Turned on headlights, car died.

[jas280z]

I was driving my '78 the other day and went to turn on the headlights, as it was getting dark out. As soon as I switched them, the whole car died.

 

My fuel pump is not turning on, and I am fairly certain that the injectors are not getting power (I have a pressure gauge on my rail, and it showed constant pressure when cranking even though the pump was not working). I would test the injectors with a noid light, but I have the relays out of the car to test them.

 

The 4 fusible links under the covers check out (have continuity) as well as the two that clip onto the side of the relay housing. My main fuel injection relay, and fuel pump relay both check out.

 

The fuel pump control relay I am not sure about. It does click, and has proper continuity when NOT grounded, but it does not show the continuity that it should when grounded. I am not sure if the proplem is the relay though, or my inability to find a suitable ground.

 

I have also tested the wires that bring current to the relays. The main fuel relay has voltage running to and from the battery, as does the fuel pump control relay.

 

I thought I had the problem solved when the car started working again after putting it all back together and checking the ground on the intake manifold, as well as the ground near the oil pressure sending unit. It turns out this must have been a fluke because the same problem occured the next day, and I have not been able to fix it.

 

 

 

I decided to start tracing the voltage and continuity in the headlight system, to find if there is a break. I decided to follow the headlights, as they seem to be what causes the rest of the car to not want to function.

 

The RB and RW wires from the headlights to the combination switch both have contuinity and carry 12 volts when applied. the WR wire from the fusible link has 12 volts at connection C-9, and just below 12 at the plug where it connects to the combination switch. Continuing on, I believe that the WR wire goes through the combo-switch, and powers the R wire when the headlights are turned on. The R wire shows the same voltage as WR when the combo-switch is in the on position, coming right out of the Combo-switch.

 

Here is where I am dumbfounded. If I remove the right and left headlight fuses, I see the same nearly 12 volts (around 11.8) at the R wire where it goes into the fuse box. If I connect either of the two headlight fuses, it instantly drops to zero. I do have to add that the right headlight is currently disconnected, as my Dad thought that the po's wiring job on it might have been the culprit. Could that be causing the odd voltage drop at the fuse box? I doubt it as I think it would be similar to the headlight being blown, but I am no electrician so I could be (and probably am) wrong.

 

I will continue trying to figure this out, but I was wondering if anybody might have any suggestions, or if there may be something I am missing. Any help would be appreciated.

 

Thanks!

 

Edit: I realize that I left the fuel pump control relay not completely tested. If I can figure out a good way to ground it I will test it, but I don't know what that could have to do with the headlights, which is why I switched my focus to what seemed to be the cause of the problem.

Edited June 28, 2011 by jas280z

[_Donovan_]

Dumb question, but is the alternator putting out the correct voltage.

[jas280z]

Dumb question, but is the alternator putting out the correct voltage.

 

It hasn't given me a problem before, unless my dad switched it with the one in his 280zx without telling me. Even if that was the problem, I would think that the headlights and fuel system would turn on when connected to a charger like they are now. Voltage in the car has always been at 12 or above.

Edited June 28, 2011 by jas280z

[jas280z]

So I went back and tried to check the fuel pump control relay again. I am still having trouble telling if it is properly grounded. I wrapped a wire around the ground prong on the relay (prong 96) and attached it to a bolt on my12 volt battery charger (what I am using as my 12 volt source). When I put my multimeter on prong 96 and a bare spot on the charger, I get continuity, so I believe that it would be grounded. I hear a click when I apply 12 volts to the relay, but the continuity does not change as it should. I think it is a bad relay, but I am still not sure if I have it properly grounded. Any suggestions? I might just try to use my car battery as the 12 volt source, and ground it somewhere on the car, at least then I will know it is grounded.

[NewZed]

Are you saying that the engine will run now, as long as you don't turn on the headlights? You can start the engine and drive around as long as the headlights are off? Or the engine ran, until the headlights were turned on, now everything is dead? One is a reproducible problem, the other is more random.

 

Reproducible problems are easier to troubleshoot.

[jas280z]

I just rechecked the relay off of the battery, grounding prong 96 to the car. I found that the switches worked as they are supposed to, except for the 95-96 switch. When no current is being applied,there is no contintuity, which is correct. When a current is applied and not grounded, it also works as it is supposed to, having continuity. The problem seems to lie in it being grounded, and having current applied. When that happens there is no continuity, even though there is supposed to be. If you have the test all set up, but ungrounded, it appears fine, but as soon as I touch the ground wire to a known ground on the car, continuity disappears.

 

I think that this has a lot to do with my fuel problems, but I don't know if it has any bearing on the headlight situation. Guess I'll have to order a new one and see what happens.

[mad28max]

The headlight dimmer switch provides a ground path to illuminate the lights (ie. ground is provided for either hi or low beam filament). The 12 v is always there when the headlight switch is on.

 

Almost sounds like a dead short but that should pop a fuse. Try removing the dimmer switch from the column and cleaning the contacts real easy with some 600 grit. While your there look for anything shorting the switch.

 

Sorry about that, should have been dimmer switch.

 

Have you tried attaching a ground wire from the engine to the chassis?

Edited June 29, 2011 by mad28max

[jas280z]

Once I turned on the headlights, the engine was dead for good. I cannot get the headlights, fuel pump, or injectors to turn on. The sidelights, and everything else I have tried still works, just those 3 components are dead.

 

I am will continue going through the connections, and cleaning everything. Z Man of Washington told me that just because I see 12 volts down the line, not to rule out connections right near the battery (i.e. battery cables or links) as the multimeter does not put a load on the circuit, so corrosion could be hampering the system still.

[jas280z]

I figured out the problem. I decided to start running current directly to the headlights, starting at the steering column. I found out that the dead link was the white wire from the starter to the fusible links. I took off the electrical tape to find that all the splits were falling apart and corroded. I replaced that wire and everything worked.

 

Lesson learned: try to hot-wire whatever is not working, multimeters may not put enough load on a circuit to show a corroded but still attached connection.