lift pump pressure?

[welpro222]

Hey guys, i recently installed a lift pump pressure gauge inline to my injection pump, when running the gauge fluctuates between 9-11 psi. Is it suppose to jump like that or be a steady reading? I have a mechanical lift pump. Also after shutting off the vehicle the pressure drops after a few hours?

 

[welpro222]

help

 

[Skinny]

What is the reason for the pressure gauge? Are you having hard start or low power symptoms?

I would imagine you would get some pulsations with a mechanical lift pump. As far as your pressure, I would consult the TM for a spec.

 

[welpro222]

I had a extra lift pump gauge and decided to permanently install it. No problems with engine or starting, just wanted to know if these things were normal.

 

[MarcusOReallyus]

I don't know about the pulsating, because I've never looked at a gauge on the lift pump, but those numbers sound right.

 

[cpf240]

Of course, one could look in the TM to find the spec, as well as the test procedure...

 

[doghead]

Are you using rubber hose, that will show pulsing at the gauge.

 

[welpro222]

Im using standard fuel line hose

 

[rsh4364]

I have fuel psi gauge into filter and 1 for after filter,they bounced around a bit like yours,was told small air bubbles was cause.They have since equaled out and read steady.

 

[Barrman]

I have a psi gauge on my M715 with the 6.2. At idle, the gauge will flip around between 6-10 psi. Going down the road it is steady at around 6 psi.

I have always attributed the pulsing at idle to the mecahnical pump pumping fuel that has no place to go since the engine isn't using very much at idle. When going down road, the fuel is used as pumped. Whatever the theory, 2 years of running and no issues from me.