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Thread: 1978 280Z Fuel Pouring From Throttle Body

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    Default 1978 280Z Fuel Pouring From Throttle Body

    Stock 1978 280Z suddenly won't start and fuel pours out of the throttle body and fills up the air filter housing. If you push pedal to floor, it will start after about ten seconds, backfire and die as soon as you release the pedal. If you partially hold the pedal down it will run but it surges. As soon as you turn the key fuel pours out in a steady stream from the throttle body.

    Please help my son is trying to leave for college

    Thank You
    Randy

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    Sounds like your cold start valve (CSV) is stuck open. It's either getting voltage all of the time, instead of just at start, or it's physically stuck.

    Try unplugging the connector and see if it stops. If it stops, the problem is electrical and you can just leave it unplugged. Make sure you insulate the end of the connector though so you don't get a short.

    If not, you can remove it, block the intake port, and plug the hose,if you're in a hurry. It's only real value is for cold weather starting. It's more of a convenience than a necessity.

    The CSV is the valve/injector on its own separate fuel line up close to the throttle body. Follow the fuel lines if you're not sure where it is.

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    Thanks is the CSV available for replacement and if it is electrical what part would be bad.

    Does anyone have a picture of the CSV?

    Where can I find a repair manual for this car?

    Could it possibly be the fuel pressure regulator?

    Thanks
    Randy

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    In a very nice way ZedHead fixed your problem. Google "280z cold start valve" then click images. They're still available too. Use that Google thing again.

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    I apologize for the glib remark. If your Fuel pressure regulator is bad it would dump fuel through return line to the gas tank, no way it would effect the throttle body. Here's a picture and a source for another. http://www.google.com/imgres?q=280z+...9,r:3,s:0,i:84

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    No problem site thanks for the help!

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    I've taken some pictures to show what he's talking about. That's the cold start injector hanging down in the mouth of the intake manifold. It'd be more like a garden hose sprayer compared to the 6 injectors which would spray a finer mist like a kitchen sink sprayer. The other picture shows how close it is to the mouth of the throttle body and the tendency to flow with gravity down into the air filter which I think would be dangerous for your son to drive. As hot as it is at Road Atlanta this time of year you should just unplug it and tape the connector up real good. When it gets cold in January it might take a couple more seconds to crank. Ahhh January.
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    Site thank you so much for the pictures and help.
    I discounted the CSV and plugged the fuel line, no more fuel coming out of the throttle body.

    It stills takes about 10 seconds to start running with the throttle held wide open. It dies immediately when you release the throttle. What is the proper setting for the Idle setting ( the bolt with the spring on top of the throttle body)?

    I also replaced the tempature sensor and the fuel pressure regulator, Any ideas on what to do next?

    Thanks
    Randy

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    Now it's looking like you might have a vacuum leak, a big one. All air must pass through the Air Flow Meter (AFM) otherwise the mixture will be lean and the engine will die or run funny. The crankcase is connected to the intake manifold through the PCV system also, so any leaks there will also be a vacuum leak. The oil filler cap, the dip stick, all vacuum hoses connected to the intake manifold, all must be intact and leak-free. If you've disconnected anything, thinking that you would re-connect it after you got the engine running, reassemble and try again. And check any hoses that you've reefed around while working on the engine to see if they split or cracked.

    The engine should start right up without messing with the idle screw. Counterclockwise gives a faster idle if you get close and need to keep it running.

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    Check the two hoses that connect to the AFM, if you got a break in them it could cause the problems you speak of. I have brand new in the box Nissan CSVs too.

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    Two questions: have you downloaded the Factory service manual yet? And is there a possibility that the plugs for the water temp sensor and cold start injectors have been swapped? Factory Service Manual at: http://www.xenons30.com/reference.html
    1977 280z
    1974 260z long gone

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    Zed thanks for all your help!

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    Grant thanks I tried to download the service manual but it won't work on my Ipad

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    Hmm, Ipads cannot read pdf files? I could email you the efi chapter in pdf. Or try a P.C. I have the 77 Manual, but I reference the 78 more often because it is laid out in separate files per chapter.
    I have the Hains and Chilton manuals but they are next to useless compared to the FSM, so I never even open them anymore.
    Last edited by grantf; 07-30-2012 at 04:30 PM.
    1977 280z
    1974 260z long gone

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    It could be ANY injector that's stuck open, although the CSV is the most likely culprit.

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    Update I left the key on yesterday when I went to the auto parts store and when I returned and discovered my bone head move I found the motor hydro locked with fuel and a ton of fuel in the oil.

    I changed the oil and plugs and found that the engine ran better when I disconnected the 6th injector. So I picked up 6 injectors from Autozone and am in the process of changing them out.

    I also found a rip in the boot between the AFM and the throttle body so I got two boots coming from MSA along with a cold start valve and a thermo time switch. I like to keep everything stock and everything working as originally designed.

    I hope all this will solve my problem!

    Thanks
    Randy
    Last edited by Irish Wake; 07-30-2012 at 06:19 PM. Reason: Misspelled words

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    Grant if you can email me the file it would be great send it to premiergrowers@bellsouth.net

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    Somehow Wade must have cursed you when he mentioned that any injector could be open. Amazing.

    The more symptoms you describe though, the more it becomes apparent that reading the Engine Fuel section of the FSM would really help you out.

    There are a few things wrong with what just happened. First, the fuel pump should not have power when the key is on unless the engine is running. You couldn't fill your crankcase with gas unless the fuel pump was running. So that's not right. Kind of missed that in Post 1. And, unless the injector is physically jammed open, the only way to get constant fuel flow is if it's constantly grounded since the injectors always have power when the key is on. So your problem might just be a shorted wire on the ground side of the injector circuit. Or it could be a shorted ECU, which happens sometimes.

    You should get that FSM chapter and a multimeter and do some testing before you install the injectors, you might be wasting time and money. Or, at least, turn the key on with all of the injectors attached to see if they're all stuck or just one, before you install all new injectors.

    In the beginning, it looked a like a simple problem with a simple solution but now it's looking more complicated. It might be time to get methodical.

    The FSMs are in ZIP form on the xenons30 site, maybe that's why you couldn't open them. You have to download then unzip them.

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    I have sent you the Fuel section of the FSM and the EFI bible, I hope you can open them and they help. You really need the whole FSM for you car though, including an understanding of the wiring that is involved with the EFI system. This helps greatly in diagnosing these problems. I agree with zead head 100%
    As a mater of fact He was one of the people that helped me track down some of my troubles in the past regarding the fuel injection system.
    You need to read through and understand how it works a little then do some simple tests. then you will find the culprit. It's not that difficult once you understand the basics.
    I did not mean to confuse the situation but I had the conectors swapped on mine in the past. It's an easy mistake to make and resulted in a similar condition.
    1977 280z
    1974 260z long gone

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    Again let us know if you got the files. You should do a continuity check at the ECU connector to be shure that the WTS is operating normally.
    1977 280z
    1974 260z long gone

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    Thanks Grant I got them

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    Zed I'm lost and confused now. Everything I described happened. Sat night my son called and said the car would start up and immediately die I went to the car Sunday and the air filter housing was full of gas and when I pulled the boot from the throttle body gas poured out in a stream.

    It may be that all the fuel in the engine happened on Sat but I got it cranked and drove it home and when I returned from the parts store, the engine wouldn't turn over and when I removed the spark plugs and cranked it fuel shot out of each cylinder about 10 feet in the air like a fountain.

    When I plugged the line and disconnected the CSV the fuel leak from the throttle body stopped. When I turned the key to the start position I could hear the fuel pump on and turn off when I turned the key off.

    I'm in the position of having little time so I am trying to replace any parts that could cause the problems so the car will be reliable for my son when he leaves for college.

    Could the car being parked nose down cause the fuel to siphon into the engine if the pressure regulator was bad? Just grasping at straws I guess

    Thanks
    Randy

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    Default might be injector seals

    parking nose down wouldn't cause it to flood. I had a vehicle do this years ago and it was the injector seals, like a $5.00 part, might not be your issue but its what i'm guessing is the issue. It could be that cold start valve, I wouldn't think a bad regulator would let it blow through the injectors that bad. WORD TO THE WISE, CHANGE YOUR OIL MULTIPLE MULTIPLE TIMES AFTER REPAIR!!!! Gas will wash bearings out faster than you can shut that thing off if it runs like this. Don't be surprised if oil leaks pop up after this either, sometimes a motor filled with gas will then leak from the oil pan, rear and front main seals because the gas makes the rubber seals swell. Been there, not fun but at least you know what to look for after its fixed.
    Last edited by MotoManMike; 07-31-2012 at 06:22 AM. Reason: forgot a word

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    Over here on the other side of the internet we have to make assumptions about how all of the other parts on your engine are working, so it's easy to miss a critical clue. That's why the methodical approach, with the FSM and a meter, works best, starting from scratch.

    I still see something that doesn't sound right. You said that you can hear the pump when you turn the key to start. "Start" is when the engine is cranking, so unless you disconnected the small wire at the starter, you wouldn't be able to hear the pump because of the noise from the starter turning the engine. Maybe you mean "Run" or "On" which is the position the key is in right before Start. The pump should not run unless the starter is cranking, or the the engine is running. Maybe you have a relay that's shorted, causing the fuel pump to run even with the key off? Or did you leave the key On when you went in to the store?

    You never said if the CSV that you took off had constant power causing it to stay open or if it was stuck physically. That would be an important clue. Something weird happened to cause several problems at the same time. CSV stuck, pump running, injectors open... I would break out a multimeter and take some measurements.

    How much time do you have left?

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    Zed sorry for my lack of clarity, I disconnected the solenoid wire from the starter and then turned the key to the start (crank) position and could hear the fuel pump run.

    I have till the end of next week to figure it out, I spoke to John Williams and I will bring it to him if I can't solve it by Monday.

    I will check the constant voltage tomorrow and let you know.

    Thanks again for all your help
    Randy

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    Update! First of all Thanks for this forum and everyone that helped me.

    The car is running better then ever, I never realized how poorly it was running till now. In no particular order here is what I did I don't know what the original problem was but it is running great now.

    New cold start injector

    New thermo time switch

    Six new injectors

    Adjusted valves

    New reciever/dryer (only part not replaced 2 years ago when I got the A/C system working)

    New AFM boots

    New spark plugs

    New distributor cap and rotor

    Any way thanks again to everyone

    Randy

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    That's the old raise the radiator cap and back another car under there and lower the cap. Just kidding! Those new injectors should really help. Put a Fram G3 fuel filter from walmart, $4 bucks, between the tank and the pump and keep all the new goodies nice and clean. Nice work, do it right the first time.

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    Quote Originally Posted by Irish Wake View Post
    Update! First of all Thanks for this forum and everyone that helped me.

    The car is running better then ever, I never realized how poorly it was running till now. In no particular order here is what I did I don't know what the original problem was but it is running great now.

    New cold start injector

    New thermo time switch

    Six new injectors

    Adjusted valves

    New reciever/dryer (only part not replaced 2 years ago when I got the A/C system working)

    New AFM boots

    New spark plugs

    New distributor cap and rotor

    Any way thanks again to everyone

    Randy
    All smart moves from my point of view, the car will give you many more years of solid running now.

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    Normally I would say throwing parts at the problem is a waist of money, but most of the items you described are common replacements for a tune up and maintenance, but what do you think the main culprit was? glad to here you're up and running again. How much did the injectors set you back?
    1977 280z
    1974 260z long gone

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    I got the injectors from autozonepro.com They dropped the price to 35 per injector at the pick up counter. They were new injectors (GP brand) made in Germany.

    If I had to guess I would say the CSV got stuck open.

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