97' Tahoe issues

[Underpsi]

recenty a friend bought this 1997 Tahoe. We started to drive it home and about 3 miles down the road it lost all power. It would then try to turn over but couldn't quite. So we needed up tighten all battery connections and it fired up as it was a new battery. Got another 2 miles down the road and I was behind him and noticed when he would stop and then take off it would puff out little black smoke almost like a diesel. Anyways then it dies again. He thought it was the alternator was bad so replaced it and the starter as well and fired up. Then goes around the block after about an hour of driving around and noticed no oil pressure on his gauge and had some tapping/knocking but still ran fine. Was told that the crank position sensor was bad so he is replacing that in the morning and was also told that the distr. cap was new but was some cheap off brand from auto zone so was told to buy an Ac Delco and see if that helps and also check the oil pressure sensor since its behind the distr. has anyone had any of these problems and if so what could be some causes and/ or some things we can look at to fix them
Thanks

 

[SunlitComet]

a crank sensor does not effect a oil pressure sender but if you heard tapping and knocking stop running it and consider replacing the oil pump and shaft. if oil level it good.

 

[Underpsi]

ok he said he can start it up just fine after replacing the alternator and starter. but now after about 10-15 mins of running the oil pressure starts dropping off. so he is going to start with getting a high pressure oil pump and seeing if that helps. before this he did add sea foam to the oil and when he changed the oil he noticed some gunk coming out of the oil when changing it after running sea foam through it. the previous owner said he changed out the oil pump when he swapped the heads out but could the pump go bad that quick?

 

[1995Tahoe]

so he is going to start with getting a high pressure oil pump and seeing if that helps. before this he did add sea foam to the oil and when he changed the oil he noticed some gunk coming out of the oil when changing it after running sea foam through it. the previous owner said he changed out the oil pump when he swapped the heads out but could the pump go bad that quick?

High pressure or high flow?

The oil pickup could be clogged from all the gunk that got loosened up. It's very possible it's been causing the oil pump not to work.

 

[Underpsi]

new oil pump was installed and when started it would jump up to 40 psi and stay there for about 10 mins then once the engine warms up it drops to about 10 psi... along with this there is some tapping still going on in the valve train it seems. didnt run it to long as not sure what could be the problem and it was not driven either just idled for about 10 mins

 

[drakon543]

If the heads were recently replaced pop the valve covers off and check to see how loose the rockers are. If the heads were replaced with new or rebuilt they should be retorqued after a period.