Just a note for others in case you have this problem now or in the future. I have a 1989 ford van as well as a 1991" b". No problems with the "b" as far as starting but my 89 would crank and not start when it got to be freezing and as soon as the temp went up the van would start immediatly. After a trip to a couple of shops both of which could not figure out what was wrong, I went to a third shop and mentioned that I thought it was either a cracked distributor cap or a short in the wiring. Turns out that after a complete tune up and replaced wiring and parts the problem came up again as soon as the temp dropped. Back to the shop and this time after being in the cold for a week the problem was found and solved. Problem, water in the coil receptacle where the wire goes out to the distributor. When it was warm there was electrical contact but when it got cold, the water would freeze and no electricity could flow. Drying up the little bit of water, and I mean little bit of water, the problem is no more. Never heard of this problem before but I will never forget it and I hope this might help others now or in the future. Don't know how the water got there except maybe when I clean the engine in the summer so I will use a little more caution next time.
Here's another tip that might help someone else...
Mine would occasionally be slow to start turning over, but would always fire up immediately once the starter started running. Well, today, it wouldn't start at all (while it was blocking my driveway, naturally). When I'd turn the key, the starter wouldn't run at all. Battery seemed strong and jumping it didn't help. Starter hasn't ever given me any issues either. The battery terminals seemed tight, and though there's some corrosion it's not a lot.
The answer turned out to be a wire on the relay was loose. This wire can't be more than 16 gauge or so, and it has a rubber boot on the end that slides over a terminal on the relay, but the rubber is apparently worn out and now it doesn't hold it securely. I pushed that back on and tried to start it, and it fired right up! The wire in question is red. The relay is mounted in front of the engine battery; you kind of have to lean over the battery to see it. Follow the positive wire from the battery and you should find it quickly.
It must be some kind of voltage sensing wire or something, because I don't think it's even heavy enough to be the ignition wire. It's certainly not one of the battery cables or anything like that.
Just a note for others in case you have this problem now or in the future. I have a 1989 ford van as well as a 1991" b". No problems with the "b" as far as starting but my 89 would crank and not start when it got to be freezing and as soon as the temp went up the van would start immediatly. After a trip to a couple of shops both of which could not figure out what was wrong, I went to a third shop and mentioned that I thought it was either a cracked distributor cap or a short in the wiring. Turns out that after a complete tune up and replaced wiring and parts the problem came up again as soon as the temp dropped. Back to the shop and this time after being in the cold for a week the problem was found and solved. 
Problem, water in the coil receptacle where the wire goes out to the distributor. When it was warm there was electrical contact but when it got cold, the water would freeze and no electricity could flow. Drying up the little bit of water, and I mean little bit of water, the problem is no more. Never heard of this problem before but I will never forget it and I hope this might help others now or in the future. Don't know how the water got there except maybe when I clean the engine in the summer so I will use a little more caution next time.
