Bersaglieri
Ron Swanson's Brother
- Joined
- Jan 8, 2008
- Messages
- 1,957
A few years ago I pin timed my injection pump. The truck had many issues at the time it was something I could check off the general maintenance list without having to buy special tools or anything.
Fast forward to last week. Since I added compound turbos and larger injectors, and I had the proper tools, I figured it was time to advance the pump timing. I was also curious to see if the timing had slipped and where it was relative to plunger lift.
Now come the problems and confusion. From this point forward I'll try to keep things objective. I'm going to write everything out even if it's seems like common knowledge because I am screwing up somewhere.
Is this "common" knowledge correct? The Cummins is a 4 stroke diesel. Top dead center on #1 occurs after the intake valve closes, but before the exhaust opens as the motor [crank pulley] moves clockwise. The intake only opens once per full combustion cycle [720 degrees of crank rotation]. The injection pump operates in the same direction of the motor. So the plunger lift should be measured on the ramp as the motor rotates clockwise from the base circle of the pump cam.
Chronological order of events:
Found TDC [Or what we think is TDC]. Pulled an injector and used a dial indicator to find TDC and dwell time. TDC occurs after the intake valve opens but before the exhaust.
Read current timing. We got .15XX" which is around 11* Truck ran fine, no excessive white smoke, however the EGT's were a bit high and the truck would sputter at high RPM on a free rev.
Reset timing to what we though was .18XX" [16 degrees static] using plunger lift. The truck didn't want to start, it surged badly, blew smoke rings and white smoke. Truck injection pump sounded like a powerstroke's when revved. I added two clicks to each side of the GSK to see if the idle would bump up, it didn't. Turns out this time we read the gauge wrong or something and the truck was actually at .08XX plunger lift [2 degrees static]. We also found the #1 injector leaking between the injector hold down nut and the body. We tightened it down and didn't notice any more leaking.
Reset timing again. This time we set it to .198X [17 degrees static] plunger lift. We double checked it with the timing light today. The timing light showed 10 degrees. Injection pump wasn't noisy anymore. The truck was hard to start, lots of white smoke, had some occasional flame in the exhaust. Wouldn't surge too much but still wouldn't idle without holding down the pedal a little.
Reset the timing again. This time we were aiming to get the timing right using the timing light. We set the plunger lift for .2560" [24 degrees]. We measured it with the light and it was 19 degrees. Well the white smoke was a little less, but still too much. The truck still wouldn't idle unassisted but there was no surging. Now the screwed up stuff. We somehow noticed the upper radiator hose being hot and holding what seemed to be ALOT of pressure. However the radiator was not hot. I'm not sure what to make of that but my diesel buddy joked "it's probably just a blown head gasket."
So I called it quits for the day and went inside.
I'm contemplating eliminating some variables and pin timing it again. If it runs fine, then I'm just screwing up the timing, if not I'll know I developed other issues somewhere along the way.
What am I screwing up?
Fast forward to last week. Since I added compound turbos and larger injectors, and I had the proper tools, I figured it was time to advance the pump timing. I was also curious to see if the timing had slipped and where it was relative to plunger lift.
Now come the problems and confusion. From this point forward I'll try to keep things objective. I'm going to write everything out even if it's seems like common knowledge because I am screwing up somewhere.
Is this "common" knowledge correct? The Cummins is a 4 stroke diesel. Top dead center on #1 occurs after the intake valve closes, but before the exhaust opens as the motor [crank pulley] moves clockwise. The intake only opens once per full combustion cycle [720 degrees of crank rotation]. The injection pump operates in the same direction of the motor. So the plunger lift should be measured on the ramp as the motor rotates clockwise from the base circle of the pump cam.
Chronological order of events:
Found TDC [Or what we think is TDC]. Pulled an injector and used a dial indicator to find TDC and dwell time. TDC occurs after the intake valve opens but before the exhaust.
Read current timing. We got .15XX" which is around 11* Truck ran fine, no excessive white smoke, however the EGT's were a bit high and the truck would sputter at high RPM on a free rev.
Reset timing to what we though was .18XX" [16 degrees static] using plunger lift. The truck didn't want to start, it surged badly, blew smoke rings and white smoke. Truck injection pump sounded like a powerstroke's when revved. I added two clicks to each side of the GSK to see if the idle would bump up, it didn't. Turns out this time we read the gauge wrong or something and the truck was actually at .08XX plunger lift [2 degrees static]. We also found the #1 injector leaking between the injector hold down nut and the body. We tightened it down and didn't notice any more leaking.
Reset timing again. This time we set it to .198X [17 degrees static] plunger lift. We double checked it with the timing light today. The timing light showed 10 degrees. Injection pump wasn't noisy anymore. The truck was hard to start, lots of white smoke, had some occasional flame in the exhaust. Wouldn't surge too much but still wouldn't idle without holding down the pedal a little.
Reset the timing again. This time we were aiming to get the timing right using the timing light. We set the plunger lift for .2560" [24 degrees]. We measured it with the light and it was 19 degrees. Well the white smoke was a little less, but still too much. The truck still wouldn't idle unassisted but there was no surging. Now the screwed up stuff. We somehow noticed the upper radiator hose being hot and holding what seemed to be ALOT of pressure. However the radiator was not hot. I'm not sure what to make of that but my diesel buddy joked "it's probably just a blown head gasket."
So I called it quits for the day and went inside.
I'm contemplating eliminating some variables and pin timing it again. If it runs fine, then I'm just screwing up the timing, if not I'll know I developed other issues somewhere along the way.
What am I screwing up?
