Ignition help needed on '78 280z

[Zed Head]

If there is power to the coil and the engine turns over it should start or at least pop a few times, assuming that everything else is right.

But, I think that you need to tell us the whole story of the car.  You're starting in the middle and there are many things that could be wrong.  You could spend weeks on here, giving small details, when there is something simple that will solve the problem.  Tell us a story.

It's not clear that the engine has ever even run one time.

[jrod81]

My apologies. Yes, the car has run fine in the past and even ran well up until a month or so ago. Then I started having issues with starting the car. It would crank and wind over but not start.  Just shotgunning around i decided to jump the fuse box from the ignition to battery and the car fired up (i read somewhere or someone told me i can't recall). Now my current situation is that it winds over and cranks same as it did before, however, jumping the fuse box no longer works  I do not think that it is a mechanical issue because the car runs well (if i can get it fired up). I feel something is loose, bad relay, bad switch, bad fusible link.

Correct there are 4 fusible links and I have power to 2 of them and according to the FSM schematic that seems correct?

[Patcon]

Would jumping from the fuse box to the battery fry anything? ECU, relays, injectors?

[jrod81]

1 hour ago, Patcon said:

Would jumping from the fuse box to the battery fry anything? ECU, relays, injectors?

I'm a newbie to Zs but if I read the FSM electrical schematic correctly, jumping the fuse box is essentially bypassing the ignition relay?  Correct me if i am wrong.

[Patcon]

18 minutes ago, jrod81 said:

I'm a newbie to Zs but if I read the FSM electrical schematic correctly, jumping the fuse box is essentially bypassing the ignition relay?  Correct me if i am wrong.

I was posing the question in general. I don't know the EFI cars that well. I will have to defer to some of the other guys.

[Zed Head]

4 hours ago, jrod81 said:

 i decided to jump the fuse box from the ignition to battery and the car fired up (i read somewhere or someone told me i can't recall). Now my current situation is that it winds over and cranks same as it did before, however, jumping the fuse box no longer works

Might be that you actually have two problems. Have you tried starting fluid?  If you have power at the coil and still no start, check for spark.  If you have no spark consider the igntion module.

Edited February 28, 2018 by Zed Head

[SteveJ]

You checked for voltage at the coil with the ignition switch in the ON position. Did you also test for voltage at the coil with someone holding the ignition switch in the START position? If you lose voltage then, the car won't start.

[JSM]

4 hours ago, jrod81 said:

Correct there are 4 fusible links and I have power to 2 of them and according to the FSM schematic that seems correct?

I thought all 4 should have constant power?

[jrod81]

2 hours ago, Zed Head said:

Might be that you actually have two problems. Have you tried starting fluid?  If you have power at the coil and still no start, check for spark.  If you have no spark consider the igntion module.

I have not tried with fluid, not sure how to use fluid with EFI. I will check for spark.

[jrod81]

2 hours ago, SteveJ said:

You checked for voltage at the coil with the ignition switch in the ON position. Did you also test for voltage at the coil with someone holding the ignition switch in the START position? If you lose voltage then, the car won't start.

Not yet i will try next with the ignition in "Start" position. If there is a voltage drop does that mean there is an issue with ignition switch? I'm thinking of hooking the ignition coil directly to the battery and then jumping the starter. Essentially bypassing the cabin/ignition switch electrical. What do you think?

[SteveJ]

Try my way first. If you jump out the ignition switch, you could have issues if you need to kill the engine quickly. You might get away with that, but it's not something I would do personally. 

When you are doing this test, I would expect to see some voltage drop while starting. The starter motor pulls some good current, so that can cause a drop of a volt or two, especially if the battery is older. If you lose voltage at the coil when starting (drop to near zero), that would indicate an issue with the switch.

Jumper wires are a poor substitute for good testing.

[SteveJ]

9 hours ago, JSM said:

I thought all 4 should have constant power?

You are close. All 5 (6?) should have constant power.