chevy mechanics HELP

[tepco]

I have a 94 Chevy C1500 it has a cold start problem. Specs are 4.3 vortec v6,throtle body,ac, 2WD. The problem is that it seems to flood out when its cold. More when its cold out. When the exterior temp. is above 70 it starts much easier. After i crank it for a while it eventually starts.When it does start it blows out black smoke.I know there is a service bulliten about the fual pump pulsator, but i believe that would make it starve for gas untill it builds up pressure. I have had chevy test the electronics which all seems to read fine. I have changed: Fuel pump,fuel pump relay,fuel presure regulator,map sensor,throttle position sensor,oil pressure sending unit,temp sensor(for the computer),pick-up coil,idle air control valve,computer,cap,rotor,plugs,wires,air filter,and i have removed the throttle bottle to clean any carbon build up, which was very little.There are other parts that i cant remember off hand. :think: I am running out of options and money. At this rate i will probably need a new starter soon. If anyone knows my vehicles problem please help.I forgot to add it has 165k miles and gets a nice blue spark. I've also cleaned all the grounds. And made shure the timeing is set right and advancing properly which it is.Im still hunting for the problem.No check engine lights either.

 

[Highbeam]

Compression test while cold, just to make sure you have some compression. Then since you've replaced nearly all the fuel parts I would check to see if you're getting a good spark. Ground a wire where you can see it and have someone turn the engine over and see if you get a nice fat spark when everything is cold. Once you do get it running, set the timing per the book's specs. While the timing light is hooked up, slowly rev the engine and watch the timing marks to make sure the distributor is advancing properly.

Since you have plenty of fuel, I suspect a crappy ignition or a burnt valve.

 

[yo its matt!]

ok from a 20 year chevy mechanic, hows the ign system? specifically cap and rotor, coil and wire look at both ends of coil wire, also any check engine light? the ecm sees coolant temp and adjusts fuel acordingly especialy on cold start, look at the coolant temp sensor on the intake how many miles? distributer magnets can give trouble at higher milages, post or email me at badmkf@aol.com this shouldnt be to hard to fix

 

[MikeT]

Just latching on, want to see how this goes... Good luck!

 

[MikeT]

Any luck yet??? Does anybody have any other suggestions on this??

 

[enduro400]

How about the fuel pressure regulator?

 

[Racinante]

Originally posted by tepco
There are other parts that i cant remember off hand. :think

Was a fuel filter one of these? I assume it was since you replaced so much. You never said what your compression was. How is it?

The fuel pump pulsator is part of the fuel pump and that was all replaced, right?

How's your catalytic converter? If it's slightly restricted, it could affect start up.

Did the Chevy dealer check your electrical when it was cold? A computer can only diagnose a problem when it is happening. Pontiac had my Grand Prix for a day and couldn't solve my intermittent no start problem cause it always started for them. I finally figured it out myself. It was the crank sensor. The connector on the sensor was corroded and after cleaning it with a small file and filling it with dielectric grease I haven't had a problem. I don't think you have a crank sensor, though cause you have a distributor, right? I have 209K on my GP!

If it's going to be cold the next morning, I'd have Chevy "record" the computer data as they attempt to start it in the morning. They should have a scanner that can be plugged in to your data port that can "capture" all computer functions.

Before you do that, you might want to see if you have a spark when you first try to start it.

I hope something here helps. I feel your pain! :(

 

[tepco]

I replaced the fuel pump and filter,and had the chevy dealer do a diognostic check when it was about 40 degrees out and they said everything looked fine,even though it was hard starting for them as well. I havent had time to do a compression check yet and i didnt ghange the fuel pump pulsator( i later relized that they have had problems with this in other trucks befor). so im going to change that first and hopefully that will fix it. But i dont see why external temperature would make a difference. It gets a good spark when cold. Im thinking that maybe the computer prom is not processing the incomming information properly. I have already replaced the computer but used the same prom. I cant wait to fix it so i can spend my free time riding instead of working on my truck.

 

[MikeT]

Originally posted by tepco
I cant wait to fix it so i can spend my free time riding instead of working on my truck.

Really?

 

[MikeT]

check your PM

 

[tepco]

I finally got a chance to check the compression. I did it with a external temp. of aprox 88 degrees and the truck was sitting all day except for the drive to the garage about 25ft. the results were consistent but possibly a little high.? R
190/190
195/190
190/180
F
A couple of the plugs had a small amount of light brown build up on them nothing major,basically the color looked good on them all. I had the coil bench tested in the past and it was fine. Could it still be putting out a weak spark? I also pulled the fuel pump (Which i already replaced) to remove the pulsator. But it was already done. I am still batteling this problem any help would be greatly apreciated.

 

[MikeT]

Come on guys, give a bro, my bro, a hand!

 

[IrishEKU]

Tepco,
Have you ever run your tank dry? I know from working on Hummers for(deisel yes but same pricipals) over 11 years that (You didn't say if you changed this ofr not) if the electrical tank pup is out it will take for ever for your mecanical pump on the side of the block to pick up the fuel. Here is an easy check w/o dropping the tank, pull the supply line off your block mounted pump and just turn on your ignition to ACC. No fuel check your relay and fuses. If they are good then your in tank pump is gone.
Hope this Helps!
Happy Trails!
PK

 

[Highbeam]

The newer gasoline engines don't have mechanical pumps. The tank mounted electric pump provides 60+ psi of pressure. Perhaps a run dry tank may cause a fuel filter clogature.

 

[Neil Wig]

Pull the glove box liner out, and check the computer connection (wiggle it while cranking). I used to keep a stick in my truck to smack the computer when the engine started missing. Worked like a charm, but added to my road rage so I thought I should fix it...
The computer connection should not be temperature sensitive, but it's free and easy to check. I had the connector pins replace on my '90 Chev for about $100.

 

[tepco]

I fixed it.. :) .It was the coil. I had it bench tested near the beginning of this repair effort which showed it to be fine. After replaceing almost everything else i figured i might as well change that to. Its been two days now and it started fine every time. Thanks for everyones advise.. ;) Now i can start putting my money into my XR instead of my truck....

 

[MikeT]

:) :) :) :aj:

Good job! Way to go Bro!