98 c1500 lopes like a dragster.

[Ken K]

I bought a 98 1500 with a 5.0 ran when i looked at it. Picked up the next day fuel pump was out. Truck ran but poorly when i checked it. Changed fuel pump truck runs but lopes heavy. No cam in it but sounds like it. Smelt fuel found injectors were bad and leaking. Replaced spider still ran the same for about 5 minutes then cleared up and purred like a demon kitten. Drove truck 1 mile ran fine. Parked and qhen restarted back to loping. On live data stft at -31 both banks map at 20 when it clears itself up map at 10 fuel trim at -3 to 3 both ltft and stft. Have gotten code p0300 and p1351 only when it's loping. When its in that mood it starts and dies or tries to. When its in a good mood runs perfect starts quick no issues. The fuel system is new delphi pump new style delphi injectors. New crank purge map and ect sensors both ect. New egr new plugs wires rotor cap. New iac. New coil and icm. New O2 sensors as well. Only parts not replaced are maf iat and cam sensor. No cgamge when i unplug maf so i ruled that one out. All my grounds check good. There is no play in the distributor when i try to move rotor. . Im leaning toward either cam sensor or pcm. Tight on cash and wifes gettin tired of it not being reliable. Need help please i want to fix my baby.

Find the EGR. No mention of temperature at startup. They used a VSV the size of a pack of smokes. They get moisture in the lines or vacuum switch valve. It blocks, freezes and holds the EGR on. Use gloves or shop rag, find a position to put one finger on the diaphragm. No EGR at idle, cold or deceleration. Just a thought but you have a lot of your wallet in there.

 

[Chuck p]

Update got a new fuel tester and found out fuel pressure extremely slow to rise and tops at 50 with a whining from injectors when hooked up to schrader valve. If i unhook the fuel lines from injectors and engage fuel pump it pega to 70 instantly seriously the blink of an eye. I hear no clicking or anything from the injectors when energized. Im questioning if injectors are bad they are new like put on last month havent driven but a few miles with em b4 problem arose. I have the fuel return line unhooked and its dumping fuel the instant pump energizes which ia what leads me to believe its tge injectors maybe pcm ao if anyone knows how to tell which it is with a multumeter i would GREATLY appreciate it

 

[stutaeng]

Update got a new fuel tester and found out fuel pressure extremely slow to rise and tops at 50 with a whining from injectors when hooked up to schrader valve. If i unhook the fuel lines from injectors and engage fuel pump it pega to 70 instantly seriously the blink of an eye. I hear no clicking or anything from the injectors when energized. Im questioning if injectors are bad they are new like put on last month havent driven but a few miles with em b4 problem arose. I have the fuel return line unhooked and its dumping fuel the instant pump energizes which ia what leads me to believe its tge injectors maybe pcm ao if anyone knows how to tell which it is with a multumeter i would GREATLY appreciate it

I get some of what you are saying, but not 100%...

I think if you pinch the return line the fuel pressure should hold (to see if you have a faulty fuel pressure regulator.) But I'm not sure how you can do this on this engine. The fuel lines are hard lines. I'm not even sure how you are "unhooking fuel lines from the injectors"...the Spider injectors?

You will normally have fuel on the return side when you engage the pump. The fuel pressure regulator is responsible for this. If you could unhook and plug the return fuel line, it will peg to around 70 psi. I'm not sure if that's what you did.

When you replaced the injectors, it came with a f.p.r., right?

Not sure what would cause the fuel pressure to rise slowly, but that would explain the lean condition... The only definitive way to test the injectors is by doing a "injector balance test."

I would recommend you take it a good mechanic and tell him all that you have replaced. Stop throwing money away. At the minimum go watch a basic video on return style fuel systems before you continue. YouTube Schrodinger's Box has a good video, as well as South Main Auto.

 

[Chuck p]

Update pulled fuel lines found fuel return line had been cut and repaired with a section of rubber fuel line. Not the problem. Problem was fuel return line. The braided hose was kinked at the front by the top fuel line connection( at the back of the engine) and at the fuel punp against the frame. Now the fun part am trying to find new fuel lines send and return. Might as well while they are out. Im an extended cab and thus far lines for regular cab is all i am seeing. Just started looking though.

 

[Chuck p]

Repaired with high pressure fuel injectiin hose. She lives lol.

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[Steve OConnor]

I agree with everyone on the vacuum leak. When it's cold open a propane torch up on very low and wave it around the intake and see if you see any change in rpm. Sounds like a leak.
Cheers
Steve O

 

[Steve OConnor]

I agree with everyone on the vacuum leak. When it's cold open a propane torch up on very low and wave it around the intake and see if you see any change in rpm. Sounds like a leak.
Cheers
Steve O

LMAO just read the found the fix my bad I'm on heavy meds.