esde

I recently noticed a new sound from the 12 valve in my truck. It is only under load/ acceleration from about 1k on up. I have checked the valves and they are adjusted correctly. Pulled the hood and drove w the windows opened to try and figure what is making it, it's coming from the pump side of the engine. I have the 160hp california pump, it came with a #6 plate, and a 3k GSK though I haven't verified the spring. I have the plate and star wheel adjusted so it makes good power w out a lot of smoke. Any thoughts on what to check or look before pulling the pump and taking it to a shop? Like I said, it's only under load. If I manually downshift to slow down and the rpms go up, it doesn't make the noise at all. It's making me nervous. Thanks.

infidel

First thing to do is check fuel pressure.
Instructions> http://www.cumminsforum.com/forum/94...-12-valve.html

esde

Took a while for me to find the time, but I tapped the supply bolt and installed a gauge as suggested. 12-14psi at idle, 25psi max around 2000 rpm. I also bought, but have yet to install this
http://www.torkteknology.com/product...VE-OFV010.html
was suggested on another thread. There are some good tech articles on fuel pressure to be read on that site as well. So the sound is still there, just under load, and only above 1000 rpm. Thoughts? My gut tells me the pump is going to have to come off, go to a shop to get run on the bench. Down side is the cost, upside is I'll get to reset the timing to 15 degrees.

infidel

Personally I'd replace the lift pump before going as far as rebuilding the injection pump.
Cummins or geno's garage have the best prices on pumps.

What helps immensely when replacing the pump is to toss the stock pump bolts and replace with a pair of 8mm x 30mm x 1.25 pitch studs with nuts.

esde

Infidel, thank you. I am going to put in the new overflow valve today, as I have it, and will see what my pressure is afterwards. I have most of the receipts for the truck, none indicate lift pump or overflow valve, so it might be time. Do you know what the minimum and maximum pressures for the stock lift pump are when new?

esde

New overflow valve in, 20-25 psi at idle, 30+ psi at 2000 rpm. I bought a shitty gauge, getting a better one next week so exact #s are hard to get. It's raining and slippery, so I haven't nailed it to see if the noise is still there. Kind of hard to watch the gauges, listen, and keep the truck in a straight line all at once.

infidel

Your pressure readings are perfect.
Your lift pump can make great pressure and still tick though.
What happens is the spring that keeps the pump piston tight up against the cam gets weak or breaks and the piston slaps against the cam with every engine rotation causing a tick.

I've never experienced it personally but have heard that many miles of this slapping/ticking can ruin the lobe on the cam.

esde

Thank you Infidel! the noise is still there, though somewhat less loud. I'm speculating that pumping against the new overflow valve has lessened the clatter. Just picked up the studs and nuts, next to order the lift pump. I've heard of people removing the starter and getting it from below, but I had another thought. Has anyone removed the drivers wheel and plastic inner fender? Looks like it would be a much more comfortable way to go about it.