ddmracing05 Posted August 28, 2009 Report Share Posted August 28, 2009 I have a 1958 Mercedes Benz with a Datsun L20B swap from a king cab in it. Well I had some issues with the motor and my buddy got under the hood and messed with the air fuel mixture screw on the left side of the carb on the bottom and now its got me all messed up. Anyone know how much that needs to be backed out? My thottle is alllllll messed up now and cant drive it.:( All help appriciated. Quote Link to comment
datzenmike Posted August 28, 2009 Report Share Posted August 28, 2009 (edited) The screw to the rear is the idle speed screw, the one forward of that is the idle mixture screw. Neither have any effect above idle or when driving. Turn the idle mixture screw in gently until it bottoms out and back it out about 2 turns. Turn the idle speed up so it will run, then turn the mixture screw in until it starts to stumble. Now turn it out until it stumbles and then set half way in between where it gives the fastest smooth idle. Now turn the idle speed screw down as low as you can and again turn the mixture screw in till the idle becomes erratic, then out until erratic, and set about half way in between. Lower the idle speed and repeat until you have a smooth stable idle around 6-700 RPMs. The motor must be warmed up and the ignition timing set properly first or this is wasted. Edited August 28, 2009 by datzenmike Quote Link to comment
ddmracing05 Posted August 29, 2009 Author Report Share Posted August 29, 2009 Thanks!!! I did get it started, and I usually can, but it wont stay running and if I give it gas it dies. Im pretty sure I gotta rebuild the carb. When I went to clean out my gas tank I dont think I got it all and REALLY BLACK GAS went through both filters and got into the carb and messed it up and ever since then hasnt ran. So I cleaned out the tank again and put CLEAR filters in so I can see (great this time around) and new lines, but it just doesnt wanna go anywhere now. Quote Link to comment
banzai510(hainz) Posted August 29, 2009 Report Share Posted August 29, 2009 Is this a stock carb or a Weber DGV. later Datsun carb had a idle cut off selinoid also. this is a EZ fix. Quote Link to comment
ddmracing05 Posted August 30, 2009 Author Report Share Posted August 30, 2009 Yeah it has an idle cut off cylinoid. Although I did get it running beautifully, then I ran into another problem 2 minutes into driving... I think the T in my metal fuel lines that go around the motor are clogged up (near the carb) cause no gas is coming out of the return fuel line like it normally should. Is there any way to fix this? Greatly appriciate the help! Glad I found these forums. Search button is pretty helpful too! lol Helped me a ton Quote Link to comment
datzenmike Posted August 30, 2009 Report Share Posted August 30, 2009 Where the metal return line ends and the rubber return line is clamped on, is a restriction with a pin hole opening which is easily plugged. Remove the fuel rail and clean out. Be sure to use a new fuel filter to keep the crap out of the lines. Quote Link to comment
ddmracing05 Posted August 30, 2009 Author Report Share Posted August 30, 2009 How do I clean it out is my main question? Quote Link to comment
datzenmike Posted August 31, 2009 Report Share Posted August 31, 2009 Blow out with compressed air. Maybe WD-40 using the red straw. Quote Link to comment
ddmracing05 Posted August 31, 2009 Author Report Share Posted August 31, 2009 Filled it up with carb cleaner. and fixed that problem. But now a new problem... Is there a Valve in that T part deal?? It sounds like theres a leak somewhere inside that tubing. It just simply sounds like air moving through a hollow tube but I cant figure out where its coming from and its neither of my vaccume lines. The sound goes away when I stop the flow on my return line and then pressure builds up and finally fills up the bowl. But as long as that sound is there, there is no pressure into the carb and the motor will not stay running cause it drains the bowl out. Any ideas on what this could be? Quote Link to comment
datzenmike Posted August 31, 2009 Report Share Posted August 31, 2009 (edited) In a manner of speaking there is a valve. The end of the return tube has a very small hole to restrict flow so pressure will build and force flow into the carb. Without the restriction fuel will just flow back into the tank and by-pass the carb. Its located just above the L fuel pump... http://i138.photobucket.com/albums/q251/datzenmike/L%20Z%20Heads%20and%20Motors/fuelreturn001Large.jpg[/img]"] Edited August 31, 2009 by datzenmike Quote Link to comment
ddmracing05 Posted August 31, 2009 Author Report Share Posted August 31, 2009 Mine doesnt have that!? Hmm. For now I just put a hose clamp randomly on the hose and cranked it down and it seems to be ok but I hate half assing stuff. Quote Link to comment
ddmracing05 Posted August 31, 2009 Author Report Share Posted August 31, 2009 Another question, what is normal running temps?? Looked like it was sittin around 240 degrees but my other mercedes isnt near that... Quote Link to comment
yello620 Posted August 31, 2009 Report Share Posted August 31, 2009 Operating temperature should be close to the temperature that your thermostat opens at. Typically about 190 degrees F, in a Datsun. Quote Link to comment
ddmracing05 Posted August 31, 2009 Author Report Share Posted August 31, 2009 Alright, that sounds about right. Thanks. Still cant figure out why I dont have that pin hole Quote Link to comment
philip1 Posted September 1, 2009 Report Share Posted September 1, 2009 some car had return lines (the pin hole pipe) some didn't. I think your problem lies more in the plugged jet realm. If you live near me I can rebuild your carb for you if you wish to keep a stock carb on your engine. Quote Link to comment
ddmracing05 Posted September 21, 2009 Author Report Share Posted September 21, 2009 Hmm you dont live far from me at all, maybe like 3 hours. Although the car is running now, ive been using it as a daily driver but I gotta pull the tank and fix a leak on it. It does have an occasional back fire and takes for ever to warm up but I just gotta tune it a bit. Quote Link to comment
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