No start issues

Posted this earlier i will stay online now, just trying to get some diagnosis on my only day off today this week lol thanks

Fuse box is original as well as a member asked.

- rode my xj750 a 1983 home about a month ago and the next day it wouldnt start and still hasnt to this day. I have a brand new agm battery on it fully charged, fresh gas, new plugs and everything. I believe i am not gettin spark to from the coils as the plugs wont spark when taken out, grounded to the motor and attempting to turn it over but i am not 100% that this is the culprit. No loose wires either i checked all of them even at the coils. I have a multimeter but i have been really busy with work to fix it recently but i am off tomorrow and the next day and figured i could put some work diagnosing to try and save repair shop costs if i could. Any ideas why it ran to the house then once cold wouldnt start anymore? Ive tried choke, no choke about half a dozen times over the last month along with the other things i tried to no availhelp is appreciated, thanks all!

 

Have you checked all the chassis ground wires.and are you getting a light at all of your power points like the tci, coils etc? And at both end of your fuse holders.?

 

I havwnt checked the coils or fuse box with my multimeter yet as im not sure how i was thinking about upgrading my fuse box but i dont want to dump what little i have left of my paycheck this week into that id that isnt the no start problem i need to check it first. As for the ground connections i have checked them from the battery and are tight against its mounting point no movement at all.

 

After 30 years it may be time to undo all of those bolts and clean underneath, as a small amound of corrosion can show voltage but not give you any amperage to the elec components.
Also the ground wire mounted at coils
Even all of those plastic block plugs in headlight bucket and under tank etc can look ok but those are also hiding bad connections

 

Really? You think a corroded connection could cause the bike to just not run all the sudden after turning it off one day? Ill try it all but Should i redo my fuse box could that be the issue as well?

 

This sounds a lot like another thread....... http://www.xjbikes.com/forums/threads/problems-with-1981-seca-xj750.62060/unread

Corrosion may or may not be the cause of your problem, but ensuring that the electrical system is sound is a basic step in diagnosis.

 

Yes as K-moe stated do the basics first it's cheaper than buying a bunch of new components you don't need!

 

Okay if after checking and cleaning all connections including fuses and that doesnt work what should i check next? And also how do i go about checking my tci and coils with the multimeter?

 

you could pickup an inline bald fuse holder and 2 alligator clips and use it to bypass glass fuse for the ignition to see if it solves your problem of it does splice it in there are 2 kinds of the fuse holder regular size blade and mini size blade get the ones with covers

did you track your voltages to the tci?

 

Oh you think it could be an ignition issue? I dont think im getting any spark on any plugs either. I was going to create a new style blade fuse box but i dont think thats why its not starting the carbs are full of gas and the plugs are new.

 

if you do not have one wire diagram links thanks dave_jack
http://members.tripod.com/dave_jack/wiringdiag/d11a.jpg

http://members.tripod.com/dave_jack/wiringdiag/d11b.jpg

 

if you are getting no spark, make sure you have voltage to the tci . wire runs from fuse to run switch then back to tci and other componets . you could have a loose connector or a loose connector inside a connector body.

you are saying you have everything you need to run the motor it turns over but no spark.
check the voltages

 

Okay thanks so much how do i test the tci and coils though with my multimeter? Like what to touch together and what ohm setting to set it on to check?

 

Best way to check spark is with a new spare plug as the wasted spark system needs a complete circuit to function properly. Here is a good post on the theory and troubleshooting of a no spark condition, and step one covers checking for spark. If you don't have the corresponding plug connected and grounded, you actually risk damaging the coils as excessive voltage is created within the secondary of the coil because of the open circuit.

http://www.xjbikes.com/forums/threads/how-to-ignition-troubleshooting.21932/

Cleaning connectors and protecting them from oxidation is a good idea and should be part of periodic maintenance. However if possible, I like to know what was the root cause of the problem. Therefore, doing some voltage checks with the DMM is a good place to start. At a minimum, checking power to the TCI if you do indeed have no spark. For example, doing as suggested in step 2 of the ignition troubleshooting guide.

A bad fuse box can cause voltage drop and cause the bike not to start. There are few members stating they still have original and OK, but most are not. My bike has been garaged for its entire life, has only 17.000 miles on it, and yet the fuse box had the typical failure of one side of the clip breaking loose causing an intermittent connection. You can replace with blade fuses or there are options to repair using similar clips. The repair process requires some soldering skills.

 

You can test resistance on the coils using a DMM.

The primary side can be checked directly at the coils if you have the tank off. Or, you can check at the TCI where the main harness plugs into the TCI, which is actually the best place to start. To do this, remove the 4 pin connector from the TCI, place the positive lead on the R/W of the main harness, place the black lead on the Orange wire. Should get a reading of 2.5 ohms +/- 10%. Next move the negative lead to the Gray wire, and once again you should get a reading of 2.5 ohms +/-10%.

The secondary side of the coils can be checked by removing the spark plug caps from the plugs. Insert one lead in plug number one where it touches the metal up inside the cap, insert the other lead in plug number 4 cap touching the metal. Repeat for 2 and 3. In each case the measured resistance should be the secondary of the coil plus the plug caps. Secondary equals 11 Kohms and plug cap equals 5 Kohms X 2. Therefore, you should get a reading of 21 Kohms +/- 20% for 1 and 4 and likewise for 2 and 3.

If you are new to using a DMM the basic principle when checking resistance is to set it to a scale that exceeds your expected results. Or, some have auto settings, and will display a reading which needs just a bit of interpretation. Same is true for voltage and all readings whether auto or set to scale will be set to Volts DC.

 

From the thread he started today.

 

Thank you k moe i apologize this does make alot more sense to help diagnostic s wise

 

John, I'm just curious, how was the bike running before this happened... Was it acting up or just running sweet? If you have not seen this yet, I found this link to be helpful. http://www.xjbikes.com/forums/threads/how-to-test-your-starter-circuit.7828/

 

It was running fair id say it did have some issues starting but none i could pinpoint down to as a root cause of them just usually changed out the plugs or something else