OK...what now

[kenaijoe]

98 Jimmy...4.3, 128K miles. Just purchased for my son.. Fuel pump works(60lbs) Have spark from coil. No codes from scans. New cap/rotor/plug wires/plugs. Truck attempts to start then sputters and dies. Runs about 4 secs. New gas....I'm at a loss here...don't know what to look for next. Any ideas would be greatly appreicated....thanks and peace

[rjer3]

does it have good compression?

[MT-2500]

Any security lighs staying on?
Any add on remote starts or anti theft stuff?
Doe it start and run normal for 2-3 seconds the shut off like key off?
Is that 60 lbs of fuel pressure engine cranking?
Try a little carb cleaner and see if it will start or run a few seconds on carb cleaner.
No starter fuid pease!!!
You need 65-66 lbs engine cranking pressure or the injector will not squirt on a cold start.


The only true test on a fuel pump is to check the direct fuel pressure from fuel pump.
A quick test is to block off the return line and see if fuel pressure comes up to 75-85 lbs.
But do not run the pump at full pressure very long.
Also when testing fuel pump and pressure you need to tape a gauge to outside windshield or outside mirror and drive it on the road for 20 -30 minutes
until the pump gets has run a while to check for a pump fading out after hot.

Hard to start cold or hot and fuel pressure testing guide lines.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
If pump has full pressure with return line blocked and low pressure without it blocked most usually the fuel pressure regulator is leaking or not holding pressure.
Later V6 and V8 gm engines should have 60-66 fuel pressure.
Cold start should be 64-65 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 60-66 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak in system.
Post back fuel pressure readings.
MT

[randy78]

check sensors

check MAF sensor especially

check cam/crank sensor

check cat converter for being plugged up


check for cracked vacuum hose anywhere on intake or TB unit


it will be something stupid or common

[old_master]

No SES light tells you it's not a problem with the OBDII system or it's sensors. I'm with MT, check fuel pressure and leakdown.