4.9strait six not getting fire to the plugs what is a good check for that

SOURCE: 1986 dodge 3/4 ton, 3.7 slant six. no fire to

Sounds like fusible link. It's a thick (thicker than normal) wire coming from battery to junction block on firewall. They burn through and/or break down internally - you can replace it with an inline 30amp fuse & holder.

SOURCE: not firing right on no.4

First check plug and make sure the right plug for this vehicle,make sure that the heat rating for this plug is correct. Your problem could be a wrong heat rating plug been installed. Also make sure that the misfire is due to a bad plug and NOT a bad injector or injector wiring or uneven compression or even bad coil. Check injector wiring and make sure it not shorting or broken. To check injector pulse use a NOID light can be bought at almost any auto parts store like Auto-zone etc. Also compression can be checked with compression guage. A rule of thumb to go by is if any cylinder has more than 10 PSI in difference in compression there is a problem like a burnt valv etc. Here is a n example cyl# 1 170psi cyl#2 176 psi cyl#172psi cyl# 4 150 psi, there is a problem with cylinder # 4 and will cause a miss from cylinder #4. Good luck and thank for using FIX YA

SOURCE: no,4 plug not fireing changed plug wires.new coil.plug ran good for 100 miles then 4 stop again

are you losing the spark? or fouling the plug? if you clean and reuse it in a neighboring cylinder... does the problem stay with the part or with #4. now, what deposits are on the plugs? is it wet and fuel fouled? or black and carbon fouled? or oily and chunked up with debris? now you can run a compression test. once you determine compression is even on all 4, following a wet compression test, you can reverify the part used is still good for the spark in a neighboring hole. depending on your findings, you can logically pick the problem apart and reevaluate