dwinters14
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- Apr 10, 2020
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I believe I've figured out my issue but I wanted to get a second opinion and also create a thread for future reference for others with the same issue.
Vehicle:
2007 Suburban LT, 5.3L, 2WD Flex Fuel
Problem:
Delayed start when cold. Truck always starts, and idles afterwards, and will fire first crank the second time.
*** Most probable cause E85 ***
Troubleshooting:
Firstly, NO CODES. I exclusively fuel my truck with E85 for the cost savings and also the drivability compared to regular octane fuel. In my live data the truck read 69% alcohol content. In the past two years I've replaced the following items associated with starting. Battery, alternator, purge valve on engine, vent valve by fuel tank and fuel pump. I haven't changed anything else. The first thing I did to narrow down the issue is check cold cranking voltage on the battery which has been a steady 12.2v to 12.8v. Starter fires every time. I recently replaced both the purge valve on the engine and verified it's working properly as well as the vent valve by the fuel tank and also verified it's working properly.
The next test was to check out the fuel pump/check valve assembly. I threw a gauge on the fuel rail and here were my numbers:
Dry: 0 PSI
Key in, on position: 50 PSI
Started and idling: 58 PSI steady
Off: 51 PSI
10 Minutes off: 49 PSI
1 Hour off: 25 PSI
From here the only other thing I can extrapolate besides fuel is something deeper, timing, cam position sensor, ECM issue with the alcohol content or a multitude of other gremlins. Once on, the truck holds and idles very well and has power throughout the entire powerband through every gear. The engine fires every time when warm as well.
I did do some research on E85 and it seems problematic when igniting on a cold engine. This issue has come and gone since I've owned it, but I never knew where to point the finger as all the other parts listed above were bad. Now that I've narrowed them out I'm looking at what's left. The easiest way to confirm or deny my concerns is to run the tank dry and put regular octane fuel in it and see, or combine it with the ethanol already in the tank to see if it helps ignite better.
Before I get to that stage, does anyone have any other potential ideas? I like to explore all avenues as I have frequently found really odd things can disguise themselves in their symptoms.
Vehicle:
2007 Suburban LT, 5.3L, 2WD Flex Fuel
Problem:
Delayed start when cold. Truck always starts, and idles afterwards, and will fire first crank the second time.
*** Most probable cause E85 ***
Troubleshooting:
Firstly, NO CODES. I exclusively fuel my truck with E85 for the cost savings and also the drivability compared to regular octane fuel. In my live data the truck read 69% alcohol content. In the past two years I've replaced the following items associated with starting. Battery, alternator, purge valve on engine, vent valve by fuel tank and fuel pump. I haven't changed anything else. The first thing I did to narrow down the issue is check cold cranking voltage on the battery which has been a steady 12.2v to 12.8v. Starter fires every time. I recently replaced both the purge valve on the engine and verified it's working properly as well as the vent valve by the fuel tank and also verified it's working properly.
The next test was to check out the fuel pump/check valve assembly. I threw a gauge on the fuel rail and here were my numbers:
Dry: 0 PSI
Key in, on position: 50 PSI
Started and idling: 58 PSI steady
Off: 51 PSI
10 Minutes off: 49 PSI
1 Hour off: 25 PSI
From here the only other thing I can extrapolate besides fuel is something deeper, timing, cam position sensor, ECM issue with the alcohol content or a multitude of other gremlins. Once on, the truck holds and idles very well and has power throughout the entire powerband through every gear. The engine fires every time when warm as well.
I did do some research on E85 and it seems problematic when igniting on a cold engine. This issue has come and gone since I've owned it, but I never knew where to point the finger as all the other parts listed above were bad. Now that I've narrowed them out I'm looking at what's left. The easiest way to confirm or deny my concerns is to run the tank dry and put regular octane fuel in it and see, or combine it with the ethanol already in the tank to see if it helps ignite better.
Before I get to that stage, does anyone have any other potential ideas? I like to explore all avenues as I have frequently found really odd things can disguise themselves in their symptoms.
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