280z not starting after rebuild

[Kelson]

Hello all!

This is my first post on this forum so feel free to welcome me or whatever :-).  I've got a very strange problem with my 280z that I have had no luck solving.  So a little information about this car.  The motor was running at one point (of course) before my father in law pulled it for a rebuild.  there was not a need to rebuild it, but he was working on restoring the car so he rebuilt the engine. The motor went back into the car (all stock except for some tube headers) and hasn't really ran since.  Eventually my father-in-law lost interest in the project and ended up giving the car to me. Now I'm trying to get it on the road before the end of the month because I'm getting kicked out of the garage that it is currently in.  

 

So here's the details of the problem:

Motor turns over, so that's good.  

Checked the compression across all the cylinders, no problem there.  

Fuel? maybe or maybe not but I'll worry about that after I get the spark working well.  

Spark? sometimes intermittently

 

Basically I'll crank the motor and with everything wired up like stock I get 10V to the coil + terminal (after the ballast resistor).  No spark from the coil though.  I tried everything with a good coil out of my truck, no difference, so I've ruled out the coil as the issue.  I checked the connection between the coil and transistor ignition unit it was good.  Transistor ignition unit gets power as well.

 

If I bypass the ballast resistor by putting a jumper wire from battery + to coil + terminal, I get some activity from the coil but it is very strange. I'll crank the motor and get no spark but when I stop cranking the coil fires continuously and the fuel injectors fire too.  You can see this behavior and hear the fuel injectors firing in the video bellow.  The spark plug is hooked up directly to the coil-to-distributor jumper.

 

https://www.youtube.com/watch?v=r3HfOv-vkMI

 

additionally with the ballast resistor bypassed I do get random fires in the cylinders but they are not consistent.  You can see in the video bellow here the motor trying to start.  The fuel injectors may or may not be firing I'm not sure.  Starting fluid was sprayed into the intake manifold for this to ensure that there was fuel provided to the motor.  

 

https://www.youtube.com/watch?v=_2On-__gsP4

 

So yeah any help would be great! like I mentioned before the motor came out and was put back in be someone other then me.  The wiring is a mess but all the important bits seem to be connected, but I don't know, maybe not?  could be something simple that I don't know to look for.  I'm pretty good with cars but this is my first datsun.  

 

 

 

 

 

 

 

[datzenmike]

Welcome to Ratsun Kelson

 

'79 would be a 280zx unless you mean any year below that then a 280z.  I'm not aware that a ballast resistor was used on a transistor ignition.

 

 

Those do not look like NGK plugs. This won't stop it starting but L engines run better with the factory plugs.

 

Take the cap off and watch while cranking it over. Does the rotor turn?

 

 

Set engine to TDC on #1 plug... look at rotor. Is it pointing to the #1 plug wire on the cap above it? 

[Doctor510]

Check the plugs wires for proper firing order, COUNTER CLOCKWISE, 1-5-3-5-2-4 You have some wrong plugs, use the 11 series. BP6ES-11 NGK or BPR6ES-11

[Kelson]

Welcome to Ratsun Kelson

 

'79 would be a 280zx unless you mean any year below that then a 280z.  I'm not aware that a ballast resistor was used on a transistor ignition.

 

 

Those do not look like NGK plugs. This won't stop it starting but L engines run better with the factory plugs.

 

Take the cap off and watch while cranking it over. Does the rotor turn?

 

 

Set engine to TDC on #1 plug... look at rotor. Is it pointing to the #1 plug wire on the cap above it? 

 

 

Thank you, you are right, it is a '75.  just a typo, my bad.  I believe a ballast resistor is used.  it is pictured in the repair manual that I have and I'm not sure how it would end up in the car if it wasn't original to the car.  anyways it doesn't work with the ballast resistor or with the resistor bypassed so I think that is unlikely the problem.  The plugs came with the car, they may not be correct but they are brand new.  like you said they should still work (even if not the best).  rotor definitely turns.  I also tried two different brand new distributor caps.  either way I'm not getting consistent spark from the coil while cranking as you can see in the video.  I'm pretty sure the timing is set correctly, but i will confirm this.  But since so spark is coming from the coil it would not be the source of the problem.   Other ideas?

 

 

Check the plugs wires for proper firing order, COUNTER CLOCKWISE, 1-5-3-5-2-4 You have some wrong plugs, use the 11 series. BP6ES-11 NGK or BPR6ES-11

 

spark plug order is correct but no consistent spark from coil so.....

[banzai510(hainz)]

dude dont crank the motor that long !!!!!!!!

 

if going to start its going to start.

 

ck spark at the coil wire thats went to center dist cap not at end of spark plug. If spark then coil is good and maybe dist installed wrong dist was installed wrong.

[Kelson]

dude dont crank the motor that long !!!!!!!!

 

if going to start its going to start.

 

ck spark at the coil wire thats went to center dist cap not at end of spark plug. If spark then coil is good and maybe dist installed wrong dist was installed wrong.

 

no spark from coil, no spark from coil, spark plug in video is attached strait to the coil, no spark from the coil. distributor irrelevant. 

[HRH]

Check the connector that goes to the water temperature sender on the thermostat housing.  They often times break or wiggle just off of contact.  If the ECU doesn't have that information, it won't run.

[Kelson]

Check the connector that goes to the water temperature sender on the thermostat housing.  They often times break or wiggle just off of contact.  If the ECU doesn't have that information, it won't run.

 

interesting.  That's the kind of information I'm looking for.  I will check to see if this is the problem later today.  

[banzai510(hainz)]

I was at Schucks once and a guy had a 810 with the FI motor. Sounded like NO spark also.

Found out there was a wire going to the + side battery that fell off and once hooked back up ran fine.

 

temp send wire broke ECU wont run? Crap I hate shit like that

[Kelson]

I was at Schucks once and a guy had a 810 with the FI motor. Sounded like NO spark also.

Found out there was a wire going to the + side battery that fell off and once hooked back up ran fine.

 

temp send wire broke ECU wont run? Crap I hate shit like that

 

any thoughts on what that wire was to?  I've got 1 big wire the the starter (alternator is wired to the starter terminal) and 1 small wire that disappears into the wiring harness.  I assume this goes to the key ignition switch since I have power there.  everything seems to power on properly with the key.  fuel pump, lights, power to injectors, power to ballast resistor ect....

[Draker]

Do you have continuity though the ignition module?

[Kelson]

Do you have continuity though the ignition module?

 

Could you elaborate on this?  continuity through which terminals?

[Draker]

The ignition module on the dizzy. It should have two prongs forming a T. 

[Kelson]

The ignition module on the dizzy. It should have two prongs forming a T. 

 

Sorry, this might be a stupid question.  I'm not familiar with all the different ignition systems on these z cars.  the dizzy on my Z has two hall-effect sensors wired to an "transistor ignition unit" under the passenger side dash.  Would this setup still  have the ignition module on the dizzy like you said? I don't remember seeing one. 

[Draker]

Sorry, this might be a stupid question.  I'm not familiar with all the different ignition systems on these z cars.  the dizzy on my Z has two hall-effect sensors wired to an "transistor ignition unit" under the passenger side dash.  Would this setup still  have the ignition module on the dizzy like you said? I don't remember seeing one. 

 

And I might be talking out of my ass. I'm not a Z person. :) At least... not this type of Z person.

[KoHeartsGPA]

Step 1: get service manual, and find the wiring diagram corresponding to your car.

Step 2: trace EVERY wire and verify they are connected to the corresponding circuit.

Step 3: if step 1&2 are done correctly, check for loose/broken terminals.

 

That's how I resolved my no spark issue, turned out to be a broken terminal to the + of the coil, at simple eye view it looked good, when I started pulling on wires it was revealed, most of the time it is something silly when all major components are properly installed....

[Kelson]

And I might be talking out of my ass. I'm not a Z person. :) At least... not this type of Z person.

 

Haha, Ditto. I'll check for the ignition module when I go work on the car later today.  

[dgi]

4 positions on the resistor, right?   From above looking over the fender, left to right.

 

+12V Ignition circuit input ------   +12V Starter circuit input ------ resistor output to coil +  -------  blue wire from coil -

                                                                                                    also to radio suppressor          goes to ignition module

                                                                                                    

Reverse those last two and you get similar symptoms, may try to fire when you release the starter.

[Kelson]

I found my problem!  3 wires from the distributor hall effect sensors were not attached to the terminal block by the fender. They got lost in they mess of wires.  So basically the transistor ignition unit did not have a timing signal.  Now the engine fires and runs but runs very poorly.  It is breaking up, backfiring and wont stay idling.  I'll begin checking on this problem tonight.  I know this may be any number of things, mechanical timing, spark plug gap, vacuum leaks, fuel pressure, bad grounds ect...  I will post more questions here when/if I have them.  In the mean time any suggestions on what specifically to look at would be appreciated.  Thanks everyone.  

[datzenmike]

These don't cost anything and best to confirm than to chase some other thing only to find out later it was a tight valve.

 

Check valve lash when hot.

Re-check timing and plug order

[Kelson]

Today I found damage to my coolant temperature sensor.  as I understand it this will cause it to run very rich. I bought a new sensor and will install it tomorrow and see where that gets me.  

[Kelson]

Today I got through some more trouble shooting.  I confirmed that all the mechanical timing is synced up.  Crank, Cam, distributor.  I also checked valve lash which was good.  I replaced the water temperature sensor.  I did find a major problem though.  Fuel pressure is very low. On the gauge I hooked up it reads about 15psi.  I'm not sure if the problem comes from a bad pump or a bad regulator.  i have an aftermarket adjustable FPR that I will be putting on tomorrow to see it that fixes it.  In the mean time I have a couple of question for you guys.  

 

when the ignition is turned to on the fuel injector and the coil fire intermittently.  I took this video so you can seen.  Mostly you can hear the fuel injectors clicking but if you watch the needle you will see the pressure dip slightly every time the injectors fire.  I find this behavior very odd.  any Ideas on what might be causing it?

 

 

 

I also have some mixed up wires that I'm hoping to get sorted out.  all the wires around the thermostat got mixed up.  I'm hoping somebody will recognize something so I don't have to check the connection of every single wire.  

 

first I have one connector to the left side thermotime switch.  this was connected when I got the car. this connector runs to two white wire with bullet connectors.

 

 

 

Next I have a connector that looks identical to the first but is hooked up to the temperature sensor.  They are the same connector which is why I'm worried they may have gotten mixed up at some point.  this connector runs to a splice covered in heat shrink so I'm unsure of the wire colors

 

 

Next I have this nice mess of wires.  The yellow goes to the temperature sensor for the gauge.  

 

 

Lastly I have these nice blue and brown wires with bullet connectors.  they aren't connected.  I'm not sure what they are to. 

 

 

Oh yeah and this is broken.  is this what the unpaired wires are to?

[dgi]

This link may be of some help to you

http://elfecc.no-ip.info/280z/1975_%20280z_FSM.pdf#page=164

You may have to blow it up some, but you can see the thermostat housing expanded with the three sensors.  The rear most one should have two wires coming out of it and they have bullet style connectors.  I don't know the colors right off.  I'll check when I get home to my color coded chart.   But, I believe the pair that you show are the ones that originally connected to the water temperature sensor, go into the EFI harness, into the cabin and to the ECU.

 

If the water temperature sensor is not connected, it will not prevent the engine from starting.  Likely will make it run rich at operating temperature though.

 

On the front of the thermostat housing, facing it, the right most sensor is the one that feeds the instrument panel, and it should have one yellow wire connected to it.  That wire goes into a wrapped harness that feeds over to a round connector near the driver's side front corner, back across the front of the car, down the passenger side, into the cabin harness and eventually feeds the temperature gauge.  This sensor should only have one male bullet style connector on it.

 

On the front of the thermostat housing, facing it, the left most sensor is the thermotime switch.  It should have a rectangular connector containing two leads.  This controls the cold start valve to provide the engine more fuel during startup.  It should time out after key on in about 20 seconds and the cold start valve stops operating.  This functions like the "choke" system on old carburetor style fuel systems.

 

Fuel pressure may be the cause of your running problem.  The '75 spec for the EFI system is 36.27psi.  The fuel pump runs on the starter circuit, and then when cranked and the switch falls back to ignition on, a sensor in the air flow meter then tells the pump to keep pumping to maintain pressure.  If not enough air flow is sensed, that sensor cuts the pump off. and the engine stumbles and dies. Trouble shoot that by propping the air flow meter open slightly with a screwdriver.

 

1975 280Z Factory Service Manual  --->   http://elfecc.no-ip.info/280z/1975_%20280z_FSM.pdf