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Discussion Starter · #1 ·
Hello first time I’ve ever owned a duramax I bought it from a buddy they truck used to run great but then the trans went out and he sent it to a shop it get fixed and he ended up getting new truck so he parked this one for about 5-7 months we went to fire it up the other day and it won’t fire unless we use break clean and it will not stay running, the system will prime up but that’s all is there any chance there’s a wire by the trans that got ripped up and stopped the cp3? Should I get a new cp3 not sure where to start

Premium Member
704 Posts
Belated welcome!

Welcome to the Forum and apologies for being ignored for so long.

Although diesel fuel does not keep well in storage, 6 months does not seem to be a particularly long time past “freshness date” to become completely useless.

You said your buddy parked the truck, so can we presume it was driven to its current resting place?

You are no doubt aware of the dangers of using ether (brake clean?) for starting but I guess you were desperate. Such chemicals can explode (vs burn rapidly) in the combustion chamber and when that happens connecting rods have been bent.

Since the engine did try to run and you have been able to prime the fuel system (firm primer button, right?) you might be inclined to rule out fuel delivery, but replacing the CP3 might be an expensive exercise in “hanging parts”.

Many owners recommend starting with a fuel filter change (an opportunity to check off this critical part of the fuel system) and a low cost effort.

TORQUE is an inexpensive, downloadable app (Android and iOS) that will provide info you need to continue with diagnosis, specifically rail pressure. The Fuel Injection Control Module (FICM) will not wake up the injectors till minimum rail pressure is achieved (5-6k?) and you can obviously crank all day without effect. Spraying in starting fluid bypasses that system but if a brief shot only results in an equally brief run time, at least you know you likely have compression. Still, not recommended.

There is also a bleeder fitting on the line feeding the CP3 (after the FICM) that can be tapped to determine if fuel is reaching that point, but adapting a gauge can be finicky. As you may know, the CP3 establishes a low pressure to pull fuel from the tank, and unless a lift pump has been installed (not necessary unless the engine has a tuner) you should read a slight vacuum there when cranking.

Also, when you are cranking, what do you smell at the exhaust? If nothing, that’s what the police call a clue and injectors are definitely not being activated.

Again, welcome and please go to User Control Panel (CP) and fill in your signature line.

You have come to a good place for valuable, reliable 411 and I’m sure others will weigh in soon.

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