Rob Posted December 4, 2011 Share Posted December 4, 2011 Well, this R795 ran out of fuel in the shop today again with a full 75 gallon tank. Been a real bitch to locate the problem but finally did. Here is the scenario that has happened several times:The engine idles fine for over an hour without presenting any problems, stumbles, or anything out of the ordinary. Also for the limited amount of driving I can do on my property, there have been no problems exhibited.Tonight I filled the cooling system with a 50/50 mix of green coolant, new coolant filter/conditioner and started the engine to let the coolant circulate. After about 1/2 hour of the engine running with no movement of the temperature gauge, I hold the idle at about 850 rpm for about three minutes. The temperature gauge rises to just over 160 degees indicated so I back the idle down to about 700 rpm. About 45 seconds later the engine starts to slow and characteristically starts missing on a couple cylinders, then starves out. As usual I pull the filters and the primary is plum full, the secondary is near empty. Same thing I've seen literally a dozen times. The discharge hose, (#8 size braided) from the secondary filter runs up to the top of the engine and connects to the fuel gallery within the injection pump. This hose slightly rubs on the intake manifold and barely had a pin sized hole rubbed through it. It was not enough to leak fuel to give itself away. I found it by taking the line loose to twist and allow evaluation on the underside; it was barely wet.I'll stop by the Parker Store for replacements on Monday. Be nice to put this one to bed finally. It was so strane the primary filter stays full, yet the secondary starves out. I can only imagine the secondary has a smaller capacity. These are all Mack filers, Red, Green, and Gray.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/21937-finally-found-it/ Share on other sites More sharing options...
Mike Posted December 4, 2011 Share Posted December 4, 2011 I just wonder if the hose or line from the primary to secondary has a hole in it causing the loss of fuel trying to return?mike Quote Link to comment https://www.bigmacktrucks.com/topic/21937-finally-found-it/#findComment-92897 Share on other sites More sharing options...
Rob Posted December 4, 2011 Author Share Posted December 4, 2011 I just wonder if the hose or line from the primary to secondary has a hole in it causing the loss of fuel trying to return?mikeThe transfer pump mounted to the rear of the injection pump pulls fuel from the tank through the primary filter. The transfer pump then pushes cleaned fuel through the secondary filter. The transfer pumps on the V8 engines are not really a pressure type pump but rather a circulator pump. They move fuel well if they are submerged. This makes the engine very difficult to restart when starved.I might have a weak transfer pump to suck the secondary filter dry before the pump can keep it filled.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/21937-finally-found-it/#findComment-92898 Share on other sites More sharing options...
Mike Posted December 4, 2011 Share Posted December 4, 2011 Transfer pump is what it sounds like.mike Quote Link to comment https://www.bigmacktrucks.com/topic/21937-finally-found-it/#findComment-92901 Share on other sites More sharing options...
leversole Posted December 4, 2011 Share Posted December 4, 2011 Mine lays on the intake also and pulses a little bit....I better get it tied up or protected! Quote Link to comment https://www.bigmacktrucks.com/topic/21937-finally-found-it/#findComment-92903 Share on other sites More sharing options...
Rob Posted December 28, 2011 Author Share Posted December 28, 2011 Finally run the new fuel lines on the engine this evening. Now tomorrow I'll give the truck a full service including new filters and go from there. Sure hope this fixes the running out of fuel problem.Swear I'm the only one in the world that can starve out for fuel when the tanks are full......Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/21937-finally-found-it/#findComment-95709 Share on other sites More sharing options...
unclebilly Posted January 16, 2012 Share Posted January 16, 2012 I had a very similar problem with my unimog a few years ago... It would run out of fuel and suck air in through the priming pump. The problem?A previous owner had used cheapo fuel tank patch compound that you pour in the tank and then roll around in the tank. The crap was coming off and would make a flat slab that would cover up the fuel intake line in the tank (an accidental check valve). The thing would always plug up at he wrong time. Quote Link to comment https://www.bigmacktrucks.com/topic/21937-finally-found-it/#findComment-98384 Share on other sites More sharing options...
Rob Posted January 16, 2012 Author Share Posted January 16, 2012 I induced another problem when I changed the filters. The primary fuel filter did not seal at the crimp and allowed the secondary fuel filter to deplete yet not pull through the primary starving out again. I spent hours chasing the same problem again after changing the fuel lines.Rob Quote Plodding along with no job nor practical application for my existence, but still trying to fix what's broke. Link to comment https://www.bigmacktrucks.com/topic/21937-finally-found-it/#findComment-98386 Share on other sites More sharing options...
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