perattzi

Hello all, need a little direction with this one. Sorry but this is a long post lol. Back story: about 1 month ago my charge light came on while driving home, I thought crap my alternator is going out. The next day I go out to try and investigate and the truck starts right up and the charge light goes out like normal after starting. Checking the voltage at the battery it was around 14.5 revved with no lights, 13.x with lights, at idle it was around 12.8 or so. Seemed normal, if not a little high after 2000 rpm. So figured all is well, maybe just a fluke, or perhaps with the lights off the regulator is letting it overcharge at revs. Then about a week ago the charge light starting coming on again, usually at idle and would dim and go out when driving with normal revs. Sometimes it would pop back on and other times not at all, whether at idle or driving revs. Seemed totally random. Then one evening I left my headlights on for several hours by accident and killed the battery. I took battery out and tried to recharge..only getting to about 12.4volts resting. The battery sticker said it was 9 years old! So I figured time for a new battery. So I bought a Les Schwab 500cca 60 month battery, new battery cables, (ground straps are also newer from when I had issues with my throttle cable seizing!) Installed battery and the charge light stayed on for a short time then goes off. Then was normal for a few days, no light at all. Then when driving home on Monday I stopped at a store and was idling for maybe 10 minutes then drove off up a hill and the truck sputtered and died. At this point the charge light was not on, so I had no warning. I tried to restart the motor and nothing, battery was discharged so much that starter would not turn over. I waited a few minutes and tried again and got the truck to start. I managed to drive it home without using headlights or turn signals. It died once on the way and I had to get a jump which worked getting me home. The battery was below 6 volts when I checked it at home. Seemingly I had been driving on just the battery for awhile. But why no charging light if the battery was not being charged? I recharged the battery, it is right around 12.9. Which I believe is good for a 6 cell. So I looked further into it today and noticed that my oil pressure light was also not coming on when you turn the key to on(not start) I pulled the bulbs and swapped them to the parking brake socket and they both worked there. Then I pulled the oil pressure wire off the sending unit and grounded it, still no light. So I did what was probably the dumb thing and removed the gauge cluster to look at the 12 pin connector and printed circuit board, everything looks fine, nothing shorted etc. All fuses are good, 12v to both sides of fuse holders. So I just started tugging on the loom going to alternator/oil pressure switch...the oil light then popped on. So I unplugged the round 6 pin connector that connects the wires to alternator, oil pressure switch, b/y to starter, and a smaller loom that heads down towards the transmission. The large black wire terminals were badly corrorded/oxidized and the large yellow's were so corroded that the male pin had broken away from wires. So obviously this is a problem. I cleaned up the black connectors and pulled the two ends of the yellow out of the connector halves and cut away to clean wire and jumped them with a spare wire. Still no charge light when I turn the key on. So my question is where should I test from here? My friends are like 'just take it to Autozone and have the alternator tested". But I understand that the charge light is integral to the alternator starting the charging process. So it seems silly to test the alternator until I figure out why the light does not come on. Am I way off base here? Thanks for any tips! P.s. I have the factory manual but it doesn't provide much insight at all into the charge light... and the black/white wiring diagram makes my head want to explode haha.

Yes indeed! Now just to solve the cooling mystery. So in order to test that the temp gauge is working correctly I need to use a resistor correct? Do I put the resistor on the wire after pulling it off the sender then ground it? Thanks.

Ok I got my truck to pass DEQ! Just adjusted the idle mixture to where it was revving the highest then brought the idle speed down and then leaned the mix just a touch.

Damn, sorry to hear that. I bought a cap that has a pressure release lever. Kinda nifty.

Ha yes you are correct that must be exactly what I did. Probably could have just leaned it a smidge and had been ok, but went overboard. It was idling rough and shaking a bit. A vaccum gauge is something that should have but do not, I need one for tuning bikes anyhow. Thanks for the tips I will check the basics as you have stated. As for the engine temps... still a mystery. When I drove home from deq the gauge was reading pretty will in the middle the entire time, except dropping a bit at idle. Then I turned on the heater just see what would happen, to my surprise the gauge needle went HOTTER. Anyway, for good measure I went and bought a new 180* thermostat and tested it in a pot of water on the stove with a cooking thermometer and my infrared to verify, it opens and closes as it should. IN addition to installing that I changed the oil/filter and spark plugs. The p.o. had just put new plug wires on. But I will double check timing etc. I really just want to sneak this thing by DEQ any way possible then legimately fix any and all problems. It's just a time issue bc I only have a trip permit to get around in it until I can register it. BAhhhh

Thanks again for the replies, the pick n pull database says theres no 620's near me, but I supposed any l20b with the same would work correct? The tiny leak is only present when the motor is cold, after stared/driving it seals so maybe I just need to retighten the thermostat outlet cover. So I tried the DEQ again. Failed again! But for different reasons this time. When they test they just put a sniffer in the exhaust. They test at idle, then rev to about 2500rpm then retest when idle drops again. The first time I went my HydroCarbons readings were 89 first idle and 97 the second, the standard is less than 300, so I was good there. However, I failed the CO level, mine were 2.7 while the standard is 2.5. So i was super close the first time, but not close enough. So this time before I went I drove the truck for about 20 minutes to warm it up, then I removed the air filter and turned in the idle mixture screw in til it was stumbling quite a bit, then raise the idle mixture so it would idle good enough. Then I drove it around revving quite a bit, the temp gauge wasn't going up high like before... then I had to wait in line and idle for like 15 minutes, and of course the engine temp dipped like before. This time my result were: HC #1 1112 HC #2 617 CO #1 .21 CO #2 .22 So, obviously leaning out my idle mix lowered the CO dramatically. But why did my unburned HC got up so much? I'm guessing it is due to the low idle temps, like my thermostat is sticking open?

Hmm interesting. Here is a photo of the thermostat housing on my engine It has some sort of outlet with a hose right below the sending unit, the hose then connects to a hard line that goes to the heater hose on the lower right side next to the block. Also on the left side of the thermostat housing there is a small chunk of metal missing on the outside of the threads where the thermostat cover/outlet bolts on. Somebody must have torqued that bolt down too hard at some point and broke that off. Only a few threads engage but I figured it would be fine. I used a bit of sealant on the gasket but it seems I may need to retighten and see what happens bc I seem to have tiny leak there, it's a bit moist. I think I may try and source a new housing and in the meantime take the thermostat out and test it/drill a hole/replace if necessary. Thanks for trying to help Wayno I really appreciate it.

My thermostat housing does not have that fitting/hose. Again today when I drove home from work the temp gauge would creep up while driving, then fall below the 'normal' mark to the cool side when I stopped and let it idle. I checked the temp at the thermostat and it read 160* the block read around 180-190*, this was maybe 2 min after it was just reading hot on the gauge, but now reading cool. Does a motor cool down that quickly? I also observed that the radiator hoses are stiff and under pressure, the upper hose is warm but the bottom hose is not, it is pretty cool to the touch, not sure how the system flows, I suspect from the bottom up?

Sorry bout that, the truck is a 78 with an all stock l20b motor and stock 4 spd. I replaced the radiator with one I ordered from Advanced Auto Parts, aluminum with plastic tanks, direct fit in place or the crusty original.

So I've been struggling with a strange temp issue with my truck. Seems troubles with the temp gauge are somewhat common on these old vehicles, but I'm not sure it's a gauge issue. It started right after I bought the truck a few weeks ago, my temp was gauge reading in the upper 3/4 of the hot zone and up to the first line even. Then a small coolant hose that was super old and crusty failed. So I replaced that, along with the sending unit, thermostat, and junked the old deteriorated radiator and cap for a new one. Flushed the coolant and filled with new. Adjusted the water pump belt. The fan clutch is good. Tested the gauge by grounding the wire from the sending unit, and it climbed to FULL hot as it should. Now when I drive it the temps will climb up to middle, sometimes stay there for a bit..but then climb to hot..and now will sometimes drop below the middle range. This afternoon when I saw the temps rise up, I pulled over and took readings with my infrared thermometer, the upper 180's and lower 190's are the highest readings from the sending unit and head areas. It seems when I am driving the needles raises but when I stop at an idle the temp is falling down. Maybe my new thermostat is no good? This leads me to my next issue. I live in Portland, Or and am subject the DEQ testing. I stopped by today to what would happen and I failed the CO test. The HC etc were well below the acceptable level and the the CO was 2.7 when the limit is 2.5. So not far off. I was planning on just lean out the idle mixture bc they test it at idle. But I noticed that when I had to wait in line, the temps were creeping down low. So maybe my engine just wasn't up to full efficiency when they tested it? Ill try letting it idle and get some temp readings then. Thanks for any help guys!

Update on my 'overheat' issue: so I replaced the thermostat, sending unit, hoses, and radiator/rad cap with new parts. I flushed and bled the system. The rad was super crusty..some of the rows were totally disconnected from the tanks and the small hose that connects right under the sending unit was split, so I figured that mustve been the main problem. The fan clutch has some resistance when you turn it by hand but not excessive, so I assume it is fine. I also adjusted the belt , although it's deflection was in spec at 12mm which is on the loose end, i still tightened it up a bit to around 9mm. After I buttoned it all up I took it for a test drive and everything was fine, the temp gauge would creep high and low a bit but mostly stayed in the middle. Double checked for leaks etc...everything looked good. Then I drove it home and again the temp gauge would shoot up to almost the overheat mark when driving across town. Turning the heater on (which works great) made no difference. When I got home I let the truck idle for a while, the temp gauge was back down again! I think my gauge is possessed lol! I grabbed my Harbor Freight infrared thermometer and took readings all over the cooling system/engine, the highest reading I got was 192* right near the thermostat housing.. So would it seem that my truck is not in fact running hot or is for some reason running hot while at higher revs? The one component that is still left is the water pump. I really wish I would've replaced that while I was in there but the only one I have or could find locally were the crappy stamped impeller type. I plan to order a refurbed one with the cast impeller and chuck it on for good measure. Thanks for any help!

After looking at the header that is on my motor it seems different than the spare I have pictured, the current one has a hose running up to the intake. Smog b.s.? Also looked into my running hot issue, at a stop light the temp gauge will climb wayyy up and go down a bit when I start moving. The weird thing is when I pulled over the temp gauge went back down to the middle area. Strange. So I bought an infrared temp gun and ran the truck around to get it up to full temp, even though the gauge is reading hot, if I take a reading of the thermostat housing it reads around 180*. I then uplugged the wire to the temp sending unit and grounded it and the needle immediately went all the way hot. I assume this means my gauge is ok? So should I look towards the sending unit itself? Thanks for any insight.

Any ideas what's up with the manifold and header pictured? I can go read the castings if that helps.

more pics:

Thanks for the reply. The clutch turns like it should, with some resistance. It looks new actually, as does the thermostat housing. I noticed some kind of compressor looking guy that runs to a blue air cleaner type part on the right hand side of the engine bay, not sure what it is, perhaps that's a noisy item? Emission related? After I get it through the ridiculous emissions testing here I plan to remove a lot of that stuff and upgrade to a weber perhaps. It runs pretty damn well, no smoke or anything. Hopefully I pass without too much trouble. The exhaust from the header back is brand new. No cat though. However, a few issues I have noticed: 1) On sunday when it was pretty warm around 85* out the temp gauge was creeping up towards the 3/4 area, not in the 'H' zone but definitely leaning that way. It didn't really come back down when I took it out on an open road cruising about 50 mph like I thought it would. It has the original radiator, which I just noticed is wet a bit on top where the top meets the cooling rows. Doesn't seem to be coming from the cap, but could be. Perhaps it's plugged up AND leaking, thus not cooling properly. I may just replace the rad as a matter of security. I have a brand new water pump in a box that was included, so just do it all once. Cooling system parts are just too important and simple to replace to let go IMHO. I also unplugged the wire from the temp sender and grounded it to see what happened and the gauge rose all the way to the hot zone, definitely further right than it was when I was driving. 2) It rides horribly LOL, the previous owner has 4" lowering blocks on the rear and I assume the front has been by just as much. The shocks look brand, but I am not sure if they are stock length/dampening etc. I will try and get a pic of them, see what you guys think. The low-pro tires don't help either. Don't get me wrong I 'm conflicted bc I love the lowered look, but I'm probably going to raise it back up a bit and get some meatier rubber to retain the utility aspect of having a pickup. I also dig a slightly forward raked look. 3) I get a noticeable deep rattle when accelerating hard, no clue where to even start, sounds like it's coming from the front. The fueling could use help for sure at the 3/4-full throttle positions. Perhaps too lean in that circuit. Im no stranger at all to carbs, but I am to car carbs! Rebuilt/tuned/modified countless motorcycle carbs, but not a single car carb so I'm excited about learning new things. 4) A belt will squeal like crazy when I first take off from a stop. I'm guessing not tensioned correctly. I have two new belts in a box, hopefully all the pulley bearings are good. Alas Ill shut up.... and post a few more pics of parts that were included... lemme know if anything jumps out as desirable. Sorry for crappy quality. That's the plan, thanks! I plan to repaint the truck at some point, but I would never ruin that tailgate, it's just too cool of a relic!

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Well, I've been wanting a Datsun for a few years now... a Z of course, but living in Ohio they just don't really exist. I don't think most people back there under the age of 40 have seen a Datsun lol. So, a year ago I moved to Portland, Or and these old cars are just everywhere! Dreams of 240Z's still fill my head but motorcycles are my main thing and I'm always needing to haul a bike around so a pickup seemed more functional. Looked at some Hilux's etc. but they just didn't seem to have the personality of a Datsun. This truck may have been posted on here before, I'm not sure. But it's mine now! The previous owner bought it from the original owner 3 years ago in Salem. Oregon. So that makes me the 3rd owner. I wasn't even considering the truck from the pics in the cl ad but I was nearby so I figured I would look at it. Immediately I could tell the overall condition was much higher than trucks only a few hundred dollars less. The lack of rust and interior is what really grabbed me, so I made a deal and drove it home with a bed full of spare parts. So much 70s/80's flair! The polaroid at the bottom is from 1982. I'll post up some more pics soon, as well as of the spares I got along with it. Hopefully you guys can let me know if I got a few good parts too, bc I'm new to Datsun's and don't yet know what I'm looking at. The truck runs well, but needs some attention here and there. One question: do all of these things sound like a city bus?! It has a brand new exhaust system which is nice and quiet but there is so much wooshing, whirring, air sound going on it's insane lol! I definitely have plans for this little guy, and I'm thankful what a great resource this site is. More pics/info to come.