I'm fixing up a 1984 Sportster XLX 1000. This was the "last of the iron heads" sportster but it has an ignition system with the computerized control module.

Here's what's going on.... I got the bike from a friend. It had sat in his garage for about 8 years without being used. I got a new battery, rebuilt the carb, cleaned the tank but couldn't get it to start. I started going through the troubleshooting process in the FSM. The coil was bad so I got a new one. That got the bike to start although it was very hard to start. The starting woes have continued though....

Right now, it will crank and crank and not start. I am continually checking for spark and it is intermittent. I have one of those inline spark plug test lights. It will go from having regular spark to having spark on the just the first few cranks to having no spark in no particular order. It's like there is something going on that is randomly disabling the ignition. It'll crank and crank, then I'll mess around with some stuff and it'll fire right up on first touch of the switch. It'll idle but when I try to rev it a bit, it'll die and won't start back up.

There is no rhyme or reason as to when it will have spark and when it won't.

I've gone through the troubleshooting steps again and done the following....
1. Checked condition of plugs and wires - all look good
2. Test for spark - this is the test that comes back with varied results
3. Check battery voltage while cranking - got 11.75v
4. Check ignition module ground - removed, cleaned and reinstalled ground wire
5. Check voltage to coil - was within half a volt of reading at battery
6. Check voltage across coil - was within half a volt of reading at battery
7. Check voltage from computerized control module - got 5.05v which is what it's supposed to be
8. Check voltage from computerized control module while plugged in - got 5.05v
9. Check voltage from sensor plate when rotor is in slot - got 5.05v
10. Check voltage from sensor plate when rotor is not in slot - got .01v
11. Checked VOES and found that it was not holding vacuum - disconnected it, capped fitting on carb, grounded signal wire from computerized control module so it would always be in the high vacuum state which is what I want to get the bike to idle and run at low load. I'll replace this switch later so the bike will advance timing while riding under load.

So, any thoughts as to where to go next???? This is driving me nuts!

 

It would seem that the inconsistent spark is the problem. The coil is new so we hope that is not the problem. Hoping is not good enough, and new parts have been known to be no good. I wonder if the old coil might actually be good, if both coils are good, and if the problem is elsewhere? Or if the new coil is actually no good

I wonder is the wires to the spark plugs have good connections at both ends? and if the wires themselves and the plugs are still good?

So answering these may require purchasing new plugs, wires, and perhaps yet another coil

Anyway, it is late, I am tired, and those are my thoughts for now. See what others may say. I'll look in again tomorrow evening

 

i would agree with Mick, Start by replacing the plug wires and the plugs themselves, gapped correctly. This will eliminate them as a cause and is relatively inexpensive. When you were checking the sensor did it appear the timing was close?

 

 

[QUOTE=Soarer77;17753656]I'm fixing up a 1984 Sportster XLX 1000. This was the "last of the iron heads" sportster but it has an ignition system with the computerized control module.

Here's what's going on.... I got the bike from a friend. It had sat in his garage for about 8 years without being used. I got a new battery, rebuilt the carb, cleaned the tank but couldn't get it to start. I started going through the troubleshooting process in the FSM. The coil was bad so I got a new one. That got the bike to start although it was very hard to start. The starting woes have continued though....

Right now, it will crank and crank and not start. I am continually checking for spark and it is intermittent. I have one of those inline spark plug test lights. It will go from having regular spark to having spark on the just the first few cranks to having no spark in no particular order. It's like there is something going on that is randomly disabling the ignition. It'll crank and crank, then I'll mess around with some stuff and it'll fire right up on first touch of the switch. It'll idle but when I try to rev it a bit, it'll die and won't start back up.

There is no rhyme or reason as to when it will have spark and when it won't.

I've gone through the troubleshooting steps again and done the following....
1. Checked condition of plugs and wires - all look good
2. Test for spark - this is the test that comes back with varied results
3. Check battery voltage while cranking - got 11.75v
4. Check ignition module ground - removed, cleaned and reinstalled ground wire
5. Check voltage to coil - was within half a volt of reading at battery
6. Check voltage across coil - was within half a volt of reading at battery
7. Check voltage from computerized control module - got 5.05v which is what it's supposed to be
8. Check voltage from computerized control module while plugged in - got 5.05v
9. Check voltage from sensor plate when rotor is in slot - got 5.05v
10. Check voltage from sensor plate when rotor is not in slot - got .01v
11. Checked VOES and found that it was not holding vacuum - disconnected it, capped fitting on carb, grounded signal wire from computerized control module so it would always be in the high vacuum state which is what I want to get the bike to idle and run at low load. I'll replace this switch later so the bike will advance timing while riding under load.


I'm actually having the exact same problem. Same, bike too. '84 harley sportster xlx. It too sat in a garage for about 7 years, and i just began trying to restore it. I'm having the same spark issues. Put on a new coil, wires, and plugs. It still just sparks when it wants to. I was thinking maybe, ignition module? Any pointers would be appreciated

 

Unfortunately Soarer77 did not come back and post his results

It looks like you deleted the [/QUOTE] so it is not exactly clear which of the above is completely yours ? I went back and checked so OK

I don't like the idea of throwing parts at a problem hoping for a fix, but it seems like you have done everything else, and from the symptoms it could be a bad ignition module. I would replace the ignition module with the ULTIMA unit. This is the one that "we all" use. It is not expensive.

My favorite eBay seller for this item:
https://www.ebay.com/itm/Ultima-Prog...9vF3:rk:7:pf:0

https://www.hdforums.com/forum/ironh...-ignition.html

http://www.ultimaproducts.com/53-644_Ignition.pdf

http://www.ultimaproducts.com/programmableignition.html

NOTE: You do not need to get the programming kit, just the complete ignition kit. Do not get just the ignition module.

 

IronMick is right on it

But one thing to try--- "The grounds " The bike is old and been seating -- grounds go bad much less the Ing Module sets on chrome or Alum , chrome is the worst thing to conduct elect and grounds

Try running a jumper wire from the Ing module mounting screw to the NEG battery post , and even back off the screw and tighten it bask to disrupt any connection

 

These old electronic ignition systems need a good, FULLY-CHARGED battery to operate correctly. Otherwise, the electric starter draws too much current away and you only get a spark here and there. Your battery connections also need to be clean and tight (both ends of the cables), and the ground under the seat from the ignition module needs to be in good contact with the frame.

 

I agree with Mick, the Ultima kit is great and cheap as well. I put one on my 1984 XLX and it ran much better.

 

The resistance across the old coil confirmed that it was bad. The new one reads within range. This fix got the bike running sporadically. The wires have low mileage and are in excellent shape. The plugs are good too. I'm confident the issue lies elsewhere.