Transistor box style ignition

[Beer Snob]

Hey guys,

 Got a 78 620 with the transistor style ignition box located in the pass. side kick panel. The "box" says only checkable by a tech, but I'll bet someone out there knows something about it. Any knowledge appreciated even if it's "throw it away and use matchbox".  Ive got a start/no start issue that's driving me crazy. Ive had it running (poorly) and then it just wont start. "Feels" like spark or timing. I'll try not to run on but hears what it does...If it starts, runs like its not firing on all cylinders. If you pull off #1 wire...noticeable difference. Same with #4 same. No noticeable difference when pulling #2 or#3. But.. Hmm, If #2 and #3 were not firing, I'd think that pulling  #1 ( or #4 ) would kill it. Not likely to run on 1 cylinder right??  Ive got "visible" spark but maybe weak, Im testng coils now. Obvious things Ive done...It has good plugs/wires, valve lash adjusted, compression check completed, firing order like 100 times, not 180 out. Even with a "splash" of fuel down the carb not even a "cough ". I feel like its something stupid but fuel, air, spark, compression, timing, Datsun RUN?!?! I'll keep plugging along  just picking brains......Thanks all enjoy the weekend🍻

[datzenmike]

Not the transistor box and very unlikely it's the coil for the following reason...  It can't know what cylinder it's firing and select which ones it wants to turn off.

 

 

First, check that your plug wires are correct order. The firing order is 1 3 4 2 in a counter clockwise direction on the distributor.

 

Second, check your valve lash. A too tight valve will not close and seal properly and miss fire. Check on a cold engine. intake 0.008" and exhaust 0.010".

 

Is this with the engine completely warmed up for over 10 minutes? When warm, check that the choke has opened fully.

 

 

[banzai510(hainz)]

i tight valve will make a cylinder drop off also like no spark cause yyou dont have compression  check your lash pad under the valve and set it using a feeler gage

[Beer Snob]

So at this point I now have a NO start condition. I did another compression test and got 150-153 across the board on all for cylinders. I did a valve adjustment prior ( a month ago or so). The compression numbers suggest that the valves are closing , yes? The thing is, its started and ran many times in the past and as recently as last week, (poorly but would idle and be capable of moving the truck in and out of the garage. Swapped in a carb off another project that 100% runs well, so not a fuel issue. Fuel pump is also pumping well. It REALLY feels like an ignition issue. Dizzy? Bad pickup coil in the dizzy? 

 Here's something I was playing with, ( it was unintentional and may be pointless but....), when installing the dizzy I rotated the shaft to align it with the drive gear on the oil  pump and forgot I had left the ign. on. I'm assuming when the reluctor passed by the pickup coil is why I got a big ol Blue spark and "pop" out of the coil ( it's unplugged from the cap obviously). Makes sense, right? Ign. on, so 12v flowing through the ign. system and you're basically simulating the engine turning the dizzy like its trying to start. If I keep rotating the dizzy shaft 360 degrees I can hear 4 "little" spark attempts, then sometimes only 1, sometimes 2, and sometimes random numbers of "little" sparks, and every now and then a Big Ol spark. My question is, if everything is functioning properly should I be getting 4 "Big sparks" out of the coil with every 360 degree turn, or is this a pointless trouble shooting endeavor? I put another identical style dizzy in ( unknown condition )  and did the same and got nothing. 

 If anyone can make heads or tails out of what I'm sayin or has any ideas feel free to throw anything out there to check. I've never been stumped this bad on a no start issue, and I'm feeling really F&#king stupid and frustrated. Anyway thanks for reading, I'll keep fighting and let ya know WHEN I figure this shit out. 🍻

[Beer Snob]

Everyone like pics so...you can see that 2&3 were not firing like 1&2. Correct plugs??? 

[datzenmike]

Leave your  feelings out of this. Connect everything up and pull one of the plug wires off, stick any plug in the end and hold tightly against the grounded head. Have someone spin the engine with the starter. Do you have spark????? If yes it isn't the ignition.

 

 

Correct plugs.

 

Two plugs are dirty. This does not necessarily bean they are not getting spark. But check the firing order. 1 3 4 2 in a counter clockwise direction on the distributor. If set going clockwise then yes, 2 & 3 they fire but 180 out . 1 and 4 would fire normally.

[Beer Snob]

OK fair enough. I've only looked for spark at the end of the plug wire itself not all the way through the plug. I will do, give me a bit. In the mean time, so we agree on some principals...TDC compression stroke, #1 piston up, camshaft lobes at their highest point ( leaving both rocker arms loose, valves closed), rotor will point where it points as it can only go in 1 way since its not on a 20 tooth gear but an offset drive spline from the oil pump. So, if you call wherever the rotor points  #1 and go 1,3,4,2 counter clockwise.....correct? TDC compression stroke.

 Hear is my set up in pics, 

 

[datzenmike]

Correct. It should point near to the #1 plug wire on the cap.

 

Make sure distributor mount bolts are snug and the timing adjustment tight. The distributor has to ground to the engine through it's case.

[Beer Snob]

Cool, before I get a chance to check spark at the plugs hears one more thing. I'm making sure I've not made a stupid mistake....pictured is how I understand valve adj. Pictured is valves adjusted on compression stroke (red exhaust/blue intake), then rotate 360 degrees and do the other 4. 

[banzai510(hainz)]

doesnt even look like oil is in this engine.

 

i would just pull the center wire out of the distributor cap and place near ground and start an look if the spark is consistant. If yout think its doing 4 sparks per rev then ignition is good.  Then do the Mike sugesstion of pulling the plug wire to see if a cyl falls off or dont do anything.

 

if you didnt drop the oil pump then whats on the photos look like TDC to me and rotor should be on #1 plug wire when you install the dist.

[Beer Snob]

Just for clarity, my last check last night....

[banzai510(hainz)]

if you got 150 across the board your fine. or another way is just wiggle the rocker arm when the lobe it pointing up off the back side of the lobe this means the rocker is off the valve and closed.  you have 150 so you have compression  your GOOD.  Gas and ignition is next  of coarse timing.

 

maybe a plug is bad? I rarely see this  but I seen it fix other vehicles before.

 

 

I hate to find out you got bad splug wires!!!!!!!!!!!!! NE64 NGK brand is the one to get ,cheap

Edited June 9, 2023 by banzai510(hainz)

[Beer Snob]

Good eye bro, motor has oil, old pic after cleaning up. Going to check spark on all 4 plugs later as bad or incorrect plugs crossed my mind but there brand new, although we've all had bad brand new parts at sometime if you've played with cars long enough right!?!? And to confirm the proper rockers are loose, and the others are tight. Doesn't prove clearances are correct but....yeah. Last time it ran I could pull #1 and #4 wires off and it would drop off, #2,and #3 no difference in how the motor ran. If you look at the pics of the plugs it seems to confirm something....I'll let you guys know what I find later when I check for spark on the plugs themselves. 🍻

[datzenmike]

1 hour ago, banzai510(hainz) said:

doesnt even look like oil is in this engine.

 

 

 

You just never seen a clean L engine!

 

There's no change time on plug wires. If they look crappy, they are. Mine are at least 12 years old but I take them off once a year and wipe down with WD-40.  Try plug in the #2 & #3 wires. See if spark is dimmer. Cap could be bad also.

 

 

Correct on the valve lash setting.

[Beer Snob]

waiting for a buddy to come over to test spark at plugs. While Im waiting started checking odd ball stuff. My plug wires seem to have between 8 and 9 ohms resistance. When I pull good Denso wires of my 84 toyota (22r carb.) they measure at 1.25-1.8 ohms resistance. Is this alarming or should I forget about it? They are new but just cheap Schuck's parts.....🍻

[datzenmike]

Check what scale your meter is on but several thousand ohms per foot is fine. 

 

[banzai510(hainz)]

I woulnt worry abiut the resisitance soem wires if all close to the same then could be the resisitive type. Really the coil goes up higher voltage before it jumps to ground

 

if 2 and 3 dont change then the wires maybe swpped or the plugs bad and or the rotor contacks.

 

 

you got compression so the cylinders I say is good and not cracked valve or seat.

 

 

I met a 620 guy I was trouble shooting his rig then more or less went to his house. I put my plugs on his motor and it ran fine. I was PISSED!!!!  4$ fix!!!!

another time ,I saw this 240sx at this house. talked to the kid. he had a spare KA motor said was bad. He swapped a motor in and now was running. I called Icehouse on here he picked it up free installed in a 510. I said what was the fix. He said he swapped sparkplugs. That was it. So make sure you do the simple shit first!  I would have got new plugs already and put them in if you notice they dont dropoff when you pull the plug wire, Fuck waiting for your friend.

Edited June 10, 2023 by banzai510(hainz)