280zx Fuel Tank Vacuum and Fuel Check Valve
Posted 17 July 2009 - 01:29 PM
I am trying to locate a source for the subject part. No luck so far. Nissan Dealers have poor reference drawing for the 280zx. This part is under the car near the fuel pump and under a cover plate. The part is generally between the fuel tank and the Carbon Canister and is referred to as Fuel Check Valve.
I am generally trying to eliminate excessive pressure in the fuel tank in hot weather (100+ degrees).
Posted 17 July 2009 - 03:42 PM
1974 610 N/A
Posted 17 July 2009 - 04:05 PM
Courtesy Nissan in Texas and local United Nissan are unable to ID this part. Also, Motor Sport and Black Dragon do not carry this part. This is a major part of the Emissions System and no one can ID it.
I will attempt to attach a photo of the part. If I am successful the PN noted on the pic is apparently not correct (PN 17330-P7900).
Edited by oldschool2, 17 July 2009 - 04:10 PM.
Posted 21 July 2009 - 12:54 PM
Bad news is that the part is no longer available. At least I (hopefully) have something solid to go on.
Posted 27 July 2009 - 03:30 PM
I know what part you are looking for its under the plastic cover by the differential and the evaporative line from tank goes to it. Try Z Car Source of Arizona 623-581-9228. I've gotten hard to find parts from them.
The fuel tank vacuun relief valve part of the check valve , was relocated to the gas cap in 1982.
79-81 gas caps do not have vacuum relief built in them therefore the 3-way type check valve.
The 82-83 gas caps have vacuum relief in them, therefore 2-way check valve.
This also implies 79-81ZX fuel caps will not work on 82-83 ZX
Edited by Randy 80ZX, 4 weeks ago.
Posted 28 July 2009 - 08:58 AM
As an update: I have drilled a hole in the gas cap to eliminate the excessive pressure build-up in the fuel tank. Now no more pressure (not-vacuum) problems, and the affected fuel pump is quiet now that it is not working so hard. This is in 110+ degree weather (Las Vegas).
I have about concluded that the 280zx is unable to handle these extreme temps. The combination of fuel expansion in the fuel tank and heat soak/vapor lock "symptoms" makes this a car suited for below 90 degrees driving only. I have replaced almost every part in the FI system, including removing the strainer in the fuel tank (I added the fram inline before the fuel pump). Everything has helped the car run excellent except for the fuel tank pressure (now solved via the hole in gas cap). Plus the start-up problem when trying to restart after driving in 110 (in shade) temps. I have also wrapped the fuel lines with insulation.
I have noted that the 300zx has a fuel temp sensor. Not sure of it's purpose. I just know that this seems to be a common problem and some desert runners say they have no such problem. These old Zcars have frequently been modified to the extent that there is no telling what is or is not under the hood. My car is not modified.
Posted 28 July 2009 - 09:08 AM
I have about concluded that the 280zx is unable to handle these extreme temps. The combination of fuel expansion in the fuel tank and heat soak/vapor lock "symptoms" makes this a car suited for below 90 degrees driving only.
Or just bypass it with a short length of hose. That way, the tank simply vents w/o back pressure through the carbon canister. It really has nothing to do with "vapor lock" since it's not on the fuel side of the circuit. I did that and my ZX runs just fine at 100-100F without restart problems at all.
Posted 28 July 2009 - 12:44 PM
The heat soak/vapor lock I mentioned is a separate problem. With no pressure build-up in the fuel tank due to the hole in the gas cap I still am unable to restart the engine without raising the hood (to speed-up cooling) and waiting 10 to 20 minutes.
I have read numerous posts regarding this problem (cars in general, not just the Zcars). I have not heard anyone mention that when the pavement is maybe 150+ degrees pushing hot air up, and the engine and undercarriage is around 200 degrees pushing hot air up/down sandwiching hot air from two sources (payment and undercarriage) the fuel seems to vaporize in the fuel tank and fuel lines.
Before I drilled a hole in my gas cap I drove about 40 miles in 110+ degree temperature. I stopped the car, shut off the engine and loosened the gas cap. There was so much pressure (not Vacuum) in the fuel tank that gas came squirting out in high volume. I was just barely able to retighten the cap. That was when I decided to drill the gas cap.
Posted 29 July 2009 - 05:39 AM
Posted 29 July 2009 - 05:47 AM
The starting problem is probably a leaky injector or a bad "check valve" in the fuel pump itself. A fuel system leak will allow the pressure in the fuel rail to go to zero. When it goes to zero, it vaporized(boils) quickly and you get vapor lock.
Last design feature of the ZX is the FAN that cools the injectors. Usually some dumbazz previous owner removes the injector fan (and heat shields) because they want to strip out "all the crap" out from under the hood. The fan blows a layer of air to the fuel rail that deflects rising heat when you shut off the engine.
If you drilled a hole in the tank, have a fuel leak, and have no injector fan, then of course there will issues with hot starts at 110F. Make sure you have the fan and add an $18 fuel pressure gauge just after the fuel filter (so you can SEE if there is leakdown or not.
The ZX had lots of improvements to the EFI system, engine compartment venting, and cooling fans and so it's almost immune to heat related problems.
Posted 29 July 2009 - 08:57 AM
The hole in the gas cap is a "quick-fix." I am eliminating potential problem areas one at a time. I have not received the Valve Assy-Fuel check part yet. When I have the new Valve Assy part, I will put my NEW vac vented gas cap back on, and take it from there.
To Date I have installed: New Fuel Pump, Fuel Damper, Fuel Filters, Fuel Pressure Reg. (holds pressure to specs), Fuel Injectors, Air Regulator (idle was off), 02 Sensor, Crankcase hose (the big one), Vac hoses, Fuel Tank inspected 2 times, no rust or crud. Heat Shields are in place. The FI Aux fan works to specs. New Spark Plugs and wires, MSD Coil (Mild Version).
Car runs excellect. Problems begin at around 95 degrees. Generally, the fuel tank has moderate pressure (with vac vented cap in place). Then when super hot days come along the pressure goes out of wac.
I have experimented with vent to atmosphere instead of Carbon Canister (no apparent affect). I am not sure about the Fuel Return hose and the vac to distributor hose in regards to their affect on (if any) engine restart.
Not sure of elevation affects. Las Vegas 2000+ feet, Phoenix 1000+ feet, Los Angeles average 300 feet. Just tossed this in to point out that there are many variables to be considered. My supercharged 1996 Nissan Maxima (Stillen Kit) would not run in Colorado at 6000 feet. That was fixed with a oxygen Sensor adjustment.
Posted 29 July 2009 - 01:29 PM
Posted 30 July 2009 - 07:39 AM
Fuel Pressure was checked. My then new FP Regulator was not holding pressure to specs, so a second FP Regulator was purchased. Now FP is held to specs. No problems with the radiator or water temp.. Timing has not been checked specifically. When I get the new Valve Assy/Fuel Check part I will have the timing checked. I do know that the car runs without a "hickup."
Car is running hot only in the sence that it is totally heat soaked. Also, this car is painted BLACK.
Posted 04 August 2009 - 06:08 PM
Posted 17 August 2009 - 04:55 PM
I took my car (1982 280ZX, Non-Turbo, Auto Trans to the only Zcar garage I know of in Las Vegas. They said they were to busy to look under the car (real class act). They said the part I had in hand was for a California Emissions car only. I have a Federal Emissions car. The part I have been referring to, and that is on page 59 of the Haynes repair Manual, and susposedly under the car, appears to be the same as is on the "carbon Canister."
I have no clue as to what is under my car. I am trying to attach a pic.
Summary: My car has no cover plate with a Valve/fuel check part as noted in the repair manual page 59.
Posted 17 August 2009 - 08:53 PM
Posted 18 August 2009 - 06:11 AM
It seems that my "hot-restart-problem" is not directly caused by pressure in my fuel tank, and related comments in this thread. I still have the problem when I vent to the atmosphere by using a fuel cap with a hole in it.
Heat is indeed causing my problems with a hot restart, but that's another thread.
I will probably just attempt to do a "bypass" of whatever is in the place where the subject "Fuel Tank Vacuum and Check Valve" is currently located. I'm thinking of using the new part I have in the bypass. I really would like to know what that part is in the pic I attached above (2 post up).
I live in a Condo with no car repairs allowed. I have to go to a local speed shop to get things done. Kinda slows the process.
Posted 21 August 2009 - 05:28 PM
The attached pic shows the PN 17330-P7103 on the left and the PN 17330-P7900 on the right.
Rather than wasting time trying to determine which is intended for my cars configuration, I will simply do a few days of trial and error.
1. I will run the car with a bypass (of any check valve) and hook-up (Vapor Line) directly from the fuel tank to the Charcoal Canister.
2. Next I will install the larger PN 17330-P7103 to see what happens. I know the PN 17330-P7900 does not work so it is "out of the equasion."
I will post an update in a few days.
Posted 23 August 2009 - 11:53 AM
1. Direct hook-up between fuel tank and Charcoal Canister (no check valves), and new fuel cap with built-in Vac Vent resulted in zero pressure in fuel tank. As expected/hoped for.
2. I relocated the "new" Vac Relief/Fuel Check Valve PN 17330-P7103 to the Charcoal Canister area. Keeping the new Vac Relief Valve Fuel Cap in place. Results are that the fuel tank now has "moderate pressure" in 95 degree weather.
I think may car actually uses the PN 17330-P7900 (smaller valve), but "if it works do not fit it" is the current plan I am on. I suspect that the difference in the two check valves is that the larger check valve has a Vac Relief "air in" tube, and the smaller PN 17330-P7900 does not.
I think that I have set-up a double Vac Relief Valve system where the Fuel Cap and the Check Valve have Vac reliel capabilities.
Posted 15 February 2017 - 10:29 AM
updated my other post with gas cap information as to why check valve changed
79-81 gas caps do not have vacuum relief built in them therefore the 3-way type fuel check valve.
The 82-83 gas caps have vacuum relief valve added to them , therefore the newer check valve is only 2-way.
This also implies 79-81ZX fuel caps will not work on 82-83 ZX
Edited by Randy 80ZX, 4 weeks ago.
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