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How to rebuild your motor through misdiagnosis and head scratching


supererogator

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Hello.  I have read this forum for a while, but never gotten so stuck I could not use your existing advice and fix it.  I have read the entirety of an older thread ( http://community.ratsun.net/topic/43444-replaced-timing-chain-and-some-gaskets-and-i-cant-get-my-l18-started-again/

 )

, and watched the video posted there (Fantastic video BTW).  These things have gotten me to where I am, but not on the road.

Basically, I replaced the timing chain, tensioner, races, and gaskets...you know, all the stuff in the kits.  At this point, I can manually crank the motor and all marks line up to TDC.  The distributor points at 1 as well.  The dizzy pin is at the 11:28 position (but I have tried 180 out and a tooth or two off either way).  I have clean spark at the plugs, and I can see gas going into the carb when I pump it.  Dizzy cap is new, plugs and wires are new, rotor is new, vac lines are only 3 years old..... It still has the craptastic Hitachi carb, but that seems functional.

 

Any ideas on why I cannot get it to start?  I can get a sputter and sometimes a backfire, but never a run.  I have drained the battery twice trying all these things over and over.

 

This is an automatic that formerly had AC (still in, but disconnected before I got it years ago).  Many of the emissions control items have been blocked off.  It ran with the accelerator to the floor when I took it apart, but only all the way to the floor, and very poorly then.

 

Thank you in advance.

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Set to TDC compression stroke on #1.

 

Check that the #1 cam lobes are at 10 o'clock exhaust and 2 o'clock on the intake as viewed from the front.

 

The following valves should be closed and have enough clearance so that the rocker arm will wiggle slightly by hand.

 

#1 int. and ex.

#2 int.

#3 ex.

 

Turn the motor ONE full turn and back up to the TDC mark. The following valves should now be closed and the rocker clearance such that it will wiggle slightly by hand...

 

#2 ex.

#3 int.

#4 int and ex.

 

If any of these rockers are tight and will not move then the valve lash is incorrect and needs to be set.

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...I have clean spark at the plugs, and I can see gas going into the carb when I pump it...

 

 

...It ran with the accelerator to the floor when I took it apart, but only all the way to the floor, and very poorly then.

 

Thank you in advance.

Has spark but didn't run well to begin with. If it ran with it floored it wasn't the timing chain.

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You mentioned that "it still has the craptastic Hitachi carb", it is quite likely your issue if everything else is correct, it sounds like you had issues before the timing chain, if everything else is correct, and you need to double check to make sure you put the firing order on the cap COUNTER CLOCK WISE, as a lot of guys screw this up, I would then start thinking about a new weber carb myself.

Keep this in mind after reading my post, I dislike down draft carbs, including webers, they have been nothing but a pain in the ass all my life, if I let them sit any length of time, they always screw me over, I seem to have nothing but problems with them, but others have been very happy with a weber.

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Hello.  I have read this forum for a while, but never gotten so stuck I could not use your existing advice and fix it.  I have read the entirety of an older thread ( http://community.ratsun.net/topic/43444-replaced-timing-chain-and-some-gaskets-and-i-cant-get-my-l18-started-again/

 )

, and watched the video posted there (Fantastic video BTW).  These things have gotten me to where I am, but not on the road.

 

Basically, I replaced the timing chain, tensioner, races, and gaskets...you know, all the stuff in the kits.  At this point, I can manually crank the motor and all marks line up to TDC.  The distributor points at 1 as well.  The dizzy pin is at the 11:28 position (but I have tried 180 out and a tooth or two off either way).  I have clean spark at the plugs, and I can see gas going into the carb when I pump it.  Dizzy cap is new, plugs and wires are new, rotor is new, vac lines are only 3 years old..... It still has the craptastic Hitachi carb, but that seems functional.

 

Any ideas on why I cannot get it to start?  I can get a sputter and sometimes a backfire, but never a run.  I have drained the battery twice trying all these things over and over.

 

This is an automatic that formerly had AC (still in, but disconnected before I got it years ago).  Many of the emissions control items have been blocked off.  It ran with the accelerator to the floor when I took it apart, but only all the way to the floor, and very poorly then.

 

Thank you in advance.

 

 

 

Where in oregon?

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Firing order is correct. Choke sticks open and has for quite some time. A Weber is on my list. Valves are correct, 1 at 10 and 2. I have a friend coming with new eyes this eve.

Oh, Eugene.

Thanks. I am going to beat this.

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i would say the carb is the issue.... my first thoughts were firing order, as i have put the plugs on the distrib cap the wrong way and my truck would not fire at all... then i realized I had the wires on the wrong holes for the cap.. if you spray starting fluid in the carb and it fires right up, then id throw on a webber 32 36 .. 

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Yes, that's the way. Use starting fluid. It if catches then its the carb.

 

We used to fire up engines on the ground that were missing the carbs, starting fluid and palm covering the manifold would make them catch, to demonstrate the engine was in working condition.

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I have already gone through half a can of starter fluid. I am still leaning toward the carb and some mystery vac line having been bumped off it's place. Thank you for the new direction. Now I can stop moving the oil pump spindle over and over.

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Update.

I just had a pal over, and we have eliminated the valves (good compression), and have found that there is fuel all the way to the cylinders (can feel it when cranking), so I am leaning away from the carb.  I even got the choke to close.  Spark at all plugs...etc as before.

Could the dizzy be in the wrong position?  When reading the books I have (one is the Datsun factory manual), the 11:28 position for the pin/shaft is mentioned.  This puts my rotor at roughly 8:30 and that points at what has been #1.  Could it be that I have been running with the dizzy out for the last few years?  I am measuring the position from the driver's side of the motor, not from the front, as that is what I could see in the video and books.  Should  be measuring the position from the front of the truck?  I would be currently about 90 degrees out at that point.

Also, another friend mentioned the "vac on the governor".  Not being very familiar with automatics, and coming from an old Ford family (Dad has a '30 A, Mom had a '56 bird, I have a '65 Mustang), vacuum reliance is pretty new to me.  Is this a concern?  What should I check there?

Again thank you.  I am at a real loss on this one and I am dragging my friends down with me.

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Where the rotor points isn't that important as long as at TDC it's generally under the #1 plug wire. As mentioned the order is backwards or counter clockwise 1342. The most common mix up is 3 and 4 swapped.

 

Loosen the timing adjustment screw and try rotating the dizzy slightly clockwise to advance the timing as you crank it. If that doesn't work try the other way to retard it. Watch the fan blades.

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I don't know what you mean by 8:30, if you standing on the driver side of the engine looking down the dist. hole, and the shaft is at 11:28, that would put the rotor at 4:00, or maybe 10:00 on an L16.

motordistributortiming.jpg

The cam needs to look like this.

TDC1.jpg

Here is the link for that thread I got these photos from.

https://www.google.com/url?q=http://community.ratsun.net/topic/31235-1128-position-for-timing/&sa=U&ei=K1hHU9OtIaKa8QGR2IG4BA&ved=0CAYQFjAA&client=internal-uds-cse&usg=AFQjCNErZQ06jf33fbGV5DPGqbs8kTeJyA

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  • 2 weeks later...

New update.  After replacing the coil (spark is not necessarily enough), to accomplish a strong spark, she runs again, but very poorly.  Further inspection has shown no vacuum from the carb, so, Y'all were right, by my figuring.  Problem was, I couldn't get far enough to diagnose the issue as a fuel issue.  Carb rebuild in process.

I have not seen a rebuild for the DHC-113 carb yet, maybe I have not looked far enough, but I will work on getting some progress pictures along the way.

 

Thanks again.  You folks are awesome.

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so this a 80 L20b.

 

if you went by the video and when crank is linked up to Zero and your rotor is right on #1 plug wire, your n the middle of the timming plate adjustment your pretty much correct.

if you your distributor is fine and coil I think you would get spark.

Once you have spark ck the valve lash. so you not letting compression out so its not firing(even if you have good spark)

then ck the carb intake for tightness. If looks tight I would then shoot starting fluid. If it fires  right I would think its good. You got a duel delivery or vaccum issue. maybe a bad dizzy .

But I say your mechanical part of the engine is good unlelss you got a hole in piston ,valve ect. But you said compression is good so I say motor itsself is good. Look at the carb or dizzy. use a EI coil for a 79/80nissan.

 

 

once I went to a guys house and his 620 wouldnt start. I cked everything. Changed the spark plugs it started right up.  I waisted my time and he no longer drives this truck. Cause he wanted a KA motor and never got around to getting that done.

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To further explain...  The ports on the passenger side of the carb had no vacuum.  After spending yesterday rebuilding the carb, I put it on this morning.  Started right up and ran like it hasn't in almost a month (since I was roadside).  The hiccough in the "started right up", is that it only does so if the choke is propped open.  It seems to be leaking somewhere, and the float reservoir won't stay full.  I am slowly diagnosing the issue.  Also, all the adjustment screws don't quite hit the plates (i.e. the one that hits the bottom of the idler cam, and is supposed to be touching the second step, of the idler cam.  I have been slowly adjusting the connecting rods and this is almost achieved.  I have also discovered that I am missing the main throttle return spring.  The one that goes on the throttle assembly arm, just before the anti-stall dashpot (automatic only).  It has been missing for a while, since I did not remove it while disassembling.  Gonna have to get one on my next parts store run I suppose.

If anyone has traced down a leak in a rebuilt carb, ideas on how to do that could be helpful, but tinkering will probably get me there.

I have detailed pics of the carb rebuild, but am too busy wrenching to figure out how to post them now.  I will get to that in a few days.

Thanks again for your help.

OH!  To clarify the dizzy placement... The picture above of the cam at 11:28 is totally correct.  Smaller side to front of vehicle.  What I couldn't figure is which way my rotor should point after the dizzy was in.  It always seemed like it was 180 out on my truck.  Well, #1 on my truck is toward the back of the truck, when the dizzy is installed correctly.  All the pictures I saw of other Datsuns seemed to show #1 being at the front of the truck, in the dizzy.   This is what I remembered when I took it apart.  As it turns out, with all the dots matching, mine is not that way, and may have been running 180 out since I got it, with the plug wires also 180 out.  Mine now matches the Datsun factory manual, and with the light on it, it is centered in it's adjustment slider and near perfect 12 degrees below TDC.  Does that clear my original question up, or just make it muddier?

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weather the rorotppoints in fron or back dont really matter as long its on #1 plug wire.

I think L16 rorots pointed in front and L20s in back but who cares long as it lines up.  the vaccum advance maybe 180 out if the pedastal was mounted on 180 out from orginal but still run.

 

Be hones save your pain on a Hitachi carb.

Find the rebuild kit box. then find a bigger box place both units in box then go to nearest river and throw it in.

Buy a weber 3236 DGV 5a manual carb. yes manual!!!!!!!!! simple.

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It seems to be leaking somewhere, and the float reservoir won't stay full. I am slowly diagnosing the issue.

 

...

 

If anyone has traced down a leak in a rebuilt carb, ideas on how to do that could be helpful, but tinkering will probably get me there.

Congrats on the Ratsun spirit of DIY.

 

If the fuel bowl runs dry overnight, it is usually either the fuel bowl seal or the jet plugs on the bottom. Both are accessible without removing the carb. Try tightening the plugs a little.

 

Fuel bowl running dry overnight won't cause the engine to run poorly.

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