OldSkoolFool

Hi Z enthusiasts. I have a '78 280Z with 64k miles and is in stock condition. I have never had the problem I am having right now with it in the three or so years I've had it. It has just started to run somewhat rough, almost like it is not running on all cylinders, maybe down one. It holds an idle but is not as smooth as it used to be. When driving, it feels down on power throughout the rev range and no matter how much throttle is applied. At idle, it will gradually accelerate overall fine but still with somewhat of a stumble, and as mentioned down on power when driving. When more abrupt throttle is applied, the engine stalls for a second or so before it revs up. Below is a video of that symptom. I am looking for advice on where to start. The fuel tank has been restored when I first got it about three years ago. A couple fuel system items have been replaced (ex: filter, pressure regulator?, one injector, etc.). It seemed like clogged injectors were a common problem on these cars. Those can be checked with a stethoscope? I checked to make sure the plug wires were tight. It is bad enough to warrant not driving the Z. Thoughts? Regards, Shane

Thank you for the posts and making me think about the brake a little more. It turns out it was a very simple fix... the two bolts that held the caliper on were threaded far enough through to make contact with the rotor when the lugs were tightened. Not sure if I got the bolts switched around with something else or what but it is now fixed and good to go! Thanks again for the help!

It has rear disc brakes. I will try torquing it without the wheel on to see what happens. If I remember correctly, I tried this and it did the same thing. I know for sure the wheel is not hitting the caliper or any parts of the brakes.

Hey Z car fans, I have a 1974 260Z vintage race car. In the rear it has an R200, stock half shafts, and stock stub axles, stock hubs, etc. A very odd issue is occurring since I put the rear end back together. When I tighten the lug nuts, the left rear axle does not want to spin at all! When the lugs are not tightened, it spins fine. The car is not drive-able when the lugs are torqued as it can barely move and makes a sound that sounds like it is coming from the hub of the left rear. I recently had the trans, drive shaft, diff, half shafts, and female parts that go over the stub axles and held on with the big nut out of the car and reassembled it. Right now I am guessing something is going on with the left hub (I had never had an issue before and it all looked good in there, spindle included) or something else with the left rear. It is not the brake caliper itself as the wheel spins when the lugs are not torqued. My plan is to take the half shaft and female stub axle part apart and see what I can figure out. From what I remember I do not think there is too much margin for error when reinstalling the female stub axle part and nut. Other thoughts? What should I be looking for? Thanks, Shane

Current update: We tried Blue's suggestion and same symptoms were happening... it was not pumping out fuel (and yes we did have the gas can high enough). But here is the good news... my father hooked the fuel pump directly up to a battery, while it was hooked up to the 280Z's fuel tank, it shot out fuel like crazy. So it seems like a fuel tank issue is ruled out... phew! Sounds like we have a voltage/current issue. We plan to spend a little more time this weekend to dig in and figure it out.

Thanks for the next round of suggestions/info. Couple things: The pump is mounted in the exact stock location. The line going to it looks to be the original set up from the lower right front corner of the tank kind of behind the passenger rear wheel then to the pump. The diaphragm/tank looking thing that evens out the fuel pulses is present as well. Going from the pump to that has a good loop/180 degree? turn then like another 90 degrees towards the front of the car (I am trying to picture it from memory, car not in front of me) but looks to be the stock set up. Just called my father to clear up what happened last time. Fuel pump is receiving power. It does kind of seem like the fuel pump is spinning air. When removing the fuel line that goes from the tank to the fuel pump, it does let fuel come out BUT only for about 5 seconds then stops. In regards to a floater being in the tank that would clocg the hole, would this be a floater on the sending unit then or...? Say if it is a floater clogging the outlet, how would/could that cause the car to run well until about warm then run rough? I sure hope it isn't the sending unit as it looks like they are no longer available and used ones on Ebay for $400+. Is it possible there is something else going with a pressure/suction issue in the tank not allowing the fuel to come out? We did try it with the fuel cap open as well. To recap: -Car originally started and ran very nice for a few minutes then would run more and more rough to the point of so lean it would kill. Fuel pressure was never held at the 30 PSI mark, usually was around 15 PSI. -Installed three different pumps and now we cannot even get the car to start. No pressure read on the gauge. FastWoman, looks like our Z's are identical twins. Yours a five speed too? Zed Head, the wife and I took the 911 from WI to the West Coast from Washington through Oregon. Beautiful country! Loved it. Here's a pic from Crater Lake:

Gents, I somehow missed the most recent replies, sorry about that. Thanks again for all the info, help, and time. That's why I love the Z car community! So, we received and installed a new fuel pump and pressure regulator. At this point we can not get any of the three pumps to make fuel flow to the front of the car. It is like they are not pumping the fuel or not able to for some reason. This most recent stint I was not present for so am going off of my father's description. He used a vacuum to get the fuel flowing from the tank and it flows freely. I am not 100% sure if he stated the fuel pump is actually turning on and running or not. We are getting very close to pulling our hair out now and might be having a professional mechanic look at it in the next couple days. So, from what I understand from the replies, the fuel pump in a '78 relies on input from the alternator AND oil pressure switch? I am glad I do not have to worry about the ECU. I guess I do not understand what exactly I should be diagnosing right now or where to go from here.

Oh, and when I put the new fuel pump on, I will be putting one of those clear fuel filters on before it.

Here is a weekend update: -Checked the hoses from tank to filter: all good -Checked the fuel filter in the front: fuel that came out was excellent, no evidence of rust -There was an aftermarket new fuel pump in the car. No screen to check on the input side of it. Absolutely no evidence there of rusty fuel. Not sure if it was a bad fuel pump or not. Does not look like a 100% stock replacement item. -Tried running the car briefly without the fuel filter (no PSI difference), without the part right after the fuel pump that evens out the flow (no PSI difference), and tried playing with the fuel pressure regulator (no difference). -It still would run for a few minutes when cold at about 20-30 PSI then would settle down to about 10 PSI. Not sure what we did, but it would hold pretty consistent for awhile from 15 PSI to 22 PSI. -Absolutely nothing we took apart/did suggested there was a rust issue in the tank. I did have the stock Nissan pump. I check to make sure it worked before putting it in, and it did spin. We put it in and the car would not start at all, no pressure at all. Not sure if too much air got in the line or what. Is it possible that too much air in the line could cause it not to work? Put test leads at the stock pump and it apparently was not getting power. Messed with the leads and added another longer wire to the positive and that let it get power. It still would not spin/turn on when cranking the car and was getting 11 volts + at the pump. So, not sure what is going on there. I did pull out the thimble filter and it was super clean. I have on order a stock replacement fuel pump and a stock replacement pressure regulator that should be in tomorrow. It was suggested that if the pressure is that low that the aftermarket fuel pump might actually be bad/not producing the necessary PSI. Thoughts? Is there anything from the computer that would cause it to make the fuel pump run intermittently? Not sure how it is supposed to be on the 280Z but the fuel pump does not run constantly when the ignition is turned to the on position.

Gents, Thanks for all of the replies and resources. I will be out working on the car again this weekend and will do what has been suggested, and will make sure to keep matches away from the garage! Where exactly on the tank is the "inlet screen" located? Also, I know which one is the fuel pressure regulator but how do I check if the pressure regulator is good? I have yet to dive deeper into the provided resources so apologize if those answers are in there. Read through my Hayne's manual prior to posting too and it didn't have logical suggestions like provided here. I will post up what the issue was once determined. Just for fun, here's a pic from a couple weeks ago. Car is on the ground now, new emblems, etc. Just itching to take it on its first drive in 20 years (yes, all other fluids were changed & other recommended tasks). Thanks for the help, Shane

Hey All, My father and I have brought back to its former glory a 62k, prior one owner, 280Z 5 speed. We did some concours/close to concours bodywork/paintwork and are working on the finishing touches. One of those finishing touches is getting it running real nice. Here is some background: -Sat for 20 years or so (prior owner passed away) -Prior owner's brother this year drained the old fuel, put on new fuel filter, new fuel pump (not sure what brand), and put on a fuel pressure gauge -Tank has at least 4+ gallons of good fuel in it right now. So here is what happens: When we first start the car, it runs real sweet! Nice and smooth, revs up all the way real easy, etc. It will run real sweet for about 3 minutes the first time from cold. Fuel pressure shows about 10-20 psi (I am not familiar with what it should be at) right after the fuel filter. After about three minutes, it starts to run rougher, then even rougher, then to the point pushing the accelerator pedal causes some stalling, then to the point it pops/backfires through the intake, to the point it basically is not able to idle any longer. The mass airflow meter seems great. Ignition system seems great and adjusting the distributor not really affecting this. So what I am wondering if a sensor for running when cold is working fine but when the engine warms up a little the air/fuel mixture becomes way off (lean?). So what should I do/look for? Thanks, Shane

Thanks for the replies. I'll start first with the two areas of adjustment and see how that goes. As the brake pedal is pushed, the clevis and rod that is directly attached to the pedal goes in towards the front of the car or back towards the rear?

Jon, Thanks for the reply. So you would say the master cylinder is most likely just fine? I have tried adjusting the pedal before with the new/1st master cylinder but do not think I have done so with the current set up so that will be my first step. How can you tell there is 1/8" free play in the master cylinder? As the pedal is adjusted to the floor, the rod in the booster that comes in contact with the master cylinder goes towards the master cylinder or away? Thanks for the help!

Car is a 1971 240Z with stock components. Once I drive the car for about 10 minutes and it warms up, the brakes start to drag and continually get worse. If continuing to drive, it gets to the point where the brakes drag so much that the car is unable to drive. The front and the rear brakes both drag. Once this occurs, I stop the car and bleed both the front and rear bleeders on the master cylinder. Fluid comes out. The brakes then work fine and I can continue to drive without the brakes dragging. If I stop driving the car for multiple hours and let it cool down, I have to do bleed the master cylinder again once the car warms up. I have spent hours and hours on this issue and am at my wits end. 1.) Assume, as if I have done nothing mechanically, what might be the issue? 2.) Now.... below is what I have tried: -New master cylinder (installed by previous owner) -Different master cylinder (from my parts bin) -Combined parts from the "different" master cylinder and the "new" master cylinder as the front seal seemed tight on the new one (this is what is on there now) -Bled the brakes -Different vac booster (from my parts bin. Pedal used to have a very odd feel to it. It would be super sensitive and easy to move for about 1/2" then after that rock hard. My parts bin booster has solved that odd pedal feel.) -Different front calipers (from my parts bin) -Adjusting the rod/piston further in and out on the back of the booster (so the master cylinder guts travel further or not as far)