Starting Problem

[hotdamn]

Last Saturday I changed engines in my 280Z, the engine and electrical system were swapped from a running 1978 parts car.

After completing the swap the car will start and immediately die. It runs for only a few seconds(with or without starting fluid doesn't seem to change anything). We have checked the fuel pump and pressure (38 psi). The fuel injection relay has power to three out of the six wires leading to it. The fuel injectors also have power running to them, but items like the cold-start valve, and AFM do not have any power running to them.

Ideas?

 

Evan,

[hotdamn]

I read through the FSM/archives last night and tried a few things, I found out I have power to only a few pins. I also cleaned the connections and now have power to my throttle position switch but only when cranking, is this normal? The AFM also has power as I can see internals move(covers off). How many pins should have power? And how can I check if my ECU is bad, would I be able to put in the old ECU from my 75' car in the 78' system?

 

Thanks, Evan

Edited April 10, 2011 by hotdamn

[NewZed]

What year is the car that you put the 78 gear in to? Did you change the wiring harness also?

[hotdamn]

The car is a 1975. I completely changed all of the wires from the a running 78', dash, ecu harness, etc. I tried plugging in the old ECU from the 1975 car and it still will not start, so it seems either I can not swap the ECU between years even though the numbers of the labels are the same, or that ECU is bad. The car still starts then stalls. I can not give it any gas during the quick second it does run or it will just completely die. Im going to run the tests for the ECU from the FSM.

Edited April 10, 2011 by hotdamn

[NewZed]

I found the same thing with the ECUs. I found that 76 and 78 have the same part number but 78 won't run a 76. The pins are different (look at the pins on the ECUs if you have both). I've also found that my 78 ECU doesn't match the 78 FSM wiring diagram (the cold start valve circuit and a wire to a relay were different if I recall correctly).

 

Did you bring all of the relays over too? That would be quite a job to swap the complete wiring harness. 1978 used more relays and less ECU to control some functions. You might take a look at the wiring diagrams between 75 and 78 and see if you need to add some relays or do some custom wiring. The Engine fuel section has some good breakouts of the ECU wiring. You can get both FSMs from the xenons30 web site -http://www.xenons30.com/reference.html

 

If it starts, but won't run it might also be the fuel pump safety circuit, which is different for 1978, using the alternator or oil pressure switch to keep the fuel flowing.

[hotdamn]

I changed every thing over, and I looked at the two ECU's they do have different pins. I think ive narrowed down the problem alittle, I have power to both terminals on the injectors, I thought I read somewhere that this is right, but the FSM is telling me different. I printed out both the 75' and 78' FSM sections regrading the engine fuel, electrical, and other related areas to help. I tried using a 3 Ohm bulb to see if it would flash, but it does not. The FSM says that this is a control unit failure, Im going to get another ECU asap. NewZed ill try your suggestions and update you once I'm finished.

 

thanks, Evan

[NewZed]

Power to both terminals is correct. The ECU grounds the circuit, energizing the injector solenoids when the ECU sees the pulse from the negative side of the coil on Pin 1 at the ECU. Check that Pin 1 is getting the signal from the negative post of the tachometer. The tachometer has to be installed for the Pin 1 signal to get through. You might be starting on the cold start valve which only squirts during Start, but not firing the injectors.

[hotdamn]

NewZed I seem to be able to start the car even with the cold start valve terminal connected. I went through the entire series of tests in the "EFI Bible" I did find something which interests me. In the picture attached you can see how I currently have the power run to the ECU/EFI relay. This is how I put it together when I stored it so I thought it was right but my test doesnt support this. I ran a Voltage test between the correct pin(pin 10 I believe, cant remember now) and the body ground when the ingition was in the "ON" position. That read roughly .03 Volts(when reading in the 20 volt setting). I thought this is maybe because of the dropping resistor but shouldn't the full 12 volts travel to the ECU then back to the dropping resistor to bring it down in voltage for the injectors?

 

 

I also ran a resistance test between one of the terminals on the EFI relay plug-in(two of the terminals currently have power) and the Blue wire shown in picture three(highlighted in Green). To get power to the entire bottom end of the terminal should I connect the black wire(highlighted in Yellow) to the positive terminal of the battery? This seems to be where the main problem resides, so should the entire bottom portion of picture two have power running to it? and if so is it as simple as running the black wire(which connects to the blue) to the postive terminal?

 

Terminals that currently receive power shown in Red.(EFI relay plug-in)

 

Thanks, Evan

Edited April 11, 2011 by hotdamn

[NewZed]

I am definitely not an expert on the Datsun EFI system (still learning) so can't really answer that question, but I would recommend moving on to the wiring diagram in the 1978 FSM. Page EF-36 shows the ECU, the relays, the power sources, injectors, cold start valve, etc all on one page. Just a quick look shows that Pin 10 gets its power from the electronic fuel injection main relay, which gets it power from the ignition relay. With the diagram and your meter, you should be able to back track to the power sources and make sure that you have good circuits.

 

Be aware that your fusible links can be bad with no external signs. They're designed to contain the melted wire inside the silicone cover. You might check power at the end of those fusible links (the two green wires in your picture) to be sure they're good.

 

The dropping resistors won't show a voltage drop until current is flowing. So you'll get 12 volts on either side of the dropping resistors if they're intact, engine not running, key on.

 

Good luck. Download that FSM, it's broken up in to chapters, easy to use. If you're using the EFI Bible now it's the logical next step, it's more specific to the model.

 

p.s. to the others on this forum who know the EFI system very well, feel free to add any thoughts or corrections.

[hotdamn]

I checked the fusible link shown in the picture and I get a full 12 volts across it. If anyone else is looking who would be able to look at there stock EFI system for me to compare or show pictures it would be greatly appreciated. If there is someone that can help me with picture or just a idea please describe where the two wires which plug into the fusible link go to. On my car one(red) is going to the positive terminal and the other(Blue) is connected to the negative, is this correct? If not please tell me what I have done wrong.

 

Thanks again NewZed for all the help.

[NewZed]

Those are both positive power supply to two different components. Two different circuits, with two separate fusible links for protection. Don't connect either one to ground.

 

I gave you the wrong page number above. It's page EF-26, not 36. Not sure why you don't want to take a look. Every time I look through there I learn something new (one reason I like to browse the forum).

 

Those are the fuel injection harness fusible links. The diagram shows that one feeds power through the EFI main relay (72 in, 43 out) to the dropping resistors and the other feeds through the same relay to Pin 10 on the ECU (71 in, 10 out). So you should be able to check the circuit to the relay, through the relay and to the target. You won't get power to the targets until the relay is powered up through the ignition relay. But you have power to the injectors so you know at least one side of your main relay works correctly. Check for 12 volts at the Pin 10 connection to the ECU for the other half.

 

There's a good diagram of the main relay in there also, with the pins numbered as referenced above.

 

I would check continuity from Pin 1 at the ECU to the negative post of the coil. There's a resistor in-line but you should still have a circuit there. If Pin 1 doesn't see what's happening at the coil, your injectors won't fire.

 

I'll leave you alone now.

[hotdamn]

I switched the fusible link that was connected to the negative terminal and put it on the positive terminal and the car fired right up

 

Thank you so much NewZed for all the help, and I will from now on consult the FSM first, forums second.

 

Few more weeks and the car should be road ready.

[NewZed]

You mean I could have just suggested moving a wire from negative to positive, without all the extra writing, and looked genius?! An opportunity missed...

Edited April 12, 2011 by NewZed