How to keep motor running???
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How to keep motor running???
After my 280zx ran out of fuel it picked up sludge and water from bottom of fuel tank after cleaning out all the lines replacing the fuel filter blew out return line 3 times engine would not start.After fitting new set of spark plugs for some reason the spark plugs stop working after 6 months for some reason?The motor started with the new plugs black smoke rough running reflushed lines motor started running with no smoke motor ideled for approx 20 mins not missing or smoking.When I tried to drive it after about two or three mins it started running rough and stalled just like it was running out of fuel.After making a few tests to the filter and supply line were full of fuel under pressure nother came out of the return line after removing the fuel supply line and starting the motor it ran ok fuel started coming out the return line.Replaced the fuel line ran for half hour at 2000 revs did not stall or miss soon as it went back on the road about 2 mins later it died again.The only way the engine would start was to relieve pressure on the fuel line and it would run again same as before.After checking the pressure regulator made no diff if vaccum line was on or off didnt seem to do anything.Does this block off the return line as the vaccum isnt working on it and I wonder if this is stopping the fuel and the pump.Fuel pump is new ..pressure test return line tested 2 quarts in under a min so this should be ok.Bubbles in the bottle is this normal?Would the fuel tank vaccum relief check valve stop the motor if it was blocked? Is there a gauze filter in the intake of the fuel pump.this is an australian car not sure what type of pump was fitted or any diff to the american version.Where else would I check if it is a blockage? what makes me wonder as sometimes theres alot of pressure in the line other times not muchappreciate any help.. 
Registered User
Joined: Mar 2005
Posts: 181
From: Bay Area
I think though you need to look at the pressure regulator as you culpret. The FSM says. "The pressure reugulator controls the pressure of fule so that a pressure difference of 250.a kPa (2.55 kg/cm2, 36.3 psi) can be maintained between the fuel pressure and intake manifold vacuum. The pressure regualtor is divided into the air chamber and fuel chamber by the diagram. Intake manifold vacuum is introduced into the air chamber, thereby keeping differential pressure contrant causing excessive fuel pressure constant, causing excessive fuel to return to the fuel tankthrough the return side port. This constant differential pressure provides optimum fuel injection in every mode of engine operation." and I think the last sentence is the key for you. If there is no vacuum or if the pressure relator isn't working it would affect it in this way. Hope this works for you.
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81s280zx
FS: 240Z,260Z,280Z & 280ZX (70-83)
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Oct 7, 2005 10:48 AM
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