ok after installing my injectors friday the engine now stumbles and breaks down under load. sounds like a subaru when idling... seems like an igntion issue but i don't know. the injectors are all firing. i installed new plugs, cap and rotor. all spark plug wires are on. i was thinking maybe the coil is failing. if i rev it really high it smooths out some but i really have to rev it. like 5000 rpm. trying to think if i could have hit something or moved something while taking the fuel rail off. any help would be appreciated. i may need someone to stop over if they can. it's my 1978 datsun 280z. thanks

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

Because you changed all the ignition stuff, I would start by going back and ensuring everything was right. Timing (and vacuum advance) are likely culprits. What's controlling your vacuum advance?

If the coil was OK before you tore everything apart, it's OK now, too.

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1970 240Z

What Frank said..
Did you change the plug wires wire for wire ? Is the cap facing the right direction ?
Its possible one of the injectors has junk / build up from old gas. I'm curious as to why you changed them out

the old ones were shot. they were never replaced since i got the car. and the injectors i put in are brand new. didn't replace wires only plugs, cap and rotor. it as running fine after that. only after replacing the injectors did this happen. the only thing different was the return lines outer rubber had turned brittle and broke a part. maybe air is getting into the lines? so i will replace that since that is the only thing that is different from after reassembly. finally getting a new tank cause mine is leaking worse now. so after that i pretty much have cured most of the big issues on this car. could be just a lot of air in the system.

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

Mike I know this sounds like a lot of work and I know the injectors are all new but do you still have the old ones?

It just sounds to me when swapping out the injectors, some wire on the intake side of the engine harness wasn't put back together or contact isn't being made. I know we went through testing to see if the injectors themselves are the issue and they are not. Just to be sure without a doubt maye swap back in the old ones.

Also - what kind of new plugs did you put in? Platinum plugs are no good for our old Z cars and I ran into that problem last year on 240z. Double check the plugs, wires and rotor/cap before changine the injectors back out.

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Clive Bogle President - New York Z Car Club - NYZCC.COM
1971 240Z - LS1/T56
1974 260Z-L30
1976 Fairlady Z

Yup, back to basics. Check the plug firing order, timing, fuel pressure. Make sure each plug wire is getting a spark. You can use a timing light, or the "shock yourself" method, you pick.

Sometimes, simply fiddling with the old fuel system, knocks debris into the fuel lines in the engine bay. A chunk of rubber will quickly plug up a new injector.

Ultimately, if you don't find anything, you will need to test the injectors for spray pattern. you take the whole rail off, run the fuel pump and energize the injector with a few volts. Careful! Dangerous! Flammable! Do it outside with an extinguisher handy.

Or just swap in the old injectors...

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-Dave
76Z Turbo'd
72 In Progress---DONE!

i can retrieve some of them. plugs are ngk iridium i believe. ordered from msa. and the only wiring connections removed were the injector clips. should i take them out and reconnect again? can i unplug one connector at a time and see what happens?

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

Yes, do that with injectors, or plug wires to isolate the miss.

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-Dave
76Z Turbo'd
72 In Progress---DONE!

And confirm your new spark plug gaps.

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1970 240Z

removed

Well I didn't gap them when I first put them in. Are they self gapping? it's not the plugs that are the problem. You should see the old plugs. The car was running normal after I out the cap and rotor and plugs in. This was before work last Friday. I drove her to work and home and had improved power but after installing the new injectors is when I had my running issue.

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

I have read iridium can be gapped if the owner desires.

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

I'll most likely order anothe set just in case but the way she is running is not the plugs. I gapped my first NGKs and she ran great. I'm hoping it's just the return line. And if I can't resolve the issue I'm going round top SU's.

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Mike Tubiak
1978 Datsun 280Z - HLS30-438694

Have you actually listened to the injectors firing? Using a srewdriver to the ear as a stethoscope? Old crusty injector connectors could be an issue. Swap over to some Volvo ones. Go to junk yard...snip, snip. I have some, but way out hear.