1975 280z Electrical Issue

[Zed Head]

It's possible to install the oil pump drive shaft incorrectly, and that's what drives the distributor through the quill.  Happens often.  If you can move the plug wires so that #1 wire is where the rotor points under the cap that might do it for you.  Put #1 there then install the wires in the correct order, 1-5-3-6-2-4 counterclockwise.  Leave the distributor position where it is, it's correlated to the crankshaft position.  

It will probably start.  Maybe you'll get lucky and the dead cylinder just has a stuck ring.

Worth a shot.
 

[Barefootdan]

2 hours ago, Zed Head said:

It's possible to install the oil pump drive shaft incorrectly, and that's what drives the distributor through the quill.  Happens often.  If you can move the plug wires so that #1 wire is where the rotor points under the cap that might do it for you.  Put #1 there then install the wires in the correct order, 1-5-3-6-2-4 counterclockwise.  Leave the distributor position where it is, it's correlated to the crankshaft position.  

It will probably start.  Maybe you'll get lucky and the dead cylinder just has a stuck ring.

Worth a shot.
 

Excellent idea. I had it going for a couple seconds!!! But then it died...probably because I didnt replace the AFM back in line after spraying starter fluid. I assume that fixing the 180 off will make it run smoother/longer? Or should I continue to try and start as is for the time being

[Zed Head]

I would get all of your timing marks set to known correct positions then see where #1 should be and go from there.  The cam lobes/compression stroke/TDC and the damper pulley mark ( which should be zero at TDC), then put wire #1 where the rotor is pointing and set the remaining five accordingly.  It never hurts to reverify that things are correct.

I put my wires on backward rotation (clockwise) once and the engine still started and ran, but it ran really poorly.  I assume that a few cylinders still got spark close enough to make the engine go around.  #1 was right for sure but I never sat down and figured out which others got spark that would work.  But it "ran".

[Barefootdan]

17 hours ago, Zed Head said:

I would get all of your timing marks set to known correct positions then see where #1 should be and go from there.  The cam lobes/compression stroke/TDC and the damper pulley mark ( which should be zero at TDC), then put wire #1 where the rotor is pointing and set the remaining five accordingly.  It never hurts to reverify that things are correct.

I put my wires on backward rotation (clockwise) once and the engine still started and ran, but it ran really poorly.  I assume that a few cylinders still got spark close enough to make the engine go around.  #1 was right for sure but I never sat down and figured out which others got spark that would work.  But it "ran".

Timing is definitely way off. When the distributor points to the real #1 plug location, cylinder #6 is at TDC. Looks like the previous owner had it backwards.

I tried looking for my cam timing mark, but I dont see the same Camshaft Gear Sprocket as in the FSM. Mine has 3 view points, not 4. Regardless, at TDC for cylinder #1, no view point is at the top to let me see the timing mark on the cam. Is there another way to time this? I'll search in the meantime.

I see some high temp gasket maker in random spots, so someone has definitely been in here. The came bolt is also chewed up. Definitely going to get a new one. 

Bright side, I got it running! Sounds like a tractor probably due to the cylinder 3 issues and timing being so bad. But it was running! I was able to keep it alive for nearly a minute by having the throttle cracked a hair. I needed to adjust the idle screw but it died before I could grab my flathead. 

Thank you all for the help. My next steps will be to re-time the engine in hopes it runs smoother. Then we can dive into the cylinder 3 issues. 

 

[Zed Head]

4 minutes ago, Barefootdan said:

I needed to adjust the idle screw but it died before I could grab my flathead. 

The idle speed screw uses a Phillips, but the screw head is so big that you can actually turn it by hand/fingers.  It's not the idle air adjustment screw in the AFM.  Leave that one alone.

[Barefootdan]

14 minutes ago, Zed Head said:

The idle speed screw uses a Phillips, but the screw head is so big that you can actually turn it by hand/fingers.  It's not the idle air adjustment screw in the AFM.  Leave that one alone.

Interesting, mine looks to be flat head. I can snap a photo later to ensure it is the right one. But it is big and has knurling to grab by hand. 

[Barefootdan]

Also, I was rummaging through the box of parts that came with the car and I found the OE cam and crank sprockets. They look rusted as can but no major signs of damage. Maybe they replaced these when doing the timing chain as preventative maintenance? 

anyways, the OE has the 4 holes and a clear timing mark. Mine has 3 which looks like a Cloyes S462 Sprocket below:

 

 

I see no timing marks, so I may need to resort to counting links. Can this be done with only the valve cover removed? 

[Zed Head]

34 minutes ago, Barefootdan said:

Interesting, mine looks to be flat head. I can snap a photo later to ensure it is the right one. But it is big and has knurling to grab by hand. 

75 was the first year of EFI.  Might be that they changed it later.

Looks like it's either on mine.

Edited March 24, 2021 by Zed Head

[Barefootdan]

I got the distributor aligned correctly now. Only took a couple tries thankfully. 

New issue!! Got it started again today and ran it for about a minute before cutting it on purpose (no coolant yet, dont want to overheat). I went back to crank it and it doesnt even try to get going. This is the second time after the initial start that it wont run. It seems like sitting overnight is the only way to get it going. After that, its just endless cranks.

I unplugged the injectors, gave it WOT, and it will run for a few seconds before sputtering out. My thought is it is getting flooded. But even after re-connecting the injectors, its a no-go. I unplug the injectors again, runs for a couple seconds. rinse and repeat. I can only get about a handful of attempts before my poor battery gives out and I need to wait for the charger to give it back some juice. Thoughts? 

[Zed Head]

If there's no coolant in the engine it might be that the coolant sensor is getting "steamed", and showing 212 F , from condensing steam, instead of the true temperature.   So when you try to restart it's too lean.  But that doesn't explain the WOT starting procedure.  Not sure what's happening there.

You can run straight water with no problems.  Are you missing a radiator or something?

Another possibility is that the ECU is going bad.  I mentioned this earlier but that's one way that they die.  They flood the engine to begin as they start to die, then eventually they just don't do anything.  I had a 78 ECU do that.  It died while I was out testing it, then restarted, then died twice more as I tried to get home, then wouldn't start at all.  I put the stock ECU back in and the engine cranked right up.  Never really figured out what was wrong with it but I assume that something inside overheated due to current flow. 

You'll find a bunch out there about ECU's running rich due to bad solder joints.  One quick fix is to bang on the side of it.  Apparently that really works.

Your 75 is the first year of the ECU's so might be the most likely to do that.  If you can find a loaner or a cheap one to buy, it's always good to have a spare.  Any of the 75-78 ECU's should work.

[Barefootdan]

On 3/25/2021 at 7:54 PM, Zed Head said:

If there's no coolant in the engine it might be that the coolant sensor is getting "steamed", and showing 212 F , from condensing steam, instead of the true temperature.   So when you try to restart it's too lean.  But that doesn't explain the WOT starting procedure.  Not sure what's happening there.

You can run straight water with no problems.  Are you missing a radiator or something?

Another possibility is that the ECU is going bad.  I mentioned this earlier but that's one way that they die.  They flood the engine to begin as they start to die, then eventually they just don't do anything.  I had a 78 ECU do that.  It died while I was out testing it, then restarted, then died twice more as I tried to get home, then wouldn't start at all.  I put the stock ECU back in and the engine cranked right up.  Never really figured out what was wrong with it but I assume that something inside overheated due to current flow. 

You'll find a bunch out there about ECU's running rich due to bad solder joints.  One quick fix is to bang on the side of it.  Apparently that really works.

Your 75 is the first year of the ECU's so might be the most likely to do that.  If you can find a loaner or a cheap one to buy, it's always good to have a spare.  Any of the 75-78 ECU's should work.

Long weekend and made tons of progress. There is no radiator, so cant fill it up with anything yet. But I was able to get it started easy everytime. Not sure exactly what the issue was, but I did fix the dizzy timing and now she runs great...for 5/6 cylinders. I verified I am still not getting compression in #3, and thats after the valve adjustments and running it for a handful of 1-minute runs. So off with the head!

Glad I did so, nearly every bolt minus the head studs were not torqued. Maybe this is a blessing in disguise as taking the manifolds off was cake. No seized bolts, which was my big worry. The coolant passages are rough too so I am glad I took this off. I think I will start a build thread, but this thread deserves some pics first!

Here is the block with the head off. Everything looked good, gasket was fairly fresh (i think) and no major issues that I spotted. Cylinder #3 was the problem child and I expected a larger "kiss" from the valve than what is there. I noticed that Cylinder #1 actually has a bigger impact from the valve. but it had compression. Now is my time to start thinking of how I want to approach this build. It will always be a weekend car, never tracked or daily. I am leaning towards a cam, headers, and maybe flat top pistons. I want to stick with the original EFI for now for cost, so I'll need to keep that in mind with my cam choice.

 

[Zed Head]

How about a shot of the bottom of the cylinder head?  You can stand them on end, they'll balance.

Seems like somebody over-revved, or had some stuck valves in the past, or didn't get their cam timing right during install.  The dings are covered with soot so they're not fresh.

Check your cylinder head number too, see if it's an N42, that would have come on a 75 engine.