Check with a diesel injection service -- I'm not familiar with this particular pump, but a failed pressure valve or a worn rotor will give this problem, along with low power warm. You should NOT be able to get vapor lock, as the injection lines should be holding pressure up to the pop pressure of the injectors! 1500 psi is typical, now way the fuel can get hot enough to boil unless the pressure isn't holding in the lines.
Might be time for a pump overhaul, those distributor pumps often require lubrication supplement with ultra low sulfur fuel or they wear fast. My old Volvo pump had to be rebuilt for this reason. Peter -----Original Message----- >From: MG <trainpain2...@yahoo.com> >Sent: Jun 20, 2010 5:20 PM >To: Mercedes Discussion List <mercedes@okiebenz.com> >Subject: Re: [MBZ] Hard start problem returns- Update > >The injection pump is a distributor type pump, the same one that >is used on the 6.2 just turned up a bit. It doesn't have any air >leaks. There is a small valve on top of the final filter that >never has any air under it unless I have just changed the >filters. The supply pump is an electric unit that I installed >right next to the tank so the whole supply line except two >connections and about 6" of hose is under pressure. The pump >starts when the key is turned and you can hear the tone change >when the pressure in the system is up to the limit that the pump >can push which is about 7-8 lbs. That is the same amount as the >original engine mounted pump did. I replaced it to make bleeding >the filters easier after replacement and because the engine >mounted pump has a habit of leaking fuel into the oil when the >diaphragm goes bad. > >A bit of oil smoke after starting cold but it still starts right >when you turn the key after the glow plugs cycle. No turning over >to speak of just turn to start and it starts right now. > >The only thing that matches the problem is a vapor lock problem. >It changes with the fuel supply and outside temp and if you have >ever seen a big block in a van then you know about the clearance >and heat issues in the engine compartment. The 6.5 is the same >size as a big block. The other thing is that I remember it as >starting back when they started with this super low sulfur fuel. > > >Manfred > > > >Date: Sat, 19 Jun 2010 20:04:29 -0500 >From: Peter Frederick <psf...@earthlink.net> >Subject: Re: [MBZ] Hard start problem returns- Update > > >Mid to late 70's Chevy V8s were terrible about roasting starters. > As >noted, this won't be the case if you have "vapor lock" in the >injection lines. > >I'd lean toward a leak on the suction side of the fuel system. I'm >not familiar with that particular engine, does it have a distributor >type pump or an in-line? If it has unit injectors, you definitely >have an air leak or a bad supply pump. > >I doubt it could be a compression problem, as that would give you >fits starting cold, not hot, and would produce copious white >smoke as >you cranked and it did not start. No smoke, it's a fuel supply >issue >somewhere. > >Peter > > > >_______________________________________ >http://www.okiebenz.com >For new and used parts go to www.okiebenz.com >To search list archives http://www.okiebenz.com/archive/ > >To Unsubscribe or change delivery options go to: >http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com _______________________________________ http://www.okiebenz.com For new and used parts go to www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
