champ200

Hi all. Been reading posts for hours and finally thought I would post my question. I have a 1992 VIN W 4.3L with 25,000 on a rebuilt engine all new ignition parts, fuel pump, ect. This thing starts and runs fine if it's warm outside. Here's my problem, when it's cold outside it just won't start. If it's 60 degrees it will start on the first turn of the key but if it's 30 degrees, when you crank it just sputters, try several times and it just wont start. If you let it set several minutes and try again most of the time it will finally start. It doesnt miss sputter or have any other problems other that if it's cold it just wont start. No check engine light and no codes. Any starting point to what I'm looking for other than for it to stay above 60 degrees outside, LOL? I really need and appreciate the help.

champ200

Update to my previous post. Just went out to start it and wouldn't start and it's 55 degrees. Got the scanner out and it shows a code 43 Electronic Spark Control Failure. Does that mean it's time for a new ignition module? Both the ignition module and knock sensor were replace with the rebuilt engine. Here are a few other values from the scanner.
Coolant Temp = 100.4
Start Up Coolant Temp = 99.0
Throttle Sensor = 0.45 Volts
Oxygen Sensor = 664 mVolts
02 Cross Counts = 175
Idle Air Motor Position = 90 Steps
Manifold Air Temp = 66.2
EGR Duty Cycle = 0.0%
Spark Advance = 6.3
Knock Sensor = 0 Counts
Knock Retard = 0%
There's more info on the scanner but hated to list every one. Does this info give anyone more of an idea of where to start?


****Well, new update it's not the code 43, it has no trouble codes and the problem is somewhere in the fuel pressure (has new filter). According to specs it needs 61 psi fuel pressure to start. When I first went out tonight it would get to 58 and drop and wouldnt start. After several tries got it to go to 61 psi and it started and runs fine since. Try the drop test again and it holds pressure so I would think that would rule out a leak in the fuel sysytem. So its got to be the "nut kit" going to the spyder injection or the fuel pump. I'd think if it was the "nut kit" it wouldnt have held the pressure after I got it to run. So do I pull the tank for the fuel pump or the upper intake for the "nut kit'? Any idea on how to determine which one?

old_master

The fuel pressure must be 60psi to 66psi. Less than 60psi you'll have problems starting cold. Possibly a problem with the pump.

Your leakdown rate is excessive. There is only one way to tell what's leaking. A shut off valve needs to be installed in the pressure line between the pump and the intake manifold. Pressureize the system with the pump. Shut off the pump and the valve simultaneously and watch the fuel pressure. If it drops, the problem is in the plenum. If pressure holds, the check valve in the pump is bad.

champ200

Thank You for the help, I'll try the shut off valve tomorrow night. One question though. How long do these systems hold pressure? Surely if the problem is in the plenum it should go down pretty quick, right? I mean if it doesnt get started for a couple of days the fuel system wont hold pressure all that time will it? I went out and looked and it's down to 40 psi after setting for about 45 minutes.

old_master

In a perfect world, theoretically the system should hold pressure indefinitely, (this isn't a perfect world, it’s a GM ). It doesn't matter how long the system holds pressure, just so it doesn't drop below 55psi after 5 minutes. At the next start up, the pump will prime the system and satisfy the fuel pressure regulator. It's not a bad idea to allow the pump to prime and shut off before attempting to start the engine each time.

The size of the leak determines how long the system will hold pressure. If there's a leak anywhere in the pressurized portion of the fuel system, the fuel pressure gauge will indicate a drop in pressure. If the fuel return line leaks, the fuel pressure gauge will not indicate it because the line is not under pressure.

champ200

Old Master Thank You for all of your help!!! Replaced the fuel pump and it's like new again. Turn the key and it goes right to 65 psi and starts on the first crank.

old_master

If you understand how something is supposed to work, you can diagnose it correctly when it doesn't work. Glad you got her going, glad I could help.