PC's Z

Thanks for taking a look at this post and offering help in advance! I finally got my 1975 running and driving and unfortunately it had to sit for about 2 weeks and now it's fuel pump, which is brand new by the way before you ask, doesn't want to run, the dinger doesn't even go off anymore when I have the key in the ignition. any advice on how to approach it? it ran the first time I put in the pump, it just took a minute before it started working and the dinger was working then but I've been at it for about 2 days now and with no luck, no ding, no fuel, it's just as if it's lost all of it's power.

beg3yrs

No dinger? Did you check your battery?

PC's Z

Thank you for the reply. The battery is brand new and I charge it. It has the power to turn the motor over but it just refuses to engage the fuel pump. I have checked my AFM repeatedly but still the pump refuses to run.

beg3yrs

I'm no expert in the 280Z but will cogitate on it. Hopefully someone else with more experience will chime in sooner. If not, I'll take a look at the circuit diagrams and make some suggestions.

BTW, specifically, what is the "dinger"? Is that a chime that sounds when you put the key in the ignition?

PC's Z

It's exactly that. it's just a chime that let's you know the door is open or that the keys are in the ignition, etc etc. Usually when the chime is present, it is only a short amount of time before the fuel pump kicks back on.

beg3yrs

OK, after a good sleep and fresh thoughts, I took a look at the FSM for your 1975 Z. You do have one of those don't you?

If not, download it at XenonS30

There are a couple of versions of the 1975 manual. The searchable one has lots of artifacts (problems with converting a scanned page to digital text) but can help you quickly get to relevant sections. The other versions should be complete scans but won't be very searchable.

My first thought after looking at the simplest circuit, the door chime (part of the anti-theft system), and coupling that with your statement that once the chime works the fuel pump starts, I'm thinking they only thing they likely share is a ground connection.

There is a body ground point coming off connector C4 which is part of that multi-connector bracket located above and to the right of the passenger footwell. That ground is specifically called out in the door chime circuit diagram and the fuel pump relay assembly is located near that connector as well. I couldn't easily figure out where the fuel pump relay is getting its ground but since they're physically close, that's where I'd start looking.

Loose, missing, broken or corroded ground connections can cause all sorts of gremlin problems in these cars.

Steve260Z74

Inspect the fusible links.

Zdon

Both Beg3 and Steve26 have narrowed down the trouble shooting to the nearest denominator. Always voltage first before components. Let us know how it works out.

Zdon

Both Beg3 and Steve26 have narrowed down the trouble shooting to the nearest denominator. Always voltage first before components. Let us know how it works out.

PC's Z

After Spends long hours with the FSM and cleaning all of my connections, the car runs again but i t seems to run really roungh, missing a lot which is new. It is not a fuel issue anymore but I also noticed I have to brake pedal pressure. I press it and it holds pressure only for a moment then loses it again then next. The master Cylinder is new but I hear this hissing when y
The pedal is pressed. I believe the booster could be at fault but I don't want to spend 120$ on it unless I know it is the problem.

beg3yrs

First of all, congrats on cleaning your connections and getting things running. The more I read the FSM, the more I find just what a valuable and actually well-organized document it is.
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Yeah, I think you're right to suspect the vacuum booster.

Pull the booster's vacuum line off and cap the source. See if your brake behavior changes and the hissing goes away. You should still have brakes, just no power assist. If your brake pressure is now constant, it's likely to be the booster losing vacuum (the hissing) and hence the change in brake feel.

Boosters can be rebuilt, the FSM tells you how to do it. Just that these days the rebuild parts are probably hard to find and along with the time and effort, spending $120 might make sense.

As my car begins to run, I'm thinking I might have a problem in the same area. No hissing but I do get an odd brake feel when the motor is running. Hence, I have a high level of interest in what you find.

PC's Z

After taking it to work and diagnosing it in my down time, I am a tech working towards my masters, I did find that the booster was at fault. The motor was sputtering and misfiring because there was now a vacuum leak through the booster. I replaced all the vacuum lines while I was at it and now no longer have the misfiring problem and my brakes are feeling 100%.

beg3yrs

Glad you got your ride working!

Keep up the studies, soon we'll be looking to you for ALL our answers.