnections/index.html

[Marios280Z]

That last video was informative.  Did you "prime" the fuel system like you describe above or just try it with zero fuel pressure?  That would make a difference.

 

Yes, I did prime the fuel pump like I described above.

 

Another thing to look at is the TVS (aka TPS).  It's the switch on the throttle body that tells the ECU the engine is at idle, so it can add a little fuel.  And are you starting with your foot off the gas pedal or are you pressing it?  These engines start best with no pressure on the pedal.  When the AAR is working correctly.

I have though about TPS, but have not look into it.I was a bit "scared" to remove it since EFI bible talks about some very specific way of reconnecting the switch, and I did not want to mess it up. I leave my foot off the until (only sometimes) the very end when I see that engine is sputtering and is almost there to catch it, then I give it gentle tap.Sometimes it works, others it doesn't. 

 

Also, the fact that you can run the fuel pump with the key alone (which you never explained, above) could indicate a wring issue.  Maybe your ACC circuit is enabled at Start and the voltage drop is weakening the spark.  Could be that the ballast resistor is incorrectly wired, with Start passing through the resistor.  Weak spark plus lean mixture = hard starting.

Not sure what kind of explanation you are looking for. As i stated above: "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." the fuel pump does not really run "run" with the ignition key in ON position. It looks more like it's getting energized just for a split of a second. I can definitely tell when pump is running when I disconnect the positive terminal from the starter and turn ignition key to start. As soon as I let go of the key I no longer hear the pump. As far as I know, and I can confirm with previous owner who never had this starting problem, the wiring on this car is all original and was not messed with, so I have hard time believing the ballast resistor is wired wrong. Dirty?-maybe. However, if the spark was week due to corroded/dirty wiring, I would most likely notice driveability issues other than just starting.

I've performed several tests form FSM in the cold start department and have not found anything incorrect. There is definitely more tests to run, like the TPS. I've looked at that graph form FMS to try and get some clues on what may be causing the issue.

 

 

I've thought that maybe your throttle plate is crudded up around the bottom and not letting any air pass by like it should, it affects idle.    

 

It may not help your current problem but cleaning all the electrical connections is always helpful.  You already know about atlanticz's tech tips so look at this, http://atlanticz.ca/zclub/techtips/electricalconnections/index.html

When I pulled out the AFM the other day  I got access to throttle plate. I used electrical connector cleaner and sprayed and wiped it inside. Got a lot of black grime out of there. I did that one evening and interestingly enough next morning the car started with a touch of a key! I was excited like a 5 year old in a candy store. later that afternoon when I was leaving work that car started nicely again- that was like Christmas in August. Unfortunately the next morning the problem came back as well as the following afternoon.  In all the cases I primed the fuel pump as described above (I do try to stay consistent with the way I do/test things and try to varied only one variable at a time). I also did NOT change/adjust anything between the day the car started and the next day when it did not. Later today when I come back from work I will post a video of the car starting correctly, just as a reference to what it is capable of. I will perform all electrical connections/grounds clean up as described in the atlanticzcar post. I have done some of it (battery positive cable terminal replacement, thermotime switch and water temp sensor connector replacement, as well as AAR and  CSV connector clean up.)

 

Thanks for your help guys, and please keep throwing ideas at me.

[Marios280Z]

Here is an exampe of how she starts up when she plays nice. This was caround 3 hours after I came back from wark. Engine wasn't hot, but it wasn't cold eithere, around 110 degrees according to the engine temp gage in tha car. I did prime the pump as before since the pressure was showing 0psi.

 

[Hodgimus-maximus]

There could be an issue in the afm. I can't remember exactly for the 78 but the 75 has a connection for one of the pins that kills the fuel pump when the vain isn't actuated. Does it look like the cover for the afm had been removed?

Sent from my iPhone using Tapatalk

[Marios280Z]

There could be an issue in the afm. I can't remember exactly for the 78 but the 75 has a connection for one of the pins that kills the fuel pump when the vain isn't actuated. Does it look like the cover for the afm had been removed?

 Are you thinking that the the fuel pressure drop may be caused by that possibly faulty connection in AFM? Or you're  thinking that it may be causing hard start issue? 

Answering your question, yes, the AFM has been opened few years back by the previous owner and adjusted according to some procedure. I can find the paper work he gave me for it and let you know what the source of the procedure was. Keep in mind that he has never had this starting issue. From what he told me he was trying to adjust rich/lean fuel mixture.

I have not had a chance to do any more testing and or ground connection cleaning last night so nothing to report.

[Hodgimus-maximus]

I'm think it might be causing the fuel pump to cut off intermittently during start up causing a hard start issue but like I said I can't remember when they switched over from the fuel pump cut off being controlled by the afm to being controlled by the oil pressure.

[siteunseen]

I'm 99.9% sure the '78s had the switch in the oil pressure sending unit.  He may have the wrong year oil sender or the wire could be loose or corroded.

 

From MSA;

 

Oil Pressure Sender, 70-2/77 240Z-260Z-280Z
Code:17-8001
Price: $47.30
Quantity in Basket: none

  Oil Pressure Sender, 3/77-84 280Z-280ZX-300ZX
Code:17-8003
Price: $59.95
Qua

[Marios280Z]

My oil sender looks like the one for 3/77-84 280Z. I do have that two prong connector, unlike the earlier Zs that have that single nipple. I have read somewhere (it might have been the EFI bible or some other forum post) that  I could trigger the fuel pump by setting ignition key to ON and moving the AFM flap passed the resting point. Is that not the case for my car because I have the trigger inside the oil pressure sender?

 

I have noticed in the past that the connector on my oil sender unit is oily, as if the sender itself was slightly leaking the oil through the connector portion of the sender (white plastic and the prongs). 

[Zed Head]

Here's the 1978 fuel pump control scheme.  BUT, back to my other point, this scheme does not provide power to the pump by turning the key On/Off as described earlier.  In a correct system you should not be able to "prime" the fuel system with the key.  

 

So you're studying something that has already been shown to be modified somehow.  OR, your oil pressure switch is bad, but this would just give power via two methods, one when the switch is open, and one when the switch is closed.  Neither scenario cuts power to the pump.  The Start circuit bypasses the control scheme anyway.

 

I see FSM avoidance.  It's not as bad as it seems, it's actually very educational and a good read.