or maybe the bosh 44 configuration has been bench tested and found not to deliver whats required under all circumstances with what is easily achievable in an on vehicle configuration. It's also not a simple drop in solution that can be done easily, effectively and reliably as an on the side of the road repair. Its also not possible to mount it up inside the tank along with the LP pump to handle the prime and filtraion in the OEM carrier due to the space restrictions of the carrier.
The 044 does not like being made to draw fuel through a filter if the filter causes too much of a pressure drop getting it to try and draw fuel through the LP pump, then the filter then the existing HP pump and then raise the pressure to whats required for the engine to operate normally, just isnt going to happen, not reliably at any rate.
Its actually possible to get the td5 to run on a 15psi faucet style pump, but not well because in reality to get it to turning over under its own power you just need to get enough pressure to fill the injectors as has been stated the injectors do all the HP work. The problem becomes your feed pressure much like the LP pump primes the HP electrical pump and feeds it the feed pressure to the injectors becomes important to ensure that the injectors are filled correctly. If you raise the rail pressure that feeds the injectors you're also raising the pressure that the spill valve acts against and that can effect the injection timing, remember that the FPR is matched against a certain capacity pump. Ive already mentioned the potential outcomes of not getting the right flow rate and low delivery pressure.
FYI.
With most dead OEM pumps I've replaced then tested and dismantled Ive generally found the LP pump to be delivering below spec which means the HP stage of the pump isnt being cooled enough and isnt being fed with enough lead pressure to prevent it from cavitating and overheating.
Tie that in with any areation of the fuel from the return line or in the swirl chamber causes further starvation of the HP pump and the HP pump develops a total failure.
at the end of the run the fraction you're going to save when you get all the bits required to setup and install the alternate pumping solution so that it works correctly and ensures the full life of your alternate parts (and thats ignoring the cost of actually doing it assuming you dont account the 10 odd hours of work required to fit it all up to a defender) I dont consider to be worth the additional failure points that will be introduced nor the potential risk to the rest of the system. In the day, each injector was worth more than the pump.
As opposed to making colourful, defamatory and insulting statements, how about a little research or reading combined with a little thinking. I could probably read this thread, find the statement if you were desperate you could... and then follow that up with links to suppliers of pumps that can (on paper) deliver enough to get it to working, notice its all in the same post and then without too much effort make the leap that maybe the person who provided said information might have actually done some testing. Hell it wouldnt take much more to make the step to considering that perhaps it was at some point even done on a vehicle as a trial fitup.
