1988 F150 hot start problem (battery acts dead)

[3bobs]

Hi,

I have a 1988 F150 with a problem that is the reverse of anything I have seen before.

If you start it after sitting for a while, no problem jumps to life.

If you run for a while and go to restart it acts as if the battery is low and cranks over very very slowly. Most of the time it will restart if it catches just right. Not a fuel or spark problem I think.

Then let it sit a while and it again jumps to life.

Any help?

[knelleken]

sounds like a bad starter motor.

[mechhound]

It could be a bad starter. But I would have the ignition timing checked. Being timed too fast could also make it act that way. What is the history on the truck? Any recent work done on it? Or did you just buy it?

[3bobs]

I have owned it for a number of years. It is a beater I use for mulch, trash and stuff. As long as I have owned it it has had this problem. I have recently put a new battery in it so I know that isn't it. I was thinking the alternator was bad, but I would think the thing wouldn't crank well after sitting..battery recovering?

Anyway, I am now leaning towards bad battery cables or bad ecu or whatever that thing is mounted to the fender. I am going to do the following tests in this order (although it will be this weekend before I can get to it). Please comment if you think I have missed anything to check the starter, cables, etc.

After the problem starts (running a while):

1. Check voltage across battery during starting, if under ~11v then may be battery (although I am pretty sure this isn't it)
2. Check voltage at ECU thing, if voltage is lower than battery during starting than bad cables. (or if cables are warm)
3. Check voltage past ECU thing at starter. If lower than cable between ECU and starter.

If none of those then check current drawing by starter, if higher than ~70A then maybe bad starter?

Anyway, from reading that is what I see so far. When attempting to start the truck it turns over barely 1 or 2 times a second. It really seems like the battery is not getting juice to the starter...not sure how I understand the timing thing influencing that...wouldn't that mean it wouldn't start once the starter was turning at a regular rate.

[big white bufflo]

look at your cables i have seen them couroid inside the plactic coating

[mechhound]

To explain the timing thing and cranking very slow only when warm. When it is timed too fast, it fires before the piston get to the top of it's stroke and causes extra resistance. Why it doesn't cause hard cranking on a cold engine is a bit of a mystery, but that's just the way it is.

Even with the extra information you provided, I am still guessing a bad starter or timed too fast. It certainly could be the cables though. Let us know what you find. Good Luck.

[RahX]

I dunno, I would lean toward the alternator first, that is an easy test. Sounds like it is draining the battery and won't restart until the battery sits and recharges. Have you tried using a jumper to get it started?