1999 Chevy 1500 5.7L Vortec.
When starting from dead cold, the engine will fire immediately. However, after reaching operational temperature, being shut off then restarted (Picture driving a distance to a store, shopping in the store, then returning home.) the truck has to crank before starting. Sometimes as long as five seconds. Once running, the engine runs fine. Let it sit until dead cold, it will again fire immediately. Does this in any ambient temperature.
Issue does not seem to be getting worse but the engine does this like clockwork.
No aftermarket parts and the truck is extremely well maintained.
Any ideas?
Hard Start After Reaching Temperature
- Thread starter GeorgeKaplan
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When it starts does it come to life as it should, or flutter around/sputter for a second before smoothing out?
Sounds like a symptom of "flooding", but I don't think opening the throttle a little is the solution. Could be a fuel leak into the intake: when cold the fuel has dissipated, but when it hasn't had time to drain off it has to crank to get enough air to fire.
Distributors (which contain the cam sensor) can wear on these. Dist. caps can short out. Injectors, which actually sit in a cluster behind the throttle body, with little tubes ending in poppets clipped into the head ports, can suffer in several ways.
Are you sure the spark plugs are in good shape?
The evap system will purge the charcoal canister into the intake manifold at different times. If the system is messed up, it could be dumping air into the manifold at the wrong time, causing a lean mixture and no start. To eliminate this possible cause, remove the purge line from the intake manifold and plug both open ports. Do this only with the engine hot and when you would normally have this problem. If the problem goes away you have found the problem.
Injectors leaking down into the cylinder after shutdown might cause a flood condition.
MolaKule
Staff member
I don't know about the V8 for that year but on my 1999 S-10 with the 4.3L V6 the problem was the fuel pressure regulator leaking down and dribbling fuel into the back cylinders.
I'll have to pay closer attention. My initial response is to say it runs smooth, otherwise I think I would remember such a thing because having the engine sputtering would make me worry. I'll be leaving for the store in a little while. Cap, rotor, plugs, and wires all new (very little miles) AC Delco installed at a trusted dealer.
Problem also is that I don't drive this vehicle much, the wife does and she doesn't say anything.
Originally Posted By: Alex_V
When it starts does it come to life as it should, or flutter around/sputter for a second before smoothing out?
Sounds like a symptom of "flooding", but I don't think opening the throttle a little is the solution. Could be a fuel leak into the intake: when cold the fuel has dissipated, but when it hasn't had time to drain off it has to crank to get enough air to fire.
Distributors (which contain the cam sensor) can wear on these. Dist. caps can short out. Injectors, which actually sit in a cluster behind the throttle body, with little tubes ending in poppets clipped into the head ports, can suffer in several ways.
Are you sure the spark plugs are in good shape?
Yikes. I wouldn't know where to start. But thank you.
Originally Posted By: WobblyElvis
The evap system will purge the charcoal canister into the intake manifold at different times. If the system is messed up, it could be dumping air into the manifold at the wrong time, causing a lean mixture and no start. To eliminate this possible cause, remove the purge line from the intake manifold and plug both open ports. Do this only with the engine hot and when you would normally have this problem. If the problem goes away you have found the problem.
EVAP sounds like a good base to cover, too. Just have to determine whether you think it's excess fuel or lack of it.
Either way, I think that's one of the best (top 3 - maybe the best) gas truck engines, to boot. Dad has a '97 1/2 ton Suburban with 430K. No more oil consumption than when he got it at 170K, and it's been apart once at 340K for what wound up being a faulty injector - machine shop said the valves didn't really even need done.
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Thanks. This vehicle sits a lot. Just turned 75K. Runs like new except for this one issue. I know it's a popular and well regarded engine. I guess I was hoping it was a simple/common problem. Guess not. EVAP or leaking fuel injectors? I will have to send it in and was hoping to avoid doing that.
Originally Posted By: Alex_V
EVAP sounds like a good base to cover, too. Just have to determine whether you think it's excess fuel or lack of it.
Either way, I think that's one of the best (top 3 - maybe the best) gas truck engines, to boot. Dad has a '97 1/2 ton Suburban with 430K. No more oil consumption than when he got it at 170K, and it's been apart once at 340K for what wound up being a faulty injector - machine shop said the valves didn't really even need done.
Hopefully the dealership fixes it without fuss or a fortune.
When you do determine the cause and fix, please let us know. I'm curious on this one.
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Not sure how this engine works injection wise, but some (failing or dirty) hall effect (magnetic) sensors could exhibit erratic behavior when hot, hence the longer crank time needed before the calculator could get usable info to get the timings right (spark, fuel, etc).
Had a crankshaft position sensor go bad on my car, similar symptoms.
Evap system or injectors leaking could cause some flooding, but I don't put my money on it. Sticky fuel pump...if you let the contact (key) on several seconds before starting, what is happening?
Wonder how's the engine running after hot restart, normal smooth, or not?
Also could sound like some vapor lock symptoms from the carburetor era, haha. No leak on the fuel lines? Is there a fuel filter on this car?
Originally Posted By: MolaKule
I don't know about the V8 for that year but on my 1999 S-10 with the 4.3L V6 the problem was the fuel pressure regulator leaking down and dribbling fuel into the back cylinders.
If it's not fuel injectors leaking down on shut-down causing a flood then it sounds like Fuel Percolation in the lines.
The reason it would be a problem hot versus cold is because it doesn't have enough time to evaporate the gas that has leaked out of the injector into the cylinder in a short amount of time like a hot-restart versus sitting over night sort of thing.
Now if this isn't it, then it can be fuel percolation, which can be caused by a bad check valve in the fuel pump or a fuel pump operating at less than optimal pressure right before shut-down. If the lines are kept under proper pressure when they are warmer (Running right next to the exhaust) the fuel will not percolate in the lines. I would put up with it until the fuel pump eventually dies.
I had this same problem with a VW Carbriolet. It had a complicated mechanical fuel injection system and fuel delivery and we remedied this problem by increasing the fuel pressure at the fuel distributor with adjustment shims to keep the pressure up on shut-down due to a weak check valve in the fuel pump which was expensive to replace and hard to get to. This allowed the fuel pump to rebuild the pressure needed in the time that the fuel distributor took to use up the pressure held at shut-down.
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also the poppet valves can get sticky when hot.
the cure is a redesigned injector assy with actual injectors on each leg of the "spider"
they make a noticeable improvement in performance.
Exact same set-up with 2 more injectors, The fuel pressure regulator is almost a maintenance item on these.
Originally Posted By: clinebarger
Originally Posted By: MolaKule
I don't know about the V8 for that year but on my 1999 S-10 with the 4.3L V6 the problem was the fuel pressure regulator leaking down and dribbling fuel into the back cylinders.
Leaky pop style spider injectors, its a very common issue. Do a conversion with this to cure it.
http://www.rockauto.com/en/moreinfo.php?pk=984604&cc=1352955&jsn=477
http://www.rockauto.com/en/catalog/chevrolet,1999,c1500+pickup,5.7l+v8,1352955,fuel+&+air,fuel+injector+retaining+bracket,10778
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