← Hard start / no-start on all engines
Symptoms · GM 6.6 L8T (gas)
GM 6.6 L8T (gas): hard start, long crank or no-start
2 documented failures on this engine list this among their signs. They are ordered from the most widespread down. Each one shows the signs in its record's own words, how to tell it from the others, the usual fix and any recall or bulletin.
Not sure which engine you have, or want the recalls for your exact truck? Check your VIN: it names the engine and lists the campaigns for that model year. Whether a recall is still open on your VIN: nhtsa.gov/recalls.
aggregated
How widespread: Occasional
How it shows up
- hard starts, long crank, fuel-pressure codes; rough running under load
Its other signs
- owner-reported high-pressure fuel pump replacements at dealer rates (GM-Trucks HD forum)
How to tell it apart
- log requested vs actual rail pressure on a suspected HPFP fault; rule out the low-pressure side first
- check injector balance/contribution before replacing hardware; verify fuel quality
Usual fix
replace the failed HPFP or injector(s); keep the fuel system clean - DI pumps are unforgiving of contamination
Root cause, parts and sources →
aggregated
How widespread: Occasional
How it shows up
- misfire codes, rough idle, hard starts as plugs/coils reach service life (routine wear, not a defect pattern)
How to tell it apart
- coil-swap or plug-well inspection to localize a misfire before ordering coils
Usual fix
replace spark plugs at the service interval; replace the failed coil(s) localized by swap test
Root cause, parts and sources →
Other symptoms on the GM 6.6 L8T (gas)
Misfire, rough idle, hesitation or surging
Everything on the GM 6.6 L8T (gas)Its recalls and bulletins