LTx Direct injection question.
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Team Owner
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From: Calgary, AB. There's a reason why white was the only color offered on every year Corvette. Proud Canadian German Jamaican!
St. Jude Donor '09, '12-'13-'14-'15-'16-'17
LTx Direct injection question.
Is it me or does the direct injection on the, mine anyway, LT1 take a long time to start the engine. I drive my car in the winter months and sometimes it takes 10 cranks to get the engine going using up a lot of juice from the battery, sometimes in fact dying, killing the battery. On the other hand my buddy's M5 starts up right away and it's DI as well. Even in summer months I notice that it takes a few cranks to get going. My C5, I would just prime the fuel pump and it would start right away...I don't get it.
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St. Jude Donor '11-'12-'13, '16-'17-'18
Takes longer to fire at colder temps (manual even mentions this) but I've never had it take anywhere NEAR 10 seconds
Burning Brakes
Joined: Oct 2017
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With you C5, all you needed was the fuel pump in the tank to supply the injectors with fuel, but in the LT1 the direct injection system has two pumps: one in the tank and then another high pressure pump that is driven off of the camshaft. So, your C5 didn't need the engine to be turning to supply adequate fuel pressure to the engine for it to crank. Your C7, on the other hand, needs the engine to be turning to spin the camshaft and drive the high pressure fuel pump to supply adequate fuel pressure to crank and start. So, starting your C7 with DI is almost like sitting in your C5 and just trying to start the engine without allowing the fuel pump to prime....it takes a few more cranks to build fuel pressure. (Except now you have more pumps and more pressure, which means it takes longer if the engine is cold.)
Melting Slicks
Joined: Apr 2002
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From: Tellico Plains Tennessee
10 cranks? I'm wondering if you mean 10 revolutions of the crank, 10 seconds cranking, or 10 starts with failures requiring a restarts. My understanding is due to the much higher fuel pressure required my DI, a mechanical fuel pump, driven by the cam shaft, is used to boost the pressure from that delivered by the electric fuel pump inside the fuel tank. This takes a few revolutions of the cam shaft to do this, thus the short delay in getting the engine to fire. This is normal.
Billy beat me to it.
Billy beat me to it.
Last edited by Frodo; Feb 5, 2019 at 08:44 AM.
Safety Car
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The ECM won't allow the injectors to "fire" until the pressure in the fuel rail rises to near commanded pressure. Pressure doesn't build until the camshaft driven high pressure fuel pump is activated by the spinning engine. In cold weather, the starting motor can't spin the engine as quickly (thicker oil, reduced battery output due to cold weather) so it takes longer to start; basically it takes "X" number of camshaft revolutions to build up sufficient rail pressure and the slower the cranking speed the longer the delay until the engine starts.
Those of us driving high pressure common rail diesel engines got used to this extended cold cranking behavior about 20 years ago
Those of us driving high pressure common rail diesel engines got used to this extended cold cranking behavior about 20 years ago
