jersey280 Posted July 7, 2022 Share Posted July 7, 2022 Hey gents! I own a 1976 280z, in which the previous owner swapped out the engine for one from a 1978 (N42 head, n42 block). Additionally, the fuel system has been modified to use a walbro external pump with a palnet fuel rail, with an after market FPR. The issue I am having is after I force the car to stall, the fuel pump continuously runs and does not turn off as it should to prevent a humam BBQ! I did notice that the 78 requires a 2 blade style oil pressure sender, and the 76 a bullet style. Currently, there is a bullet style connector on it. Would this possibly be causing the pump to run continuously due to the wrong sending unit? I am at work but I believe the wire leading to it is a single green. Any suggestions would be great! Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 7, 2022 Share Posted July 7, 2022 Take the black cover off of the side of the AFM and see if the fuel pump relay contact switch is opening when he AFM blade closes. That's what cuts power to the pump. It's shown in this link. You can bend the thick rod to adjust it. Move the counterweight and you'll see what is supposed to happen. http://www.atlanticz.ca/zclub/techtips/afm/index.html Quote Link to comment Share on other sites More sharing options...
jersey280 Posted July 7, 2022 Author Share Posted July 7, 2022 Thanks Zed, I will try that. Is this the only thing that controls the safety shut off of the pump? The pump continuously runs in the "on" position prior to turning it over to start as well. I believe it was determined that is correct on my year, can you agree? Thanks again Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 7, 2022 Share Posted July 7, 2022 Yes, the contact in the AFM provides power to the fuel pump relay, which is right above the hood latch pull. The 78 engine would not affect the fuel pump control unless a 78 AFM was used that does not have the contact. Many 78 AFM's do have the contacts but they are not used in the 78 cars. But they will work in 76, I had one on mine. The black cover just pops off by hand, it might have a little sealant on it. It's the quickest way to see where you're at on the problem scale. Not uncommon for people to rewire things though. If there's a vacuum leak the AFM tends to run closer to closed and can cut fuel. People create new problems trying to solve others. Quote Link to comment Share on other sites More sharing options...
jersey280 Posted July 8, 2022 Author Share Posted July 8, 2022 Newzed, this indeed solved the issue! Bent the tiny rod just so slightly and now the pump stops when stalled. Additionally, it solved the continuous pump running problem while in "on" position. Thanks for your help! Quote Link to comment Share on other sites More sharing options...
NewZed Posted July 10, 2022 Share Posted July 10, 2022 You're welcome. I spent some time working on the opposite problem, the pump cutting off at low PRM when the engine was cold, and got familiar with the system. Don't mess around with the spring adjustment if you start thinking you need to adjust fuel-air ratios. There are better ways. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.