Need some help guys...

paint94979

paint94979

Beer Nazi
Sep 18, 2006
11,714
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so long story short 2010 LMM comes into my buddies shop for a lift pump PPE to be exact. After fire up the truck had injector rattle and lope. Checked RP and it was commanding 4,351 actual was roughly 10,000. Verified psi at fuel filter housing was good, it was 11psi. We changed fuel filter. At idle rail pressure is 10,000 but reving in park or drive actual follows commanded to 19,000 psi but truck won't command over that. Truck runs really shitty. Then we thought it was the regulator... maybe should got through and is causing it to stick? change out with a brand new LMM regulator no change. Thinking rail pressure sensor has failed? balance rates at idle are 0.x with one being 1.x so there doesnt appear to be an issue there. Kinda lost.
 
02greysixer

02greysixer

Active member
Jun 4, 2011
1,829
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North Central FL
What did they tap for the key on signal wire to the lift pump relay? I agree it sounds like the rp sensor, but weird it started after the pump was put on.

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paint94979

paint94979

Beer Nazi
Sep 18, 2006
11,714
7
38
37
Ya it has RP issues with the pump on or off. I also used the DVT function and commanding 26k and it followed however if i commanded 0.0 it wouldn't drop below 10,000 neither turn off like it should have?
 
02greysixer

02greysixer

Active member
Jun 4, 2011
1,829
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38
North Central FL
What's it read for rail pressure with key on engine off? Anything more than 150 psi or so kind of points to an issue there

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NC-smokinlmm

NC-smokinlmm

<<<Future tuna killer
May 29, 2011
5,053
252
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At Da Beach
Muff said:
That wasnt at all meant to be taken as me being a smartass. I was interested in learning how to do what you had mentioned? Sorry for coming across wrong.
Click to expand...

My bad...:eek:

Ohm testing is a measure of electrical resistance. To put it simply. Each electronic devise has a specfic set of ranges in which it operates. You can test these ranges with a multimeter, but first you need to contact the manufacturer for a spec sheet. If the devise has a short or bad resister in the board for example, the ohm specs will be off thus indicating a internal issue that requires repair or replacement. It is the easiest and most basic way of starting to diagnose anything electrical...
 
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