5.7 vortec long crank

[slow_c1500]

I will get a comp test within the next day or so. Also does anyone know if there are any sensors/electronic components that could potentially contribute to the hard start in my case (when engine hasn’t been sitting for very long)? Coolant temp sensor? ICM?

 

[Schurkey]

ALL of them, under the right circumstances.

Not saying that's likely without causing other problems as well...but a scan tool could tell that tale.

 

[1990Z71Swede]

When you tested your fuel pressure , it was somewhat low but more importantly it was dropping too fast. That obviously means you have a leak somewhere. There are three posibilities if we rule out external leaks which you probably would have found by now.

#1 Fuel pressure regulator, not sure how the Vortec's are but it is common for regulators to be referenced to engine Vacuum.(Tiny vacuum hose going from reg. to manifold port) There is a diaphragm inside the regulator that if damaged may leak fuel into the manifold. The leak would have to be small as the regulator seems to be able to hold atleast 54psi when the pump is running.

#2 Leaking injector

#3 Check valve in fuel pump, not likely becuse that would not make it start better when cold.

Typical signs of #1 and #2 are long cranks when sitting for a longer while( like a couple of hours), but will start better when sitting over night and sometimes when sitting for just 5-10 minutes. Smell of gasoline around the vehicle after a long crank start. (Thats why @Caman96 asked about fuel smell, me thinks)
Also if this has been ongoing for a while, you might possibly smell fuel in the engine oil, especially if the vehicle is mostly used for shorter trips.

The reason it starts better when cold is that there is only a leak as long as there is pressure in the line, if left sitting over night, the leak will diminish as the pressure drops, while alot of the fuel will evaporate, or trickle past the piston rings, and on cold starts an overly rich mixture is better tolerated by the engine.

The reason it may start better when hot if it has just been sitting for minutes is the simple fact that not alot of fuel has had time to leak into the engine to create a real problem.

 

[Caman96]

I can’t help but suspect that eBay spider, or the fuel pressure regulator that probably came with it. If it was me and you end up removing upper plenum, I’d just replace it regardless with an Acdelco, Delphi or an SMP.

 

[slow_c1500]

When you tested your fuel pressure , it was somewhat low but more importantly it was dropping too fast. That obviously means you have a leak somewhere. There are three posibilities if we rule out external leaks which you probably would have found by now.

#1 Fuel pressure regulator, not sure how the Vortec's are but it is common for regulators to be referenced to engine Vacuum.(Tiny vacuum hose going from reg. to manifold port) There is a diaphragm inside the regulator that if damaged may leak fuel into the manifold. The leak would have to be small as the regulator seems to be able to hold atleast 54psi when the pump is running.

#2 Leaking injector

#3 Check valve in fuel pump, not likely becuse that would not make it start better when cold.

Typical signs of #1 and #2 are long cranks when sitting for a longer while( like a couple of hours), but will start better when sitting over night and sometimes when sitting for just 5-10 minutes. Smell of gasoline around the vehicle after a long crank start. (Thats why @Caman96 asked about fuel smell, me thinks)
Also if this has been ongoing for a while, you might possibly smell fuel in the engine oil, especially if the vehicle is mostly used for shorter trips.

The reason it starts better when cold is that there is only a leak as long as there is pressure in the line, if left sitting over night, the leak will diminish as the pressure drops, while alot of the fuel will evaporate, or trickle past the piston rings, and on cold starts an overly rich mixture is better tolerated by the engine.

The reason it may start better when hot if it has just been sitting for minutes is the simple fact that not alot of fuel has had time to leak into the engine to create a real problem.

Thank you for the explanation, that makes a lot of sense. There are no external fuel leaks. And you did bring something else to my attention: come to think of it, it does sometimes start normally after only sitting 5-10 minutes. I will probably end up replacing the spider/FPR with a quality one anyway. I’ve seen the GP Sorensen MPFI injectors at autozone for 300$, are they any good?
Also this may be a dumb question, but when I do a compression test, can I just have my distributor cap off? I wouldn’t want it to be on because it isn’t secure due to the stripped screw.
Or is the comp test even necessary at this point? Every symptom is pointing to a bad spider:

-Hard start when sitting for a few hours

-normal start when sitting overnight or 5-10 min

-fuel pressure low and dropping continually

-fuel on spark plugs (loose dizzy cap would contribute to this because of weak spark)

 

[Erik the Awful]

I wouldn't bother with a compression test right now. Having the cap off wouldn't be an issue, though.

Now's a great opportunity to replace the cap with a United Motor Products blue cap with brass terminals.

Once you get the problem sorted, replace the spark plugs. Once fouled, they'll always try to foul.

 

[slow_c1500]

I wouldn't bother with a compression test right now. Having the cap off wouldn't be an issue, though.

Now's a great opportunity to replace the cap with a United Motor Products blue cap with brass terminals.

Once you get the problem sorted, replace the spark plugs. Once fouled, they'll always try to foul.

I wouldn't bother with a compression test right now. Having the cap off wouldn't be an issue, though.

Now's a great opportunity to replace the cap with a United Motor Products blue cap with brass terminals.

Once you get the problem sorted, replace the spark plugs. Once fouled, they'll always try to foul.

The cap I have is fairly new and already has brass terminals. The inside seemed perfectly fine, so I will keep it for now. I will replace it with that blue one though if it gives me issues.

thanks for the tip about the plugs, I didn’t know that

 

[Schurkey]

Disable the ignition coil before performing a compression test. It's hard on the coil to be firing sparks into an open circuit.

Just pull the 12V electrical connector off of the coil.

 

[slow_c1500]

I am very convinced at this point that the spider/reg is bad so I probably wouldn’t take the time to do a comp test, I appreciate the suggestion though.

The only name brand spider that is readily available to me at the moment is the GP Sorensen injectors at autozone. Everything else is either out of stock, can’t be shipped to my location, or takes way too long to ship. I have heard that GP Sorensen is a fairly reputable brand, can anyone speak from experience as to how good their parts are?

 

[Schurkey]

Owned by Standard Motor Products.

Potentially identical to Standard, Blue Streak, Echlin, and BWD brands.

Tend to be less-expensive. Whether that's reflected in the quality, I don't know.