03 cummins hard starting - Dodge Cummins Diesel Forum
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post #1 of 3 (permalink) Old 12-04-2006, 12:19 AM Thread Starter
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03 cummins hard starting

I recently purchased an 03 ram cummins that won't start if it is cold. It will start at around 50 degrees but it cranks a few seconds. If it is colder than that it won't even attempt to fire unless I plug in the block heater. I replaced the crank position sensor and the coolant temp sensor because they had set a couple of codes, but they didn't help. It has new batteries and sounds like it is cranking plenty fast. It doesn't make any white smoke when it is cranking and when it does start the exhaust is clear instantly. I have voltage to the intake heat grid but I'm not sure it is working well enough because the manifold gets warm, but not hot to the touch. How hot should it get? The intake heater cycles for 10-15 seconds when cold. The fuel pump will run for 25 seconds if I bump the key, but even cycling the pump and the intake heater make no difference. I replaced the fuel filter, no difference. It got very cold (-10) about three days ago and the truck hasn't started since, even after being plugged in and a small heater blowing on the engine. My work truck is a Duramax and it started when it was that cold and both trucks run the same treated fuel. The truck has 103,000 miles, gets 18-20 mpg and runs great if the thing will just start, any ideas?! IAT sensor or MAP sensor maybe? Where can I find good troubleshooting info? Please help!! -Alan

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post #2 of 3 (permalink) Old 12-04-2006, 12:26 AM
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Can you hear the lift pump running? When you first turn the key on? Fuel may be gelling or just a weak lift pump may be having a hard time pushing the thick fuel. FP when running?

These trucks should start way into the cold numbers. Mine would start every morning no proble in WA when its was 28-30 overnight.

I also use sythetic oil, which makes cold starts much easier due to the lower pour point. Cold temp flow is much better.

Do you have #2 in the tank or #1 or a winter blend?

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post #3 of 3 (permalink) Old 12-04-2006, 08:15 PM Thread Starter
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Yes the fuel pump is running. I read somewhere that if you just bump the key to make it crank the fuel pump will run for 25 seconds, and it does this. If I just turn the key on like normal it runs a few seconds. I am running treated winter fuel. I tried opening the fuel filter drain valve and then bumped the ignition and it pumped a bunch of fuel out very quickly. It seems good but I haven't tried an actual pressure test, I am having trouble finding specs. The truck has the same starting problem at temperatures way above the point of fuel gelling. I originally thought it was a fuel problem until I tried the block heater and it made a big difference, but plugging it in at 50 degrees isn't a good option. Really at that temp it should start even without the intake grid. I would suspect low compression, but the truck runs so good, when it runs, that I really don't think it's a problem, but I won't know for sure unless I run a compression test. I read some other posts about having the computer "flashed" for hard starting problems, maybe thats what I need.
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