98 3500 12 valve cummins knock
 

So, a few weeks ago my brothers and I replaced the stock turbo on his 98 3500 cummins. We were running 40 psi for about 3 minutes until we warped the head and blew the head gasket. So that inspired us to install arp head studs, 60lb spring and cummins oem head gasket. The head was shaved ".012 by the local shop. After the re-assembly the truck ran great. Several test drives later we wanted to test the new turbo and arp studs. We did a few pulls upto 40 psi. We figured the truck was good. When I drove it from my house back to my brothers house, about 80 miles of highway. While driving I did several pulls uphills without issue. Egt's maxed at 1300, water temp stayed at 190. While cresting a hill, as I let off the throttle the truck "coughed", blew a quick puff of white smoke. As I put the truck in neutral to pull over, the engine stalled. I checked everything out. Found nothin obviously wrong. The truck started right back up and drove fine. But after 10 miles I noticed a slight knock. It was worse at idle and faded away at 1500 rpm. We had the injectors pop tested, which all nozzles released at 220 bar. Factory is 260 bar. We readjusted the valve lash but still have the knock. It's loud all around the engine and now hazes a lot. Any input would help. The truck is a 5 speed manual, bd superb turbo, arp head stud, 215 hp pump set at 16 degrees. Fuel plate ground to 0.

Also I had at steady 40 psi oil pressure before durning and after the incident. The truck is a 96 not a 98...

An injector could have just failed on you. Sometimes theres no warning. Might also be a piston wrist pin issue. Get a mechanics stethoscope and start probing around the head and injectors as well as the bottom end. That should help narrow things down a bit.

That was my next step, the truck is at my brothers house and he's been workin on it. He says he's narrowed the noise down to bottom driver side. It's noticeable everywhere but it's loudest driverside bottom. He thinks it might be the lift pump. Truck is hard to start and has 190k.

if it has the stock lift pump, might what your hearing its driven off the cam. post up a vid

My brother installed the new lift pump today. It's still knocking.. Any ideas?

I know this is an old thread but I would really like to know the solution that u came up with