Major trouble starting Ford F-150 1991 5.0L
So I have had my Ford F-150 2wd extra-cab Lariat for just a little over 2 years now. It only had about 135,000 miles on it when I bought it. I was trying to leave work yesterday and my truck would not start and I have already done many things due to starting issues in the past. So a few days ago I noticed my blinker changing from a flashing turn signal to just a solid turn signal without flashing. As I was driving to work yesterday, I noticed the volt gauge meter on my dashboard console was twitching back and forth like a fast pendulum or clock. I tried to start my truck later that day during my lunch break and I heard a few clicks when I was turning the keys on the ignition and then it died and wouldn't start. My girlfriend picked up my battery from me which was just a few months old and took it to autozone. They said the battery was low but not in bad condition and they had charged it full. I reconnected the fully charged battery after work and the dome light would turn on when I opened the door but it would shut off as soon I tried to start my truck and nothing electrical would work anymore and nothing electrical would work after one or two attempts to start vehicle. I took battery back to autozone and they said that it was still fully holding a charge at 12.5 volts so I figured the battery was the not the issue. I had also replaced the new battery cable connectors/terminals two months ago, replaced the solenoid starter by the battery with a new one two months ago, replaced the ignition/key switch with a new one two months ago, and replaced the actual main starter less than a year ago. The next day after my truck wouldn't start, I tried starting it again and dome light came on and I heard a few clicks when trying to start it and then everything shut off again and dome light would no longer go on again for a few hours. I tried tapping the starter while a friend tried to turn the truck on and also creating a start with a wire and still nothing. I took off starter and replaced it with a new one and still my truck wouldn't start. Dome light came on and the dashboard lights and then immediately shut off when I actually tried cranking the ignition switch after hearing one or two clicking noises. I checked all the fuses and all the fuses were just fine under the compartment below the steering wheel. I used an ohm meter to check my relays and they were also just fine. So my battery is holding a full charge and is fine, battery connections good, new starter, new solenoid starter, new ignition switch, fuses fine and relays fine, and I can't think what else it could be. I had also replaced all the spark plugs, wires, and distributor cap as well within the past year. When the dome would work when I was opening door, and then I would turn ignition switch, I could hear the fuel pump engage so I know thats also not an issue. I have been told by several people that my truck should still start even if a bad alternator is the problem since my battery is fine, but my truck does not start at all. I have also been told possibly the voltage regulator and have also been told that the voltage regulator probably isn't the problem. I have been putting a lot of time and money into trying to fix this problem but I am running out of ideas and would appreciate any helpful feedback or ideas on what else I could try or what else could potentially be the problem based on my story above. Thanks fellow Ford F-150 owners and be safe out there on the road.

 

Check the resistance of your ground cable.
It doesn't matter that it's new, they can rot out pretty quickly

 

The problem is likely in your cables or connections if your losing all power when trying to start. The Ford OEM cables are known to fail and many after market ones aren't much better. Check the battery terminals and the cable that goes from the battery to the fender mounted relay. Check the grounds, I always add one right from the alternator bracket to the radiator support and to the battery. New doesn't always mean good.
Regards
rikard

 

Thanks, Ill have to check the cables and connections out again to see if maybe that could be the underlying issue. At this point I might have to get it towed to an auto shop and have them run diagnostics to see exactly what it is. I appreciate all the helpful feedback and hopefully these posts can help another individual in the future as well if they have a similar problem. If I do get the diagnostics done, I'll report back what the actual cause was.

 

DON'T HAVE IT TOWED TILL YOU RUN ONE VERY SIMPLE TEST.
connect your jumper cable from the (-) post on the battery to a convenient spot on the engine block. Don't clip onto a bracket but find a bolt or stud that goes directly into the block. See if it starts. If it does, it's your ground cable.

If not make sure it's in park/neutral, switch the ignition to "on" (not to start) and take your jumper and connect the (+) battery post to the output side of the relay. It should start instantly. If it does you have a bad power cable

 

Thanks StrangeRanger, I will perform those simple tests to see if its bad cables or the ground cable being bad. I was also told by a helpful worker at autozone that it could potentially be the ignition module. That is new to me so I'm gonna look into that as well being the cause.

 

The Zoo guy is wrong. A defective ICM will keep the engine from starting, it will not keep it from cranking. All your symptoms point to a cable and the ground cable is a known problem area on these trucks.

 

It ended up being the ground cable after all like you mentioned, It was weird cause the cable terminals were only a month or two old at the time, it turns out the coating on them prevented a connection, i got the colored ones at autozone in which I had to switch back to the regular metal ones. What a pain this project was but a good learning experience, thanks for all the helpful feedback