Quote:
Originally Posted by Beaner81
I have a 98 K1500 with 240000 miles on the 5.7L Vortec. I start getting misfires very shortly after startup, especially when towing large loads. Idles rough and spits black smoke while misfiring. I had my buddy hook up his solice and cylendar 2, 4, 6, and 8 are all missing. Both bank 2 O2 sensors are reading bad and I have O2 heater error. Sensor 1 is reading around 200 and sensor 2 is reading 700 +/- 20. Less than a year ago I replaced the cap, rotor, wires, and plugs so I'm thinking its not the cap. My thoughts are possible fuel pressure regulator leak? All vaccum lines look good. Does anyone have any suggestions before I dive into this one. It seems unlikely that both O2 sensors on that bank go bad at once while all cylendars on that side are misfiring. Again to me this looks like a fuel delivery issue.
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What codes does it have?
How many misfires on each cylinder?
What is camshaft retard reading?
What are fuel trim readings?
Sounds like time to run a complete fuel pressure test.
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.