I have a 1983 280zx Turbo. Is the gas cap vented or non-vented?

The reason I ask is.....With the cap on and screwed down tight the car does not want to run above 3000 rpm if you have it to the floor. It bogs and bucks. If you let off the accelerator a little it will take off and run right up to top speed with power. Once it takes the fuel you can floorboard it and it runs like a scaled dog.

Take the cap off and it runs all the way up to full speed without bogging/bucking. BUT is doesn't seem to have as much power and get up to top speed as fast.

Put the cap back on and it acts just like the first paragraph I wrote on bogging/bucking unless you ease off a little.

Any help greatly appreciated.........RoscoP

 

Assuming original gas cap is working right, sounds like the tank pressure equalization/venting set up isn't performing. Your FSM diagrams show a carbon canister in the loop - along with a pile of other stuff. If that's original, could be blocked up - or you may have a bad hose somewhere in the loop. Fuel pump apparently working right. I would go through the FSM and check everything that gets involved in regulating your tank pressure when the cap is in place and your pump is sucking fuel out. Excess negative pressure could cause the symptoms you describe.

 

Thank you....I'll print out a schematic and start checking everything out. This is an all original car with only 8500.0 miles and I tested the fuel cap and it seems to be working properly.

You can suck on the cap and there is some resistance.

It has been in storage for the past 10 years and not run. I replaced the fuel, spark plugs, fluids, air filter, fuel filter and hoses.

It fired right up and runs perfectly except for this bog/buck when you want to put your foot in it and kick in the Turbo.

 

Amazing find for an '83! Lucky guy.

There have been a lot of posts here on how to carefully bring back a car that has been in long term storage. There's a lot to consider. We have some great 280 guys here. Good for you that it is running!

I suspect your hoses didn't take too well to all that down time. When you finish catching up with the regular maintenance it has missed, you will have a real prize there.

We would all like to see some pics when you get the time.

 

Along the same lines as having a pressurized tank or a gas cap not venting properly....When it comes to the EEC filter on the bottom of the charcoal canister...Since I'm not in Cali, and I doubt if it will ever see the day it has to be smog checked....If I do not replace the filter, and just leave it off, what are the results????


I see that the fuel tank vapor vent line goes to the canister, one line is the ported Thermal vacuum valve, down to the valve on the front of the throttle chamber...The other line to the center of the throttle chamber, the canister purge line.

I can't see where the fuel tank vapor vent line would suffer it it didn't wasn't filtered.

I'm referring to page 59 and pages 136 and 137 of the Haynes manual.


Old Codger

 

Yeah, OC, I agree. The car would probably run just fine. I believe that system is there to keep gasoline vapors out of the atmosphere. I think it was about that time (80s) when the authorities decided gasoline and its fumes had to be kept in the cars and in the gas pumps - and not allowed to escape. Nissan did their best to meet the standard - and sold Z31s in the USA.

In new cars the pollution controls are more elaborate, computerized and much more successful. We like to complain but if you want to breathe what we would have here without all those controls, pop down to Mexico. During rush hour, you have a hard time breathing in the street whether you are in a car or just walking down the sidewalk. It's a lung-challenging experience.

 

I took a schematic of the Engine Fuel & Emission Control System pages 125-126 in the FSM.

A. Carbon Canister Purge Control Valve checks out OK (no leak).
B. Carbon Canister Constant Purge Orifice does not check out (does not leak) like it is supposed to leak.

I blew short spurts of air (120 p.s.i. as suggested on page 126) through attached hose and it did not free it up.

It says to remove Purge Control Valve and check constant purge orifice for leak. How do I remove the Purge Control Valve without breaking it?

I see no way for it to come off.

I've enclosed pictures of FSM dealing with this self check.

All help and suggestions greatly appreciated.

 

Can you post pics of the canister and the valve you are checking? Also, is there any chance this problem started after you replaced your hoses or did other work?

Thanks.

 

Here is the picture right out of the FSM page 126. Turbo is type "B". I've had the car about 3 months and it has had this problem right from day one.

I did not replace any of the hoses on the canister. They are all fine. I only replaced one hose that was cracked coming from another location.

Thank you~~~~~~~~Rosco

 

OK, I'm seeing some basic Japanese problem with English here. (Glad they got better at it in later years.)

SEC586 shows that they mean a whole assembly when they say "Purge Control Valve"

SEC585 shows the 'valve assembly' as that cap-like unit on top and to the right - with the hose(s) coming off it. So that's what they tell you to remove. The valve housing looks like it's cast in one piece, so they must mean remove just the center part of it - with the spring, etc.

Since the center part wasn't born in that position but was put there by the assembler, it must screw, snap or pop off. You get to experiment. Looks to me like you would turn or twist or pull it by the hose fitting - and pop it out.

Since you already found non-standard canister performance above, have you thought about just replacing it? I think I would have gone to a recycler and just dropped in a used canister to see if it works better. If no recyclers have one, you don't have any choice but to repair this one. Which looks like it means taking it apart.

Maybe another option is to circumvent the canister altogether - but we don't have emissions to pass around here - and it would take expert instructions I can't give you. You could send Old Codger above a note to see if he has any ideas and how his Z runs after his mod to the emissions stuff.

 

My reply to Rosco...


Rosco, consider that I'm a SIMPLE man with a SIMPLE mind....On your original post you made mention of a possible fuel restriction, and that you didn't know where it might be coming from...From time to time, my 81 2 x 2 would act up the same way. First start of the day, and everything is fine. Go run for miles and miles, no problem..But if I stopped for say up to 15 minutes, then went to run...it would start, but run terrible....I found that if I loosened the gas cap, then ran, everything was fine again...Or if I didn't loosened the gas cap, then it took a little bit of pumping the gas pedal to get it to smooth out, and everything was fine again...Sort of like the symptoms you described.

So my question to the forum was, what would happen if I just took out the charcoal filter from the canister

Then the vent would not have any restrictions from the charcoal canister anyway.

So to keep things SIMPLE, all I've done is just take out the charcoal filter, but left the canister and all of the lines hooked up. So any of the so called fuel fumes would just go straight thru.

My thoughts on that were, the air that comes from the fuel tank vent would not really need to be filtered, because it's not anywhere that dirt and dust could get in...

So basically, the vent is now unfiltered air, from the canister, going directly to the intake manifold.

If you have a Haynes repair manual...look on page 143 and you'll see where the canister purge line goes to.

On that fuel check valve that is just outside of the fuel tank...I don't know if I can by pass it too. But if I do, I can't see where I really need it??????

If you're at a state that has to do emmisions, then things would probably get screwed up. I'm not....

As far as driving with out the filter in the canister??? I sure don't notice any difference. Starts and runs fine...I can stop for 10 or 15 minutes, get back in, start right up and runs just fine.

Hope this might help.


Old Codger

 

OC: You got my old brain working after your original post. So...I disconnected all the hoses from the canister and plugged the 3 going to the engine. I left the hose coming from the fuel tank unplugged. The gas cap is screwed down tight.

It performs perfectly (idle, acceleration and etc.)

If and when I get ready to sell, the new owner can buy a canister that is working properly if he so desires. Mine had the valve plugged inside the canister (little hose running to engine).

I live in Florida with no emission inspections.

Thanks again for everyone that answered my original post.

RoscoP

 

Rosco be dah man. Is this the same as running with the gas cap off?

 

It appears to run the same as when I had the gas cap off and all hoses hooked to the canister. I now have the cap screwed down tight with the 4 hoses disconnected from the canister.

I plugged the 3 to the engine and left the one from the tank unplugged.:

I'm very happy with the performance.: