This is a weird one that I've never encountered before. Truck is an 86 F250 4x4. I have had some other unrelated starting problems over the last year or two that I have fixed one by one. So now the truck has new battery, new alternator, new starter, new solenoid and brand new battery and starter cables. The battery holds charge well and I tested the alternator and it is charging correctly.

Let me give you 2 scenarios to explain what's going on.

Scenario 1

I get up to go to work in the morning. Crank it once and it fires up IMMEDIATELY, no hesitation, no struggling or anything. Runs like a champ all the way to work (30 mins). Park it, goto work, come out at the end of day its the exact same thing, it fires up immediately without issues, runs smoothly all the way home, everything is good with the world.

Scenario 2

Same as scenario #1 except this time on the way home from work, I stop at the grocery store to pick up some milk...so after 25 mins drive I park and turn off the engine. Come back out a few mins later, it will not even turn the engine over. It feels almost like the engine is partly seized or something, like the starter is struggling to turn it and just can't muster enough torque to do so...sounds like a dead battery but it's not, battery voltage reads normal and putting a jump on it does nothing, same problem. Now, if I let it sit for 45 mins - 60 mins? It starts up immediately without issues!

WTF is going on here guys?

 

Your timing is too far advanced. What engine is this?

 

It's a 351W

But why do you say its the timing? The engine runs perfectly and the issue only arises after it's been run awhile, never on initial first start after sitting.
Also, this came out of nowhere, I didn't muck with the timing at all

 

Because it cranks fine cold or if it cools off. If you haven't messed with the timing ,one other thing it could be is an exhaust leak puffing on the starter overheating it. Do you have headers on it? That can cause it also.

I would check the timing to be sure though.

 

No, no custom headers or anything

can you point me to an article on here on setting the timing...been awhile since I did that, and it wasn't on an old truck like this

thanks

 

Duplicate the fault. Drive the truck and then let it sit, following the same pattern as when it acts up. With the fault active, run this test:

https://www.ford-trucks.com/forums/1...w-starter.html


This test disables the ignition, so that is completely removed from the equation. If your starter is still dragging, that test will quickly pinpoint the source.

 

!st thing to so is crawl under the front of the truck with some white out or something similiar, and some brake cleaner and a rag and a flashlight. You are going to want to look behind the front lower pulley, there will be timing marks and numbers there. Usually at zero there is a deep groove. You want to find about 10 BTDC, and put a white out mark on it. Clean the dirt and the grease off so you can see it and mark it.

Then get the timing light, hook the sensor wire to the very front pass side sparkplug. Hook the other leads to the battery, unplug the vacuum line from the distributor and put a screw in it so the hose won't suck air, and then start the engine. At idle point your timing light down at the pulley area on top, even though you cleaned it up and marked it on the bottom. There should be a pointer on top. When the light flashes you should be able to see your white out mark, the groove for zero, and where the pointer is pointing. If you are way up there around 15 or higher, turn it back to 10, I bet your problem goes away.

To turn it back, turn the engine off, find the clamp bolt at the bottom of the distributor, and loosen it so you can just turn the dist. Play with it so it takes some effort to move the dist, but its not to easy. Then start the engine back up, shine the light down there, and take the dist with your hand and start twisting it while you watch the marks and the pointer. The engine will slow down some if you turn the timing back, so you might have to reset the idle speed.

 

This is most likely a starter issue. This is quite a common mode of failure for starters that have a short on one of the field windings. When the starter heats up and everything in it is heat soaked from engine heat the starter it;s case and field windings expand. At this point one of the field windings and can make contact with the case or the adjacent winding when warm, you then lose a huge chunk of the magnetic force needed to spin the armature, and turn over the engine. When this happens it will give the exact symptoms you describe. Acts like a weak battery when warm but fine when cold.
This can be aggravating cause it can be intermittent also.

This mode of failure was very very common back in the day when the field windings were paper wrapped and not linen wrapped.
To rule out all possibilities do check the starter cable connection to make sure it is clean and making proper contact before replacing the starter.

If it was timing it would turn over but be hard to start all the time and increasingly so when warm.
if you want to just rule it out when it's being hard to turn over just pull the coil wire and see if it changes

But I would say ignore the timing issue. Sorry, Franklin, think you are off base on this one.

 

Unlikely because the starter is literally 2 weeks old...also it was exhibiting this behavior BEFORE the starter was replaced

 

Sorry missed that in the orginal post.

Pull the coil wire when it is slow cranking. And you replaced the starter cable and both battery cables?
And don't rule out you got a dud starter either.

 

I had that same exact problem a few years ago, and it turned out to be a very simple grounding issue.

Carefully check your negative battery cable, especially where is bolts to the frame and engine block. Remove and clean the bolts, washers, and mating surfaces of all rust. Bolt everything back up and try it again.

 

Yes ALL cables and contacts were replaced, that's one of the first things I did.
Understand that something environmental is going on here, it always exhibits the behavior I have described in my initial post, it's not like it randomly starts sometimes and not others...that I would agree would point to a bad connection getting shaken around by driving etc.
I can try pulling the coil wire when it acts up but what will that tell me? (what should I be looking for here is what I mean)?

But it starts immediately on the first start, I only have issues after the truck has been running awhile...there's something else going on here

 

"Starter Kickback" can occur when the initial ignition timing is too far advanced, but it only rears its head when engine is warmed up and hot. So it starts OK when cold. By removing the coil wire or otherwise disabling the ignition, it removes the ignition timing from the equation. What's happening is the starter is fighting against the piston combustion that is occurring too early in the cycle. Compression increases when engine is warmed up. No spark, no fire.

If the engine turns over freely with the ignition disabled, when hot, when otherwise the engine is "locked up" as it were, you've isolated the problem to excessive ignition timing.

 

Pulling the coil wire will disable the ignition, therefore, eliminating overly advanced timing as a cause it is a simple 5-second test.

And how did this problem start was it slow onset or suddenly?

 

My 460 truck does this frequently, though the starter does turn the engine over but the first few rev's are very slow (almost like a hydro lock situation on a cylinder, starter spins for a split, slows for a few revs, and then speeds up). This has also happened when its cold as well though very intermittent, so it seems like the starter is going faulty. But then again, I'm also running ~14-15 deg of initial timing so that could be contributing to the problem. Its not loosing coolant or oil, so its not actually hydro locking but that's the best description I can provide above.