Here's a head scratcher

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JimT

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I have a 1999 Expedition with the triton 5.4 and roughly 145K miles. The vehicle was running fine, no codes, no loss of power, no pinging, no rattling and wasn't idling rough. The only thing I could hear was a very faint ticking that sounded like a lifter but not as pronounced, didn't accelerate with the engine when I picked the RPM's up and didn't happen all the time. I don't know if it was a symptom of if there is something loose somewhere.

I had the truck in the shop for a replacement of the power steering pump and at the time it was throwing a code which indicated that a vacuum hose on the top passenger side needed to be replaced. When we got the truck back it ran fine for about a week then suddenly wouldn't start. It would crank but not catch. I thought maybe it flooded so I let it sit and about 15 min later it started right up.

This went on very intermittently for about a month with the wait time being anywhere between 5 minutes and overnight. I did some research and opted to replace the fuel pump relay and it ran fine for a couple of weeks...then it happened and wouldn't start. I let it sit, still wouldn't start and after a couple of days of trying the engine adopted a different sound when it was cranking...kind of like the fuel pump had given out and there was no fuel getting to the engine.

Took it to the shop and the fuel pump tested fine. It's getting fuel, spark and air, and it still won't start. My mechanic thinks the timing chain jumped but the lack of any symptoms makes me question this.

Anyone have any ideas? :banghead:
 

riphip

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Personally, for the age of the truck, I would 'first' go thru it and replace all vacuum rubber and hoses + PCV. Due for it from the generated heat over the years. Any cracks, melts & deterioration can cause problems that mimic other suspected 'expensive' repairs.
You or mechanic can pull the plugs & valve covers, inspect rocker arms & followers (no lifters), manually turn the crank to see if it has jumped timing before spending anymore $$. 145k is not many miles on these engines.

Could be Camshaft sensor or Crankshaft sensor but should throw a code.


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JimT

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Thanks riphip, I replaced the PVC at about 103K/5 years ago but is a cheap fix will check that. Most of the hoses under the hood have also been replaced which likely leaves the sensors or a BIG repair. :(
 

riphip

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Crank position sensor will cause some jumping/humping but not sure how to test besides replacing and saving old one for later if good.
Does tach move while cranking/trying to start?
 
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JimT

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It did initially but when the sound changed while cranking it stopped moving.
 
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JimT

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Yea that's what I'm thinking as well....after 22 years, she doesn't owe me anything. I was hoping to get another couple years out of her but at this point, I may call it good. She still has the original shocks, struts and exhaust, and the rear end which we had rebuilt a couple of years ago is starting to make an all too familiar vibration.

Thanks for all your help, it's really appreciated!
 

riphip

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The sensors are not that expensive. Yours and mine do not have the problems with tensioners like the 2008 link. May be a broken rocker, etc under a valve cover. As stated earlier, 145k is not that many miles especially if proper maintenance was performed. You could get out of this cheaper than you think. Check under the covers before you throw any parts at it.
 

Hamfisted

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JamaicaJoe

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What about a bad battery? Once my 01 would crank and start fine, but the tach and other gauges would not respond until a few seconds after starting. If the battery is weak, you may not be getting proper spark and no tach reading.

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