i've been doing a lot of research between the different ford truck enthusiasts sites (hence my low post count!) but each situation is so unique, i could not find a great solution for my current issue. so i apologize in advance for any overlap with other common threads.

1993 F-150 5.0, 4x4 XLS

background: the following have been installed in the last year on the truck:

- plugs
- wires
- fuel filter (twice)
- egr valve (and associated sensor)
- all vac hoses
- front tank fuel pump (sending unit, etc. - rear tank does not function)
- air filter
- all engine mounts
- several non-engine components (not pertinent to the thread)

the truck is mostly used for hauling of big/heavy items, winter driving, etc. It's not a daily driver most of the time. the batter was tested last summer (apparently fairly new) and the test result was good.

current issue #1:
a couple weeks ago, as i was driving at night, i noticed the lights began to dim, and then back to normal, then dim, back to normal, and so on. this didn't happen every time, but once it started, it happened a lot. this included the interior dash lights and i noticed the battery gauge fluctuating from middle (normal) to about 1/4 (right at the tip of 'N' on the gauge cluster) which is when the lights would dim.

i thought what you are probably thinking already: alternator. so i removed it from the truck, took it to a shop and had it tested. it tested fine. apparently it was changed just before i bought the truck (1 1/2 years ago) and it's a rebuilt ford variety, stock amperage. i have no extra electrical pulls on the truck. the alternator did have some rubber debris on it (belt being chewed up somewhere) so i then changed the tension pulley assembly. i re-installed the alternator and that's when issue #2 started. more on that in a minute.

it appeared to be working but not for long. last night as i was driving it home from the shop it did it again. but this time it stayed in the 1/4 voltage area for much of the trip. the truck seems to continue to run fine, but it's not an easy feeling.

i thought i would clean off the battery terminals and perhaps the ground wires to the side of the truck and see if that helps. any other suggestions??

Issue #2:
after i re-installed the alternator, i started the truck. it ran for about 15 seconds just perfect and then died like i had turned the key off. it would then not start easily. once it started it would not stay running unless i kept my foot fairly far down on the pedal. if i let off it would die. however, after a second restart it seemed to stay running and continued on without dying. WTF.

i took it to my shop guy and he gave it a look-over. he cleaned the throttle body out with cleaner and checked a few other things.

we thought that had fixed it and it was coincidence that it started that after my re-install of the alternator. but then this morning, as i was letting the truck warm up (temp ~0 degrees with wind chill), i think it died after initial high idle. i started it again (would NOT start very easy, even with priming it several times) and then it was fine...as in it did not die from the time i drove it til i got to work.

it also appears to be getting even worse mpg than normal (normal for this truck appears to be 12-15).

i guess i could recheck my alternator install but that's not a complicated process. maybe i didn't get something seated correctly. it was cold as *** out when i changed it.

thoughts on this???

many apologies for the extra long post. but i figured it was best to be out with it initially to minimize the normal questions (e.g. WHAT ENGINE, DUMMY?!) and give as much detail as possible.

any suggestions/info is appreciated.

 

you need to get a multi meter and check your voltage at different key points in the system. 1 if at the battery, second is at the alternator (know they said it was fine but check) and then find where the body is grounded to the frame and test there. I know mine was so rusted and worn that I will need to replace it. should be on the pass bottom side of the motor. the lights dimming seem strange for a new bat and perfect alternator.

 

when you say yours was so rusted, do you mean your grounding wire? i see one ground on the passenger side just next to the battery. i'll follow the grounding wires all around (i think i recall seeing 2 run from the negative terminal). mine are a little corroded at the terminal. not sure about anywhere else yet.

 

so i wasn't completely correct. i don't see corrosion anywhere. even the battery terminals are squeaky clean. i followed the wire to the block (awfully hard to follow that thing...not in a convenient spot at all) and it looks fine. there's a little gunk on there, probably from road grime and/or any fluid that ever got on there and dried. but there is no rust throughout the entire wire.

i tested the battery and it's good (12.69v). i kept the multimeter on the battery as i started the engine to test the volts. voltage was 14.6'ish. i then turned on the fan full blast, the lights, and radio. same volts. i then manually revved the engine to what i think was around 2k rpm for a few seconds. i let off and it dropped back to normal. although during one attempted it dropped all the way to 8v but that was for less than a few milliseconds and then back to 14.6'ish.

so then i drove the truck around as that's when this has always happened. of course now that i'm ready...nothing. ran great. lame! i think i'll let it cool down (which should take no time per cold as eff out) and try again. although i'm not sure if temp is part of the issue, i thought i'd check that as well.

anyways, i'm sure it'll happen again i just have to catch it. hard to diagnose something when it's hiding.

 

update: so this morning, the temp was somewhere in the negative 0s and i popped the hood. checked the battery: 12.6v. Started the truck and it jumped to just over 14. turned on the fan as well (which started to sound awful...sweet!) and volts remained. after several seconds (high idle didn't really happen, due to temp i imagine) the engine died. no change in the volts of the battery.

anyone have any clue WTF this could be?! i'm kind of ruling out the alternator for issue #2. i can't get it to do issue #1 again yet.