Locorotc

Good morning Chevy nation, I am in need of some help. My fiancé has a 1993 Chevrolet C1500 5.7L that was her daily driver, now the truck sits because her father found fuel mixing with the oil and was causing the engine to start knocking. I was thinking it was the head gasket but before I go and just start replacing head gaskets I wanna be 100%sure it's that before I replace. I was reading that it could possibly be the PCM pushing too much fuel into the system. Any help would be appreciated.

cleveland63b

A leaking injector or running rich would be about the only cause, how long does it take before its noticeable? or since the oil was changed? Those TBI engines ran a little rich anyway

Locorotc

At the current moment I do not know how long ago the oil was changed, she just told me about it recently. I can find out and post back as soon as I find out. How would I determine a leaking injector?

Locorotc

I found out that the last time her oil was changed, it hasn't been done in 6 months, however at that time the oil was fuel soaked as well. Her dad said it has been like this for over a year. Any help on this please.

Richard Till

I`d suspect a bad injector or fuel pressure regulator. Too much gas is getting past the rings and piston into the crankcase. Pull every plug, lay them out in order and compare them to each other. Look for one or more to be wet with fuel. Knocking? Has the oil level risen or just get the smell from the dipstick? Change the oil asap.

Locorotc

Thank you for replying, yes sir they said the truck does have a knock when she's running as well. Thoughts as to why? I'm going to be working on it next weekend, we got new intake manifold gaskets and a throttle body gasket set, new oil and filter. I want to replace the plugs as well.

Locorotc

Good evening, I know it has been a while since logging into here and since posting about this truck, but here these past couple of weeks I have been working on the old '93. I replaced all the gaskets topside, pulled both heads off and cleaned under them and the piston heads, replaced every spark plug, wire, gasket, and changed the oil since getting antifreeze in the oil from pulling the heads. I put everything together and started filling the coolant up when the head started leaking, once again tore it down and cleaned it up, not too sure why it was leaking when the gaskets were flush and sealed, so I resealed them and torqued everything down as I did before. I get it all back together, put the number 1 cylinder at top dead center and then refill the oil since I did not fill it after taking the engine apart the first time. I get it all 100% together, check and make sure everything is tight and then I hook up the battery and try starting it and I get rotation but no start. I pull the number one plug and check for spark and sure enough have spark, I check the TBI and see if I'm getting fuel and yup there's fuel there. I decide to put the engine at TDC and pull the distributor cap and find the rotor at 180 off so I fix it back to number 1, put it all back together and I try starting it again, I get backfire and then crank that's it. I am continually trying to crank it and it will occasionally backfire with still no start. I'm not too sure what it could be. Here's a list of everything that's been replaced: head gaskets, intake manifold gaskets, valve cover gaskets, rotor button, distributor cap, all wires, all spark plugs, water pump gaskets, TBI mounting gasket, oil pressure sensor, both coolant temperature sensors, pcv valve, and the TBI is used off a donor 1993 5.7L at a salvage yard. I see the TBI spraying fuel, I unplugged one and tried starting it and nothing, tried unplugging the other one and plugging the first one back in and starting it still nothing. I bumped the ignition to achieve TDC as well as manually placed it. I really hope this thing didn't jump timing and I hope that the timing chain isn't bad. The engine sounds different than before I took it apart, it sounds a lot tighter, like maybe the starter cant spin the engine fast enough to start it, but it sounds like all you hear is the starter when you engage the key. Could the specs in the Haynes manual be incorrect for the rocker nuts? The book says nothing about the 5.7L torque so I went with the 7.4 since it was a little more than the 4.3L but I'm thinking it may be too much, anybody have the torque spec for it maybe? And anybody agree with me on the torque being too tight? Again any help will be appreciated, I am willing to try anything. I apologize for the long posting.

Locorotc

So I am a dummy and didn't realize that I had to tighten the rocker arms per the lashing, so I took a look at the pushrods last night and now I have to replace all 16 because of my stupid mistake. Will post back when new ones are in.

oilcanhenry

Did you check the cylinder heads for distortion?

Locorotc

Yes sir they were perfectly alright before placing them into the vehicle.