steady88

I've come along way, but I still have a problem and I'm pretty sure it's fuel pressure related. I have a fuel pressure gauge hooked up between the fuel filter and the rail and discovered after a short amount of driving, or even just idling, the fuel pressure sometimes drops from around 30-34psi to as low as 15psi. I found that removing the fuel cap would solve the problem and so I though it was an issue with vacuum or the tank breathing. But, this no longer makes any difference. I have changed the fuel lines from the tank to the pump and also and have changed the fuel filter a couple of times and have even cut the filters open to discover they weren't clogged, just a couple of black specs. The pressure doesn't always consistently drop down low, just have noticed it a few times. I have also changed the pressure regulator, but perhaps the replacement could be stuffed. I know that if I revv the engine, the fuel pressure drops about 6 - 8 PSI. At the moment, the car is drivable, but it does run very rough and struggles to get over 60kmph. Up until about 2 weeks ago, It was running much better, not perfect, but I was able to comfortably cruiser on the highway at 110. On a side note, might be unrelated - the other night when I stopped the car, I checked the pressure and it was 15PSI, then next morning, without starting the car, the pressure was sitting at 30PSI.

Got it solved!!! I had tried what you suggested a while ago, but it made no difference. I have since tried driving with the fuel cap off and it runs perfectly! I think the valve in the fuel cap is stuffed and not letting air into the tank.

So I have a 1979 280zx and have been having an issue with my engine (1 of 2 issues preventing me from getting her registered). I have posted in another section about my problem a few months ago, but I think I may have narrowed it down to the fuel system in particular. The engine is running pretty rough and has a lack of power. I have noticed an interesting pattern though after working on it. Every time I open up the fuel system to work on it and then close it back up (reconnect and tighten all hoses) it runs great for around 5 - 10 minutes! What's going on here? I have replaced the fuel pressure regulator and installed a pressure gauge between the filter and rail and all appears okay. What on earth is going on!!! I would appreciate your help, I'm so confused! Thanks! steady88

Thanks for the offer. I have the R180 diff and have read that the mounts are different between the 2 diffs. But, doing more research, it may seem that the diff mounts are in fact the same, but just have different part numbers. Do you know if this could be the case, if so, I would be very keen to accept for offer!

Yes, being the auto it is an R180.

I'm looking for a rear diff mount for my 79 auto 280zx. If anyone has one, or knows where I could possible find one, It would be great to hear from you! Cheers, steady88

I electronically disconnected the fuel pump. Besides wiping it out with metho, I didn't clean the tank as it was clean and there was no crud in the tank at all. The only crud was actually in the sender pipe going to the pump. Even the strainer in the tank was clean. I have since checked the strainer and pipes and all were still clean. Even the fuel filter was clean. But what you are staying is interesting. There could be a build up somewhere which goes down when reducing that pressure. But, the fuel pressure gauge shows about 31psi and doesn't change at all when the car has a lack of power. You would think there would be a change in pressure. When I originally saw the red gunk, I thought exactly the same. Rust. But, I now think it was the old fuel in the pipe. It seems to have only been in the metal pipe, not in the rubber hoses. Perhaps some sort of reaction to metal. Inside the tank is amazingly clean. There was some discolouration on the bottom, but thats about it. I did my best and wiped it out with metho while I had it open. But, I'm confident it is clean.

I have checked the sensors with a multimeter and they are all good. I have tried to test the harness connector at the ECU, as per the FSM only to discover that the pins do not match the FSM, in fact, many are missing. One thing I will note, if I disconnect the TPS, there is no difference to the way the car runs. Not sure how big of a difference it is suppose to make... I'm new to this world and want to learn and have the enjoyment of fixing the car myself.

Thanks for the advice everyone! I cleaned out the fuel sender unit from the tank, as the fuel line to the pump was full of red gunk. I also replaced the fuel pump as it was also full of gunk. Now the car runs very well and has lots of up and go! My problem now is, the runs great for about 5 - 10 minutes, then slowly starts to run worse and loose power. Now here's the interesting thing which I can't work out. I wanted to rule out if this was a fuel pressure issue, or something else, so I disconnected the fuel pump to relieve the pressure. When I do this, and plug the pump back in, the car runs great for another 5 - 10 minutes. I thought, ah, this has to be fuel pressure. I swapped my fuel pressure regulator for another one and put a fuel pressure gauge between the filter and the rail, and the pressure is right on spec. I don't understand??? Why does reducing the fuel pressure (unplug the fuel pump for a minute) make it run good for another 5 - 10 minutes - because, as soon as I plug the pump back in, the pressure builds up straight away anyway. I should also note, that the car is warmed up and appears to make no difference if the car is warm or cold. Cheers!

I think I have made a major discovery. Cylinders 1, 2 and 3 are not firing. I'm getting spark and the injectors are receiving pulse. I can unplug the first 3 injectors and they make no difference to the way the car runs. I can swap the injector cables around and still no difference. Unplug one of the last 3 injectors and the car nearly stalls.

No signs of rats in the engine bay. I have removed all of the old fuel (very little), and replaced the fuel filter. I bled any old fuel out of the fuel rails and fuel lines.

I probably didn't explain that too well. The timing marker is at -10 degrees before 0. When revving up, it continues to move further backwards towards -20, then to -30. The manual I have, says 10 degrees BTDC. The auto was factory and the car does move when in drive. Just gets to 1500rpm and wont go any higher. Sometimes, if I'm lucky, it takes off for a second, but then something happens and it only revs to 1500. Car also moves in reverse and in 1st and 2nd. Though, in 1st it moves very slowly and doesnt appear to rev as high. The car doesnt stall at all, but when it does warm up (temp meter at half way) it will stall, miss, backfire and hardly move at all. Wait 5 mins, so worries.

Yes, I have been doing some research on replacing the advance unit and intend to. But, at the same time been looking at perhaps replacing the distributor. I did come across this on eBay, which is nearly the same cost as repairing or sourcing a new advance unit. Perhaps this might be a better option? http://www.ebay.com.au/itm/ws/eBayISAPI.dll?ViewItem&item=200806516048#ht_2808wt_920

Saturday Update! Well, today, I checked the fuel pump and discovered it is a little different to the one shown in the manual and it has no filter. It must be after market... I did change the fuel filter again just to be sure and emptied the old fuel from the filter into a clear container. The fuel was a very light yellow colour, smelt fresh and had a few very small brown specs in it. I also had a spare ignition module and swapped that over. I took the cover off the TPS and all looked okay and tested out okay on the multimeter, I did make a slight adjustment to the angle though. The timing does appear to advance when I rev it up, though, Im assuming the white line moving from 10 to 20 + is advancing or should be it going backwards towards TDC? Car rolls in neutral, brakes definitely are not sticking... A few things I have noticed, which may be related. When I put the car into D or R (or put load on the motor I guess), there is a whinging, hissing, squealing type sound that comes from the throttle, distributor area. Not sure if this is normal... Also when the car warms up, it seems to start missing and runs really rough (also backfires if I plant my foot, esp under load). Let it cool for 5 mins and all is good again for a bit. An interesting thing I noticed today, it backfired as it was warming up and I was accelerating very slowly in D, but just after the backfire or pop under the bonnet, it felt like it had full power and was about to take off for 2 secs. But then dropped back down to 1500rpm. hmmmmmmm!

Thanks for the advice everyone! I'm going to try your suggestions this weekend and I will report back!

Hmmmm, interesting. I have checked them and cleaned them. An interesting thing, is that when I disconnect the TPS, there is no difference to how the car behaves. Not sure if it is meant to make a difference or not. I have tested the unit with a multimeter and it all seems good. I will have another clean and check again. Cheers1=!

Thanks. I know that in 1st is revs even lower and hardly moves at all. Reverse is the same as drive, struggles up to 1500.

Ah, okay. How do I go about checking this? Is it in the actual pump?

So you may have read on some other threads that I'm having a little problem with my automatic 280zx. I thought I should post a dedicated thread to my problem, in the hope someone else has had this issue and might be able to give some advice. After reading plenty of other treads, I just can't seem to pinpoint what is happening and I'm unsure what to do next. I should also mention that the car has been sitting for 6 years (long story), but was in perfectly running order before it sat. I have removed the old fuel from the tank and flushed out any old fuel from the fuel rails and fuel lines, and replaced the fuel filter. My 280zx starts fine, idles smoothly, revs up nicely and freely, but when in drive it has no power and will not rev past 1500rpm. Things that have been replaced. - New spark plugs - New coil - New fuel filter - Replaced 2 broken pipes - New fuel injectors - New oil filter and oil This I know and or tested: - Every injector is receiving a pulse - Every spark plug is receiving spark - Vacuum advance is leaking vacuum and not working - Checked other vacuum pipes for leaks, all looks okay. (Not sure if there is a vacuum to the auto that could be causing this issue) - Timing light shows the timing is 10-11 degrees from TDC. - Checked air flow meter and appears to be working. - Tested the throttle position switch and it appears to be working. - Unplugging the temp sensors makes the car run rough, so I think they are working. I'd really appreciate anyone who might be able to help! Cheers, Steady!

Hey, I'm having problems with my 280. It has no power at all when I put my foot down under load and wont rev past 1500 in drive. I know for a fact that there is a vacuum leak in the advance diaphragm which I want to replace or repair. I was wondering though if this in fact is my problem. Does the vac advance make a big difference to performance? If it is not working, would I experience no power at all? Cheers, Steady!

Well, I gave all of the connectors a good clean and still no luck. I have noticed that the car stalls when it warms up and will not start again until it cools down. In fact, if I do manage to keep the car running, it runs really bad once it warms up to operating temperature.

Well, after cleaning the TPS, AFM, and the connector going to the distributer and the other going to a valve on top of the throttle. The car seems to be idling just a little bit better. Unplugging the TPS makes no difference to the way the car runs though. Perhaps this in itself indicates a problem?

Yeah, well it made some difference to the idling. Tomorrow I'm going to clean every connector and see how I go.

Thanks for the advice! Well, I unplugged the connector and discovered it was pretty corroded. So I cleaned it out with WD40, started the car up and it did appear to idle a lot smoother. But, it still wanted to stall after revving and had no power when accelerating. Also, when idling, the car just stopped, just like turning it off which I thought was a little odd. Might be unrelated..

Well, good news. It definitely was the injectors and the car is now running! My next problem is that it has a rough erratic idle, but revs up okay. Also, it has no power under load and if I was to put it in drive and put my foot to the floor, it will only rev up to about 1500 rpm and move slowly. Also, after revving the motor while stationary, if I take my foot off the accerlator fast, the car will stall. The only way to stop it from stalling is to slowly take my foot off. It tends to idle at about 400 - 600 after giving it a few revs. My research suggests that the air flow meter is not working correctly... It does look like it has been opened and siliconed back together a few times... But could also be a vac leak or one of the many sensors not working....