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Discussion Starter · #1 ·
Hello all and thank you in advance for you're help. This is my first post so forgive me if i don't know the proper way to use this site. I am completely perplexed by my z. It has been sitting in the field for about 12 years. I've cleaned the fuel tank put a new pump on. All new fuel lines. All lines flow great and return to the tank. I've checked all the pins according to the fsm. They all check out within spec. I have continuity between the pin 1 and negative side of coil. The car starts and immediately dies. I get 12v to the ignition coil when key is in on position and start position. The problem seems to be with the coil this is my 2nd one i have tried both were new. I get 12v from negative side of coil until it starts then it only puts out about 2-3 volts until it sits for a while then it will start back and do the same thing. Is it possible that the electronic ignition transistor control unit is keeping the coil grounded causing the low voltage? If i unplug the negative side it goes back to 12v. But when i hook it back up it acts like it is grounded. Is there some way the transistor unit could stick in the closed circuit position or something?

Thank you for the help!
 

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So you have spark but after the engine starts running spark disappears? Try looking at your pickup coil (the little black piece in your distributor that has the 2 wires coming out of it. If the wires or connections to that piece are in bad shape the car will not send spark to the coil.
 

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Discussion Starter · #4 ·
So you have spark but after the engine starts running spark disappears? Try looking at your pickup coil (the little black piece in your distributor that has the 2 wires coming out of it. If the wires or connections to that piece are in bad shape the car will not send spark to the coil.
I checked the wires going to the two pickup coils and they seem to be good. No visible bad spots and no continuity to ground either. I can tap the blue ignition wire to the negative side of the coil and it arcs then it randomly stops and so i hook it up. Fires up and immediately dies. Unhook the blue wire and its apparently grounded again because its arcing when i tap it to the negative side of coil. I don't know what could be grounding the wire to make it do this in such a way. It will do it again and again like clockwork. Very strange.

All help is greatly appreciated.
 

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I checked the wires going to the two pickup coils and they seem to be good. No visible bad spots and no continuity to ground either. I can tap the blue ignition wire to the negative side of the coil and it arcs then it randomly stops and so i hook it up. Fires up and immediately dies. Unhook the blue wire and its apparently grounded again because its arcing when i tap it to the negative side of coil. I don't know what could be grounding the wire to make it do this in such a way. It will do it again and again like clockwork. Very strange.

All help is greatly appreciated.
test the pickup coil using the methods outlined in the factory service manual. I believe its something like use a multimeter with the resistance setting on there and touch the 2 wires and it should have something like 600 ohms resistance (I might be wrong on that number).

The factory service manual has a lot of diagnostic tests you can try and is available here for download: XenonZcar.com S30 Factory Service manuals
 

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could be a fuel pump running issue, the pump runs whenever the key is in the START but in RUN it relies on the signal from the AFM to tell the fuel pump relay to stay on.

Test this by putting the key in ON and them manually move the afm vane (you have to remove the air filter to AFM hose to get to the vane) with your hand, listen or better yet hook up a fuel pressure gauge and confirm the pump is running and building pressure (about 36psi, engine off key on flap moved). The AFM in the 75 uses a micro switch in the AFM to keep the pump running as long as the AFM vane is open due to air movement thru it. Don't try to work around this, its a safety thing (kills the pump in case of a engine fire from damage that would let the pump run with the engine off as in a wreak).
 

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could be a fuel pump running issue, the pump runs whenever the key is in the START but in RUN it relies on the signal from the AFM to tell the fuel pump relay to stay on.

The AFM in the 75 uses a micro switch in the AFM to keep the pump running as long as the AFM vane is open due to air movement thru it.
The contacts of this switch may be oxidized and not getting continuity between them. When the contacts are closed, they should read close to "zero" with an ohm meter. I have had success cleaning the contacts by holding them closed and running a thin piece of cardboard between them. You have to be extremely careful as the contact arms are very thin and bend easily.
 

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I suspect a fuel problem. A fuel pressure gauge installed semi permanently until you get the car running well is useful. You need to know when the pump is running at what pressure and whether the return check valve is working.

Then you can move onto testing for spark. We can bet that either fuel or spark is ending or it would keep running.
 

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It could certainly be a fuel issue, a simple way you could check that is to spray some starting fluid in there and see if it will keep running. My car had similar issues and it was a bad fuel pressure regulator, but it was also a timing issue. I have a megasquirt so I can't speak to the specific issue you're having but I had the same symptoms.
 

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Discussion Starter · #10 ·
test the pickup coil using the methods outlined in the factory service manual. I believe its something like use a multimeter with the resistance setting on there and touch the 2 wires and it should have something like 600 ohms resistance (I might be wrong on that number).

The factory service manual has a lot of diagnostic tests you can try and is available here for download: XenonZcar.com S30 Factory Service manuals

I checked the pickup coils and they have 660ohms the manual says 720ohms but i have a cheap tester so not sure if they are good or bad. So i tried to crank it up and it starts and runs for about 10 seconds and dies. When i check it the negative side of coil is grounding out. I pulled the harness to the ecu and the wire is still grounding. So i pulled the ignition module and pulled the pulse wire and the ground goes away. Could the ignition module be the problem? Switching to ground and not releasing it?
 

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Discussion Starter · #11 ·
could be a fuel pump running issue, the pump runs whenever the key is in the START but in RUN it relies on the signal from the AFM to tell the fuel pump relay to stay on.

Test this by putting the key in ON and them manually move the afm vane (you have to remove the air filter to AFM hose to get to the vane) with your hand, listen or better yet hook up a fuel pressure gauge and confirm the pump is running and building pressure (about 36psi, engine off key on flap moved). The AFM in the 75 uses a micro switch in the AFM to keep the pump running as long as the AFM vane is open due to air movement thru it. Don't try to work around this, its a safety thing (kills the pump in case of a engine fire from damage that would let the pump run with the engine off as in a wreak).
I am not sure why but the pump runs all the time. As soon as you turn the ignition to on the pump runs and never shuts off. I will have to wait to get a preasure gauge next time i go to town as i live way out in the sticks. Thank you for your help
 

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Discussion Starter · #12 ·
I suspect a fuel problem. A fuel pressure gauge installed semi permanently until you get the car running well is useful. You need to know when the pump is running at what pressure and whether the return check valve is working.

Then you can move onto testing for spark. We can bet that either fuel or spark is ending or it would keep running.
I will be getting a fuel preasure gauge next time i go to town. Thanks for your help
 

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Discussion Starter · #13 ·
It could certainly be a fuel issue, a simple way you could check that is to spray some starting fluid in there and see if it will keep running. My car had similar issues and it was a bad fuel pressure regulator, but it was also a timing issue. I have a megasquirt so I can't speak to the specific issue you're having but I had the same symptoms.
If i hook up the cold start valve to power the car will stay running. Thanks for your help
 

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can you hear the injectors clicking while it runs on the cold start? check your ECU if not for proper grounding and power supply, see the ECU. Make sure the wire from the coil that triggers the ECU is intact.
 

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Discussion Starter · #15 ·
can you hear the injectors clicking while it runs on the cold start? check your ECU if not for proper grounding and power supply, see the ECU. Make sure the wire from the coil that triggers the ECU is intact.
Yes i can hear them clicking. Thank you for the reply
 

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if they are clicking then it points to the supply of fuel. Rusted lines are a common issue, the FP gauge will be a good start but you must confirm volume as well. its covered in the FSM.

You could also have plugged up injectors. the only way to know for sure if you cant read the plugs as getting wet would be to actually pull the injectors out of the manifold and observe them during a start attempt. Not easy and could be dangerous due to gas spraying everywhere. look for gas on plugs, see if they are dry (clicking injectors with adequate gas supply leaves you with plugged injectors and the culprit).
 

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If i hook up the cold start valve to power the car will stay running. Thanks for your help
The car stays running when you hook up the cold start valve? The cold start valve only sprays gas when attempting to crank the car when the coolant temp is below a certain temperature. Going off of memory, I think it's 57 degrees F, but not 100% sure. After the car starts, the cold start valve shuts off, and does not spray any gas into the intake during operation, unless it's leaking.

Do you know if the fuel pressure regulator is good?
 
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