osirus9
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Posts posted by osirus9
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14 is mixed suburb driving and highway during last summer/autumn on nice days. If it was city or I was making short trips then yea, 14's not a big deal, but I was not.
So I tried pressurizing the system and then clamping off both fuel lines leaving the fuel pressure gauge in the little section of fuel rail I closed off from the rest of the system. Sure enough My pressure dropped right off with the lines clamped, so I definitely have a leaking injector. I poured a bottle of seafoam in the tank and let her idle for a few minutes until she got all warmed up and revved her a few times. Maybe the seafoam will do something but I kinda doubt it. I want to at least give it a chance before pulling the rail off though so I'll use most of this tank of gas then see if the injector is still leaking.
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Oh wow for some reason it never occurred to me to just use a clamp on the line. Great idea!
Also I'm not saying I think I should get 27mpg the way I drive, but I think 20 is achievable. 14 is way too low. I'll run some seafoam through the injectors as well and see if that helps. I only run premium gas so hopefully that is helping to clean any gunk out of there too.
I'll look at the FSM for how to check the vacuum advance too. That is definitely one thing I forgot existed.
Thanks!
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Just finished doing a hot valve adjustment and 4 of the valves were really off. After that I started the car and it idles better than it ever has, so that definitely helped. As for the fuel pressure going down I think the next thing I'm going to do is pull the rail off and put a paper towel under the injectors and just lay them on the manifold but still hooked up to the fuel lines, then unplug the starter signal wire and pressurize the system. If an injector is leaking I'll be able to see it on the towel. If I get no leaks then I'll know I need a new fuel pump.
Phantom, I used to have a fuel system like that on my rx7 running a haltech, but watching the fuel pressure gauge on the Z, pressure goes up a little on accessory (like 20psi), but it goes up more (33psi) when I disconnect the starter and "start" the car.
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Haven't seen a "leaky injector" YET that wasn't an EXTERNAL leak. If you don't see it, they're not leaking.
FPR seat is far more likely BUT...
THE FUEL EXPANDS due to heat soak after shutdown. As it does the FPR dumps pressure. (This can happen from 5-15 minutes after hot shutdown)---after that point, the fuel cools and contracts. Maybe a 10% volume change of a hydraulic fluid in a closed container can make for a big difference in the pressure that remains.
Do this: tomorrow morning with the engine STONE COLD, crank up the car with your fuel gauge in place. Once it's started and the fuel pressure is stabilised shut it off. We're talking maybe 30 seconds of run time max.
Then repeat your checks and please post the results. Use the same gauge and same tming intervals for best comparison.
THEN...
Without starting the car AT ALL...rig up your Fuel Pump to run "key on"... You may have to move the AFM Flap, jumper the Oil Pressure Switch, etc... Run the pump ONLY until pressure stabilises, the repeat your test as above at the same testing intervals.
Remember this: in a RUNNING CAR with the shown 17" HG idle vacuum, fuel pressure will be FPR set point minus 8.5psi. AS SOON AS YOU SHUT OFF THE ENGINE the FPR changes to a 3X pis regulator. So the car WAS running with 24-27 psi, then rises to FPR set point and relieves, and then cools and contracts and as a result the pressure will drop dramatically. As soon as you crank the car the pressure should be 24, and the initial pulse of the cold start injector may be killing your pressure if it's slightly low. That's why they ran the pump to prime on the ZX's, to prevent extended cranking and flooding of the engine!
You will see (should) marked differences in the two tests above between where the car starts running vacuum, and funning straight upon the FPR. From your starter test, your fuel pressure is FINE!
Smelling gas on the dipstick is VERY subjective. I don't know if I would jump off that bridge just yet!
Actually the two tests you are describing are exactly what I did in my last post. Maybe I didn't describe it as well as you though. The car was cold and I just ran it for a few seconds to get the fuel pressure numbers I posted. I then disconnected the starter signal wire and cranked the car to get the 33psi number. I didn't monitor it as thoroughly the second time but the pressure dropped off at about the same rate. The pressure also never stops bleeding off and if I let the car sit for a few hours the pressure is 0psi.
There is definitely no external leak on the car, I see no drips and if I pressurize the system without starting the engine I don't smell or see any gas at all. So this leads me to believe it is either A. Leaking Injector, or B. Bad fuel pump check valve.
Then again if it was just the fuel pump check valve then I wouldn't be getting bad mileage...
EDIT
I am going out to do a valve adjustment now and see if that helps anything. car has 95k on it and I have no idea if anybody ever did a valve adjustment. I have verified the timing is set correctly with a timing light as well.
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Thanks Phantom. I just pulled the dipstick and it smelled like gas about 3 hours after I was running the car. Would you suggest just replacing all the injectors? I have 2 sets so it it pretty likely I could make 1 good set out of the 12 I have, but how can I test them to see which one is leaking?
I'll order a new FPR now and see if that helps first though.
EDIT
Just tried starting the car with the starter unplugged. Fuel pressure goes straight to 33psi. Shouldn't it be at 36psi?
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It is most likely rust/debris in the fuel tank. That is a very common issue on these cars. Fixing that requires dropping the tank and either cleaning it or having it cleaned. Then blow air through the fuel lines to clear them out and replace the fuel filter. Not a super expensive problem but pretty time consuming. I suppose it could be a bad pump but most of the time on these cars the pump goes bad because it gets clogged. It is possible that it is an electrical problem too, but much less likely. The electrical systems on these cars are very simplistic though so anybody with a multimeter and the ability to solder can easily repair it.
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OK, so bringing this thread back from hibernation. I finally got my car back and am trying to troubleshoot my bad mileage and low power issues. First thing I did was check the coolant temp sensor, that had a shitty connector so I replaced it and I got good readings at the ECU connector. Next was the TPS. That was totally out of alignment and it thought I was cruising at idle and ~5% throttle was WOT. Got that adjusted but I haven't driven enough to see if mpgs improved much. The car still smells very strongly of gas and doesn't have as much power as I feel like it should, (my gf's miata feels WAY faster, I feel like they should be pretty comparable).
Anyway, next to check was the AFM. That failed all the resistance checks, so I swapped it with another that passed them spot on. Tested with these numbers: http://www.atlanticz.ca/zclub/techtips/afm/ car ran like total garbage! I swapped back to the "bad" AFM I was using before and the car ran like normal again.
I also found that the ECU had been replaced with an ECU supposedly from a '77 automatic (yellow junkyard marker written on the side), does that matter? My car is a '78 Manual.
Here is a video of my fuel pressure and vacuum:
Does that seem normal to anybody? Fuel pressure looks if anything maybe on the low side to me...
I also monitored fuel pressure over time after shutdown to check for a leaking injector. Do these numbers look normal to people?
31psi @ Shutdown
31psi @ +2 minutes
29psi @ +7 minutes
24psi @ +15 minutes
23psi @ +17 minutes
22psi @ +20 minutes
21psi @ +23 minutes
20psi @ +26 minutes
19psi @ +29 minutes
18psi @ +32 minutes
12psi @ +52 minutes
I know fuel pressure bleeds off over time, but this seems like it is bleeding off faster than it should. Possible leaking Injector?
Also, I have to crank the car a few times to get it to start. It will start then die usually 3 times if it has been sitting for a while, then start fine on the 4th try. If I try to rev it it will make angry noises and not rev until about a minute has passed then it will rev freely and normally. If it has just been running maybe an hour or two ago I can start it on the first try no problem.
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Lots of drifters weld their diffs. It's the cheapest and easiest way to get more traction in the back wheels. The downside is already explained here... Your "regular" turning ability is decreased because the wheels are locked together. This will make your rear end squirrelly in corners (which is intentional on drift cars), but is pretty annoying in a daily driver. You'll also get dumb stuff like the wheels chirping in the back as you take a corner at 3mph in the parking lot.
If you're not putting down lots of power, or drive normally and never race, stick with the open diff. If you find yourself making "one tire fires" then go get an LSD.
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Neat, so it looks like just about any Nissan or Honda cap will fit. Thanks guys!
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I actually ended up cancelling my order in November. I ordered a Megan coilover kit from McKinney motorsports and I'm having that welded in instead. Honestly I would have sold the tokicos anyway since I'm going to need the adjustable suspension to get the car to look and handle the way I want. So it was kinda lucky they were on ultra backorder.
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http://www.zhome.com/ZCMnL/tech/GearRatios.html
http://www.csgnetwork.com/multirpmcalc.html
You should be able to calculate which you have with these two sites. Hope that helps!
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Oh wow, I totally thought that the PO had made that as a failed attempt at a front diff brace or something. It looked so homemade I never even thought it was OEM. tbh, I never noticed a difference with it on vs off...
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Is your brake booster to manifold line leaking air?
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If it has an LSD you'll definitely want to swap that into your car.
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Thanks puretone. I know that ebay cap is fugly, but it's the interchangeability that counts! If all those engines have the same oil cap, then I can search for an oil cap for THAT car and get a nice one to paint.
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Installed pics:
This is with the Datsun Spirit spark plug wire kit.
So far the paint is holding up fine, and I've got no vacuum leaks!
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I didn't use any sealant on my manifold gasket and it works fine. I'd avoid it.
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They'll look a lot better once I get coilovers installed.
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I found a nice billet aluminum cap on the ground with a Honda emblem on it. It fit my L28 just fine!! I removed the Honda sticker and installed a Z sticker from msa that was made for aftermarket wheel center caps!!
I have no idea what Honda it fell off from, but I'm sure if you Google for them you will find your answer
Weird. Do you have any pictures of it? Does it basically just look like the one I linked on ebay?
Thanks, it's not cracked through or causing vacuum issues, its just an eye sore as some of the side tabs are missing.
Btw, is this an oem cap?
Yea its an OEM cap. In good shape.
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There are only 2 wires, so one of them must not be getting a signal. Try your multimeter skills out to test continuity, and check to make sure paint or something isn't blocking the signal.
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That's terrible.
Rest in peace Ross.
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Mine's cracked, I would like to know as well.
Hey, if you're on the north side I'll give you my extra one if you need it quickly.
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Hey everyone,
So I recently shaved and painted my valve cover, and I'm looking for a new oil cap that is smooth and that I can paint to match. I went searching on ebay for oil caps and a ton of generic stuff comes up, but I don't want to buy it unless it will actually fit. I searched around the web a bit and I couldn't find any information on this particular subject.
Does anybody know if the oil caps from other, newer, cars will fit our L series engines? There are certainly a TON more options for newer cars.
For example this guy right here: http://www.ebay.com/itm/FOR-NISSAN-200SX-240Z-240SX-260Z-280ZX-300Z-300ZX-ALUMINUM-ENGINE-OIL-CAP-RED-/111274214591?pt=Motors_Car_Truck_Parts_Accessories&hash=item19e875c4bf&vxp=mtr
It claims to fit the 200SX-240Z-240SX-260Z-280ZX-300Z-300ZX
Does anybody know if all these cars/engines have interchangeable oil caps?
So I heard these cars are rated to 27mpg highway?
in S30 Series - 240z, 260z, 280z
Posted
Yea I did it cold.
I'm gonna give the seafoam a chance and then pull the rail and swap out whichever injector(s) are leaking with spare ones I have. I don't have a stimulator, but that sounds pretty cool.
The thing is, I've got a perfect idle at like 800rpms and she revvs cleanly, so the only way to tell my injectors are leaking is shitty mileage and fuel pressure drop after shutdown. So I'll have to fart around with it some more then report back.