pump stumble?

Lucky Jeff

Lucky Jeff

Stock Sucks
Joined
Apr 3, 2007
Messages
5,784
I can't seem to find anyone that can figure this one out yet. When I hit the throttle real quick in 1st, the truck will cut out a few times real quick. I was able to get it do it in 3rd when I was screwing around on some gravel roads this weekend too but just once real quick.

The timing was set a couple years ago at 15.5* and re-checked by DDP a year ago. Fuel pressure is right where it should be. I know my power is down quite a bit lower then it should be last time I ran on the dyno. I had a blown head gasket at the time but it was between the oil and water passages so I don't think that would have caused any power loss..
 
I know how the timing feels, I've felt it on other trucks. And it's always when you try and run the RPM's too high. Mine will do it throughout the RPM range, the motor just has to rev fast enough to do it. This one has had the timing checked twice so far and has never shown any signs of slipping.
 
what about the overflow check valve? Maybe have a plunger hanging up in the P7100? Does it do it hot or cold?
 
Snedge said:
what about the overflow check valve? Maybe have a plunger hanging up in the P7100? Does it do it hot or cold?
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I have no idea if it does it cold. I'm always too afraid to nail it if the temps not up.
 
My truck experiences similar problems once in a while after it does it there's a big puff of white smoke?

Justin
 
It's at 15.5*... I'm not one to give it a bunch just cause I can, I still want to keep it reliable.
 
mine's currently at 15.5* and does the same thing you describe... been lazy about bumping it... been down this road before... a stumble on free rev or hard acceleration in lower gears without enough boost = not enough timing.

I'm planning on setting mine at 18.5 or so. try 17, should help and shouldn't hurt the stock head gasekt
 
Good info thanks my timing is set at 15.5 and stumbles on Free Rev and low boost sounds like it's time to buy the head studs and bump the timing.

Justin
 
Forrest Nearing said:
it'll usually be worse when it's cold, and a larger later spooling turbo will make it more pronounced.
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well that explains a lot.. This new turbo doesn't like to lite..
 
the higher the timing, the higher the RPM you're optimizing... too much timing can make the engine feel soggy down low and hurt spool up, but too little timing hurts in other ways. if you've got your timing set to optimize a stock turbo and about a 2800rpm power band, putting a bigger turbo on it means you're no longer optimized.

I think you'll like the truck with a couple/few more degrees in it
 
I'm set at 19* and it feels great...actually I think the engine wants more....with the stock injectors I was running around on 23* timing unknown thanks to a particular cummins only shop out here who said he just "bumped" it a few degrees....yeah like 10!!!

but I have too much power for my tire anyway as it is....gettin new ones this week....and a posi :) so who knows...maybe I'll push it up again
 
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