PBean Posted June 8, 2010 Share Posted June 8, 2010 Another one for you guys since you helped me with my other question. My RD Mack has a 350 E7 in it bought about 3 years ago its a 1995 runs good in very good shape 10 wheel with jake and has mack 13 speed trans truck will go on down the road when empty but when you put 20 tons on it the thing has no power at all.Does not smoke least little bit even in a strain.We got the truck at a really good price and it was a rental truck.Is it posible that because it was a rental truck some one turned the fuel adjustment down on it or is it something else.Did notice that the lead wire seal was broken on the cap where you would adjust the fuel seting on the back of the pump, truck only has about 250 thousand on it.Not realy wanting to turn up hihger than stock but just dont think its puting out would it should for a 350 hp truck.Should i just start adjusting the fuel up a little at a time to see if it makes a differnce or is there another way of checking it? Thanks Quote Link to comment https://www.bigmacktrucks.com/topic/14256-rd-mack-question/ Share on other sites More sharing options...
daveigou Posted June 8, 2010 Share Posted June 8, 2010 Everybody's perception is different. If you want to know for sure, if you want to get it right, run it on a dyno.Dave Quote See my Flickr photostream page http://www.flickr.com/photos/96692978@N05/ Link to comment https://www.bigmacktrucks.com/topic/14256-rd-mack-question/#findComment-56812 Share on other sites More sharing options...
HK Trucking Posted June 8, 2010 Share Posted June 8, 2010 Sounds like maybe the diaphragm is ruptured in the LDA, and the rack cant ever go to full fuel. Quote "If You Can't Shift It Smoothly, You Shouldn't Be Driving It" Link to comment https://www.bigmacktrucks.com/topic/14256-rd-mack-question/#findComment-56813 Share on other sites More sharing options...
fjh Posted June 8, 2010 Share Posted June 8, 2010 Another one for you guys since you helped me with my other question. My RD Mack has a 350 E7 in it bought about 3 years ago its a 1995 runs good in very good shape 10 wheel with jake and has mack 13 speed trans truck will go on down the road when empty but when you put 20 tons on it the thing has no power at all.Does not smoke least little bit even in a strain.We got the truck at a really good price and it was a rental truck.Is it posible that because it was a rental truck some one turned the fuel adjustment down on it or is it something else.Did notice that the lead wire seal was broken on the cap where you would adjust the fuel seting on the back of the pump, truck only has about 250 thousand on it.Not realy wanting to turn up hihger than stock but just dont think its puting out would it should for a 350 hp truck.Should i just start adjusting the fuel up a little at a time to see if it makes a differnce or is there another way of checking it? ThanksI agree with Herb, the smoke limit ( LDA) likly has a hole in it!The way to check it is to remove the line to where it goes on the manifold and suck on that line if it will not hold the vacuam you create with your mouth it has a hole in it and it needs replacing!Also you need to varify that the throtle is going to full fuel open! and the stop to fuel open. Quote Link to comment https://www.bigmacktrucks.com/topic/14256-rd-mack-question/#findComment-56816 Share on other sites More sharing options...
PBean Posted June 9, 2010 Author Share Posted June 9, 2010 I agree with Herb, the smoke limit ( LDA) likly has a hole in it!The way to check it is to remove the line to where it goes on the manifold and suck on that line if it will not hold the vacuam you create with your mouth it has a hole in it and it needs replacing!Also you need to varify that the throtle is going to full fuel open! and the stop to fuel open.I have checked the throtle it is opening all the way but will check out diafram and fuel shut off too thanks Quote Link to comment https://www.bigmacktrucks.com/topic/14256-rd-mack-question/#findComment-56833 Share on other sites More sharing options...
PBean Posted June 9, 2010 Author Share Posted June 9, 2010 (edited) Checked the fuel shut off it is opening all the way and also un hooked the line from the manifold about a 3/8 line that runs from back of pump to the manifold un hooked there and tryed sucking air though it did find some suction but was very hard to tell.Is it worth pulling the cap off off the pump where that line goes im asumming that is the diafram or LDA you guys are talking about.the housing is kind of shaped like there could be a diafram inside. Also noticed that the throttle at the pump opens all the way and then hits a stop that is like a idle screw .Can i find any specs for this Edited June 9, 2010 by PBean Quote Link to comment https://www.bigmacktrucks.com/topic/14256-rd-mack-question/#findComment-56841 Share on other sites More sharing options...
fjh Posted June 9, 2010 Share Posted June 9, 2010 Checked the fuel shut off it is opening all the way and also un hooked the line from the manifold about a 3/8 line that runs from back of pump to the manifold un hooked there and tryed sucking air though it did find some suction but was very hard to tell.Is it worth pulling the cap off off the pump where that line goes im asumming that is the diafram or LDA you guys are talking about.the housing is kind of shaped like there could be a diafram inside.Also noticed that the throttle at the pump opens all the way and then hits a stop that is like a idle screw .Can i find any specs for thisPull the 4 screws and have a look at the diphram its not that bigg of deal then you won't be guessing! Next you will need to check fuel preasure you need to tee into the system right at the fuel pump inlet you need 25 psi or better under fuel load!Your problem is fuel related as you have no excess smoke. Quote Link to comment https://www.bigmacktrucks.com/topic/14256-rd-mack-question/#findComment-56858 Share on other sites More sharing options...
Rob Posted June 9, 2010 Share Posted June 9, 2010 Pull the 4 screws and have a look at the diphram its not that bigg of deal then you won't be guessing!Hi Fred, I've never worked on this problem before but wouldn't it be prudent to replace the diaphram if you expose it? Can't really be that expensive I wouldn't think and could alleviate a problem further down the road.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/14256-rd-mack-question/#findComment-56860 Share on other sites More sharing options...
PBean Posted June 9, 2010 Author Share Posted June 9, 2010 Ok thanks alot for your help guys i like robs idea about replacing it once i expose it and i will check fuel presure also.Now is that whats called the puffer valve like on a 237 or does that motor even have that? Quote Link to comment https://www.bigmacktrucks.com/topic/14256-rd-mack-question/#findComment-56878 Share on other sites More sharing options...
fjh Posted June 9, 2010 Share Posted June 9, 2010 Ok thanks alot for your help guys i like robs idea about replacing it once i expose it and i will check fuel presure also.Now is that whats called the puffer valve like on a 237 or does that motor even have that?Does the same job as puff limit!yup replacing it like Rob mentioned can't hurt! It is getting old! Quote Link to comment https://www.bigmacktrucks.com/topic/14256-rd-mack-question/#findComment-56880 Share on other sites More sharing options...
PBean Posted June 10, 2010 Author Share Posted June 10, 2010 Ok thanks alot guys I realy apreaciate you taking the time to help me Quote Link to comment https://www.bigmacktrucks.com/topic/14256-rd-mack-question/#findComment-56924 Share on other sites More sharing options...
PBean Posted October 21, 2010 Author Share Posted October 21, 2010 Ok thanks alot guys I realy apreaciate you taking the time to help mejust now getting to work on this problem took off 3 flat head screws one with the plastic tamper proof piece on it the last one is what looks like a pop rivet or some kind of speacial fasnter i see more of them on the pump in other places can anyone help me with this trying to figure out how it comes out. also can i simply just change the diaphram.I read in the manual about this and it says you must take the pump off and have the settings checked seems odd because it looks like it is just a simple change out.thanks Quote Link to comment https://www.bigmacktrucks.com/topic/14256-rd-mack-question/#findComment-65618 Share on other sites More sharing options...
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