E7 350 Turbo lag

[rhinoo]

41 minutes ago, Vmac3 said:

That is a very reliable engine. Don't expect the truck to be a rocket, but it is very good.

V

 

Pressure is checking low. I guess I should try a lift pump? The pics are of idle and wot. 

[Vmac3]

Have you replaced the fuel filters?. If you have make sure there is no junk in the fuel tanks. Squeeze the return line from the pump to the tank and see if the pressure goes up. If it does then it may be a fuel return check valve. If not then the fuel pump may be no good.

V

[br549]

There is a line that comes from the intake manifold around front of engine to back of injection pump.  As the turbo pressure comes it put pressure to the back of the pump to open up fuel rack.  If the hose has a hole in it or the diagphram in the back of governor it cannot let the rack open up.  We made up a fitting and gauge to put air pressure on it to see if it would hold air  around 30 psi, if it leaked down it could have a hole in the line or the diagphram in the pump which can be easy change without removing pump.  W also used to adjust it to pick up faster if it was just slow response pickup.  You pulled the plug and there is a cog like a brake adjuster in it you take a short screw driver and click it but I can't remember which way to go.

[rhinoo]

6 minutes ago, Vmac3 said:

Have you replaced the fuel filters?. If you have make sure there is no junk in the fuel tanks. Squeeze the return line from the pump to the tank and see if the pressure goes up. If it does then it may be a fuel return check valve. If not then the fuel pump may be no good.

V

Ok, it has new filters and tanks were clean. I will pinch return off to see if it changes. I did remove the pump and the cam in the injection pump looks good. 

[rhinoo]

5 minutes ago, br549 said:

There is a line that comes from the intake manifold around front of engine to back of injection pump.  As the turbo pressure comes it put pressure to the back of the pump to open up fuel rack.  If the hose has a hole in it or the diagphram in the back of governor it cannot let the rack open up.  We made up a fitting and gauge to put air pressure on it to see if it would hold air  around 30 psi, if it leaked down it could have a hole in the line or the diagphram in the pump which can be easy change without removing pump.  W also used to adjust it to pick up faster if it was just slow response pickup.  You pulled the plug and there is a cog like a brake adjuster in it you take a short screw driver and click it but I can't remember which way to go.

This wouldn’t reflect lift pump pressure though right? I don’t mind to look into that but the lift pump pressure is half of what it should be apparently. Thanks 

[theakerstwo]

1 hour ago, rhinoo said:

Ok, thanks. Is the mechanical a good thing or bad? Trying to get teed into fuel system now but gotta go pick up a fitting. I talked to a guy at Rochester diesel earlier and he said that if someone put that s400 on without upgrading the injectors that it would be sick. I told him I was gonna check fuel pressure first and if it was ok I would call him back and order a set of injectors. 

The fuel pressure needs checked under a load.

[Vmac3]

1 hour ago, theakerstwo said:

The fuel pressure needs checked under a load.

The specifications that I gave were, no load idle and rated speed. These specs are published by Mack for this model year.

V

[rhinoo]

10 minutes ago, Vmac3 said:

The specifications that I gave were, no load idle and rated speed. These specs are published by Mack for this model year.

V

Thanks guys. Took it for a road test and still low pressure. When making boost pressure would drop to 11psi and when let out of the throttle it would bounce between 20-25psi

[theakerstwo]

1 hour ago, Vmac3 said:

The specifications that I gave were, no load idle and rated speed. These specs are published by Mack for this model year.

V

Yes thats right for a fuel pump check but for checking pressure thats got a know problem only god knows how many i have seen that would hold that pressure but as soon as you load it and start to consume more fuel per hour a restriction  or sucking air would drop the pressure.I think all manufactors of engine only give you the stactic pressure reading.Not long ago one of the guys that i work with had a power problem on his nack and it had pressure sitting here in the shop but i checked it under load and it would go to nothen.i found a big night crawling bug stuck in the primary fuel filter inlet fitting.

[Vmac3]

1 hour ago, theakerstwo said:

Yes thats right for a fuel pump check but for checking pressure thats got a know problem only god knows how many i have seen that would hold that pressure but as soon as you load it and start to consume more fuel per hour a restriction  or sucking air would drop the pressure.I think all manufactors of engine only give you the stactic pressure reading.Not long ago one of the guys that i work with had a power problem on his nack and it had pressure sitting here in the shop but i checked it under load and it would go to nothen.i found a big night crawling bug stuck in the primary fuel filter inlet fitting.

Yes are absolutely correct, but we already have low fuel pressure to begin with. The poster already mentioned that they checked all basics. So I don't see as to why the poster would have to check it under load to reconfirm that there is low fuel pressure. The only other thing is to bypass the complete fuel system and run the fuel system in a bucket straight from the transfer pump. If the pressure doesn't go up then we can confirm that the lift pump is defective.

V

V

[Joey Mack]

damn good truck... jojo

[Mark T]

I had one once , the genius driving it insisted on putting a stick in the tank ( to check the fuel level.... cause gauges aren't always right )  Blew air back from the supply line at the filters. It was full of bark .

[rhinoo]

3 hours ago, Vmac3 said:

Yes are absolutely correct, but we already have low fuel pressure to begin with. The poster already mentioned that they checked all basics. So I don't see as to why the poster would have to check it under load to reconfirm that there is low fuel pressure. The only other thing is to bypass the complete fuel system and run the fuel system in a bucket straight from the transfer pump. If the pressure doesn't go up then we can confirm that the lift pump is defective.

V

V

Thanks, I was thinking the same thing and didn’t see why running it under a load would raise the pressure at all but it was an expensive pump and easy to reinstall to try it. I will try to run straight from a bucket of fuel tomorrow to see what we get. 

[R.E.D]

20 hours ago, rhinoo said:

I’m looking at truck now and has no ecm, manual foot throttle, with Bosch inline pump.. I sat on phone with Kentuckiana Mack for 30 mins for them to tell me it was an e7-350. 🤦‍♂️

Man that's a double whammy..must be one of the last non etech engines of 98 and one of the last mechanicals of that same year.😅

[fjh]

So I have a suggestion for you Before you go any farther ! Those numbers Aren't that bad seen alot worse if that engine is maintaining 25 psi plus under load the charge pressure is OK!

REmove the 3/8 plastic line that goes to the smoke limiter at the back of the pump at the top suck on the the tube if it won't hold a vacuam  the diaphram in that device is fubar you need to go there ! Remove the four screws you'll likely find your problem!

Just sayin!

So I re read the other posts and eleven under load is to low for sure your heading the right way fuel transfer pump or a leak prior to it! also check your tank vent! The above check is worth doing if you have good fuel pressure !

 

Edited December 8, 2021 by fjh

[rhinoo]

12 hours ago, fjh said:

So I have a suggestion for you Before you go any farther ! Those numbers Aren't that bad seen alot worse if that engine is maintaining 25 psi plus under load the charge pressure is OK!

REmove the 3/8 plastic line that goes to the smoke limiter at the back of the pump at the top suck on the the tube if it won't hold a vacuam  the diaphram in that device is fubar you need to go there ! Remove the four screws you'll likely find your problem!

Just sayin!

So I re read the other posts and eleven under load is to low for sure your heading the right way fuel transfer pump or a leak prior to it! also check your tank vent! The above check is worth doing if you have good fuel pressure !

 

Thanks for the reply. I didn’t check that the way you said but yesterday I disconnected that line at the intake and applied a little bit of shop air with a rubber tip blow nozzle and held it there for a few seconds and when I pulled it off the tube it was still holding air pressure. I may try what you said tomorrow though. Did put a new lift pump on today and still have same exact pressures as I had before. Back to the drawing board. 

[rhinoo]

On 12/7/2021 at 4:45 PM, Vmac3 said:

Yes are absolutely correct, but we already have low fuel pressure to begin with. The poster already mentioned that they checked all basics. So I don't see as to why the poster would have to check it under load to reconfirm that there is low fuel pressure. The only other thing is to bypass the complete fuel system and run the fuel system in a bucket straight from the transfer pump. If the pressure doesn't go up then we can confirm that the lift pump is defective.

V

V

So, I connected lift pump directly to a bucket of fuel and still had same low pressures. Went and picked up a new lift pump at Mack today. Slapped it on and same exact pressures. I was looking at return system today wondering if something isn’t going on with that. Looked in fuel tank while truck was running and seems like a rather large steam of fuel is returning. Where the return line comes off the injection pump there is a fitting with a restrictor hole to limit return I’m guessing. On the fuel tank side of that restrictor hole is a tee fitting that has a 1/4” or so rubber line that runs over to the back side of the injection pump and connects to a port. Not exactly sure what that is but any chance I could have an issue with something here? Could that small hole be worn to a bigger size?  

[rhinoo]

12 minutes ago, rhinoo said:

So, I connected lift pump directly to a bucket of fuel and still had same low pressures. Went and picked up a new lift pump at Mack today. Slapped it on and same exact pressures. I was looking at return system today wondering if something isn’t going on with that. Looked in fuel tank while truck was running and seems like a rather large steam of fuel is returning. Where the return line comes off the injection pump there is a fitting with a restrictor hole to limit return I’m guessing. On the fuel tank side of that restrictor hole is a tee fitting that has a 1/4” or so rubber line that runs over to the back side of the injection pump and connects to a port. Not exactly sure what that is but any chance I could have an issue with something here? Could that small hole be worn to a bigger size?  

 

[fjh]

Its kind of pointing at that! how ever I never seen these fail ,the old style T type valve would break a spring from time to time  not sure on that there I  cant see the whole valve in the pic! the orfice style was used mainly on the VMAC style pump! 

[kevgibbs]

On 12/7/2021 at 7:35 AM, Joey Mack said:

V-Mac 2

Are you sure it's a VMAC?? That picture of the fuel pump looks like it has a mechanical throttle control hooked to it. If so, that truck probably doesn't have a check engine light. 

[fjh]

9 minutes ago, kevgibbs said:

Are you sure it's a VMAC?? That picture of the fuel pump looks like it has a mechanical throttle control hooked to it. If so, that truck probably doesn't have a check engine light. 

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! 

Edited December 9, 2021 by fjh

[Joey Mack]

this is a V-Mac 1 truck.  the sensors are: oil pressure, coolant level + temp, ...   i probably forgot one or two.  What has me curious, is the year, '98... I dont recall an all mechanical injection pump.. for some reason I thought that in 96 they were V-Mac II and had the electric governor housing and an F.I.C. module in the cab..  ok..  Jojo

[Joey Mack]

I realized that I posted wrong info about the series, I fixed it. sorry,jojo

[fjh]

3 minutes ago, Joey Mack said:

this is a V-Mac 1 truck.  the sensors are: oil pressure, coolant level + temp, ...   i probably forgot one or two.  What has me curious, is the year, '98... I dont recall an all mechanical injection pump.. for some reason I thought that in 96 they were V-Mac II and had the electric governor housing and an F.I.C. module in the cab..  ok..  Jojo

Agreed! I think its a transplant! the mech pump was only offered a few years after Vmac came out I beleive! could be wrong however!I know they offered it a bit longer in a 350 HP!

Edited December 9, 2021 by fjh

[Joey Mack]

yes sir, me too...  I fixed an incorrect post I made,,  the year and the engine dont match in my mind, so i fixed my post to match the engine I see and not the model year... jojo