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Old 09-14-2016, 12:55 PM   #6
fdryer
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Join Date: Jan 2006
Location: NYC
Posts: 41,444
 

2003 L-Series 3.0L Sedan
Default Re: 2005 L300 crank but no start

While spark plugs may be fine, due to ideal use of platinum electrodes for long term reliability, it's just wise to replace them. They're probably not worn but the number of heat cycles may degrade them and a reason to replace them every 100k miles. The same goes for fuel filter replacement. With difficulty in startups, this problem can be either ignition or fuel related. One way to monitor one of these two would be using a fuel pressure gauge connected to the fuel rail test port. Autozone may have pressure gauges to loan. Expect 40-55 psi when ignition is turned on without starting and remain in range with engine running. Fuel filter replacement is recommended every 100k miles.

The mystery P0421 code may or may not contribute to hard starting. A partially blocked pre-cat, between engine and firewall, may trigger the error code. While blocking half the exhaust system shouldn't affect engine starting, anything is possible in real world operating conditions. The difficulty in determining a damaged pre-cat requires removal for examination or connecting a pressure gauge to the front O2 port on each side to measure exhaust pressures - not something anyone wants to do.

One thing not discussed and brought up - is there a possibility of the maf sensor causing this problem? Removing it and spraying it with maf sensor cleaner may help.

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