Coil weak spark

merlino69 · #1 (**permalink**) 09-28-2018, 03:05 AM

Hi guys,
I have 1992 CR with Ford 302 year 1985
Car won't start so after some attemps I found very weak spark at coil, so I changed coil and ECM. After install I have still weak spark so I was thinking that probably coil resistor is damaged.
I have 4 pins coil resistor but only 2 connected, I looked for new to replace but found only coil resistance cable...
This could be the problem ? How many ohms should rate ?
thanks
Marco

Ron61 · #2 (**permalink**) 09-28-2018, 04:19 AM

Marco,

I am sure that you have already checked this but did you look inside the distributor cap to see if the terminals are worn or black with carbon dust? Also check the coil wire to see if it has gained a lot of resistance. If it is the resistor you would probably be ahead to just get a new one and put it in. I got one at NAPA a few years ago after I measured the resistance and found out what the ohms should be. Best of luck with getting it sorted out soon.

Ron

merlino69 · #3 (**permalink**) 09-28-2018, 08:12 AM

Hi Ron,
good suggestions, I'm not very skilled, I will check inside distributor but I get weak spark at coil wire. I didnt measure coil wire resistance, I will check later.
For coil resistor how do you get resistance ? Old one is 6 ohms.
I couldnt find resistance indication on new coil. Also NAPA doesnt ship overseas..., rockauto only offer resistance wire but I don't know hot to connect
Thanks
Marco

Ron61 · #4 (**permalink**) 09-28-2018, 11:15 AM

Marco,

You can check the resistance of any resistor or resistor wire with a volt/ohm meter. The coil itself will have two resistances. One for the primary winding and one for the secondary winding, but if you have a weak spark getting to the coil then the problem is back toward the distributor and ignition system.

Ron

merlino69 · #5 (**permalink**) 10-08-2018, 05:59 AM

A technician came and he told me that should be an additional wire that add power to spark during ignition

where could I find wiring diagram of ICM model MOTORCRAFT DY893 ?

Ron61 · #6 (**permalink**) 10-08-2018, 06:11 AM

I am not sure but you may be able to do a search for that unit on the Internet and find a wiring diagram. If not try talking to your local Ford dealer and see if they have a diagram they will let you look at. If that technician came and told you there was a wire missing why didn't he tell you where it goes and put it in while he was there?

Ron

merlino69 · #7 (**permalink**) 10-08-2018, 06:22 AM

Ford 302 5.0 not so common in Italy and never imported by Ford so nobody here can help me... also he just suppose
I didnt remove any wire and car was starting months ago
I tried on Internet but I found Duraspark wiring diagram and it seems without coil resistance so I'm not sure it's same

merlino69 · #8 (**permalink**) 10-08-2018, 06:32 AM

my personal idea is that coil resistance is damaged, probably absorption is too high and spark is weak
I cannot find correct ohm resistance of coil resistor, in some ford diagrams is shown 1.3 ohms

Ron61 · #9 (**permalink**) 10-08-2018, 07:27 AM

Merlin,

This link will take you to a page of pictures of Ford Control Modules and some of their diagrams. See if any of these are like what you have.

ford icm motorcraft dy893 diagram - Bing images

Ron

merlino69 · #10 (**permalink**) 10-09-2018, 06:57 AM

Probably find the solution... there is a 3 terminal starter solenoid installed and 1 wire disconnected.
Most probably disconnected wire was originally connected to "I" terminal of starter solenoid that gives 12V to coil for start
I ordered 4 terminal starter solenoid and will try, hope it works !
Thanks for your support!
Marco

Ron61 · #11 (**permalink**) 10-09-2018, 10:48 AM

Marco,

Good luck and I hope that solves your problem.

Ron