1985 Nissan 720 Fuel pump

[Alli's 720]

I have a 1985 Nissan Pickup 720. I have owned this truck for about 10 years now. I've replaced the fuel filter and pump twice already and replaced it again today. I thought about taking it to a mechanic because of the number of times I've replaced the parts already but I'm stubborn and didn't want to pay for a tow truck. 

 

I replaced the fuel pump and filter, put premium gas and a bottle of Lucas Upper Cylinder Lubricant and Fuel Injector cleaner and it started right up. It ran it about 12 miles throughout town (with multiple stops and starts) and got to an intersection near my home and started to stall and idle down. Thankfully, it stalled in my driveway and not the road. I walked away for a couple of minutes, then tried to start it to no avail. I waited longer (about 20-30 min) and it started up but ran super rich and the gas fumes were strong. It stayed running but there were still some pops and ran different (rough) than usual. I have not driven it again for concern of being stranded. 

 

There are no leaks that I can see. I do not have any whistling or humming (possibly indicating a fuel line leak). The fuel lines appear patent to me. 

 

I am thinking that the truck is running more rich and the engine is being flooded. Prior to the fuel pump and filter failing in January, It stalled on I-4 after idling for about 20-30 minutes. It ran up to about 40MPH, then started to jerk and idle down despite the amount of gas/throttle I was giving it. 

 

Please let me know if you have any ideas. I'm trying repair this on my own but I also don't want to get in over my head. 

 

Thanks!

 

Allison

 

[datzenmike]

Yeah the problem with 'tune up in a can' is they loosen crud in the tank, pump, lines and the carburetor and this can block jets and air bleeds and cause problems. Fuel injector cleaner is not needed on a carburetor engine.

 

 

The front of the carburetor has a small glass window. The fuel level should be in the middle is set right. Have a look and report back.

[Charlie69]

Hi Allison, sorry to here about your problem with your 720.  How many miles is on this truck and what fuel pumps have you been buying and replacing.  Is your truck carbureted or TBI?  I am guessing from your avatar that you 720 is a 4x4.

 

Mike is there a fuel filter at the carb on a factory carb?

[datzenmike]

It's a very very fine brass screen inside the banjo fitting. Some may be plastic.Usually they are damaged if the banjo fitting is removed.

[Buzzbomb]

Interesting. Is it safe to assume these never need to be replaced? I'd bet they're like a fail safe to keep the carb from getting plugged up from lack of maintenance. The actual fuel filter is a pretty decent size.

 

If the OP thinks it's running rich and/or flooding the engine, has she checked the fuel PRESSURE? Maybe she's using a one size fits all pump that puts out too much pressure?

[datzenmike]

You can remove and back flush them if you want but this would only be if it was plugged or not allowing gas into the float chamber fast enough.

 

If an over pressure condition the float chamber can over fill and that's easy enough to check by looking at the little glass window on the front of the carburetor. Gas should be at the dot on the glass or in the middle. Older carburetors have a glass front and w line painted on it. Having a correctly filled carburetor goes a long way to making it run right.

 

 

[bottomwatcher]

The limited speed was definitely a bad filter or pump. The popping sounds more like a vacuum leak. All of the hoses on these trucks are old, pressured ones leak out fluids, vacuum lines leak in air. Either issue=shitty running truck.