I just picked up a 2003 Mercury Mountaineer with 150k on the clock for $500. the truck cranks but will not start, the previous owner thought the cats where clogged, is this a common problem with this truck? It gets a very strong spark, and has fuel pressure based on the valve that you press in and squirts fuel. the fuse for the injectors is good also. Any common problems on these trucks I should look out for?

 

Which engine does your Mountaineer have?

-Rod

 

the 4.0 sohc v6

 

When cranking the engine over is there compression coming out of the tailpipe? Have you tried spraying some starting fluid / throttle body cleaner in the throttle body to see if the engine will fire with that?

I don't think plugged cats is necessarily common to any vehicle, but if a vehicle is not maintained, the converters can melt and plug. I certainly wouldn't assume that to be the issue though. You could remove the front oxygen sensors to rule out a plugged exhaust.

The most common issue with the 4.0L V6 is probably damaged intake manifold gaskets.

-Rod

 

even with plugged cats, you would think it would startup and run 10 seconds ?

no codes come up ?.. I had an explorer ( older) that had a coolant temp code come up. The sensor failed and the computer was trying to advance the timing to compensate for the extreme temp.... The advanced timing would not let the truck startup.

Another possibility is the crank position sensor that tells the computer when to fire the spark plug and shoot in the fuel... if it is off, its the same as a slipped timing chain.

 

No codes come up when I put a computer on it. Thats what I would also think that it would start and shut off with a bad cat. I guess I will try that sensor

 

Related to injector timing is the camshaft synchronizer/position sensor. Other than ohming it out, I don't know how else to check it without a scan tool that provides live data (assuming the signal is strong enough to measure at cranking speed).

 

anybody know where the crank shaft position sensor is?

 

mine was on a small sheetmetal bracket pointed at the crank shaft damper, behind the pulley / belt, up against the oil pan. look up from the bottom. should have a 2 wire harness on it.