Help!!!!!! - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z
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post #1 of 3 (permalink) Old 04-01-2019, 08:37 PM Thread Starter
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Exclamation Help!!!!!!

I have a 1980 280zx L28 NA 5speed with EFI....I'm currently restoring the engine and ran into and issue.


From a cold start the car idles fine performs fine if driven right away.

When put into first gear on a cold start, the car goes... until five minute have passed and every stop I make, it HESITATES THEN BUCKS, a rolling launch.

During this period when it loses power and acceleration, the fuel pump cuts off completely.



what should I check first?????

WC280zx
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post #2 of 3 (permalink) Old 04-03-2019, 08:23 PM
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I'm trying to envision what you mean by 'restoring the engine' on a car you are obviously driving. If it means you are taking stuff off and putting it back on - did the engine run normally before you did that? Has it ever run normally? Is this a completely stock engine? Don't mean to insult you or anything, but there are guys who start tearing stuff like EGRs and BCDDs off their engines and then come on here and ask why the engine is not running right.

Generally speaking, these cars really like good, solid electrical connections and they really need tight vacuum systems. I'd start by checking vacuum, then I would go around and 'freshen' every electrical connector under the hood- remove, clean, crimp or do whatever to get the metal to metal nice and fresh. This includes injector connectors, batt terminals, fusible links and even grounds bolted to the body.
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post #3 of 3 (permalink) Old 04-10-2019, 08:45 PM
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Originally Posted by 6shutr View Post
I'm trying to envision what you mean by 'restoring the engine' on a car you are obviously driving. If it means you are taking stuff off and putting it back on - did the engine run normally before you did that? Has it ever run normally? Is this a completely stock engine? Don't mean to insult you or anything, but there are guys who start tearing stuff like EGRs and BCDDs off their engines and then come on here and ask why the engine is not running right.

Generally speaking, these cars really like good, solid electrical connections and they really need tight vacuum systems. I'd start by checking vacuum, then I would go around and 'freshen' every electrical connector under the hood- remove, clean, crimp or do whatever to get the metal to metal nice and fresh. This includes injector connectors, batt terminals, fusible links and even grounds bolted to the body.
As far as removing EGR's and BCDD's on these cars, as long as it's done right it won't cause any kind of a running problem. I've been doing it for a couple of decades without any issues. For the EGR I cut the back end of the manifold off and weld it closed. For the BCDD I remove the unit as well as the steel seat that is pressed into the throttle bodies, and then weld everything up, making sure that the 2 main channels are welded independently of each other. I guess that's the difference between doing it right and "tearing stuff" off of their engine like you mentioned.
As far as the original question goes, you need to monitor the power going to the fuel pump when your engine starts bucking etc. If you're loosing power to the pump first, that can cause the bucking etc., so the source of the problem would be upstream from the pump. Could be a weak relay, or even something as off the wall as low oil pressure or a bad oil pressure switch. The main thing is this: Don't just start throwing parts at the problem. Run proper diagnostic procedures so you're making more educated decisions and not wasting your money.
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