Cold starts easy, hot starts hard

[stilly]

My 03 Duramax (138K) starts great in the garage after a night of sitting. I will have to crank it for 10-20 seconds when the engine is hot to start. Sometimes it has been longer. I brought it into the dealer - they said everything checked out fine. They told me I just need to be buying Chevron diesel, a better grade than I have been. I have been for 6 months. It seemed to start slightly easier for a few weeks, but now I am back to the same with Chevron diesel - hard starting when the engine is hot for several months. Any thoughts on what could be going on?

I have replaced the fuel filter and the secondary fuel filter before the visit to the dealer. Only about 4K on the fuel filters now.

[Mark Rinker]

I bet you have some amount of air getting sucked into the fuel system under high demand. Probably at one of the connections on the auxiliary filtration system.

Do you have an auxiliary lift pump to help with the restriction caused by the primary filter?
Stock injectors, or a new set? How many miles on?
Running any fuel additives?I like Howes, it seems to really clean up injectors that are no longer atomizing fuel properly. This can lead to hard starts. Have seen it turn around injectors whose return rates are severly out of range, to normal function. Try double dosing for a few tanks, then run at directed mix for a few more.

[stilly]

I do not have a auxiliary lift pump. I have the stock injectors with the 138K on them. I am not running any fuel additives, but I can sure give that a try.

Now that you mention the fuel filter. I have changed brands. From Fram to WIX on the engine. Racor on the auxiliary.

Where can you get Howes additive?

I will check the connections and run some additive - any other thoughts?

[Mark Rinker]

Search the forums on problems people have had with air getting in at the OEM filter housing, maybe you aren't getting a good seal with the new brand filter/o-ring?

Howes is available in various quantities at any major truckstop. I buy it in half gallons.

Great mileage on your original injectors...how long do you think they can go? Your additional filtration probably helps!

[stilly]

I suppose the injectors will make it until the warranty runs out, but it sounds like GM filed for bankruptcy today anyhow. I will keep my fingers crossed.

Thanks for the help.