datsun40146 Posted January 14, 2007 Share Posted January 14, 2007 I recently picked up a spare fuel pump and tried to get it working. I removed everything off the pump so I was just left with the pump it self, there wasn't any filters on the pump when I got done to be sure that they weren't clogged with rust ect. I then proceeded to test the pump I hooked the pump to a 12 V source and I get nothing, so I took out the four screws and took the pump a-part. The fuel inlet was clogged with rust so I cleaned that, then I noticed that the impeller was rather dirty so I took it off and cleaned it. I put everything back together the way it came out with out anyproblems and tightened down the four screws. I then removed the fuel outlet (the one going to the motor) to check the one way check valve, it worked fine, I used the blow threw test. I bottoned everything back up and tried the pump. I have air bubbles flowing out where their should be fuel flowing in. So the pump is working backwards. I knew if I reversed the neg and pos termials on the pump that the impellor would turn the other direction and possiblely fix the problem, it didn't and the same thing happened. Air bubbles flow out where the fuel should be sucked in from. I have been told that the bubbles are caused by an air leak, where could said air be coming from? I don't think it's the O-rings is there anywhere else. Thanks Air is coming out where the red arrow is pointing http://www.pbase.com/bronte/image/20034286 BTW again when I had the pump apart I plugged it into a battery to check it, it spun VERY fast and with force. Quote Link to comment Share on other sites More sharing options...
datsun40146 Posted January 14, 2007 Author Share Posted January 14, 2007 I ran some silicon around the cracks to try and fix the air leak. well see if it fixes it when it dries. Quote Link to comment Share on other sites More sharing options...
zcarnut Posted January 15, 2007 Share Posted January 15, 2007 The Nissan electric fuel pumps have a relief valve in them. What you are seeing is the action of this relief valve. If the pump is clogged then the relief valve opens and the pressured fuel is sent to the inlet connection. Since the pressured fuel is at a higher pressure than the fuel going into the pump, the result is that the fuel flows out of the pump! The most likely reason for a clogged pump is a defective check valve on the outlet of the pump. It is available separately and just screws into the pump body. If you can’t get one from Nissan, then search for “Bosch†and “check valveâ€. I got one from a Jaguar dealer once for less than $5. Quote Link to comment Share on other sites More sharing options...
datsun40146 Posted January 15, 2007 Author Share Posted January 15, 2007 Z car nut, what you said makes perfect sense, however I have already pulled off that part and blew air thorugh it. It was hard to get air though it, but it went though so that means the check valve is good right? Quote Link to comment Share on other sites More sharing options...
zcarnut Posted January 15, 2007 Share Posted January 15, 2007 Based on your description, I don’t think the check valve is causing your problem. However, the check valve can fail so that it will allow fuel through it, but it will not block the fuel return. Nissan used a cheap plastic ball in the check valve and it doesn’t last forever. When the check valve fails in this manner the symptom is a hard restart of a hot engine. The check valve is supposed to maintain fuel rail pressure and thus prevent vapor lock. Getting back to your original problem, my guess is that there are still some varnish deposits in the pump. I would try running kerosene through the pump. Kerosene will more readily dissolve the varnish left in the pump. Quote Link to comment Share on other sites More sharing options...
datsun40146 Posted January 15, 2007 Author Share Posted January 15, 2007 I submerged the fuel outlet in a container of fuel and hooked up the pump to a power source (I have been using a battery charger thought out) and turned it on. Well first I primed the pump by pouring in fuel all the way to the brim. Then I put the fuel outlet in gas and let her rip. Fuel came out of the the fuel inlet. If my terminolgy is confusing see the picture. The fuel inlet is marked by the red arrow, while the fuel oulet is marked by a green arrow I belive. Quote Link to comment Share on other sites More sharing options...
datsun40146 Posted January 15, 2007 Author Share Posted January 15, 2007 You mentioned using kerosine, can I use paint thinner, alcohol, gas, diesel, will any of those have a similar effect as the kerosine? I don't have any of that laying around. Thanks Quote Link to comment Share on other sites More sharing options...
datsun40146 Posted January 15, 2007 Author Share Posted January 15, 2007 Well I just flushed out the paint thinner I poured into the pump and man did all kinds of junk come out. It got tons of flaky brown stuff and my clear thinner turned a milky color. However the pump is still deciding not to work...arg Quote Link to comment Share on other sites More sharing options...
zcarnut Posted January 15, 2007 Share Posted January 15, 2007 DO NOT USE PAINT THINNER! The motor is wound with laminated (painted) wire. Anything strong like paint thinner or lacquer thinner will dissolve the wire coating and will create a big electrical short circuit. Fuel actually circulates through the motor windings to keep it cool. Quote Link to comment Share on other sites More sharing options...
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