Mtnmblmech

Awesome thanks for the pics. I thought it should have a mechanical pump on it, but did not look hard enough and it appears that it is hidden under the pump. This should be easy now..given the pump works. Thanks again staxx. Makes a lot more sense now, as I have never seen a setup that was plumbed the way he had it, but the old guy is hard not to believe as he has grease under his fingernails that is older than me. I will get back to you on how it goes and take care.

I was planning on rigging up some test fittings. I have everything I need somewhere. Just bought a house and seemed to have buried everything I have needed lately. Pump is and inline made by United technologies diesel systems for Mack Model no. is in original post. I did not hook up the pump just removed secondary filter temporily and added high flow pump to try to get it running. I will look to see if it has lift pump under the pump and was not ran through it. As i is the fuel supply line just goes straight into the pump and t's out to the injector line. Which didn't make any sense to me, but the old man says that's how it goes. Thanks for all the help fellas, I will go check her over again and do some testing. Enjoy your Sunday.

Thanks for the reply staxx! As far as I can tell this system has no lift pump and is a siphon feed system. This engine is not the original engine that was in the truck and I had thought that it needed to have a lift pump of some kind, but my old buddy said that it did not and was siphon fed. I had mentioned to him that it seems to be a pressure problem. We put a high flow pump on it, but I explained to him that high flow is not the same as high pressure. I imagine that if we put a high pressure pump on it we will see different results. He assures me that this engine ran fine before, but I imagine that unit had a lift pump and was not a siphon feed system. I also suspected that there may be a check valve in the system that would require a higher pressure for fuel system to operate . I will try talking him into springing for a high pressure electrical pump as there is not a mechanical on this engine. I should probably find out what max required pressure is for this pump is first. Any info on this spec would be very appreciated. I'm originally from Miles City staxx, which is not too far from Costrip. Thanks again for all the help it is very appreciated.

Hello BMT!!- I am in need of some technical help on a 79 Mack 350. I am a mechanic who mostly works on agricultural equipment and smaller diesel trucks. I was recently somewhat conned into helping my old timer neighbor into putting a 79 350 Mack engine into a 73 Mack Dump truck. Needless to say it was a bitch of a project. Considering I'm just doing this for beer, hunting rights, and use of his machine shop..it nearly made me reconsider our deal. Well the engine is in and hooked up the way it should be. Primed it and bled the injector lines and she fired right up and purred like kitten being petted by a 400lb gorilla. When I try to rev it though, it is sluggish and will die if I keep in the throttle. I can feather it back down to idle and keep it from dying when I do it by hand. I have simplified the fuel system to one filter and even put a high flow electric pump from the tank to push some fuel. I know that this should not be needed as it is a siphon feed fuel system, but the beer told me it couldn't hurt to try. My old buddy says that this engine ran fine in the truck it came out of, but I'm hesitant to believe him as he has so many old trucks, engines, parts sitting around, and is getting pretty damned senile; I could see how he could maybe have mixed this engine up with another. I'm thinking that the pump is out of time, the pump is fubar, or I'm missing something simple. The model no. on the pump is 313GC 5135P4. I have rebuilt some old john deere pumps in the past and have a pretty good understanding of how things work, so is there a chance I could most likely handle rebuilding this pump. He does not have another pump that will work from my research, so that is looking like our next option. He does not want to put much more money into this project either. I love the old fart and I would like to see the smile on his crusty old face when I drive it out of the shop. Any help would be very appreciated and thank you for your time.

I asked him if it smoked before it died and he said it didn't and never really has ever smoked. I thought it may have have been locked when I first looked at it so I pull #1,3,&6 injectors to help release compression, and tried to turn over and got nothing. Will try turning over by hand tomorrow and go from there. Appreciate the help and thank you very much.

Turning the engine over by hand was next on my list to try, going to do that tomorrow. Will cut filters if it does not turn over. Appreciate the help very much and thank you.

Howdy- I am trying to help the old boy next door get his dump truck running again and having some issues. The truck ran great for him and then all of a sudden it just died. He restarted it again and it ran for about twenty minutes and then died again. I asked him if his oil pressure was low when that happened and he said when he first started it, it was only pumping at twenty some psi. The engine now will not turn over now and is acting like its seized. I unplugged the jake to make sure it was not possibly creating and issue upon start up. It has new batteries and starter seems to be engaging fine. Just wondering how I should I go about testing without completely dismantling, other possible causes of this symptom (I was thinking injection pump gear issue or valve train/timing problem). I am a busy man but would really like to help the my neighbor out as it provides him with much needed income and he is just one of those awesome old guys that deserves to have someone else help him out for once. Please help and thank you for your time.