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


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Hi Jesus,

We have been PMing over your HEI module swap and I missed this thread altogether.

Your problem could be caused by a number of issues or even a combination.

The AFM switch is a common cause. The AFM has a cap with silicone kit. You can gently cut the kit and remove the cap to check the switch. Check the switch adjustment by reaching in from the air filter side and moving the vane or turning it by the counter weight by hand.

Check for vacuum leaks. There was a thread on here called the Yoghurt cup test, but I can find it anymore. Basically its just removing the hose between the AFM and the throttle body and blocking the hole with a yoghurt cup. The removing a hose so you can blow air into the manifold with your mouth and searching for leaks with soapy water.

Fuel pressure and pump capacity are also things that can cause your problem. Buy a simple gauge and you can do some symple test to check the pressure and flow. A blocked filter can be so bad, that the car will idle, but the pressure will drop right off when you open the throttle and need more fuel.

The fuel system has infact two filters, one in the pump inlet and the filter at front right side of the engine. See the instruction in the pdf. It is for checking leak down, but the flow test and basic pressure check while running engine is what you need.

Check the earth terminal on the top of the inlet manifold. It is very important for the EFI. And check where it connects to the body on the side of the strut tower.

Cheers

Instruction - Fuel Pressure Test 280Z RevA.pdf

FuelPressureTest1.jpg

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Edited by EuroDat
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Godd work Siteunsen. I couldn't even find that one. I did find one where someone was asking about the yogut cup test.

It might have something to do with the migrating from the old server to the new one.

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Jesus, When you check the earth wiring, check at the battery as well. The photo I posted is from a 5/77 model. Somewhere in 76 they changed from earthing the body to the battery to the style in the photo. Not sure which month they did it. 

Yours might be ok, just located at the battery. If that is the case, check the negative battery post for three cables, the large heavy duty cable for the starter, another cable with a connector (ECU ground) going over the firewall towards the brake booster and one going to the body just behind the battery.

I made a couple of screenshots to show the difference. 

Chers

 

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  • 2 weeks later...

Ok guys so I can get my car running for a few seconds whit out any throttle then die out I got it to do it by disconnecting my afm dose that mean I need a new one ? It looks pretty clean in side it idk what else can be i also cranked it when cover was off and it looks like it just flickers back and forth fast can it be that some else going to the afm is bad ? 

3C03BE6A-9646-4129-826B-AC356F4B5E2A.jpeg

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Yes, What do you mean by diconecting the AFM?

If you mean disconecting the 7-Pin plug, then yes it will start, but it will never run more than a couple seconds because the fuel switch is in the AFM.

The fuel pump is activated by the key contact when it is in start position and after that it is operated by the contacts in the afm.

What was it doing before you disconectdd it. Would not fire at all or ??

Interesting adjustment method on the 76 model. It uses a screw on the counter weight like the 78 where the 77 has a tab in the housing. Not helping you any, but just interesting to note the small changes.

AFM-2.jpg

AFM-1.png

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yes disconnecting the plug on the bottom and it will start but before doing so it will stay cranking and it will not start my car it is a 75 but not sure what year the engine came out of sense last owner did a poor job on the swap the reason why im having this problem its because last owner left the transistor sys on the ground and it sparked and i dont know what it could of killed it was running and driving when i got it so what i did is changed the ign sys whit a gm part instead of the transistor i know my relay that controls my injectors works so i dont know what else it can be  

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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.

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@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. 

 

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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.

ECU-FusableLink.jpg

ECU-PowerCable.jpg

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ECU-PartNumbers..JPG

Edited by EuroDat
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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 by Zed Head
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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 ? 

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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/

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Hi Jesus.

Looking at your post #32. You have a bosch AFM. Datsun used the bosch systems in the early models up to mid 75. Looks like the PO has been swapping parts from an early model. Did you have a chance to check the model ECU? Im almost certain the pin configuration is the same on the bosch and early JECsS systems.

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More cars have 2 turn sign. flashers, it has to do with the wattage.. the power of, and the number of bulbs..   1 flasher is for directions, mostly 3 bulbs.. for hazard it's 6 bulbs, this flasher unit has to handle twice the power.. 

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