Truck won't start, AGAIN...usual suspects ruled out


#1

1994 F-150, 194K mi.

So, for the second time in 6 months, the truck won’t start. Gradually started turning over weaker and weaker, and now–solenoid click, and nothing.

What I’ve done:

  1. Checked battery volts–between 12.6 and 12.7V. Do not have means to load test, myself…and the nearest auto parts store is a 2mi walk, so… I DID do a check by shorting the “free” ends of a pair of jumper cables–copious sparking.
  2. No “battery charge” light when driving, and the volts gauge does what it always has (not that it’s terribly accurate–I get “O” volts (on the “NORMAL” scale) key on, engine off, and “M” volts engine running).
  3. I had previously replaced the positive terminal and wires 6 months’ ago, to fix a similar starting problem. I therefore did the same to the negative. Looked pretty gnarly, but made no difference.
  4. When operating key, battery volts drop less than 1/2V with attempted start. I’d love to get voltage at the starter, but that requires an assistant.
  5. When trying to “rig” up a positive lead from the starter terminal (for attempted hot-wire), I got a huge shower of sparks when my wrench bumped the frame rail. So, it seems like enough current is getting to the starter.

My inclination is to say that it must be the starter, but that’s over $100 for the part, so I’d prefer not to “throw parts” at it without being as sure as I can be. I’ve just always heard that starters fail by developing “dead spots”: it won’t work; whack it with a stick; now it might. Do starters fail by “just getting tired?” (I.E. high internal resistance).


#2

Knowing there is power isn’t enough. You need to know how much power.

Starters can develop a bad spot but that is by no means the only way they fail.

12.6 volts is good for the battery, until you can get a load test done. Do you have the ability to remove the starter and walk it down to the store for a bench test?


#3

People often misconstue what they are doing by tapping on the starter with a hammer…That whole tap on it with a hammer “thing” originated from starters that have a piggyback solenoid…the hammer blow was meant to help the solenoid move or “Click” and thus let current flow from batt to starter motor.

Your starter has the solenoid mounted on the inner fender. IF you have a starter motor “Dead Spot” you can tap on the starter all day long with your hammer and it wouldn’t do a single bit of good.

If you indeed have a dead spot the only way to move the starter is mechanically by hand…or if its a manual trans sometimes the starter gear gets stuck in the flywheel…you can manipulate the clutch and trans to try and pop your motor over a bit to free the starter nose gear…

A dead spot is just that…when in that particular position the motor cannot move itself…it needs assistance to do so…a hammer will not do this for you. The hammer only helps starter and solenoid systems in one unit. Remove the battery and load test it…see what kind of power it really has…then you may need to drop the starter and see how it turns with your fingers.

This is a very simple system…there aren’t many failure modes or combinations.

Blackbird


#4

Replacing the battery terminals (I think you mean the connector that bolts to the battery terminal) is not enough. It could be the other end(s), or the cable(s) itself. Or the cable to the starter or the starter ground.


#5

Actually, you do have the means to do a pretty reasonable load test if you have a volt meter. You’ve started by reading the battery voltage at rest. Try reading the voltage at the battery with the headlights on. Then read it with the starter engaged. It shouldn’t drop by very much in either case.

Remove the NEGATIVE cable, then put a diagnostic lead on the positive cable at the starter, then, after restoring the negative cable read the battery voltage while cranking. It should be virtually identical to the reading at the other end of the cable.

All readings should be taken with the negative lead of your meter in exactly the same place: firmly attached to the battery’s negative terminal.

And stop touching the two ends of your jumper cables together. That tells you NOTHING, regardless of how many sparks you see.


#6

UPDATE: Yup, it was the starter motor. Got a NAPA rebuilt, installed it, and it fired right up! In retrospect, this was probably behind my prior start issue: as the starter got ever weaker, I had to upgrade “marginal” parts of the system to keep it “good enough” to compensate. Hey, it least it failed prior to it getting really cold!

This is a very simple system....there aren't many failure modes or combinations.
Oh, yeah, I recognize that. As a DIY guy, though, my skill set breaks down into "stuff that's failed on me before" vs "stuff that hasn't failed yet." For whatever reason, I've never had a starter go belly-up on me before! It seemed "prudent" to pick the brains of the combined forum members, prior to throwing down $130. (Actually, it helped a LOT just writing it down and thinking logically.)
And stop touching the two ends of your jumper cables together. That tells you NOTHING, regardless of how many sparks you see.
Really? It's an old "jump start" trick: if the target car isn't running, touching the ends together should give a nice fireworks display if the connection is good enough to jump. (If it's REALLY good, the clamps get "sticky" due to spot-welding--but you have to have a really good set of jumpers to flow that much!)

Granted, it’s qualitative vs quantitative data…but better than nothing, I always thought.