Brandon 1

Ok  that's right 

the truck is running rough and is a little down on power sometimes better sometimes worse

if you completely bleed the fuel system it will run really smoothly until it needs fuel then will be bad rest of the day

if you idle up to around 1200-1400rpm you notice a distinct miss 

and as I said will run on only when shutdown by timer 

key off shutdown perfect every time 

thanks

Yes the fan works with the key on ok 

ran a multimeter across the fuse box  there are two small posts that say serial link a and b  with a white wire connected to each they read approx 4 volts and 1 volt 

pretty much everything else at the fuse box is reading around 13 volts

can anyone tell me what these are and is this kind of voltage indicating an issue

thanks

Hi fuel pressure ranges between around 10-35 psi so should be ok 

am thinking this could be an issue with electrical signal to the govener 

if the truck is shutdown with the key it works fine but about half the time when you let it idle down it'll run on 

Will check and get back to you

Thanks  it's a v Mac 2 half mechanical unit 

have eliminated fuel lines and filters by running a direct line straight into the tank and directly  to the lift pump just briefly to test and it still ran rough

when the filters are connected and it's running bad you can undo the supply filter and it can be half to three quater full

could be the hand primer but it's new

How would you test this

Hi  we seem to be having fuel supply issues with a 98 model 454 

even though we have replaced the lift pump with a new PAI unit it seems to point back to this 

can anyone tell me what sort of pressure this should be generating , is there any adjustment inside the unit or is there a better pump that can be fitted

i have thought about adding an extra electric low pressure pump closer to the tank

thanks

Ok thanks  i will fit 6 of exactly the same I believe to be original style and give it a go , have only ever run the truck with three of each , remanufactured units that have come from the dealer here in Australia . 

I did not exchange the last set being suspicious of this so now have 6 of each style.

Hi guys, have just recently found this website and it looks awesome, im hoping i can get some help with my CH Mack Select, its a 98 model 454 v mack 2 

Since i bought it about 2 years ago it has had a bit of a miss and it seems to be related to air in the fuel system and maybe return fuel, you can bleed the air out of the system and it might run ok for a short period of time but always ends up with the air, its down on power and seems to be running a little warmer than it should.

We have tested many things including running a new fuel line directly in to the fuel tank to the lift pump and then a line directly into the main pump and it still did it.

Have had the pump tested and found ok, but when we removed the injectors we found that there were differences in the housings , some having return ports in a different place and some having an extra o ring groove.

my questions are ,

does anybody know why these differences and how many o rings should i be running on the  injectors , i believe the original injectors for this truck are the ones with the higher return port and the extra o ring groove, this truck had a badge on its hood saying High Swirl Injection.

Any help with this would be much appreciated, Thanks.