Mackpro Posted January 24, 2023 Share Posted January 24, 2023 When was the valves adjusted last ? I had this MP8 a while back and had low power and constant regen requests. 2012 was the last time the valves were adjusted. Engine brake plungers unscrewed themselves and caused some weird issues. This can happen on all pre-common rail engines. Top one is flush, middle one is starting to back out and bottom one is way out. Mack sent out tools to all the dealers to tighten and loctite them 1 Quote Link to comment https://www.bigmacktrucks.com/topic/70938-egr-fault-mass-flow-to-high/page/3/#findComment-523694 Share on other sites More sharing options...
mdixon Posted January 24, 2023 Author Share Posted January 24, 2023 You know I was thinking about pulling the valve cover next time I get it. I'm gonna have to to replace the wiring harness anyways, I'll be running the valves then. Egr dp koeo is -.1 to 0.0. Koer it's the same until the engine starts boosting at idle. Egr tests cold cause near stall drop in rpm, turbo speed <1000rpm very quickly. I'm still getting spikes in dp up to 3.4 when valve shows 0%, and my temps still drop by 150° randomly. I'm going with faulty harness with bad data causing overfuel/over command of the egr. The actuator is new, it ran fine for a month no complaints and no issues when I checked it 2 weeks ago. Quote Link to comment https://www.bigmacktrucks.com/topic/70938-egr-fault-mass-flow-to-high/page/3/#findComment-523700 Share on other sites More sharing options...
mdixon Posted January 24, 2023 Author Share Posted January 24, 2023 8 hours ago, fjh said: So not being a Guru on this How ever Our guys used to look at the fuel preasure to the 7th the reg to that injector would go fubar and need replacing or shimming could this be the case here? just asking! MP OXY ? So fuel pressure during regen in 55psi, 7th injector psi +-3. I haven't verified this yet though. Quote Link to comment https://www.bigmacktrucks.com/topic/70938-egr-fault-mass-flow-to-high/page/3/#findComment-523701 Share on other sites More sharing options...
mdixon Posted January 24, 2023 Author Share Posted January 24, 2023 Ill also say after running those regens, I drove it around the farm for 30 minutes, no codes went active. Soot level didn't rise at all, but I never got over 20mph. I don't have a CDL so I stay off the roads, no farm plates on these. It's been sent back to work, ran all day today. Quote Link to comment https://www.bigmacktrucks.com/topic/70938-egr-fault-mass-flow-to-high/page/3/#findComment-523703 Share on other sites More sharing options...
Mackpro Posted January 25, 2023 Share Posted January 25, 2023 5 hours ago, mdixon said: So fuel pressure during regen in 55psi, 7th injector psi +-3. I haven't verified this yet though. MP fuel pressure should be 55 psi idle and 65 psi at 1100-1200 rpm( regen speed). I’ve seen it lower but during a regen 57-58 psi would be my low limit. I’d be changing fuel filters, cleaning out fuel line banjo fittings and checking fuel pressure relief valve in the head. And the fuel shutoff valve/AHI fuel pressure should be the same as engine pressure when activated. Quote Link to comment https://www.bigmacktrucks.com/topic/70938-egr-fault-mass-flow-to-high/page/3/#findComment-523746 Share on other sites More sharing options...
Mackpro Posted January 25, 2023 Share Posted January 25, 2023 On the EGR differential pressure. Ive noticed on the new updated sensor with the new style Venturi pipe. During a regen using Tech Tool I see the pressure spikes that you talk about. It happens only for a second. I thought I had a bad sensor so replaced it and still same split second spike. I noticed it on several trucks. Quote Link to comment https://www.bigmacktrucks.com/topic/70938-egr-fault-mass-flow-to-high/page/3/#findComment-523747 Share on other sites More sharing options...
mdixon Posted January 25, 2023 Author Share Posted January 25, 2023 5 hours ago, Mackpro said: 55 psi idle Once warmed up this truck only making 40-45 at idle. Quote Link to comment https://www.bigmacktrucks.com/topic/70938-egr-fault-mass-flow-to-high/page/3/#findComment-523752 Share on other sites More sharing options...
Mackpro Posted January 25, 2023 Share Posted January 25, 2023 2 hours ago, mdixon said: Once warmed up this truck only making 40-45 at idle. There is a fuel pressure relief valve on the front of the head . More towards the driver side of head . It’s more like a banjo fitting that goes through a fuel line that runs back down to the fuel filter stand. The original valve was hex headed all the way to the end of the valve . The new updated valve is rounded on the end. Replaced lots of the old style valves for low fuel pressure issues. I don’t know the date the new valve came into production but somewhere between 2012-2014. Top pic is old style . Bottom pic is new style . Quote Link to comment https://www.bigmacktrucks.com/topic/70938-egr-fault-mass-flow-to-high/page/3/#findComment-523755 Share on other sites More sharing options...
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