2003 Duramax Starting hard
 

I am a 6.5 owner but told my buddy that I'd post a thread for him on the Duramax forum. His 6.6 is starting hard. He replaced glow plugs. I told him sounded like fuel bleeding back. Not sure. Any ideas? Thanks for any comments.

did he check the connector bars on the glowplugs, they go out often on the duramax. the fuel filter housing also develops leaks that a set of o-rings usually fixes which causes it to get air into the system unless the filter head is cracked. those are the usual causes. i noticed too when mine had questionable batteries in it it would crank ok but had a harder time starting, once i put new batteries in no problems.

I had a time with mine this past winter not wanting to start at all. The shop i took it to told me that I had a bad battery cable and that it was not getting enough amps to turn the motor over fast enough to start it.

There are many things that can cause hard starts on these trucks.

Air entering the fuel filter housing from the bleed screw, improper fuel (low specific gravity, etc.) or any number of problems with glow plugs or compression (but those are usually accompanied by unburned fuel smoke and are more prone to occur in the late Fall, Winter, or early Spring).


The most expensive COMMON problem is high return rates on the injectors. If the high pressure pump can't develop >4500 PSI during cranking, the truck will crank and crank and crank until either the pressure is made or the batteries die. The slower the engine turns, the lower the pressure.

I had a similar problem. When cold it seemed to take longer and longer to start. Once hot it would be crazy long. Turned out to be a faulty FPR (fuel pressure regulator). Like a 200 dollar part. I used a OTC Genisis computer to read the rail pressure. I figured it was either pump or regulator so I went with the cheapest option and it worked. Before spending the cash do the simple stuff first. Look for fuel leaks when you pressurize the fuel tank. My brother's d-max had a fuel line leak between the filter head and pump.
Good luck

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Oh yeah, don't go crazy pressurizing the tank. We only used 5 psi and a gas cap with a valvestem in it.

Where in the world did you get a regulator for $200? GM list is $368.

From Merchan Automotive - $193.00
Duramax LB7 Fuel Pressure Regulator

last time i had hard starts and it was not electrial related i had bad injectors that were leaking fuel into my oil. check the oil for any scent of diesel to make sure.

but first thigns to check would be batteries and grounds and connections for corrosion.