Cold start / Long crank

[lucky_7]

1997 GMC 1500 5.7L vortech. 147,000 miles, I have done a tune up less than 2 years ago that included, plugs, distributor cap and rotor.

Problem has been an intermittent long crank on the first start of the day, or when leaving work after my shift. Normally has been 2-3 seconds. New problem is that the long crank is getting worse (6-12 seconds) and sometimes it takes two cranks to start . It also seems to correspond with the colder temps here in Oklahoma this week.

Truck runs fine once started. It has all the power when needed. No stuttering, or slow acceleration.

[speedygonzales]

More than likely it's due to a stuck open fuel check valve in the sending unit.

Next cold start (where you would normally encounter the problem) do this. Turn Key On Engine Off for 5 seconds DO NOT CRANK THE ENGINE.
Then turn the key off for a few seconds.
Then do KOEO again for 5 seconds.
Do this process for 6 times
After the 6th time, turn it over like you normally would to start and see if this time it fires up quickly without having to crank it.
If it does now fire up quickly (after having primed the fuel system) that clearly proves the check valve is stuck. The only way to correct the problem that I've ever seen in 20 + years of owning mine is to replace the fuel sending unit.

If that does not change the problem, I guarantee the cap and rotor are the problem.

But for now focus on the culprit being the fuel problem.

As a "never hurts to try" you might consider using a complete fuel system treatment for several fill ups. I have had the stuck check valve problem 2 times in 20+ years of ownership and still to this day don't know what causes it to stick but I'm pretty sure it's not debris since the sock on the pump is a fine mesh. Good luck to you.

[lucky_7]

Thank you Sir, I will give it a try.

[speedygonzales]

Been a week, how about an update?

[lucky_7]

Sorry. Been busy, just rebuild the front end. Trucks starts normally if I cycle the fuel pump a few times. I can't change the sending unit until later, just spent 600 on the front end. I'll just keep 1/2 tank for now in case it goes all the way out.

[Kudzupatch]

very interesting. I drove to the Great White North one winter in my Suburban. Woke up to teens and it did the same exact thing. Never had given me any problem before and never knew why. SO RARE we have that low of temp here and when it does I rarely go anywhere. But good to know.

[lucky_7]

Yeah. Not sure what the colder weather would have to do with it other than chilling the valve which may shrink it some resulting it a tighter fit. Or some residue or corrosion broke free and stuck itself in the check valve. Whatever the case, the problem has cleared up recently.

[special-K]

It might be as simple as it takes more fuel to start in cold and you are still getting enough for warm weather. I mean, that is the function of the choke in carburetors, fuel enrichment

I thing to try, if you haven't already, is take the cap off and clean the inside with Lectramotive. It could have carbon but not real bad yet. I watched an old mechanic years ago take my just installed cap, toss it in the trash, pull out one he just replaced, and put it on my truck with a crank/no fire problem on a rainy night. Not all caps are created equal. Things have probably changed, but back then I learned black cap = crap and the colored ones were better bakelite. He put a tan one on my truck and from then on I only used Standard Blue Streak caps (blue). That was back before HEI. I've used black with no issues now, most all are now. Haven't had that problem. But I still only buy quality brand caps