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hello. Please forgive my Diesel ignorance, but i am still new to diesel. Can someone please explain to me what exactly is a "lift pump", what does it do? where is it located? and what does it look like (if it can be described) ? I am still trying to figure out my "chugging" problem, (i think maybe 3 posts ago) and am wondering about fuel pump, and lift pump - i read skippee's post about power - kind of sounds like my problem, except sometimes i have a LOT of power for a few seconds, but most of the time it just idles off-and-on like, and stalls. or on highway "chugs" along rocking the truck back and forwards (feels like) i have an 88 6.2 silverado, and again please forgive my ignorance, but i am new to diesel, and want to learn. Also, does my truck have a lift pump ??


thanks again, from reading posts here, you all sound like very knowledgeable and helpful people.
 

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Lift pump is a mechanical fuel pump on the right front lower ection of the engine. It is just like on a old chevy gasser.


The lift pump moves fuel from the tank to the fuel filter. It has a check vavle in it to hold pressure.


Testing it, well it should build 14 psi while cranking, and should hold 14 psi when stopped.
 

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well,


I have a 89 GMC 3500 , and the lift pump according to the gm cataloge (88-91) it's a mechanical fuel pump on the right hand side of the motor, BUT my 89 doesn't have that, I have a electric pump on the frame right under the drivers door, (on the inside) this is the setup on the 92- and up trucks, if yours has the electric there should be a relay on the firewall on the pass side, that is the problem my truck had, ( i think) I bypassed the relay and ran power to the pump and now it's fine, truck has lots of power, if you run power to the pump you should hear a ticking noise (sounds like a fish pump) if not the pumps shot... hope this helps





Todd
 

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Also, there are two pumps, lift pump and injection pump. Your lift pump pumps to the injection pump(the injection pump shouldn't really have to pull the diesel) when you say its rocking back and forward, it sounds like the same problem I had when one of my injectors werent firing... you might check them, just one not working can cause a pretty bad rocking situation. Not to mention the power loss.
 

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hope you found your lift pump by now. don't want to startanything but i never got that much psi from a lift pump (mechanical type). but try teeing in a gauge any monitor the psi before the injection pump. it should raise or stay steady as you rev the engine but definatly not get less. if so the pump is bad and then the injection pump is sucking the fuel all the way from the tank, and if there are any leaks along the way the engine realy shakes as is geting air into the system. if you do have the electric fuel pump don't bypass the relay as it's a safety also if you loose oilpsi it shuts down or in the case of a crash it stops fuel from continueing to pump.
 
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