Weird Starting Issue After Truck Sits More Than A Few Hours
- Thread starter TylerHagerdorn
- Start date
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I'm curious about the NBS fuel pressure leakdown specs. Is there a published spec for time vs how much leakdown is within reason, or acceptable? Is it different for Flex Fuel systems?
mattbta
Full Access Member
Mine has been doing this, seemingly random. No rhyme or reason, but might be more influenced by colder ambient temps. (And I'm running entirely e85.)
Trying to drive out the e85 and put some regular e10 in it and see if it keeps acting up.
Trying to drive out the e85 and put some regular e10 in it and see if it keeps acting up.
What kind of ethanol percentage are you getting from the pump in winter? Seems like it would be a reduced ethanol content for the winter mix, to help with cold starts.
I'll be firing mine up tomorrow to go into work and it will be very cold, probably near 0°F in the morning, and I have probably 60% ethanol in the tank. Will be interesting to see if it has a hard start.
mattbta
Full Access Member
Just took this...it was still in open loop - hoping it's accurate. Same percentage as when I took it in December. I think I read some folks have their sensors stuck at 70% IIRC? Still have an eighth of a tank to burn before putting some e10 in to see if it eliminates the problem. Weird thing is, it's 23* outside and my garage is like 65* and just now it fired up first time. I'm so confused...lol.
I didn't look back in the thread, Matt, but have you compared the IAT sensor value with the ECT value when it's cold? They should be within 5° of each other after a full cool down. Just a suggestion.
HACK BLOCK
Full Access Member
my money is still on the fuel pump
mattbta
Full Access Member
There's no rhyme nor reason to it. Cold motor is does it sometimes. Hot motor it does it sometimes. I'm trying to eliminate e85 coupled with low ambient temps as the cause. Still bringing my alcohol percentage down. Today it didn't want to fire first thing in the AM, but I didn't get temp checks on it then. Ran a few errands and every other start (after only sitting 20 minutes) would give me trouble. Ambient ranged from 50-75* today. Just now, after it sat for 3 hours it fired right up, so my temps aren't a good test. However, it did sit for a good while with key on RUN which may be what it needs. I've tried to "prime" the pump 2-3 times before each start attempt but that doesn't seem to do anything, either. I guess I'll try and get alky down to 10% and also slap my pressure gauge on and let it sit for a while and see what gives.
Edit. Idle fuel trims were pretty much 0 on short term and stayed at -3% LT. O2's switching as expected. Spark from 17-21*.
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Wondering if the 100° IAT reading is correct; but maybe there was some residual heat after running it (and letting it sit) that would explain that, but you don't have those kind of outside temps now, do you? Does that come down as you drive around?
mattbta
Full Access Member
The truck is garaged 100% of the time, so it's not out of the realm that under hood temps were that high. These temps were taken before before starting it and i just idled it for a few minutes. Maybe I'll toy around with looking at the temps while/after driving it. Trying to remember back to my LS1 days in the late 90's - we used to put a resistor in the IAT to "trick" it into reading lower. Not sure if that actually did anything but we tried it...those motors were brand new tech for all of us...not even aftermarket camshafts when I got one.
HACK BLOCK
Full Access Member
sorry how do I get tech 2 on a computer? I think I'd rather this than my handheld especially if it doesn't reset when Turing on the engine
mattbta
Full Access Member
I bought a VCX NANO device and it came with a "modified" version of Tech2Win which is software for a PC. This device emulates Tech2, MDI, MDI2 and J2534 passthru and is USB.
MassHoe04
Full Access Member
I believe the Tech2 can be hooked up to an older (Windows XP) computer to display and
Was originally built for older (Windows XP) computers with RS 232 jack.
I think it will run on newer devices with USB port and the right connector.
I don't know if it is truly standalone or if the Tech2 head unit is still required to interface between the OBD2 port and the laptop.
I have not tried that out yet, so I can't tell you much more.
The GM TIS 2000 Tech2Win software is included with the Tech2 scan tool.
Was originally built for older (Windows XP) computers with RS 232 jack.
I think it will run on newer devices with USB port and the right connector.
I don't know if it is truly standalone or if the Tech2 head unit is still required to interface between the OBD2 port and the laptop.
I have not tried that out yet, so I can't tell you much more.
