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4.0L OHV & SOHC V6 Tech General discussion of 4.0L OHV and SOHC V6 Ford Ranger engines.

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Old 02-26-2016
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Icon5 Randomly won't start

1997 XLT 4.0 auto tranny 4.0
238,345 miles

My Ranger has started doing something really weird. The check engine light has come on and the codes I'm pulling are, P1443 and P0420. After these codes popped up my Ranger has had 2 instances where it will not start. It does "turn over" but, will not start. The first time this happened, It ran fine the day before. I got up the next morning for work and it won't start. When my wife got home (10 am), I got her to turn it over while I checked the coil pack for spark. I took the #1 wire from the coil pack inserted a grounded spark plug into the #1 plug spot on the coil pack and told her to turn it over and it started right up.......hum!? I didn't do anything other than let it sit after trying to start it earlier that morning. The truck ran fine, for about a week, until this morning, same thing happened. When the codes first appeared, I looked them up. I am assuming the first place to start would be the gas cap. So I ordered a new Motorcraft cap, it's supposed to be here today. Would a worn out gas cap cause a severe enough vacuum leak that the truck will randomly not start?

***UPDATE:*** So the fuel pump is kicking on and the fuel rails are getting gas. The coil pack is getting power at 11.82V and the Primary has tested at .3 ohms and the Secondary(s) have tested: 1&5 at 9.6 ohms 2&6 at 9.9 ohms 3&4 at 9.8 ohms. I tried the "Grounded Sparkplug" test with the sparkplug inserted into the coil pack and I'm not getting any spark.

**Update 2** I tested the other 3 wires that go to the coil pack (with a test light) and there isn't any power coming from them when cranking the truck. Crankshaft sensor bad?

**Update 3** Replaced the Crankshaft sensor........FIRED RIGHT UP!

Last edited by BL00DPIG; 02-26-2016 at 07:11 AM.
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Old 02-26-2016
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That was quick

Good work on getting down to CKP(crank shaft position) sensor as the problem

P0420 Catalyst System Efficiency Below Threshold (Bank 1)
Cat Converter needs to be replaced
There is an O2 sensor just after the Cat(downstream sensor), it's readings are compared to the O2 sensors nearer the engine(upstream sensors), if Cat is not cleaning up the exhaust enough then you get this code.

P1443 Evaporative Emission System Control Valve (low/no flow)
EVAP system needs attention could be vacuum hose has cracked or otherwise leaking.

EVAP system uses engine vacuum(intake) to suck air(fuel vapors) out of the fuel tank thru a charcoal filter and into the engine.
It is what gives you that hissing sound when you remove the gas cap to fill up, you probably haven't heard that in awhile, if you have then could be bad pressure sensor.

Charcoal canister is usually on the rad support, bigger black box with hoses.
One hose will go back to the gas tank
Other hose will have a pressure sensor and then a Solenoid with a hose to the intake manifold.
Computer controls the solenoid, it opens it to allow engine vacuum to suck gas tank air thru the filter and into the engine, the pressure sensor tells the computer that there is vacuum present and how much.
Solenoid is a more common failure point than the sensor, but inspecting the vacuum hoses from charcoal canister to the engine is free, lol,

You can use a 9volt battery or the truck battery to test the solenoid, it will "click" open and closed when power is applied, there is no polarity on the 2 conductors it is just a coil of wire inside.

Last edited by RonD; 02-26-2016 at 11:57 AM.
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Old 02-26-2016
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Yea...I had to get to work so I had no choice but to dig in and gett'er done. Thank god for Bing (i dont google...lol). Thanks for the info Mr. D :) Your always a big help!
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