Starter solonoid

My 1990 HR Imperial would crank very slow and not start. Mechanics took 6 weeks to not fix the problem. I bought a plug-in battery reader and discovered that the starter battery would read 13+ volts but drop to less than 7 volts instantly when I cranked the engine. I replaced that battery and it would still crank slow and not start but it would keep cranking. Staring at the wiring up front one day I noticed that the 2 wall-mount starter relays were so rusty that the rust was bridging across insulating washers. I was able to easily replace one at an auto parts store and the other one I disassembled and discovered that a spark-preventing grease had hardened on the contact-washer to the point that it had to be scraped off and then scrubbed with acetone. I reinstalled it and it always starts right up now even though it still cranks slow. The grease was preventing full contact between the large terminals which fed to the starter. Be cautious...I marked the relays #A and #B and tagged each wire as i.e. A R (#A right side terminal) or B L (#B left side terminal.) It was obvious whether the wire connected to the large or small terminals by the size of the fitting at the end of the wire. I'm glad I did it that way because there were 12 wires total. Anyway, that engine starting right up after sitting for months was one of the happiest moments in my life.