I have a problem of no spark while cranking and a very small spark when ignition switch is moved from cranking to run position. I have changed the ignition module with a new one with no change, and tried a used one that I know works to make sure the new one is good. I tried changing the coil also. I cleaned all the terminals and looked for loose wires. The truck has 16K original miles. It was running fine then will not start due to no spark at the coil or distributor. The dual batteries are new and fully charged, the starter turns over as it should. Is it a distributor problem or is there a relay somewhere that went defective. There is a relay mounted on the drivers side fender with no markings except the Ford logo. It has 4 pin connectors, what does this relay do? I thought it might have a defective crank sensor, but could not locate any on this 1986 model. Thanks in advance for any help.