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Hey guys. My name is Brian. I have been lurking for a while trying to learn some things about the Duramax and HD trucks. I would like to buy one in the next year or so. Right now I have a 1972 Nova and a 1993 S-10 daily driver.


I have a question about the fuel system on these trucks. Did I read right that there is no in-tank pump like gas engines have? There's an injection pump on the motor? Is this how you can get away with using rubber hose and hose clamps for the install of the Nicktane filter kit? It's only low psi until it hits the injection pump on the motor?


Also how many PSI does the fuel system operate at? Isn't it really high. I thought I've heard that's why the Duramax engine runs so quiet. Thanks for the answering my beginner questions.


Brian
 

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Brian,
You are correct. The stock Duramax does not have a pump in the tank. Tank mounted pumps are problematic for diesel fuel since the vapor pressure of diesel is low enough to allow a mixture of oxygen and diesel vapor in the tank - a spark form a pump wouldn't be good (Gasoline vapor pressure is much higher and it forces all the air out of the tank so tank mounted pumps are not a problem). Regarding the dmax fuel pumps, there is a "dual" pump mounted on top of the engine that consists of a low pressure gear pump that feeds the high pressure rotary piston pump (Frank did I get that right?
). So the lines feeding the LP pump are under vacuum (about 2-4 inHg at idle). The output of the High Pressure pump feeds the common rail injection system with pressures up to 23,000 psi. The reason the Duramax is quiet is mainly due to pilot injection. The injection system is programmed to give a little squirt (pilot injection) followed by a big squirt. The result is less "diesel rattle".

By the way how do like your 93 S10. My 16 year old daughter is driving now and she has her heart set on getting a pickup truck - a used S-10 is her first choice (has to be a Chevy of course). Any pointers? Which engines are the best? …

 

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Thanks for the info? One more question-- what does a lift pump do? Is that just an auxillary pump to get fuel to the stock pump on the motor?


My S10 is great. It has about 87,000 miles on it with very few problems. I've owned it for a year now and put about 12,000 miles on it. Before that my friend had it and the only thing he had to replace was the fuel pump. It smokes a little on startup because it needs valve seals, but that's a common problem. I get 18-19 mpg with a 4.3 V6, 4L60E trans, and 3.42 posi rear. The only thing wrong is the bed is starting to rust where it bolts to the frame. Mechanically there is nothing wrong. I want to get about 150,000 miles out of it then retire it and buy my Dmax. A good site to check out is www.s-seriesforum.com
 

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The Bosch fuel injection system is designed to have the supply line run at a slight vac. However, in High HP uses, (read High fuel usage), the engine will not get enough fuel. So, guys will run an in-line lift pump, (read booster pump), back at the tank area to ensure that the appropriate amount of fuel is delivered when neccessary.


The other reason is to overcome cavitation head losses from adding an additional fuel filter in the engine area when ambient temps tend to run higher than under the truck or real wheel well.
 

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DavesDmax said:
The Bosch fuel injection system is designed to have the supply line run at a slight vac. However, in High HP uses, (read High fuel usage), the engine will not get enough fuel. So, guys will run an in-line lift pump, (read booster pump), back at the tank area to ensure that the appropriate amount of fuel is delivered when neccessary.
where are you guys finding info about in-line pumps or what not? i searched for hight fuel usage, and booster pump. found nothing. am i doing something wrong? dont know where to begin.
 
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