Mechanic advice needed

[oldman45]

I have a minor issue with my truck and need some opinions as to the cause and/or corrective measure needed.

Truck is a 1996 Chevy 3500 with 437,000 miles. Four months ago I had a factory new 454 engine installed. Also installed was a factory transmission, fuel pump, alt, water pump, power steering pump, idler pulley, radiator, air conditioning compressor, starter, battery, belts and hoses. All parts are OEM. Spent $14,000 for parts and labor but was cheaper than $50,000 to replace the truck.

Problem: If it sits over night, it starts immediately when the key is turned. Once it has been used during the day, starting takes about 8 seconds. The motor turns over fast but it will not catch immediately as it does when it starts for the first time in 12 hrs or more.

Any good reason why?

[walnutred]

Sounds like someone routed the fuel line too close to the exhust or engine block.

[DeadAye]

Originally Posted by walnutred

Sounds like someone routed the fuel line too close to the exhust or engine block.

Vapor lock - my first thought too...

[G.T. Smith]

A friend of mine had a Pontiac car that did the same thing. It turned out to be the water temperature sensor. I'm not sure if it started properly when it was hot or cold. Some vehicles I have had would start poorley when hot and it was the ignition coil, or coils as the case may be.
Hope you get it fixed. Sounds like you have just about replaced everything.
Have a good one,
Gordon

[ErnieDeBord]

I would suspect coil then ing module

[ErnieDeBord]

forgot to add, temp switch will def cause a flooding problem. a cheap and easy try.........as after tought i would try it 1st

[Protected]

since its a 1996, you should be able to see if there are any codes in the computer. on particular problem that may cause this is the crank or cam sensor (cant remember which), but it should do it all the time. this problem would not cause a light, but would set a code. worth a shot.

most chain auto parts stores read codes for free.

hard start "hot" can also be caused by egr problems, vapor lock (as others have stated) and weak O2 sensors, or possibly exhaust leaks.

Hope this helps.

[27145]

I work on Harley's, does it have an air temp sensor? If it does, it might be it.

[oldman45]

When the motor was installed, every sensor, coil and all the wiring was replaced. Is it possible that one of these was bad from day one?

The only thing that has not been replaced as yet since it was brand new is the exhaust system. Everything from the manifold on back to the tail pipe is original equipment.

[captorquewrench]

Originally Posted by oldman45

When the motor was installed, every sensor, coil and all the wiring was replaced. Is it possible that one of these was bad from day one?

Yes. Always a possibility that something new or refurb has a factory defect.

Vapor lock and temp switch have also been mentioned, as well as having a major auto parts store run code for you. You can also do that your self (usually turning the key on, off, on off, in sequence, and watching your engine light's "morse code" signal flashing) and checking a manual for your engine. I no longer do this since I have a tester.

[oldman45]

Originally Posted by captorquewrench

Yes. Always a possibility that something new or refurb has a factory defect.

Vapor lock and temp switch have also been mentioned, as well as having a major auto parts store run code for you. You can also do that your self (usually turning the key on, off, on off, in sequence, and watching your engine light's "morse code" signal flashing) and checking a manual for your engine. I no longer do this since I have a tester.

I have a large assortment of code readers, pressure testers, sniffers and such. Seldom use any of them. I suppose I will have to get the manual out on the code reader and see what it shows.

As I said earlier, on a cold start, it fires almost as soon as the motor begins to turn. Once started for the day, all the following starts are hard starts that takes 3-8 seconds AND there is a brownish-grey smoke that comes out of the tail pipe for a second or two once it starts. The smoke is not present in the initial daily start.

[msinc]

Codes are good...most of the time, but dont take them for gospel. When you say it takes longer to start hot does it sound as if the starter is laboring to turn the engine over??? Sometimes the battery cable routed to close to the exaust manifold or pipe can get hot...heat ='s resistance, and that will make it spin more but sound like the starter drags or like a weak battery. Many vehicles have a shield from the factory to protect the main starter cable from heat...was this reinstalled when all this stuff you say was replaced got replaced??? Many mechs mistakenly believe the shields are not needed...big mistake. A quick test is to wrap the cable in aluminum foil and try it for a few days...I have seen many times when this is caused by a mech using a shorter battery to starter cable than what the factory originally had on the vehicle {to save a little money} only to find that it has to be routed that way to clear the hot areas you dont want a cable to be in. Remember that the starter has the heaviest cable and will take most of the power in the battery to spin the starter so if there is a problem the ignition circuit will suffer {less spark} just so the starter can spin. Bad way to explain it but...

[scooter123]

Have you tried smelling that brownish gray smoke when it starts? It sounds like you may have fuel pooling in the intake manifold. If so, the exhaust should smell like raw gasoline. I would also suggest that you smell the oil on the dipstick because a problem like this can leak down the cylinders and dilute the oil with gasoline.

If the engine has a carburator you probably have a Quadrajet with a leaky fuel bowl, which was a common problem with the Q Jet. There are a couple of pressed in brass plugs in the bottom that leak when they aren't fitted properly. The normal solution for this was to use a fuel stable epoxy to seal them up.

If the engine is fuel injected, in this case I suspect that you have a situation where the fuel rail is pressurized for a short time after engine shutoff and an injector is allowing gasoline to leak into the intake. The solution for that is to replace the offending injector.

[captorquewrench]

Originally Posted by msinc

Codes are good...most of the time, but dont take them for gospel.

And you only get a code for a part or system with a sensor anyway.

[Pete99004]

Time to trade it in for a new Ford.

[-db-]

I think scooter's got it. It's not the starter if the engine turns over fine but doesn't fire. There's likely a fuel leak that evaporates/drains overnight but pools up during the day when you're using the truck, causing the hot start problem. Once you fix that, be sure to get an oil change as you don't want fuel in your oil.

[Protected]

this should be a fuel injected motor. Brown smoke = running lean. black would indicate rich mixture, white could indicate raw fuel or water.

the only thing that should be different when hot is the vehicle is in "closed loop". When the vehicle O2 sensors are below 600 degrees F, the computer takes readings from throttle position, intake temp, airflow, and manifold pressure. it then uses those readings to "guess" how much fuel to use to give you a slightly rich mixture.

when the O2 sensors are above 600, the computer also utilizes the O2 sensors to adjust "fuel trim" to achieve the proper mixture (rich for low coolant temp, and normal for "at operating temp") this is called "closed loop"

so with that being said, if the vehicle acts normally first thing in the morning, then it sort of rules out the above mentioned sensors. i would focus on O2, coolant temp (tho not likely) and intake temp sensors.

it could still be one of the first sensors, but id be willing to bet its an O2 sensor, especially if there is a check engine light.

if you can post more info as to teh weather where you are and what the codes are, i can help you further.

[sar4937]

Try a shot of ether, or a little fuel down the throttlebody. If it starts normal it probably has a weak fuel pump. These engines require a specific minimum psi to work the injectors.

[oldman45]

Originally Posted by Pete99004

Time to trade it in for a new Ford.

Naah, I work my trucks and get 400,000 miles out of them before I have repairs done. The Fords in my family never lasted 200,000.

However the Fords paint jobs held up better and looked great.

[jj2am44]

A dripping fuel injector will do exactly that. When it's cold in the AM, the fuel has already evaporated.

[m1gunner]

IIRC, there is a leak down test you can do to look for leaking injectors. All you need is a high pressure fuel pressure gauge as the fuel rail already has a schrader valve just for this.