ben92 Posted May 25, 2021 Share Posted May 25, 2021 Hi Folks, I'm not certain but I think I've once again got myself into a world of hurt! In trying to generally improve my 1975 260z recently I've done a whole number of modifications, swapping out everything that seemed unreliable and in poor condition - I've changed the alternator to an internally regulated unit (https://zcardepot.com/products/alternator-internal-regulator-280z-280zx-78-80?_pos=8&_sid=d1b3c80bb&_ss=r), following a guide (https://www.atlanticz.ca/zclub/techtips/alternatorswap/index.html), mostly because the voltage regulator was rusted with corroding wires, and I wanted to get a new alternator anyway. I have a feeling some of this new wiring or bypassing of the voltage regulator is causing my problem, but I don't think I can quite work out how to fix it on my own. So - I've made up my own fuel return rail and installed an electric pump in the rear of the car as I figured more fuel movement might require both pumps and not just the mechanical one. The pump isn't factory and wasn't used because I didn't have return lines before, but as I've decided to use the return line in hopes of curing the vapor lock on the flat top carbs, I've installed the electric fuel pump and plugged the wires back in. The car's not ready to start up yet, but as I've just recently reinstalled a lot of overhauled parts I was curious to see if the wiring seemed to hold up. I turned the key to the 'ON' position and got a huge fright when the fuel pump started up, which I've read it isn't supposed to unless the car is running at over 400 rpm (please correct me if I'm wrong). I think my question then is; what have I bypassed to make the electric pump run even in the 'ON' position? Or, if it's not possible to easily run the electric pump safely with an internally regulated alternator, would the mechanical pump suffice even when running a return line? Thanks again for the help! Ben Quote Link to comment Share on other sites More sharing options...
gilltech Posted May 25, 2021 Share Posted May 25, 2021 I don't know when the electric fuel pumps were fitted to the 260Zs. My '74 RS30 just has the mechanical pump and the pair of fuel supply & return lines. Given you have the original flat top carbs then why not install the mechanical pump and pair of fuel supply & return lines and see how you go? Surely simpler. Quote Link to comment Share on other sites More sharing options...
ben92 Posted May 25, 2021 Author Share Posted May 25, 2021 Thanks gilltech, I'll definitely try removing the electric pump again if I can't find a way to make it work. I went to all the effort of making the return line system work because the car was vapor locking without it (I think anyway), and i read the electric pump helps to keep the fuel flowing through the system properly. The vapor lock supposedly is mostly prevalent with the flat top carbs and because I've already had that issue and didn't want to swap out the carbs unless I really have to, I want to do everything I can to prevent it from being an issue, hence wanting to get the electric pump to work. gilltech 1 Quote Link to comment Share on other sites More sharing options...
Millerman Posted May 26, 2021 Share Posted May 26, 2021 Usually an electric pump will prime under ignition for a few seconds or until it builds pressure with a fuel injected car but not to sure about a carby setup sorry Quote Link to comment Share on other sites More sharing options...
peter t Posted May 27, 2021 Share Posted May 27, 2021 I deleted my carter pump and went back to a new standard pump. Problem solvered. Quote Link to comment Share on other sites More sharing options...
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