no injector pulse on 280z
 

My friend has a 78, i believe, 280z fuel injected. car just had a new engine with bigger cams and a new tranny installed. car ran fine before install with old engine and tranny. everything has been put back together and now the car wont run. have tested everything out, fuel, spark and compression are okay. however there is no pulse to the injectors. when cranking there is a very weak pulse but then it goes away almost immediately.

i was thinking computer since i know they control the pulsing. i also thought about a CAS but i don't think it has one? i'm confident that all the connections are good. any ideas will be much appreciated. thanks in advance.

Have you checked the fuse links?
Is the ecu getting power?
Is the fuel pump getting power?
What is the fuel pressure at?
-And no, there is no CAS (that's on 280ZX TURBO L28ET models only)

ill double check all those things and let you know what i come up with. thanks a bunch :)

fuel pressure and spark are good.

There was one fuse link burned, replaced it. still the same problem of no pulsing to injectors.

there is a main relay that we think might be bad. we went ahead and got one on order and it will be in tomorrow. ill let you know how that turns out.

Check out xenons30.com and download the free FSM. That should help you out immensly.

thanks

Second NismoPick's and Skittle's advice. I'd also add that while you're on the xenons30 site, scroll down to "other guides" and get the Electronic Fuel Injection Guide (aka "EFI Bible"). The FSM has a great section on that, but the supplement guide fills in some gaps and clarifies some important points.
Good luck, hope it's just the relay!
cheers,
Dave

found the problem. found a bad connection in a harness that runs back to the ECU. thanks for all the help! :)

I'm having this same problem, how did you fix yours if you don't mind me asking, thanks in advance.

Also I have try'd checking the grounds on all the injectors, and it's really weird on some days it will read 12v 's all the way across and on other days only three outa the six will be getting power and the last day I tested it, none of them where getting power, it's starting to really annoy me, and i've been trying everything.

Again thanks for the help in advance, I could use anything.

Are the dropping resistors ok? Tho I dont think they ever go bad do they?

What exactly are the dropping resisters I don't think I ever heard of them?

On the 78, they're on the left (driver's) side, by the clutch master cylinder, behind the washer tank, under the left "inspection lid". Looks like a bare metal housing/bracket, with two plugs. They're basically just big ceramic resistors which get the power correct for the system. Of course, if they're bad, then you may not have power to one or more injectors. From page 6 of the EFI guide (which has a good sketch of the location):

"When the system is operating, the battery is connected directly to each injector through a resistor. Thus there are six resistors on the 280Z. The resistor causes a voltage drop so that the injector operates on less than battery voltage. The resistor also protexts the injector from voltage surges coming from the alternator and from the effects of other components in the electrical system"

You at least want to clean the connections with contact cleaner or DeOxit, or whatever your preferred method is. And while you're at it, test the resistance of each one, to make sure you don't have a few circuits out.

cheers,
Dave

ah thank you sir