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Strange Starting Issue - Suddenly stops turning over sometimes?

s14unimog

NAXJA Forum User
Location
Georgia
The essentials: 1997 XJ - 4.0L 5-Speed - 194k - motor all stock.

So this random issue started a few weeks back and it's slowly becoming a more and more common occurrence. Essentially, when you go to turn the key to start the truck, it will turn over just fine but then sometimes it'll suddenly stop or slow as if the starter is struggling to push through the compression. The truck will start and it's not a delayed start (as to say, it doesn't sit there and just turn over) but if this little stall happens, it does seem to disrupt the firing of the engine and so will stumble a little for that first second or so of running and then all normal. I've tried to discern if it's only during a cold start but I want to say it has done this before even after the truck has been warmed up.

As I mentioned, it's not every time and so sometimes the truck just fires up like normal and away I go. Once the truck is on, it doesn't seem like there are any issues; drives and runs fine.

Any ideas?
 
If one of the brushes stops making contact (fair wear and tear) the starter can slow down and seems to draw more amps.

I've had a starter with one or two bad brushes get so hot you could fry bacon on it. It drew so much current it starved my engine management controls.

May be what is going on with you? Be careful, but a really hot starter is a tip off it may be draining to much current. I'm talking blister your fingers hot, be careful.

An oil (or mud) soaked starter can also cause pretty much the same thing. The brushes get oil soaked or covered in mud. If you have a leaky oil filter adapter, the oil can find it's way inside the starter, believe me I've seen it too many times for it to be a fluke.
 
Well it's nice to see a consensus on the possible culprit. The starter is one of the older electrical components still in service on the truck, so it's a good suspect. Not to mention, it's got it's fair share of oil and dirt on it. I've never had one partially breakdown like this, but it makes sense.

I'll investigate connections and brushes and report back. Thanks for the help!
 
So just to make that task a little easier, I opted for a new starter.

Started fine this morning but when I left for lunch on my break, sure enough, it did the same thing it had been doing. So I guess it's not the starter after all.

I'm suspecting a leaky injector now - planning to pull plugs tonight and look for any signs. I'm not gaining any oil capacity, so it doesn't seem as though it would be a significant excess of fuel leaking in while it sits, but I can't think of what else it could be that would stall the starter like that. It's not burning any oil, so it's unlikely that it's excess oil in the cylinder.

Any other ideas??
 
I took a wire brush and thoroughly cleaned both sides of the contacts and the nuts that connect to the starter. My battery connections, although a little tatty, are holding very tight and the battery itself isn't all that old. No other issues with electronics/lights/etc... in the rest of the truck. Maybe I investigate that battery harness a bit more?
 
So the harness from the battery to the starter looks fine, but I did notice that where it's crimped or pressed into the factory battery terminal, there is a fair bit of oxidation on the exposed copper stranding of the starter's 12V wire. I wiggled the connection around to sort of break that corrosion up and the starter hasn't stalled after 3 or 4 starts now....

You guys may have called it on the harness connection. I think I should redo that terminal connection and see where that leaves me. It's not exactly tight but neither loose either but I could see where it's probably a resistive connection in there.

For now, I think that's got it. Thanks for the help - possibly a resource thread for someone in the future.
 
Circling back around to this, I decided to throw some new plug wires and plugs in it while doing an oil change. Believe it or not, that was it. So it was either a plug or something up with one of the wires. Truck runs great now and hasn't skipped a beat on starting since.

I still think I might swap out those battery terminals. I suppose just for peace of mind.
 
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