fatmike Posted July 8, 2021 Share Posted July 8, 2021 Im working on a buddies truck. Im a peterbilt CAt guy and know My way around Cats only. I know nothing about Macks so I need your help. I have driven plenty of MAck rd trucks that i believe were e7 350's. They had plenty of power down low for what they were as i remeber pulling 23 ton payloads. The truck im dealing with is a 2000 mack rd triaxle dump with e7 400 motor in it. I drove it empty and it is indeed no power. No Boost gauge in truck but working on that. Put a load in that truck and its not going anywhere off the line. Heres the biggest thing that is the issue. The previous owner put a S400 turbo on it. Mack part number 631gc5173amx. According to the previous owner, MAck dealer installed it a few years back. I called local mack with vin. Truck came with from the factory an s300 part number 631gc5174amx. Borg warner cross reference to 174822. With that being said, no stage 2 injectors or tune was done with this. Would this s400 make this much lag and no power without supporting mods? And will the s300 wake this truck back from the dead on the low end? I have seen this on Cats before. Where the nimrod would slap a bigger turbo on thinking its gonna do anything but make life hell without supporting mods. Complete dog. Like i said, i know NOTHING about macks and thats why im hear. Dont want to assume ANYTHING and cost someone money. Yes i did pressure test on the system to check for leaks anywhere going into the cac and motor. Fuel filters done etc, Turbo spins freely and all good Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted July 8, 2021 Share Posted July 8, 2021 Mack's are slow and deliberate... What you have is an E-Tech. How much of the repair history do you have? The S400-SO41 turbo was used a lot on the 350/400's,and I think the 427, if I recall correctly. So with little info right now. Before I go into a Mountain when you may have a molehill,,, I will wait for more info and comments from the many "Very smart" people here... Jojo Quote Link to comment Share on other sites More sharing options...
John3406 Posted July 9, 2021 Share Posted July 9, 2021 Put a manifold pressure gauge on it and report back. That being said macks drive different then any other truck. Anyone who usually drives cat or cummins and then jumps in a mack will say the mack has no power. They weren't built for racing but go run your cat with a mack and look in your mirror the mack will still be there 2 Quote Link to comment Share on other sites More sharing options...
fatmike Posted July 9, 2021 Author Share Posted July 9, 2021 Eh, You guys arent understanding. I said that i have driven a number of mack rd with e7. They had plenty of power and were good trucks. So i know how they run. Im working on a truck that has NO power and wrong turbo on there. I dont feel like rewriting whole first post again. So please reread and give me your input. There is key points in the post. It was not a selfish post about Cats vs macks. Trying to verify something. Boost gauge is going on Thank you Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted July 9, 2021 Share Posted July 9, 2021 Have you checked fuel pressure? There was an issue with the lift pumps slipping. I have replaced dozens of them. It's an easy inspection to do... Pull the lift pump off and see if the plastic gear is slipping on the pump shaft. When this part of the fuel system is good... the pressure should be, between 80-100 PSI... The regulator is in the block, right side, below #4+#5 cyl. it's a 45 degree fitting, #6 J.I.C. fitting and may have a 1/4" barb on it with the plastic return line hooked to it. for what it's worth, I /We,do understand, You asked for help and we will ask for more info, so that we can help you the best way possible.. Keep posting, and we will get this fixed.. Jojo 1 Quote Link to comment Share on other sites More sharing options...
Onyx610 Posted July 10, 2021 Share Posted July 10, 2021 (edited) I was thinking the same thing about the gear slipping as well. Def sounds fuel related. Edited July 10, 2021 by Onyx610 Punctuation Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted July 10, 2021 Share Posted July 10, 2021 It can affect idleing, It may stumble or raise up and down about 25 rpm's. with a pressure gauge on it, you can press throttle to 100 percent, and see the fuel pressure drop, rather than raise.... dont even have to drive it.. 1 Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted July 10, 2021 Share Posted July 10, 2021 How's the diag, goin? Quote Link to comment Share on other sites More sharing options...
fatmike Posted July 11, 2021 Author Share Posted July 11, 2021 thank you! Have no idea why i didnt check fuel psi first thing on this truck. Just assumed the turbo with lag. I cant get to it till later this week. its been running and im swamped. Where can i thread in my fuel gauge on these motors? Quote Link to comment Share on other sites More sharing options...
Onyx610 Posted July 11, 2021 Share Posted July 11, 2021 I believe there are 2 plugs on the back of the block inline with the EUP’s. Also I think there is one on the front of the block above the crankcase vent canister lid. Or you could tee a gauge into the outlet of the lift pump. 1 Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted July 11, 2021 Share Posted July 11, 2021 I have a kit I put together years ago, with different fittings. I "T-in" where the regulator comes out of the block. If you have a fuel sensor on the regulator, that is good, because you can put the "T" there and plug the sensor back in so you dont create codes, and read it there. 1/4" NPT threads. I have had success with this approach. Jojo 1 Quote Link to comment Share on other sites More sharing options...
fjh Posted July 12, 2021 Share Posted July 12, 2021 (edited) The one at the front behind the blo by can is the quickest 3 inch i1/4 pipe-nipple and an elbow adapted to what ever gauge you have ! you need to take the top off the bloby can to install the nipple! Edited July 12, 2021 by fjh Quote Link to comment Share on other sites More sharing options...
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