need help car starts but will turn off after a few secs

[jesus]

2 minutes ago, tzagi1 said:

Inspect for a cracked boot between the afm and the tb, black silicone works wonders.

i have no cracked lines nor boots 

[EuroDat]

Hi Jesus.

You have been working on this problem for a while now and it must be very frustrating. It would frustrate me, and that is putting it mildly.

I just read through this thread again and some things are not clear to me. Can you answer some questions to give us and idea were you are at. We have not seen the car, so we need your feedback to give any kind of usefull advice.

1. You changed the distributor to a 79 280ZX (D6K9) with built-in TIU. Are you still using the distributor with the external HEI module?

2. The ballast resistor is now bypassed. In our pm conversation.

3. Did you replace the coil with a 12 volt coil, one with 0.6 to 1.0amp specifications?

4. Did you check the ground wires at the battery? Wires to the body and to the ECU are not swollen and distorted. That is a sign of corrosion under the insulation. Check the connection for corrosion in the spade terminal plugs.

5. While you are at it. Check the fusable link spade terminals on the ECU positive wire. They corrode too and can cause voltage drop to the ECU.

6. Have you installed a fuel gauge to confirm the fuel pressure is ok? The fuel filter is NOT only one thing that can cuase presuure to fall away.

7. Did you a "yoghurt cop" test to confirm you don't have a really bad vacuum leak?

8. Have you tried turning the distributor while starting it, or rotating it back and forward and testing if it runs? Replacing the distributor, the timing could be way off.

9. Does the tacho work when it does run for a brief couple of seconds?

Do you know what the PO has done? He changed the engine, but did he change anything else? ECU, wiring harness etc.

Here is hoping you get it solve and up and running soon.

[jesus]

@EuroDat  ok so to your first question yes it is a 79 280zx distributor i dont know if its a D6K9 it dose have external HEI witch is the little box outside it right if so yes. to your second question yes no more ballast. on to the  third question yes new coil it is a BWD coil it is a 12v  not to sure on the amp number how would i check that?. fourth question i did check the wires didnt do a supper deep check but they seem good i will go over them again and clean and check for swollen parts for all three wires. sixth question i have not installed one yet but  i been meaning to will try and do it tomorrow. seventh i do not know what a yoghurt cop test is but i did check all my lines and boots and they are pretty good boots look almost like new. eight question i have i kinda have it wear it seems to run the best wen it decides to run. nine well my tach  at first it did for less then a second but now i do not have the dash in my car and my harness is fairly clean no cuts. and about the last owner no all he told me is that he swapped the engine ECU might be stock as the harness in and outside the car looks stock as well. thanks for your help to all you guys it is very frustrating specially wen i had it running fine for less then an hour haha thank you guys a lot. 

 

[EuroDat]

ok so to your questions

1. yes it is a 79 280zx distributor i dont know if its a D6K9 it dose have external HEI witch is the little box outside it right if so yes.

What did you do to disconnect the external TIU. It could be causing issues with the HEI.

Note: The 280ZX 79 – 80 used the D6K9-02 through to D6K9-10 distributor I think. Might be more versions. They are mostly the same, but some with slightly different advance curves and vacuum advance. The only thing important here is it’s a D6K9 series with build-in TIU.

2. yes no more ballast.

3. yes new coil it is a BWD coil it is a 12v  not to sure on the amp number how would i check that?.

12 volt is the most important. If it’s a 3amp coil the HEI won’t go to current limiting. You will probably have problems running spark plug gaps of 0.040 to 0.044”. A gap 0.28 to 0.031” would be the better with a 3.0 amp coil/HEI combination.

4 & 5. i did check the wires didnt do a supper deep check but they seem good i will go over them again and clean and check for swollen parts for all three wires.

Corrosion in the terminals is a big problem and can cause voltage drop in the ECU power supply. A lot of weird issues in the ECU because the ECU does’t like low voltage. See photo's of corroded terminals.

6. i have not installed one yet but  i been meaning to will try and do it tomorrow.

Install one. You need to know what your pressure is.

7. i do not know what a yoghurt cop test is but i did check all my lines and boots and they are pretty good boots look almost like new.

A yoghurt cup test is a simple leak test you can do on the inlet manifold. Basically you remove the rubber hose between the AFM and the Throttle body. Block the hole in the throttle body with a “Yoghurt cup”. I use a plastic sheet over the open end and a Tye-rap to seal it off. After you have done that I remove the hose that goes to the AAR and blow into the manifold there (See photo for location). Even with your lungs you should feel pressure build up. My 77 holds pressure for about 15-20 seconds or more before its gone.

If you (or someone helping you) hears air blowing out the exhaust, That is valve overlap and you will need to turn the engine a little to find a spot where there is no overlap.

8. i have i kinda have it wear it seems to run the best wen it decides to run

Do you have a timing light to check it while you crank the engine? It should be around 10deg advance.

9. well my tach  at first it did for less then a second but now i do not have the dash in my car and my harness is fairly clean no cuts

That is the first you mentioned the dash is out of the car.

and about the last owner no all he told me is that he swapped the engine ECU might be stock as the harness in and outside the car looks stock as well.

Can you have a look on the ECU. You should see a number beginning with A11-xxx-xxx. Since we don’t know for certain what the PO did, you could have an ECU that doesn’t match your harness pin layout. There are a lot of different ECU’s out there and not all will work in your car.

thanks for your help to all you guys it is very frustrating specially wen i had it running fine for less then an hour haha thank you guys a lot.

You also mentioned the Transistor unit was on the ground and it sparked. Can you explain that in more detail. Things like when the key was in ON position. Or when cranking the engine it started sparking through the metal box to the chassis/floor of the car? That does not sound good at all. That could have damaged one of the fusible links in the engine bay in front of the battery.

The ignition relay might be working and supplying power to the dropping resistors (inner fender next to the brake booster) and the injectors, but the ECU grounds them. Like Zed Head said. The CSV works on a different circuit in the ECU and doesn’t need anywhere as much current to work. It could work easily on a poor power and give you enough fuel to start the engine.

A way to test this theory is to use starter fluid on the engine. When you start it, spray it into the intake and try to keep it running on that. That would confirm your injectors or pump are not doing their job.

Edited February 4, 2018 by EuroDat

[Zed Head]

I bring this up occasionally - I've had two 280Z's that wouldn't start when the tach was not installed.  Beside that, who knows what else is disconnected with the dash out.

These cars aren't like an old Chevy that justs needs a wire to the coil and some gas in the carb.  Most of the electrical needs to be connected and working for the engine to run.  Probably going to have to put it all back together and run the electrical tests in the FSM or the EFI Book.

Edit - it's probably running off of cold start valve fuel, and the EFI system isn't even powered.  The EFI relay is attached to the dash.

Edited February 4, 2018 by Zed Head

[jesus]

hmm @EuroDat  yes it was on the ground and when i got it running it sparked on the metal on the ground and it shut off thats one reason why i did the swap on the transistor after that it didnt run any more i noticed today when i was working on it that when i hold down the gas while cranking it will run for a sec then shut off. what where you talking about the thing in front of my battery that can go out ? 

[jesus]

The battery grounds are clean I was wondering what this little thing is for ? 

[tzagi1]

Hazzard/turn sig flasher

[SteveJ]

40 minutes ago, jesus said:

The battery grounds are clean I was wondering what this little thing is for ? 

That is flasher relay for turn signals or hazard lights.

[jesus]

so this car has 2 flasher relays ? there is another relay that says flasher relay on it and its looks the same a bit smaller and its like a  gold color 

[SteveJ]

59 minutes ago, jesus said:

so this car has 2 flasher relays ? there is another relay that says flasher relay on it and its looks the same a bit smaller and its like a  gold color 

Correct. There are separate relays for the hazard lights and turn signals. This may help you understand the circuits bettter: https://fiddlingwithzcars.wordpress.com/2013/01/20/hazard-switch-brake-light-turn-signal-circuit-analysis/

[tzagi1]

The turn sig flasher in on the steering column, the hazards flasher is above the pass side kick panel.