Pulled and replaced plugs a while back and they were black and sooty. A weak ignition/ rich mixture right? Well i was going to test my coil but i haven't figured out what ishould put my multimeter on. It says to test for primary and secondary resistance. Pri by touching the two prongs on the underside of coil and should read .97-1.18 ohms or .95-1.20 ohms. But what setting do i put the meter on to read this correctly. 200, 2000, 20K, 200K, or 2000K. For sec it says 11,300- 15,300 or 11,200- 13,300. What should i put it on to read this? Plus it has two different figures because evidently there are two coil types, Diamond and Toyodenso. How do i tell which one i have, i looked coil only has numbers on side, no name. I just wanted to ask if anyone could help me with which setting to put he meter on, and I wanted to check the most costly and about the only testable part first, to get it out of the way. 1992 D150 5.2L V8
P.S- I also replaced wires when i replaced plugs

 

you are not getting any codes.

 

use 200 for readings up to 200 ohms etc. Therefore for 20K for the 11-15K reading. Generaly, if the coil is shot, you will have a far out of range reading and will know. See what you get first. As for the part number, try the number at a parts store or just via google and see what you get.

 

Testing for resistance in a coil only tells you if it is completely shorted. The ohms can be fine but it can still break down and cause problems when it gets hot.

Derek

 

Well i haven't had a chance to see if it is running any codes since i put the new computer in but the check engine light hasn't come on. I am going to run the codes with the keys and then take it to a place to get a better scan with a scan tool. So if the coil isn't the problem then the rotor or cap would be my next task, right?

 

Completlyshorted means no resistance and would not return a value such as 11,000-15,000, but a zero. An open is full resistance and returns one. If the coil is open or shorted, it is bad. You can at least try a cold read, as this is when it's failing anyway (the engine will not start and therefore, the coil will not have a chance to get hot). If in the future you have a issue when running hot, let the coil heat up, and then shoot the R value, resistance will increase when hot, and sometimes be out of tollerance when hot only (as Derek mentioned).

BTW, in case you didn't know, the primary side is where the 12vdc is applied, and the secondary side is the high voltage output side.

 

No codes with key check. I have no problem with it starting or running rough or anything, just the plugs were sooty and thought that was bad.