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Engine cutting out


slodat

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'75 620, L20b, stock carb, points (I know!)

 

Drives fine 99% of the time. Every once in a while, it cuts out. I'm pretty sure it is not electrical. Acts like running out of gas (starvation). I changed the fuel filter, still happens.

 

The sight glass on the carb has the fuel about 1/2 of the way up. Is that correct? The problem seems to happen on inclines at freeway speeds. I can nurse it up the hill, but it is cutting out.

 

I'm thinking of putting the electric fuel pump I had in the 510 on it because it has the cheapo aftermarket mechanical pump and I've heard they are prone to failure and a failing fuel pump could case this.

 

Tomorrow I am putting a pertronix on it and the electric fuel pump. Any ideas on other stuff to check?

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Does that carb have the fuel cut valve? My buddys weber does and if its not hooked up or falls off it runs but really bad. I know some stock carbs do but I can't remember if the L20 hitachi does. I would also check the fuel lines back by the tank, someone could of add a filter (happened to another friend of mine) or could be really soft fuel lines. Well for being this late I think I very well :D

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slodat. bre620 was having trouble with his EI....he ran a ground from chassis to dist body and it fixed it. Like Jeff said....fuel lines maybe.....if your vent line is plugged, the tank could be sealed to tightly....have you tried running it with the gas cap loose?

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it probably just is the carb running out of fuel.

The steel lines in Datsuns can get clogged, especially if you don't have a return line. At slower speeds your fuel does a lot more setting in the line and you'll get some junk setting in there and begin to clog it up.

Disconnect the rubber line on either end and blow some air through the line both ways.

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Well, I tore into it. I got a little ahead of myself though. There are 3 hard lines going forward, not 2 like I thought. I forgot the charcoal cannister. In the rear wheelwell by the gas tank, there is a small tank with 3 fuel lines connected. I'm guessing this is the tank vent and return line tank.

 

It is going to be a BITCH to get those hoses on there, but it looks like that is what I have to do today.

 

If there is a way to eliminate this and the truck still run?

 

Update: I replaced the supply and return lines at the fuel tank. Took it for a test drive and so far so good. Going for a longer drive now.

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I think the fuel system is good now. I cut out a little bit on me on the longer drive today. Only a little bit. I'm thinking it is time I ditch the points for the Pertronix I have had on the shelf for the truck since the day I bought it.

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usually when it cuts out on me likew that, the choke is either stuck or faulty, or there might be a little piece of dirt floating around in the carb. with the dirt when you give it more gas, creates more suction in the flkoat bowl, sucking it into the jet and pluging it up. happens more with bug wings and such, lighter materials.

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Since you said you have a sight glass, then I'm guessing it's a hitachi? They're a bit more grief than the weber's, but nothing compared to the 3 barrel carb on a '85 honda!

 

Get about 3-4 cans of carb clearer....screw soaking it....you can blast all the holes with the canned stuff. Get a handfull of nitrile gloves...that stuff melts them in a couple of min. I always use an egg carton to hold the parts....I always do it so the primary side is on the left....then I put the parts from the primary on the left half of the carton and the secondary on the right....that way after I've turned the carb around a dozen times, I still know what's what.

 

Really doesn't take too long with the canned stuff since it's instant cleaning. Just make sure there's no little balls in the bottom of holes before you go blasting or you'll never find them.

 

Ted got the last one I rebuilt...that thing ran better than any weber I've had so far!!

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After driving it more today, I don't think the problem is the carb or the points. When I was driving today, freeway, slight uphill, it pulsed about 2 seconds no power, 2 seconds normal engine. Like something was cutting in and out. Like the electrics for the ignition or idle cutout solenoid were loose somewhere and something was dangling and intermittently interrupting a circuit.

 

I disconnected the wire for the idle cutout solenoid and it indeed would not idle. Reconnected and was fine. At this point, I'm not sure what to do. The problem is too intermittent to be able to troubleshoot it.

 

The return trip of the drive mentioned above was without incident.

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Thanks Ted! I think you are right! I've never rebuilt a carb and admit I am nervous to do it...

 

i got to where i could tear a carb of the rig along side the road, clean it and have the rig back on the road it 20 minutes, probly take mew long now. out of practice. i used to run with out an air cleaner all the time.

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On my first 1200 it did the same thing, I was a lot younger than and didn't really car that it cut out seeing as it got me from point A to point B.. I on accident stumbled on the problem while doing a tune up. The negative wire on the distributer was loose and during cornering and heavy acceleration it would cut out. You don't realize how bad something runs until it runs good. I know you have different distributers so try a different one (I know you are upgrading to electronic) Toms 510 had a bad dissy, it wouldn't ground even with a extra wire going straight to it. Are you sure the idle valve isn't loosing power some times? Okay I'm going to get some food, all this typing made me hungry. :D

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Shake the ignition switch, I also had that happen once. Sorry, after Pacific coast had the electronic problem I vowed to always type everything I think because. I had that same problem but it looked good in the picture so I didn't say anything about it to him. I guess since then I figure I'll say everything I think weather anyone wants to hear it or not :D So ha

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That is a good idea! I agree, always post any ideas you have. I had forgotten about changing the fuel hose at the gas tank and it was in bad shape. Didn't fix the problem, but it needed to be replaced.

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my first post to ratsun. i do alot of reading here. but never posted. thinking its time to get to know everyone. im scott from the bay area, california and i love the datsuns. haha. ill get into my life story later.

 

 

my 72 cuts will die while at a light. only when hot. sometimes cuts out while driving. but it will run shitty for about a second then die. it will start back up with a tap of the key but it will die. did that 2 times in a block once. going to replace the fuel filter and blow out the lines. if that does not help i will pull the tank out and see if anything funky is in there. haha. i dont think its the carb i have a brand new weber. maybe incorrect float level.

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Congrats on your first time.

 

I agree with icehouse, wiggle all the wires and the key while it's running and see if it cuts out. Wrong float level would mean flooding or it runs dry so it wouldn't restart as quickly as you describe. Check all engine ignition wires. Do you have the EI distributor? Is it properly grounded? Any loose wires on it or the coil? Check the ignition fuse for good contact or better, change them, all of them.

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thanks for your help. i drove it around town a little bit today. ran great today. ill check all the wiring before or after work tomorrow. before school. haha. i believe its still a point system i need to upgrade. haha. complete stock motor. added new weber. fuel delivery sucks. sometimes it will starve fuel in corners. stock suspension so no high speed stuff. im getting a l24 for free. comes with dual weber side draft carbs. all i need is the intake. you think that is overkill for a 1600?

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