charbly

WHOOPS! Solved!!!! I had my seats out after replacing the seatbelts while simultaneously doing the alt swap and I had forgotten I had unplugged the cabin connector under the seats ( where the gas gauge white connects) Plugged back in and I have power again! Oh boy, it’s nice to know it’s an easy fix but hard to swallow how thick my skull is. Thanks for responding hainz, somehow your post jogged my memory of the wire going back to the tank and bingo! Solved. Whoops!

The title says it all! I recently put in a Saturn internally regulated alternator off a 2002 Saturn sl into my 1975 620. I followed the directions in the many different alternator swap articles on this website and have had mostly success with the swap. Made a jumper pigtail out of the voltage regulator that was removed, bypassed the choke heater relay, but what I realized after jumping in my truck and starting it up, is that the temp and water gauges are not activated. I did check to make sure they work by grounding the water wire to the thermostat and the gauge climbs and works. It looks like the voltage regulator sent an 8 volt signal to these units, and I’m wondering if my alternator since it is for a separate application doesn’t have this attribute to monitor voltage to specific gauges. Can I make a voltage relay that sends 8 volts to the yellow wire which is common in both gauges so they get the correct feed? Any solutions or people with the same problem? Thanks!

I was surprised to find with a hot engine no effect on the coil. Maybe someone had installed incorrectly when attempting to adress problem. Nevertheless, I imagine this doesn't account for the fat slow circuit I'm experiencing.

So I found my heat riser valve was staying closed always, drove around town a few times until car was completely warm (thermostat popped). The riser seemed to have too much tension from the thermo-coil spring and was staying closed. There was no binding in the hinge and after removing the exhaust manifold I could verify it was all free to move inside/out, just too much tension, the counterweight had no effect on the spring. I held the riser flap in the open position and ran the throttle for a while, and monitored my afr's and there was no change in the rich Condition in the slow circuit. I'll try to adjust my riser issue so it works correctly, and look back up trail at making sure my vacuum advance is working correctly thru the throttle and not just at idle? And then start playing with my carb jetting? Does anyone know where to procure new jets for the hitachi Dch-340? Are there any compatible jets from other sources that are available to buy?

Altitude is just above sea level as I live a couple miles from the ocean. No guarantee the car was distributed nor purchased here but most likely it is a California car. I had no idea about the heat riser, years ago when I got the car I removed the air galley emission tubing as it had rotted thru and I sealed the exhaust ports with bolts so no leaking would occur. I’ll look tomorrow to find the valve. Thanks!

Those are great thanks for those numbers mike. Choke is working fine and opens normally as the engine warms. I did have that instance of switching the primary and secondary jets when I first rebuilt the carb, I couldn’t get it to idle correctly and finally re checked the jets and swapped them to their correct spot. Tranny drive from 4 speed so not to get incorrect readings. I just can’t seem to think of another reason for such a rich mixture thru the entire throttle. I guess I’ll pull the carb and look at the slow jets to see if they are set for an altitude situation. All I can find for jet information is in the 1977 FSM which notes a hitatchi dch 340-45b carb for California. Is that the same specs (jetting and Venturi sizing) as the 1975 dch340-45? Thanks!

Howdy everyone! While the title might suggest a poorly running 620, I have the opposite. My 75 620 is bone stock and I love it! I’ve spent a bunch of time tuning and getting my little truck to run properly and I have to say for being 45 years old it runs pretty dang well!!! But I’m still yielding around 15mpg, which according to a lot of people on here I should be yielding around low 20 if it’s in shape. I’ve rebuilt the carb, installed new coil, plugs, points. Everything seems to be adjusted properly, my valves are set, points gap set, timing adjusted, carb idle adjusted, 5 speed installed to lower rpms on highway. The whole nine yards have been accounted for. In my search for better fuel economy in the stock form I put a wideband 02 sensor to monitor my fuel usage. I have tuned the carb for a steady 14.7afr at idle and it holds that great, there seems to be no vacuum leakage and I have total power, no lags or bogs thru the whole powerband. The curious part of this is that it’s running rich the minute I open the throttle. As I monitor my o2 while I drive, I read 11.3-4 afr as enter the slow circuit (~1000-1500rpm) all the way up to plenty-enough rpms. Now I know that you wants relatively rich mixture when you getup in your throttle towards wot, but it seems like the slow circuit is way too rich to yield good fuel economy. Does anyone know what to expect in terms of afr range for a stock hitatchi dch340-45 if the system is running correctly? Should I look to rejet my slow circuit? Does anyone know where to acquire jets for a hitatchi dch340 if I want to lean my mixtures the primary system? Or am I missing something completely thatall you datsunoholics know about this? Thanks in advance for all the help!!! Yeehaw!

a crackpot theory afterthought. to fix this could one remove the 3/4 check ball and spring, move the shifter into 3rd, thereby double engaging the gears, and then very slightly move the shifter hopefully right between the 1st and 3rd position and drop both gears down into neutral, thereby removing your problematic 1st gear from its engaged position?! i guess the hard part would be aligning your 3/4 gate when you reinsert the check ball and spring? is this at all possible? or am i missing a major problem of removing a check ball and spring before dismantling the transmission? datzenmike? you probably have a good mental inventory of what you can and cannot do with this transmission and the limits of fixing things without removing completely. any thoughts?

hello! i have been having this same problem recently with my 5 speed in my 1975 620. i did a 4 to 5 speed swap and since then have worked on the tranny a dealing with this problem as well as having fixed a sheared roll pin. in the case of the sheared roll pin, it broke on a selector and this results in the feeling of a free swimming shifter where you cant find any of your gears, its as if they have all disappeared. i only bring this point up because a broken pin is a totally different feeling than this problem ohmrchristopher is dealing with. recently my 5 speed got stuck in first as i had the same symptoms of being able to shift to 5 and R and swing straight thru neutral until i hit 1/2 in which the gate finger was blocking me from selecting 1 or 2. i had hoped it was a sheared roll pin again that had somehow lodged the selector in 1st gear and was stuck, but upon cracking the transmission open (removing tailhousing) i was easily able to move the 1/2 gate back to neutral, and no sheared roll pins! it seemed to check out on visual inspection and the fact i was able to shift thru the gears using my hands to select gears with the gates gave me reason to believe it was a simple fluke problem. this instilled in me the idea that there were no broken roll pins or mechanical issues to address anymore. i reinstalled the transmission and the gears shifted flawlessly for a few days driving 25-40 miles a day. left for the weekend and this morning went to go to reverse out of the driveway and low and behold my tricky little tranny had crept back into first while i wasnt looking! same symptoms, cant get it into the 1/2 gate, stuck in 1st when the clutch is let out. this all being said i am left to guess that this could be a check ball problem? which i doubt because the check balls are operating correctly by the fact i cannot shift into 3/4 right now because 1/2 is engaged. so maybe it is a selector rod problem then? the selector has crept out of its original position and when operating correctly is floating closely between 1/2 and 3/4 so its able to engage 1/2 and then slip out into the rest of the gates? or a worn selector? which i also doubt because upon visual inspection it seems to be fine. im sorry i dont have an answer but i figure all the info i have gathered, although not decisive, will benefit this group problem solving going on. random notes i have acrewed in my journey -this happens to me only after the car has been parked, i drive into my driveway in 1st and engage the clutch and move the shifter into neutral to park the vehicle -before this happens (in the days prior to getting stuck) i feel a stiction as i shift from 1st to 2nd, it doesnt stop the shift from happening, but it feels as though there is resistance to the shift hope any of this helps.

thanks to doctor 510 i recieved measurements of the mystery diaphragm spring. here are the dims as relayed to me. Free length 42.41 mm Wire dia 0.88 mm # coils 7 OD 21 mm thanks for all the help!

Does anyone have any dimensions for this spring? I.e. Overall length, OD, wire size? Thank you!