w6bauer

Just picked up a real nice looking 97 Tahoe 4x4 with the 5.7. Its got 140k on the clock. PO said head gaskets were blown. I gave $800 for it.

I cannot see any evidence of truck ever getting hot, no signs of coolant loss, no leaks anywhere of any kind of any fluid. I did cyl leakdown test and it has virtually no leak down, compression test revealed over 180psi on each cylinder.

Truck will not start. I hooked up fuel pressure tester and saw 80psi at the rail....not good too high, but as soon as pump quits pressure rapidly falls to 20psi then drops to nothing after 2 minutes.

Oil shows overfull and smells of gasoline. Injectors leaking in cyls. I pulled all plugs, disabled fuel pump and cranked all the gas out of the cylinders. Cylinder 5 Blew like a fire hose.

So im in the process of removing upper intake manifold to get to the spider. I got the Throttle body off now, and just out of curiosity I hooked up my scan tool and commanded fuel pump on while looking through hole in intake where throttle body mounts. I see fuel flowing and pertty consistent rate from passenger side of spider....another note, im no longer showing fuel pressure at gauge.

Do you think my regulator failed, maybe a clogged return line, or just a bad spider unit... any input appreciated. Im headed back out to continue disassembly.

Thanks

Will

w6bauer

Removed upper intake manifold and reconnected fuel lines to spider. Commanded fuel pump on and my pressure regulator is spewing fuel into the manifold.

I hooked rubber line to fuel return and put some shop air to it. Seems as though I have a blockage in the return line. Shouldnt I be able to blow air freely throuht the return line? I do have fuel cap removed.

kevinkpk

I would think it would be free. You might get a 5 gallon clean catch bucket, rout the return line to it, and try it. If the regulator can't bypass fuel that is a problem why you are seeing 80 psig.

shamrock246

If your going in there to change a regulator i would spend the extra money and upgrade the spider assy and change the oil before you try to start it

Amazon and Rockauto have the spider assy for a good price

w6bauer

Ive got the oil changed. First thing i did when i noticed gas in it. Im on a tight budget with the lack of snofall in indianapolis this winter so i dont have much $$$$ rollin in or i would definitely do the spider. I was amazed at how clean it looked under the upper. I rebuilt the engine in my 3500 box truck after it threw a rod at 130k and it was full of soot under there. This one is clean as a hounds tooth.

I did find the culprit in the return line. Plastic lines above tank were kinked. Im suprised i was even getting pressure from the pump. I replaced with rubber.

One thing im having an issue with while everything is going back together today is a rogue vacuum fitting . Im looking at the evap purge vacuum switch directly left(passenger side) of throttke body. Ive got a hose from the back of it going to evap purge solenoid valve just behind it and one hose coming out the front that goes to the vapor canister. On the top next to where the electrical connector i have a rubber elbow that goes to nothing. Can someone help me out here.?

kevinkpk

If you can post a couple images, that would be a great help

w6bauer

Got it all back together and started her up. OH NO Spun main bearings!!!! Hardly any oil pressure, almost 6psi at 1000rpm which is the lowest acceptable. Slight knocking in bottom end and idle, noise goes away between 600-1500 rpm then gets worse anywhere above that. Darn it. Guess I will yank it out and flip it over put some mains to it. I will definitely check rod bearings while im down there. I knew I loved good deals haha.

kevinkpk

probably the gas in the oil caused the damage. Aircraft used to use gasoline to thin oil in cold weather startups. The low oil pressure now probably due to excessive bearing clearances. You might look into an oil pump when you're down there.