c west Posted September 10, 2014 Report Share Posted September 10, 2014 I have a 1984 nissan 720 Recently I have replaced my fuel pump every couple of weeks they have a lifetime warranty so they are free now but I can't figure out what the problem is filter is good not clogged the truck has 130000 orig. Miles it runs great but the fuel pump goes out and leaves me stranded put a new one on and it is fine for a while love the truck but its getting to be a hasstle. could it be electrical Quote Link to comment
Nuclear Water Boy Posted September 11, 2014 Report Share Posted September 11, 2014 Possibly a bad ground causing resistance and resistance is heat killing the pump. But is the pump internal or external? if internal is the pumps filter on the pump itself coming out dirty. If so then the pump may be over worked causing the failure. I am not familar with your particular truck and its fuel system so I may be huffing hot air DOH!!! Quote Link to comment
datzenmike Posted September 11, 2014 Report Share Posted September 11, 2014 Did you just return them or did they test bad? Fuel pump relays are problematic on the 720. They can randomly shut the fuel pump off and leave you stranded. 1 Quote Link to comment
banzai510(hainz) Posted September 11, 2014 Report Share Posted September 11, 2014 test the pumps by hooking them up directly to a 12volt souce and see if they work then you know its got to be another issue as a relay. soem pumps will pump up then stop. and turn on when needed. I guess via a relay or a pressure sensing Quote Link to comment
c west Posted September 11, 2014 Author Report Share Posted September 11, 2014 I have replaced the relay when the pump quits it sounds like its running still but no fuel comes out it is an inline pump they never tested the bad ones I just assumed one out of six had to be OK I did try running a line directly into a gas can can hear it running still pumps no fuel Quote Link to comment
datzenmike Posted September 12, 2014 Report Share Posted September 12, 2014 If you put line into gas can where did you check the output? If at the carb there may be a blockage in the line. If the pump was disconnected completely and tested I don't see how you could have 5 or 6 bad ones. Do you have a fuel filter before the pump? It should, to catch any trash in the tank. Is the pump mounted low and close to the tank? Quote Link to comment
c west Posted September 12, 2014 Author Report Share Posted September 12, 2014 I disconnected the line directly at the pump there was nothing coming out of the pump itself the filter is before the pump and the pump is mounted on the frame next to the fuel tank and it is lower than the tank Quote Link to comment
c west Posted September 12, 2014 Author Report Share Posted September 12, 2014 What kind of voltage should I be getting to the pump but if voltage was the problem would it not be constant why would it work fine for a couple of weeks and then nothing how important are the vacuum lines on the tank could they cause the pump to go bad Quote Link to comment
datzenmike Posted September 13, 2014 Report Share Posted September 13, 2014 Electric motors can overheat if not getting full voltage. Quote Link to comment
bilzbobaggins Posted September 13, 2014 Report Share Posted September 13, 2014 something getting sucked up in the pickup and causing the pump to fry? Quote Link to comment
c west Posted September 14, 2014 Author Report Share Posted September 14, 2014 I'm getting 12 volts to the pump the fuel line is not clogged Quote Link to comment
datzenmike Posted September 14, 2014 Report Share Posted September 14, 2014 Well the fuel flowing through it helps cool it also. If it somehow runs dry it will burn out. Is there a loose hose clamp anywhere between the pump and the tank that can suck air in? Six pumps.... likely not the pump unless the wrong pump for the application. Quote Link to comment
Scgreen620 Posted September 14, 2014 Report Share Posted September 14, 2014 The tank might not be clean? Quote Link to comment
datzenmike Posted September 14, 2014 Report Share Posted September 14, 2014 I have replaced the relay when the pump quits it sounds like its running still but no fuel comes out it is an inline pump they never tested the bad ones I just assumed one out of six had to be OK I did try running a line directly into a gas can can hear it running still pumps no fuel I disconnected the line directly at the pump there was nothing coming out of the pump itself the filter is before the pump and the pump is mounted on the frame next to the fuel tank and it is lower than the tank Get rid of the filter before the pump and replace with a new one. It may be partly clogged and the pump is struggling and burns out. New ones probably push enough fuel to run the truck. Quote Link to comment
c west Posted September 15, 2014 Author Report Share Posted September 15, 2014 This. Weekend when I tested the voltage I did away with the butt crimps and twisted the wires together blew air back into the tank lines seemed clear turned the key on and the pump worked fine after that started and ran fine there may be something floating in the tank and temporarily blocking the line or butt crimpers may be the problem thanks for the help I'm getting closer to finding the problem Quote Link to comment
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