newest 720 sas

[mattthom1986]

I need more pics of the truck to look at please.

[godzirra]

You got it, I have been meaning to get an actual camera to take them with instead of the verizon $40-special camera phone. The gf has a new iPhone so that should take a whole lot better pics. If tomorrow has good weather I will get some then.

 

If there are any particular shots/views anyone wants to see be sure to let me know. Might catch something I missed as far as potential problems.

 

I also SHOULD finally have a friggin front drive shaft this week, so maybe some action shots soon too :w00t:

[godzirra]

 

 

 

 

 

 

 

 

[mattthom1986]

I dig the shit out of your 720, man! Great stance. Thanks for more oics to stare at.

[godzirra]

The saga continues with yet another hard to define issue, engine related this time. And this JUST started happening today.

 

BUT here is what's happening.

 

Say I start the truck and let it idle.

Beautiful idle, right at 600-800 rpm.

Now I rev the engine, touching the gas and not too slow, up to 1000 rpm.

Then WHOOSH, very suddenly, almost instantly as it hits 1000, tachometer drops to 0 rpm and the engine soulds like it's choking.

BUT once it hits 0 rpm, *shutter shutter brump brump* right back up to 600-800 rpm and idles beautifully.

 

HOWEVER, If I stomp on the accelerator and rev quickly past 1000rpm to say 3000rpm and hold it there then let off, the revs go down like normal instead of dropping like a rock.

 

When if goes from 1000 to 0 in the blink of an eye, it is like hitting a rev. limiter or something. If you give it gas easy like taking off from the driveway and not the green light at the drag strip, the truck hits 1000 rpm and just goes "nu-uh" and shuts you down to zero untill it idles back up (usually 1 to 2 seconds).

 

Oh, and the battery light stays lit on the dash, but I wouldn't think a loose terminal or anything would cause this because the truck cranks up just fine.

 

I am thinking one of 3 things: bad gas. bad vaccume line. bad solenoid somewhere.

 

This is a problem because this happened when I was driving down the road. I could hear a very light skip start *bap...bap...bap...bap...bap...bap" real even. So I let off the gas and the tach dropped to zero. And once the thing hits zero once, it will do it every time untill you bust past 1000 to 2500 or 3000 and let it rev for a bit, THEN put it in gear at high rev.

 

If anyone needs any clarification just ask...I am kind of at a loss with this one since I can't find any vaccume leaks, it is running on a half tank of pure gasoline (non-ethanol), it has had a tank of cleaner/treatment run through it in the past 2 or 3 fill-ups, the carb is getting fuel (I have a transparent fuel line in the engnie compartment) and the carb. does not seem to be blocked by any obstructions.

[wayno]

You have a matchbox distributor?

[godzirra]

stock distributor. but while taking this picture I noticed an open solenoid just behind it to the right. with no hose on it. I referenced the Haynes manual and it mentioned nothing specific about the symptoms I am having related to the open solenoid. And considering that hose has probably been gone for a whiiiiile now and the truck has been running fine untill I stopped at this one "family owned" gas station in town to get some "pure gasoline" which I always prefer to use. It MIGHT be just a coencidence but that is the only driving/maintenance habbit that has changed.

 

 

[wayno]

I will tell you what happened to me, when driving down the road one day my engine started cutting out when I let off the gas, but if I down shifted it would come back to life, and if I hit the gas it would start working properly again eventually, sometimes I let off the gas with no issues.

It turned out to be the connection to the matchbox dist at the "T" plug on the dist, and when I wiggled the wires, my issue went away, when I let off the gas, the engine shifted and the connection was lost, but if I pushed in the clutch, or gave it the gas, the engine would shift enough to let it get power again, it was frustrating till I figured it out.

Check the "T" plug on the distributor, make sure the wires are good and that each connection is good, nothing can be loose.

[godzirra]

Well another symptom I am noticing is fluctuating oil pressure. At low rpm (idle or durring the initial take off from a stop), oil pressure will be under 45 on the guage (too low). At normal rpm (cruising at 2500-3000) the oil pressure is about 60 which is what it always has been.

 

Since the oil pump and dist. are related via that geared rod I am wondering if the oil pump might be failing. I will check on the dist. wires though.

[datzenmike]

stock distributor. but while taking this picture I noticed an open solenoid just behind it to the right. with no hose on it. I referenced the Haynes manual and it mentioned nothing specific about the symptoms I am having related to the open solenoid. And considering that hose has probably been gone for a whiiiiile now and the truck has been running fine untill I stopped at this one "family owned" gas station in town to get some "pure gasoline" which I always prefer to use. It MIGHT be just a coencidence but that is the only driving/maintenance habbit that has changed.

 

 

.

That's the BPT back pressure transducer (valve) it adds more or less EGR based on exhaust back pressure. If not connected no EGR = no worries.

 

Well another symptom I am noticing is fluctuating oil pressure. At low rpm (idle or durring the initial take off from a stop), oil pressure will be under 45 on the guage (too low). At normal rpm (cruising at 2500-3000) the oil pressure is about 60 which is what it always has been.

 

Since the oil pump and dist. are related via that geared rod I am wondering if the oil pump might be failing. I will check on the dist. wires though.

.

45PSI is tons of pressure. My tired L20B ran at 17 PSI at idle. The oil pump can only displace a certain volume of oil for every turn of the crank. At the same time oil is squishing out from all the combined main and rod bearings plus all the cam bearings. At some point the oil 'bleed' exceeds the pump's ability to replace and... the pressure will drop. You have nothing to worry about.

 

But if still concerned get a KA24E oil pump from an S13 or any KA24E or KA24DE from the D-21 Hardbody. They have internal rotors that are 13% longer and put out a corresponding increase in volume. This won't change the maximum pressure but it will increase the low speed pressure. I have one on all my L or Z series motors.

 

[godzirra]

Okay then, I was just concered when I saw the needle moving in accordance with rpm. But the more I think about it the more it makes sense, since the oil pump to dist. rod rests on the crank and as the crank goes faster the pump goes faster for more psi. I was just concerned because I have never particularly noticed it before.

 

So basically all oil pumps L through KA series have the same flange/port holes? On the remanufactured Z24i I put in a D21 I did notice the ports looked very similar for the oil pump on that one.

 

Just a question, would it be sacrilege if I asked a question about the intake wiring harness on said D21 on this thread? When I took the whole chunk out I disconnected the harness at all respective points, not cutting anything, and now that I have it all hooked back up, I have ONE 3 prong female end with no place to put it... everything else has a mate but this one. I will put pictures up when I can.

[datzenmike]

All L series 4 and 6 cylinder, Z series Z20/22/24 and the Z24i, KA24E (only in the S13) and the KA24E and LA24DE only in the D-21 have interchangeable/compatible oil pumps.

 

Some 280zx engines have the higher output pumps.... probably the TURBO automatics with the oil cooler? Hard to find though. While the S13 KAs and the D-21s DO have the high output oil pumps and are everywhere.

[godzirra]

Well I certainly might look into that upgrade, I even think the KA pumps are a little cheaper in general.

 

But yall are going to laugh your ass off at the latest story with the truck...and it does pretain to the issue at hand I believe.

 

So I am about to make this drive from cochran, ga to milledgeville, ga (about an hour and 15 min drive) for my brother's holiday/christmas party. I decide "eh, what the heck, the truck has a new oil change, new fuel filter, new breather filter, and a cleaned carb., ought to make it alright, should be a pretty good little road test."

 

Well on the way over there, faaantastic drive, scooted right along up and down and up and down several big steep hills, hit 65-70 a few times, radio playing, and made the trip safely in about an hour or so.

 

on the way back, at about 11:00pm, different story...

There is a whoooole lot of absolutely NOTHING between Milledgeville and Cochran, text book definition of rural Georgia. There are four churches, and two very small towns of about 250 people each. I am about 30 min. into my hour-long drive, jamming out to some big&rich, when the radio starts cutting in and out. In the next 30 sec. the dash lights start to go dim, and the brights go darker than the low beams.

 

By now I am thinking: twilightzonetwilightzonetwilightzonetwilightzone. The effectiveness of my headlights decreases exponentially to the point that the moon is brighter and I am driving by the reflective properties of the yellow/white stripes on the road and the occasional reflectors/road signs. Eventually all the guages except for the spedo drop to zero, and the radio dies for good.

 

SO I bee-bop onto allentown (half way point) and park it there at the bank at 12:02am. At 12:08am my knee hits the light lever on the column, the truck attempts to put on brights, and consequently dies. Battery is dead. No va.

 

Under closer examination I find that the bolt that retains the alternator on its rotating track has gone missing, presumably causing the tension on the belt to decrease and the rotation of the alternator to be less effective, thus causing all electrical functions on the truck to switch to battery power.

 

I eventually called some friends and rode back with them so the truck is at least in a safe place.

 

Regardless it needs a new battery, I am just wondering if a slack alternator would cause the skipping issue we have been discussing....

[wayno]

If the belt was not squealing, then it's likely the alt. has no power to activate it or it's bad, so it freewheels. :(

Once you charge or get a new battery, and fix the alt. so it is mounted correctly, start it and check to see if it is charging.

The radio if the modern type will cut out, the headlights will get dimmer and dimmer till it has no more power and then it will die, you might have been able to make it if you had not had to use the headlights.

My truck did the same things you are talking about when the alt. quit, except for the engine cutting out, once I knew what was happening I turned everything off and drove with the 4 ways home, the only time I have had my engine cut out, it was because of the loose wires going to the matchbox.

I have never drove a Datsun till it quit because of a dead battery, my Datsuns talk to me, they give me clues about shit going on, like the radio cutting out, that tells me it has a low battery, blinkers that blink slow is the same issue.

All this being said, I have no idea what low power will do to a stock carb(I have dual SUs), maybe the anti dieseling solenoid/valve will start opening and closing cutting the fuel off and make it run like total shit, by the way, I hate downdraft carbs, but maybe I have mentioned that before. :lol:

[godzirra]

There was no squealing, but that is the only logical explanation is that either the alternator is malfunctioning internally, or wasn't turning fast enough to do any good because of the belt being loose. And I knew that's what it was as soon as the lights started dimming, which I would have driven without if it wasn't pitch black outside.

 

Also I didn't actually DRIVE it till it died, the truck was at a low idle when I stopped at the bank, making the lowest output possible, and in the process of hopping in/out the light lever on the column switched to "brights" so the truck tried to turn on brights and there just wasn't enough output to support them.

 

Did you end up replacing the alternator on yours?

[wayno]

There was no squealing, but that is the only logical explanation is that either the alternator is malfunctioning internally, or wasn't turning fast enough to do any good because of the belt being loose. And I knew that's what it was as soon as the lights started dimming, which I would have driven without if it wasn't pitch black outside.

 

Also I didn't actually DRIVE it till it died, the truck was at a low idle when I stopped at the bank, making the lowest output possible, and in the process of hopping in/out the light lever on the column switched to "brights" so the truck tried to turn on brights and there just wasn't enough output to support them.

 

Did you end up replacing the alternator on yours?

 

At the time I had an externally regulated alternator, even though the ignition light was on for over a year it had been charging as I had it tested, but when it quit charging I didn't know because the light was already on.

Since I couldn't seem to get the light to go out even with a good externally regulated alternator, and I did replace the voltage regulator box a couple times, I changed over to an internally regulated alternator, and it started acting proper(light goes out when charging).

If you turn the ignition on(don't start it) and try turning the alternator by hand when the belt is not on it, it will not turn easily, so if you have a loose belt it will squeal when running(trying to charge), but if it is not working correctly, there is no resistance, so it freewheels, and the truck would overheat if the water pump was not turning, so circumstantial evidence says you alt. was not charging at all.

Another thing that tells you your battery is going dead is a starter that turns slowly, that's usually one of the first signs.

[datzenmike]

The alt is only 35 or 38 (optional) amps some early ones were 28 amp. If you have the high beams on, all running lights, heater and a stereo on you may have used more power than can be replaced by the alternator. Flipping down to low beams should have kept you going.

 

Did the charge light come on?

 

Was the alt belt loose? If loose enough it won't squeal.

 

I wouldn't replace the battery just yet.

[godzirra]

wayno: I DID get a chance to look under the hood before it shut off and the alternator seemed to be turning. However I did check the tension of the belt and it was comparatively loose. But as you said the alt. has resistance when turning where as the water pump does not, so would it not be possible for the belt to turn the water pump effectively but not the alt.?

 

And the battery charge light WAS on, but it has been on/off/on/off/on/off since I can remember.

 

datzenmike: I believe this one to be stock alt. so 28 amp would not surprise me. The odd thing is that the cabin/lights power decreased almost exponentially ad about 30 min. into the drive, for a good half hour it held fine. I am going this afternoon to try and jump it off just to get it home. I agree since the battery is not 6 months old...and at the time of the new battery install I had the alternator checked and it read fine (not to say it couldn't have failed between then and now).

[godzirra]

Allllright guys, I am about 99.999999999% sure wayno was right and it is the alternator that is failing. I got to the truck this afternoon and hooked jumper cables to it, waited about 5 min or so with the donor vehicle idling then tried to start it up. While charging I used a ratchet strap to move the alt. into place and and tighten the belt then bolt it in place again. Perfect start on first key turn. So I watched the battery charge guage stay at a solid 14.5. Good lights and guages, well lit.

 

So we took off the jumper cables and began the ride home. About 3 mi. away from home (with no lights of any kind any where on the truck) I lost the #4 cyl at high rpm (regained it at low rpm). Followed by #3 phasing in and out, then I was eventually just coasting on momentum. Before all the guages went out I noticed the battery guage was at BARELY 3-4. So clearly all electrical functions on the truck were being powered by the battery, spark plugs, radio, lights, guages, fuel pump, everything running on battery juice.

 

So I called and had the battery out of one of our fork lifts brought down and once installed, the truck ran perfectly and lights were at 110%, none of that skipping/choking crap.

 

The ONLY explaination that makes sense is the alternator is just no longer functioning properly causing the truck to basically run off the battery. Either lost magnetism, bearings are shot, or internal alternator wiring has malfunctioned. Seeing as it is only $50 or so for a new 36 amp one (with a lifetime warranty) and the parts store can have me one by lunch tomorrow, I'm thinking that"s the way to go.

[Boxcar]

I thought I had seen the whole post.

 Thank god for the editing controls on this sight.

As to you're alternator: I run  Delco 100 amp 1 wire conversions or Bosch or DENSO minni's depending on the need.. Never an issue.

 

[godzirra]

I did replace the alternator with the 38amp option. Had to modify a wire or two but still pretty easy. Anyway, hooked it up, crank the truck, let it run, then I removed one of the battery leads and it died.

 

So the head scratching begins. I check all of the junctions to and from the alternator. All wires to and from the battery. Then when I was about out of ideas, I realized the most simple of all checks had been overlooked, the fuse pannel.

 

So I got the meter and went to checking fuses, sure enough one of the 10s was toast. Not entirely sure what it goes to but I replaced it and then went through the same proceedure and the truck ran fine without the battery connection.

 

In doing so I noticed bubbles in the transparent fuel line I have while it was running. A little playing with the carb adjustment screw and it was running even better than before.

 

That's not to say that the alternator DIDN'T need to be replaced, I could wiggle the bearings a good 1/8 of an inch in any direction with the old one. Plus with the auxiliary lights I have in mind for this thing, 28amp wasn't going to be enough anyway.

 

 

 

btw boxcar, that is a sparkling example of an l20b. where is your thread for your sas?

[Boxcar]

620 4x4 conversion In project Dato.

 The engine is a spare I built up for a Samurai conversion I did last year. Not sure where it will end up.

[datzenmike]

In doing so I noticed bubbles in the transparent fuel line I have while it was running. A little playing with the carb adjustment screw and it was running even better than before.

You may have a loose fuel line clamp or slightly cracked hose. The pump is sucking a small amount of air in somewhere between it and the tank. It's fine if it does not become larger.

[Boxcar]

Good point Mike.

[godzirra]

Yeah the bubbles have been there for as long as I can remember. Could very well be a cracked hose since I only replaced about 1/2 of the fuel line recently.

 

One thing that is concerning me is the presistant presence of the charging/battery light. the damn thing won't go away and it's making me nervous. New alt. new battery terminals, none of the wires seem to have any faults in them to and from the battery/alternator. All the fuses were recently checked, besides that there is one (of two, square and black) relay next to the fuse box that is making this strange buzzing noise, 5 prong. I called the parts store with the part number on the back, 252...something, and they said it was some kind of a blower relay?

I am not 100% sure what that implies, the parts store wasn't either, go figure.

 

Anyway, I want that light out. It has been on before but normally goes out.

 

Oh, and I replaced a 15A/32V fusable link on the + battery cable.

 

Could the light just be reacting to the new amp output of the alternator? Or the fact that I replaced the 15A/32V fuse with a 15A/50V fuse? (all I had today).

 

As I understand it is a very vague signal. I just don't want to go motoring off into the night with that light on and end up driving back without headlights...again.