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Problems running


75Datsun620

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My 75 620 is haven’t problems running 100% sure its clogged fuel lines cause it runs then it will quit and I have to disconnect the fuel filter and blow it back down into the tank anyone have suggestions on how I could clean it without removing the tank (already done that once) and the fuel lines and cleaning them out?

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Gas doesn't come out the bottom of the tank. It rises vertically to near the top of the tank then along the lines to the engine. The entry point is an inch or so above the tank bottom so you would have to have a lot of crap sloshing around in there to plug the inlet. Most likely the lines themselves are full of sediment. Pull the line off the tank and blow it out. No sense blowing shit back into the tank. Have a care!!! That gasoline you're fucking with!

 

The tank has a drain bung... empty it out. Most of the shit (sediment) will flush out with it. Shake the truck as it empties. If it comes out all orange with rust and grit, remove it and clean it.*

 

Between properly clearing the lines and draining the tank you should be good. Blow out the return line also and know which is which. A properly functioning return line will slowly circulate all the gas in the tank through the fuel filter. This is the way it should work and you just replace the filter. The tank should never get much sediment build up in it.

 

* I carefully remove the sender and clean and save the 'rubber' O ring, it can be reused or go to machine shop and get a neoprene or urethane one that is gas resistant... NOT rubber. Throw several hands full of washed gravel in and shake the tank and roll it around. Dump it and hose it out. Repeat till the gravel comes out clean. Thoroughly rinse, drain and leave out on the lawn in the sun for the afternoon. Install tank, add gas and some gas line antifreeze (AKA methyl hydrate) about $3 at WallMart paint department for a liter. A cup full is lots and will mix with any moisture but also mix with the gas allowing it to move through the carb and be burned up. Install new fuel filter and keep an eye on it. Replace as needed or every 2 years.

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I had similar probs w/ my 620.  I was chasing a fuel delivery problem.  My truck would run great for a day or 2 then it'll bog out usually at higher speeds.  I blew out my fuel lines 10-15psi, changed all the fuel hoses, replaced the filter.  I dropped the tank, emptied the gas, only to what Datzenmike says there wasn't much crap at all.  I was surprised how clean my tank was.  So tank goes back in and truck still bogs here and there.  replaced mech fuel pump STILL bogs, at this point i'm ready to go EFI.  But luckily browsing ratsun more i found i didn't have a proper vent line.  The previous owner ripped out all the vent lines and looped it back on the tank.  My guess is that i was pulling a vaccuum on the tank every so often and the car will choke out.  I've been driving the truck great for the past few weeks, by just loosening the gas cap here and there.  I'm planning to install either a vent valve or vented gas cap.

 

In short, if you clear all your fuel lines/filter and car still bogs, check your venting.

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