67411sss Posted September 9, 2010 Report Share Posted September 9, 2010 I got my 620 going the other day, replaced the head and am trying to figure out where my temp wire is? I have swapped out some stock stuff (fuel lines, thermostat housing, manifold and exhaust for the earlier non smog parts) the stock thermo housing has 2 plastic prongs sticking up out of it but the L16 one has the electrical prong instead and i can't seem to find the wire that attaches to it (i don't want to run the engine to long without knowing how hot it's getting. Does anyone have any pics they can post that i can use for reference. I'll post some pics later. Quote Link to comment
deadmonkey Posted September 9, 2010 Report Share Posted September 9, 2010 I got my 620 going the other day, replaced the head and am trying to figure out where my temp wire is? I have swapped out some stock stuff (fuel lines, thermostat housing, manifold and exhaust for the earlier non smog parts) the stock thermo housing has 2 plastic prongs sticking up out of it but the L16 one has the electrical prong instead and i can't seem to find the wire that attaches to it (i don't want to run the engine to long without knowing how hot it's getting. Does anyone have any pics they can post that i can use for reference. I'll post some pics later. I believe the 1wire temp sender is on the lower left by the oil filter. The one on the coolant thermo switch housing is for the EGR vacumm line I believe. Quote Link to comment
67411sss Posted September 10, 2010 Author Report Share Posted September 10, 2010 So i took some pictures Is this the temp sending unit? What is the prong on the bottom of this housing for (i thought it was for the temperature) This line returns to the gas tank, right? Can i just block it off? Same with this one What are the 2 prongs on this housing for? should i keep it or change it to the L16 one and can i just block this off? I hope the pics help show what i'm trying to do here. Quote Link to comment
datzenmike Posted September 10, 2010 Report Share Posted September 10, 2010 So i took some pictures Is this the temp sending unit? yes What is the prong on the bottom of this housing for (i thought it was for the temperature) This line returns to the gas tank, right? Can i just block it off? Leave connected to the canister. Plugging could over pressurize the gas tank. The canister will collect the fumes and send back to the carb next time you start up. Same with this one That is the vacuum signal from the carb and is connected to the far side of the canister. When the engine is starte,d vacuum opens a valve and sucks out the stored fumes. The two above things have no effect on running when properly connected up. What are the 2 prongs on this housing for? should i keep it or change it to the L16 one It isn't connected to anything so just leave it. and can i just block this off? If water isn't pouring out just leave it. Quote Link to comment
67411sss Posted September 10, 2010 Author Report Share Posted September 10, 2010 Thanks Mike. Quote Link to comment
deadmonkey Posted September 11, 2010 Report Share Posted September 11, 2010 What are the 2 prongs on this housing for? should i keep it or change it to the L16 one That is a temp sensing switch for the EGR valve. Once the engine warms up, that opens and lets a vacum open/close the EGR valve. There is another peice that may not be there. Look here at the service manual for the '78. It will show you how this circuit is supposed to hooked up. http://www.olddatsuns.com/620tech.htm and can i just block this off? That is for collant. Collant flows through both sides of the intake manifold and comes out here. The set of tubes that wraps around the front of the valve cover... well one of those is for this hose. There should be a small chunch of hose that connects up to what you have in the picture. Near the thermal switch housing (large upper radiator hose); there is another pipe coming out; hook those with a small length of hose. And there is one more small length of hose that you hook up near the large lower left radiator hose. This closes off the system. You may not get anything to come out of it the way it is... but if that is the case, then something is clogged up good! Quote Link to comment
datzenmike Posted September 12, 2010 Report Share Posted September 12, 2010 I checked... he has a '75 620 with U-67 head. The 75's used exhaust heat to warm the intake and didn't have coolant holes. http://community.ratsun.net/topic/18863-620-longbed-with-pics/page__p__262284__fromsearch__1?do=findComment&comment=262284 The intake was swapped for one with the coolant passages and hose. This is why I said if it wasn't leaking to just leave it. For better cool weather running the head could be drilled out and the hose connected as you have stated.You would also need the lower rad hose connection for it, that he won't have. Quote Link to comment
67411sss Posted September 13, 2010 Author Report Share Posted September 13, 2010 I had to swap out the U67 head for a W58 (the 67 had stripped cam tower bolts) Does that change things at all? Quote Link to comment
Moedatto Posted September 13, 2010 Report Share Posted September 13, 2010 the sending unit on the side of the block on the starter side is the oil pressure sending unit. the sending unit on the front side of the thermostat housing with the one prong is the temp sending unit and like someone had said, that thing with the two ports pointing up is for the EGR vacuum! the wire that goes to the temp sending unit is yellow and should be on the end of the harness tht goes to the distributor! Good luck!! 1 Quote Link to comment
crackerjack69 Posted May 6, 2011 Report Share Posted May 6, 2011 the sending unit on the side of the block on the starter side is the oil pressure sending unit. the sending unit on the front side of the thermostat housing with the one prong is the temp sending unit and like someone had said, that thing with the two ports pointing up is for the EGR vacuum! the wire that goes to the temp sending unit is yellow and should be on the end of the harness tht goes to the distributor! Good luck!! Moedatto, u da man! My wiring got cut to #%&t by the PO, I got no idiot light stuff. Thanks to your input, I located the stubs of the wires (tucked into secret nooks) for my oil pressure, and temperature. Much appreciated. Quote Link to comment
crackerjack69 Posted May 6, 2011 Report Share Posted May 6, 2011 I mean, sure... I got a wiring diagram, but that don't really show you where to look for missing wires. Informative post, w/ lack of bad 'tude for us beginners. Thx again. Quote Link to comment
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