jas280z

I clamped off the supply line right before the fuel filter and the return line right after the FPR. Within an hour the pressure had dropped to 0. I guess that at least one injector or the csv is leaking as well. I was planning on having my injectors cleaned and tested, I was just hoping to wait until winter to do so, but I guess I may as well do it now. Next I will try clamping off the supply line right before the filter, the FPR return line, and the csv, to isolate the injectors.I am assuming that the pressure will drop, but I may as well check to make sure. I think I will also run another test in which I will clamp off the supply line after the fuel filter and pressure gauge. The purpose of this test will be to isolate the check valve, to see once and for all if that is leaking. So far all I have been able to determine with some degree of certainty is that I have more than one component allowing pressure to escape. My main suspects are the check valve and the injectors/csv. Unfortunately I cannot think of any way to isolate the FPR and still get a reading from my pressure gauge so I cannot tell for sure if that is leaking, but with the amount of crud that was in the fuel lines when I bought the car I wouldn't be surprised if that is bad as well.

My '78 280z with stock EFI does not keep fuel pressure overnight, and I have been experiencing fuel vaporization problems upon hot starts. I believe these two issues are related, so I am working to trace where the fuel pressure is escaping. Last night I ran the car for about 30 seconds to put it in its night time parking spot. I had my dad clamp off the FPR return line as soon as I shut it off. When I checked the fuel pressure this morning it had dropped to 0 overnight. This leads me to believe that either the fuel pump check valve or the injectors are leaking. Today I repeated the test, only this time I clamped the line that leads from the pump right before the fuel filter. After 2.5 hours the pressure had dropped from 36 lbs to 28 lbs. This tells me either the FPR or the injectors are leaking. As soon as I removed the clamp the pressure dropped again to 20 lbs. It would seem that the pressure before the clamp dropped as well, and the two pressures equalized when I removed the clamp. So it seems that I have at least 2 culprits, the check valve, and either the FPR, the injectors, or both. I am about to run a third test, this time clamping both the supply and return lines where I previously clamped for the last two test. I believe that if I still lose pressure that would mean that the injectors are leaking as well. Pretty much I am wondering if my tests are rationale are correct. I have a spare FPR I can put on if it comes back that it is indeed my FPR that is leaking, I was also considering putting an inline check valve in between the pump and filter to supersede the pump check valve which also seems to be leaking. I am thinking about this one from Summit Racing http://www.summitracing.com/parts/CRT-169-1002/ , after seeing that someone on Zcar.com is using it with no problems.

If I am understanding the theories presented correctly it would seem to me that newer cars fuel systems are working properly and don't allow pressure to bleed back into the tank out of the line. Keeping the liquid fuel at said pressure should make it much more resistant to vaporizing, as the vapor would need to expand and there is no area in which it can expand. In 25 years these cars may experience the same problems. Or not, their components may have benefited from the shortcomings of previous systems and not be as prone to failure.

T-Bone, the only problem I can see with that is it appears to be designed as a radiant insulation, it appears quite thin. I know in my Heat Transfer class last semester the Prof said that sufficiently thin layers of insulation can actually increase thermal conductivity due to convection. It may actually exacerbate the problem.

I hear what you are saying Tony, I probably should have worded that better. I realize that the pressure reading on my gauge will have little value in diagnosis of the problem, as fuel can leak back and the vapor will keep it at a constant pressure (kind of like a capacitor in a fluid system I suppose). I was trying to say that under normal circumstances (cooler days when this heat problem is not encountered) my fuel pressure will stay ~30lbs for at least several hours, although it is almost always at 0 by the next morning. Therefore I do believe the check valve could be allowing the lines to slowly lose pressure and I will look into replacing it as soon as I get that far. I will definitely look into extending the priming pulses as well, it made sense to me that getting the pump flowing would help move the boiled fuel out and cool down the system. As I was sitting in a parking lot the other day I was wishing my 280z had the system like my dad's 280zx where the pump will turn on for a few seconds to get the fuel flowing when the key is turned to the "on" position. And it doesn't happen very often, we are just experiencing the hottest weather in Buffalo in 3 years, as is much of the North East. But normally we are not exactly known for our sweltering conditions.

I am fairly certain in my diagnosis of it being the infamous heat/fuel problem (again I know vapor lock is not the correct term, but I haven't seen an actual name for the problem), which is why I didn't post symptoms. The main purpose of my post was to see if anyone had used compressed gas to cool the affected areas. My symptoms are that the car will not restart after it has been sitting for 5-15 minutes on VERY hot days. After it cools a bit it will start right up. It does keep pressure for several hours, although I have been planning on replacing the check valve. Unfortunately I am running the stock ECU, haven't had time to mess around with getting MS, trying to get it ready for the summer first.

I finally found a definitive answer (TonyD answer) on the purpose of the fan, as well as describing the problem I am looking to solve: "Exactly the conditions it was made to combat! There is a period from around 5 minutes after you do a hot-shutdown (in warm weather, above say 85 and running on the highway) to about 12 minutes where no matter what they tried, Nissan could not prevent the formation of vapor in the rail due to pressure rise, and FPR venting it back to the tank. Initially it starts with the fuel expanding and venting, then pressure drops and it flashes... The S30's with EFI does this, and it's the reason the S130's have a priming pulse, as well as the cooler on them. In JDM, they had a vehicles with plastic valve covers to combat heat transmission in un-vented hood engine compartments like the Cedric, Leopard, Gloria, Laurel, etc... Timer criteria is coolant temp above something like 215F, and as mentioned no longer than about 15 minutes of runtime after shutdown. It may turn on some time after shutdown as well, should the temperature rise to the point it gets triggered, but in any case it will not start after being 'ignition off' for 15 minutes no matter what happens. One thing you can do to forestall the hard-starting is simply change the 'priming pulse' for your Fuel Pump---make it run for 10-15 seconds to take that heat out of the rail and get fluid petrol up there, it may be stumbly after the start, but it is FAR better than trying to crnak and bleed that vapor out of the rail using the normal pulse and cranking/cranking/cranking. I've noticed it's exacerbated of course in hotter weather, but also as your tank level goes down. Ever do a fuel temperature reading when you go highway driving with less than a 1/4 tank of gas? Scary how hot it will get! Yeah, I know, I got WAAAY too much time on my hands to be checking crap like that out of simple idle curiosity. What can I say? I'm diseased! " Here is a link to the post to which I am referring, in case anyone would like to read it in context. http://forums.hybridz.org/index.php?/topic/68780-what-is-this-part-in-the-engine-bay/page__pid__648324#entry648324

I know it is not vapor lock per say, but it is a heat problem that is related to the fuel delivery, I haven't heard any term to describe it and vapor lock seems to be the closest thing. I am fairly certain this is the reason why Nissan installed the blower fan on 280zx's. And I wouldn't try to instantly cool the rail, just a couple quick spurts from 8-10 inches away to get some forced convection to cool the rail a bit. If worse comes to worse I may end up having to install one of those blower fans, I just don't like their looks.

If you can't find any NJ-5 you can always use the older Newton2 Meter (N2M-3) it is pretty much the same stuff.

I was wondering if anyone had ever thought of using one of those pressurized keyboard dusters on their fuel rail when experiencing vapor lock to try to cool it? I have been trying to think of something to use, because it is no fun sitting in the parking lot waiting 15 minutes with the hood open for it to cool down. I thought of a CO2 fire extinguisher, but those can get expensive and probably wouldn't last very long. I know that the propellant that comes out of the dusters is very cold, so cold that if you hold it upside down and spray it will freeze just about anything. The only problem I can think of is it may not be safe to leave in the car on hot days, kind of defeating the purpose. And police may frown upon it being in the car since it has other less than legal uses. I will also have to find the non-flammable version. Any thoughts? Apologies if this is a double post, I tried to post this today before work and couldn't find my post when I got home. I think I forgot to hit the post button .

If he has 77 or 78 bumpers, then they won't be the same (anything can fit with enough time and $). I think the 75-76 bumpers were the same as the later 260's, but I am not sure, I am just sure that the 77 and 78's were different. Either way the bumpers are going to be quite heavy, and bulky, shipping could be a pain. I think it cost something like $70 to ship a rear 240z bumper across the country to me, and that bumper is significantly lighter than a 280z bumper.

My apologies, I completely read that one wrong. Probably should have realized that someone with 3000+ post would know that. I never even heard of the s31, interesting info.

It is right in the name of the sub forums, s30 was 240-280z (70-78) s130 was 280zx.

So I got the front suspension done, Eibach springs and Tokico HP's, also all new urethane bushings from MSA. I am holding off on doing the rear, as I have a feeling it is going to be a challange. New MSA sway bars front and back. Konig Rewinds, 16 inch, with Hankook Ventus HRII rubber. 225 50's in back, 205 55's in front. I still need to put on a few badges and put the interior back together. I am bringing it to the ZCCR All Japanese Car Show this weekend so my goal is to have most of the work, minus the rear suspension, done by then Enjoy:

Yeah we destroyed the glass trying to get it out, wasn't a good day. We pulled the chrome trim from the old gaskets, the glass guy reinstalled it with the glass in the new gaskets. He actually spent most of his time with those pieces. Came out really nice. More pictures on the way, waiting for them to upload to photo bucket.

Just some dielectric grease and a brush to get any corrosion off.

Fixed the problem by removing and cleaning the connections at the fusible links, fuel pump relays, and ignition relays. Don't know which of these was causing the problem, may have been a combination, but it is better now.

Thanks for the compliments! The valve cover (as well as timing cover, engine mounting brackets, thermostat housing, intake manifold, etc...) was powder coated with, as the powder coater called it, a "flip flop flake" clear. It causes the color variations when exposed to uv light. It looks really cool in the sun. Since my last post we got the engine in and running well. I have run into a few problems here and there (check some of my recent posts) but we seem to have cured the electrical gremlins today with some cleaning of connections. I have also installed twice pipes and redid the front suspension with Eibach springs and Tokico HP struts, as well as urethane bushings from MSA. I have been taking pics here and there as we go along, once I get time I will upload them. Right now I am focusing on getting it ready for the All Japanese Car Show in Rochester held by ZCCR next weekend. I still have to get the interior put together, mount the hood and front bumper for good. Unfortunately I don't think the rear suspension will be done by then, will have to do it after.

Thanks Nigel, I should have thought to look at Black Dragon. And thanks for the offer two40zjunky, but I got one from the local Nissan dealer the next day.

That is the Auxiliary Air Regulator. If I remember correctly a plug, like a fuel injector plug, get plugged into it at the bottom left corner of the box you circled. I am not sure what pair of male and female connectors you are talking about.

Tried to start my 280z yesterday to move it in the garage, started right up, but then died immediately. Tried to restart, but noticed that the fuel pressure gauge in the engine bay wasn't showing any pressure. Looked at the gas guage and noticed that it wasn't showing anything, the needle never even went up to E. Got under the car and tried to start it and the fuel pump wasn't turning on. Tried the headlights, they didn't work, but the running lights came on. Hazards worked, but no turn signals. Voltmeter in the car showed 14 volts. Today, while trying to diagnose the problem, the problem got worse to the point where the car has not power what so ever. The car had power, I pulled the fusible link covers, looked at them, and put some di-electric connectors between the fusable links and battery, which I think are fuel pump relays. After I did this the car had no power at all. I pulled the connections back off and checked them, and they all looked fine. When I pull the negative cable from the battery and put it back on there is not very minimal sparking, and you can hear a couple clicks in the car, sounds like they are under the dashboard, but there is still no voltage. The only changes I have made since the last time it ran fine is a new differential mount insulator and currently redoing the front suspension. One other thing of note is that the headlights occasionally wouldn't turn on, but they would always turn on with the next try. I am going through the wiring diagram in the FSM, trying to figure out what the problem could be, but I was wondering if anyone had any suggestions. Thanks.

I have new mustache bar bushings with the master kit I got from MSA, just need to install them. I'll look into the RTz mount, but for now I REALLY just want to get on the road, been working on this car for about 10 months and I need to remind myself why I am doing all this work .

I have a 3.9 R200 swapped into my 280z (was originally 3.54 R200). I found that under acceleration the prop shaft hits the sway bar. I am going to replace the diff mount insulator, as I read that a worn one can cause the diff to do just this. I noticed that there is one for a 72-78 s30 and a different one for an s130. Am I safe in assuming that the difference is in the cross member that supports the diff and not in the pumpkin? I am fairly certain that the pumpkins are identical between those years. So I think I still need the insulator for an s30, is this correct?

Solved! Turns out that the prop shaft is hitting the rear sway bar under acceleration, I am thinking it may have to do with the car squatting under acceleration. I am probably going to replace the diff mount at well as possibly fabricating up a spacer to put under the diff mount to raise it 3/8 of an inch or so.

Thanks for the procedure, I will most likely try this once I change the slave. I was already planning on changing it so I had it on hand and that is my first course of action. I really hope it is just a problem with the clutch engaging via pedal or slave, I really don't want to have to pull the transmission right after installing the engine, and then of course I would have to find a replacement before July 11th when I plan on taking it for a few laps of Watkins Glen, or else I'm going around the track in a Jeep Liberty. Just a thought, could this possibly be a wheel bearing? I have never actually heard one go bad, but I understand that they grind. The sound did sound as if it was coming more from the rear end and I am fairly certain it is not the differential. Although I will look into the diff as well to rule it out.