theakerstwo Posted December 9, 2021 Share Posted December 9, 2021 That return fitting in the photo is the orfice type.If it was me i would try another gauge because that gauge there is one of them i always said may not be or it may be right. 1 Quote glenn akers Link to comment Share on other sites More sharing options...
rhinoo Posted December 9, 2021 Author Share Posted December 9, 2021 2 hours ago, fjh said: that is a manual pump and that drainback system is what was normally used on VMAC pumps how ever doesnt mean it can't be used on the manual pump! The T style is what I would think should have been on there! I called Mack earlier and asked them about the return side fittings. I could tell me and him were describing something different so I asked for a diagram of the pump. A transplant like you mentioned would make sense because according to my serial number it shows in the diagram it should have and overflow valve plumbed in coming out of the injection pump. I guess possibly someone removed it or this motor did not come in this truck and has a different return system on it. In the diagram (cb) is called an overflow valve. Quote Link to comment Share on other sites More sharing options...
rhinoo Posted December 9, 2021 Author Share Posted December 9, 2021 Just now, rhinoo said: I called Mack earlier and asked them about the return side fittings. I could tell me and him were describing something different so I asked for a diagram of the pump. A transplant like you mentioned would make sense because according to my serial number it shows in the diagram it should have and overflow valve plumbed in coming out of the injection pump. I guess possibly someone removed it or this motor did not come in this truck and has a different return system on it. In the diagram (cb) is called an overflow valve. Quote Link to comment Share on other sites More sharing options...
br549 Posted December 9, 2021 Share Posted December 9, 2021 What is the model and last 6 of the VIN, i will ck and see what it came out with. If your only complaint is the lag, I seen truck with that fuel pressure give no problem if it dont go lower under a load. If you want it to get rid of the lag, you need to ck the line and diaphgram I talked about in an earlier post. If it is OK I would pull the plug on top of the governor and you can adjust the pick up when you mash the pedal, it will get rid of the lag. it will give the fuel faster, but will put out a little bit of smoke. Quote Link to comment Share on other sites More sharing options...
rhinoo Posted December 9, 2021 Author Share Posted December 9, 2021 14 minutes ago, br549 said: What is the model and last 6 of the VIN, i will ck and see what it came out with. If your only complaint is the lag, I seen truck with that fuel pressure give no problem if it dont go lower under a load. If you want it to get rid of the lag, you need to ck the line and diaphgram I talked about in an earlier post. If it is OK I would pull the plug on top of the governor and you can adjust the pick up when you mash the pedal, it will get rid of the lag. it will give the fuel faster, but will put out a little bit of smoke. Vin# 037403…thanks Quote Link to comment Share on other sites More sharing options...
rhinoo Posted December 9, 2021 Author Share Posted December 9, 2021 Just now, rhinoo said: Vin# 037403…thanks Just now, rhinoo said: Vin# 037403…thanks Rd688s Quote Link to comment Share on other sites More sharing options...
br549 Posted December 9, 2021 Share Posted December 9, 2021 Truck built 2/24/98 E-7350 Mechanical engine 1996 EPA Quote Link to comment Share on other sites More sharing options...
rhinoo Posted December 9, 2021 Author Share Posted December 9, 2021 1 minute ago, br549 said: Truck built 2/24/98 E-7350 Mechanical engine 1996 EPA So, what’s there is possibly original it sounds like. I did notice the tag on valve cover said 1998.. I just removed that plastic line on intake that goes to diaphragm and sucked hard on it and it held a vacuum. Someone mentioned a different gauge so I guess I will check that too. That is a Matco gauge I’ve had for years but won’t hurt to eliminate that. Under load with boost pressure the fuel drops to almost 10 pounds according to the gauge I have on it. I just wonder why according to the diagram that Mack sent it appears to be missing that over flow valve? Quote Link to comment Share on other sites More sharing options...
br549 Posted December 9, 2021 Share Posted December 9, 2021 Truck built 2/24/98 E-7350 Mechanical engine 1996 EPA Quote Link to comment Share on other sites More sharing options...
br549 Posted December 9, 2021 Share Posted December 9, 2021 By the picture it also shows it came out with to fitting with a small pin hole in it from factory, not the old style over flow valve in the picture the sent you. We have also seen the plastic tubing that goes to the intake mainfold have a pin hole in it, we would pressure check the tube and diagphram together. Like I said if TURBO LAG is the only problem pull the allen head plug on top of the governor and there is a cog wheel like a brake adjuster in there, I think you turn the cog wheel toward you from the side and you can get rid of the lag, we would turn the wheel a few cogs and test drive down the road and if not enough pull over and adjust more till we got what we wanted, just a small amount of smoke and quick pickup. I will say no more. Good Luck 2 Quote Link to comment Share on other sites More sharing options...
fjh Posted December 10, 2021 Share Posted December 10, 2021 Myself I am quite surprised this 98 truck was still built with a mechanical fuel pump! i was under the impression that only carried on from 3 years past 93 introduction of VMAC! 1 Quote Link to comment Share on other sites More sharing options...
fjh Posted December 10, 2021 Share Posted December 10, 2021 On 12/8/2021 at 7:41 PM, rhinoo said: I have a question? Did you blow out the lines leading to the fuel pump before you did the bucket test ! Don't forget this is a 20 year old + truck with 20 year lines on it! ( I am still fixating on the low fuel pressure) under load what kind of boost did it make get 20 psi boost? 24-27 would be more in line in the real world! The book spec is always 24 but in reality boost is usually higher! Just askin! Quote Link to comment Share on other sites More sharing options...
br549 Posted December 10, 2021 Share Posted December 10, 2021 VMac 1 came out in 1990, VMac II came out sometime around 1995. Mechanical pumps were available until the VMac III ETech came along. Quote Link to comment Share on other sites More sharing options...
fjh Posted December 10, 2021 Share Posted December 10, 2021 3 hours ago, br549 said: VMac 1 came out in 1990, VMac II came out sometime around 1995. Mechanical pumps were available until the VMac III ETech came along. AH ! Quote Link to comment Share on other sites More sharing options...
rhinoo Posted December 15, 2021 Author Share Posted December 15, 2021 Just wanted to update on the truck: I had ordered a set of stage 2 injectors from Rochester diesel and was wanting to fix the fuel pressure issue first but after not much luck figuring it out I decided to go ahead and change them out. After getting them installed and took the truck on a test drive my fuel pressure problem was fixed. Went to 20psi just off idle and 40psi at wot. Under a load it would hold around 26psi.. doesn’t really make sense but that’s the result. I adjusted the cog wheel in the governor and removed all of the lag. I am impressed with how it is running now. Pulling hills in 2 gears higher than previously. Egt’s are a little warmer than what I would prefer but I think it will be ok if i keep an eye on it. 35psi boost and egt goes to 1000 in a long pull for usually no longer than 20 seconds. Does that sound ok or too hot? 1 Quote Link to comment Share on other sites More sharing options...
Onyx610 Posted December 15, 2021 Share Posted December 15, 2021 Well maybe the whole root cause of this was just leaky worn out injectors…🤷🏻♂️ 1 Quote Link to comment Share on other sites More sharing options...
Dirtymilkman Posted December 15, 2021 Share Posted December 15, 2021 That sounds pretty sweet running. 35psi is a lot of boost so you're making some power. 1 Quote Link to comment Share on other sites More sharing options...
fjh Posted December 15, 2021 Share Posted December 15, 2021 12 hours ago, rhinoo said: Just wanted to update on the truck: I had ordered a set of stage 2 injectors from Rochester diesel and was wanting to fix the fuel pressure issue first but after not much luck figuring it out I decided to go ahead and change them out. After getting them installed and took the truck on a test drive my fuel pressure problem was fixed. Went to 20psi just off idle and 40psi at wot. Under a load it would hold around 26psi.. doesn’t really make sense but that’s the result. I adjusted the cog wheel in the governor and removed all of the lag. I am impressed with how it is running now. Pulling hills in 2 gears higher than previously. Egt’s are a little warmer than what I would prefer but I think it will be ok if i keep an eye on it. 35psi boost and egt goes to 1000 in a long pull for usually no longer than 20 seconds. Does that sound ok or too hot? Strange But Nice! Your getting the boost of a stock 427 a little under a 460 37 - 40 ! Good job! You can bump a thousand for a bit and not hurt anything as long as the boost doesn't start falling off to much ! 1 Quote Link to comment Share on other sites More sharing options...
rhinoo Posted December 15, 2021 Author Share Posted December 15, 2021 7 minutes ago, fjh said: Strange But Nice! Your getting the boost of a stock 427 a little under a 460 37 - 40 ! Good job! You can bump a thousand for a bit and not hurt anything as long as the boost doesn't start falling off to much ! I ordered a set of valve cover gaskets for it since they are seeping a little. I figured I will go ahead and run the over head while covers are off. Does .016 and .024 sound right for that engine? Definitely harder to find info on these motors vs cat or cummins. I briefly looked for a pointer on front cover at the damper and saw a piece of casting that could be a pointer possibly but wasn’t sure. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted December 15, 2021 Share Posted December 15, 2021 .016 int. .024 exh. .021 eng. brk.. if the jake heads are updated, .017 if they are not.. jojo 1 1 Quote Link to comment Share on other sites More sharing options...
fjh Posted December 15, 2021 Share Posted December 15, 2021 10 minutes ago, Joey Mack said: .016 int. .024 exh. .021 eng. brk.. if the jake heads are updated, .017 if they are not.. jojo There should be a pointer in the engine housing The marks Valve set and TDC on the flywheel 2 Quote Link to comment Share on other sites More sharing options...
Dirtymilkman Posted December 15, 2021 Share Posted December 15, 2021 These are the easiest engines to run an overhead on. Take the little rectangle inspection cover off the bellhousing and on the flywheel you will see marks with two numbers by each one. There is like a gun sight where the inspection cover was and you line that up with the mark on the flywheel. The two numbers by the mark are the pistons which valves you can adjust. So if there's a 1 and 3 you go on top and check number 1 and 3 cylinder and see which one the rockers are loose and adjust that one. Then you'll turn the motor till you see the next line on the flywheel and do that hole. Two turns of the flywheel and you're done. 1 Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted December 15, 2021 Share Posted December 15, 2021 yep pretty easy.. The marking are 1&6... 2&5... 3&4..... it follows the firing order... 'too young,, too old,,, just right!'... 15-36-24.. when the pointer is pointing at 1&6.. look at the #2 exh. rocker. it should be 'rocked' if so ... you are up on #1, if not , you are up on #6.. easy breezy... jojo 1 Quote Link to comment Share on other sites More sharing options...
Mark T Posted December 15, 2021 Share Posted December 15, 2021 Just an FYI....a engine turning tool for a Cat ( half inch drive one looks sorta like on a starter ) is the same one for these Macks 1 Quote Link to comment Share on other sites More sharing options...
rhinoo Posted December 16, 2021 Author Share Posted December 16, 2021 6 hours ago, Joey Mack said: yep pretty easy.. The marking are 1&6... 2&5... 3&4..... it follows the firing order... 'too young,, too old,,, just right!'... 15-36-24.. when the pointer is pointing at 1&6.. look at the #2 exh. rocker. it should be 'rocked' if so ... you are up on #1, if not , you are up on #6.. easy breezy... jojo Got under truck this afternoon to try to find the marks on flywheel and pointer. The only think I saw was a part of bell housing that protrudes into the inspection hole. It would be a hole that possibly you look through but it had a metal plug in it and didn’t seem like it was going to come out very easily. But, maybe that’s not even the right thing? Quote Link to comment Share on other sites More sharing options...
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