truck died and everything but ignition works

[Sparks]

hello all. i have a 77 620 with an l20, weber, matchbox dizzy and blaster 2 coil. been having some issues lately and the last one left my truck stranded on the side of the road. the first issue was when i turned the key to start i couldnt get the engine to turn over. tried it a few more times and it would finally turn over and the truck starts. the latest issue and the worst one by far is that now i have no ignition. i cannot get a spark at the plugs. turns over with the occasional glitch as described before but now i cant get it to start. i was driving at 35 and the thing died. radio was still on and lights were still working and everything but the truck acted as though i pulled the key out. i have done almost everything i can think of to try and diagnose the issue but still cant fix it. what ive done is replaced all the fuses. cleaned all the connections inside the cab and inside the engine compartment. pulled the plugs and cleaned them. they were not fouled. checked the fuel pump and carb. no issues there. taken a multimeter to my ignition switch and my coil. i have power to the coil and to the dizzy. i have replaced the cap and rotor. replaced the coil. put new plug wires on. i pulled the valve cover and checked the timing on the engine. everything checks out there. ive cleaned all my grounds and recharged the battery after using the starter motor to get me into the nearest driveway. im at a loss here and dont have any idea what else i can do apart from replace the dizzy. if anyone has had a similar problem or can help with mine i would greatly appreciate it.

thanks in advance

-Sparks

[Eagle_Adam]

I know you said you cleaned all the connections in the cab but did you specifically clean the connection at the back of the ignition switch? That's what fixed my issue, which sounds similar to the one your are having.

[Sparks]

pulled the switch out and cleaned the connections back there. they were clean to begin with but i went over them anyways.

[datzenmike]

Pull any plug wire off and put a spare old plug in the end, lay it on the grounded valve cover and crank the engine. Spark or no???

 

 

If no spark but you have power to the coil and to the matchbox....

 

Carefully unscrew the matchbox module (you don't have to disconnect it) from the side of the dizzy. Wire brush the back of it and the dizzy where it mounts to. Install.

Usually there is a spare terminal lug on the EI dizzy for a ground wire, find it and run a separate ground to it or make one. The module (and the dizzy it's mounted on) HAS to be solidly grounded for it to work properly.

 

 

Have to ask if you are running a points coil with a ballast or not.

[Sparks]

Not running a points coil. Ballast removed. I will have to wait until after 1 am for it to get dark enough outside for me to try the plug on the valve cover. I'm in Alaska. I'll run a ground off the dizzy and see if that works too. Thank you for the input.

[ggzilla]

You can try the 'plug on the valve cover' in bright daylight

[banzai510(hainz)]

hold with fingers and a good shock should happen eday or night

[Sparks]

pulled module off dizzy and cleaned the back with a wire brush and ran a ground from the dizzy to the frame. couldnt get a spark at the plugs day or night.

[datzenmike]

It should be wired like this...

 

 

Check that you have power at the B and the + terminal on the coil.

 

Now use a short length of wire and ground one end and briefly touch to the - side of the coil... you should get a spark.

 

YES I now get a spark but not when cranking the motor.... the dizzy or module is at fault.

NO I still have no spark.... the coil is no good.

 

 

.

[banzai510(hainz)]

You have 12volts at the +side coil???????

[datzenmike]

I asked that already but there are still people out there without a test light.

[Sparks]

Tested the both the dizzy and coil and I have power to both. I did get a spark when grounding the - side of coil to the body. I guess I'm now on the hunt for a new dizzy.

[banzai510(hainz)]

That test works also

[datzenmike]

Hail Mary....

 

Crank motor over with the cap off... does the rotor turn???

 

Inspect the module to reluctor wiring

 

 

 

Any visible damage? To the reluctor or rotor inside?

[Sparks]

rotor turns. no visible damage to wiring. cleaned connections and tried again. still nothing

[datzenmike]

One last thing... Have someone crank while you check for power at the coil/B terminal on the module. On my 710 if I turn the ignition too hard or far it will crank and crank and when I release the key it fires up. In the crank position there is sometimes no power to the EI. It's the ignition switch. I just have to remember not to turn it too hard. Maybe yours has no power in the START position? Worth a look.

 

If this isn't it, we've exhausted just about everything.

[banzai510(hainz)]

MIke his truck is a 77 so it should have a HOT START wire with the system. here is whear hooking the START and the ON wire at the +side would work in the earlier Datsuns.

[ggzilla]

Yes. If you do a coil conversion -- from coil+resistor to coil w/o resistor -- there are TWO wires from the ignition switch that are needed.

NOTE 1: Some pre-1978 electronic ignition uses a 12V coil WITH the ballast resistor

 

NOTE 2: Some will work with only one wire -- because some newer Datsun ignition switches put out power at S and IGN when key is at Start -- but older ones do not. Wire it as above and it will work with all ignition switches.

[Sparks]

coil is wired correctly. checked the power to coil and distributor at start and i have power to both. the ignition failure was a sudden onset as i have been driving it for two years now with the current set up.

[cashi123]

Man I feel your pain I'm having the same problem as you with the ignition on my 74 620 truck , I have replaced the Ignition coil, distributor cap & rotor ( mine is points), fuel pump, new spark plugs, new ignition wires, fuel filter, checked my carburetor and still not starting ,me and you buddy have the same problem L

[banzai510(hainz)]

Cashi 123

Pull out a multimeter and startt reading voltages and ck for spark and gas.

Simple

 

I havent bought pluhs and dizzy cap in over 8 years.

 

Pull center coil wire from the dizzy and place near chassis and try to start. You see spark? Yes or NO.

If yes then I say ignition is good. If not points not opening or soemthing grounding out.

 

Hopefully you bnought a POint coil. and still using the ballast resisitor.

 

measure at ballast 12or slightl more volts. then at coil should be like 6-9 volts. If 12volts before ballast thats good. if not voltage after ballast is open

[ggzilla]

Yes, the distributors caps last at least 20 year unless you get them dirty. Plug last about 10 years if the engine is in good tune the whole time.

 

The problem is likely a wiring issue or adjustment issue most likely can be fixed without buying any new parts.

[Sparks]

just got another matchbox threw it on and the truck fired up on the first crank. checked running voltage and my alt is hovering around 14.9. maybe the high voltage cooked the matchbox. not sure how im going to get it to come down a little.

[ggzilla]

14.9 voltage is within spec. Glad to hear it's now working!