I don't know of a mechanism that would cause the system to lose prime when hot but then regain prime after it cooled off. That's not to say that it doesn't exist, but I'd love to hear how that works.
Let me restate your problem to make sure I understand. 123 turbo diesel - OM617.952 engine. Cold engine - fires right up with no priming and 'normal' cranking. Hot engine - no start unless you operate the priming pump. Once running there are no other symptoms (power is fine, mileage is normal, idle is smooth). History of the problem - it has existed for years. Seasonal influence - problem is worse in warm months. Have I got it right? -Max -----Original Message----- From: mercedes-boun...@okiebenz.com [mailto:mercedes-boun...@okiebenz.com] On Behalf Of Mike Esh Sent: Wednesday, June 16, 2010 7:20 PM To: Mercedes Discussion List Subject: Re: [MBZ] Hard start problem returns- Update Steel pipes and car are very good condition with minimal rust. I checked all connections on filter assembly and made sure all fittings had both washers. O-rings are new on the bolt for the filter. There are two of them, the lower one is smaller than the upper one. I hear nothing when operating pump manually. Could this be allowing fuel to return when the engine is hot and correct itself as the engine cools? No rising oil, I usually add a quart between changes. Thanks for the input, Mike On Jun 16, 2010, at 6:26 PM, Dieselhead wrote: > Assuming that all the steel pipes are not rusted. .. Some fuel > filters have o-rings on the bolt that holds the filter in place, older > ones have an aluminum seal under the head of the bolt. I think yours > has orings. Maybe someone else can say for sure. Air can leak in at > these orings. Any loose banjo fitting at the filter can leak. The > banjo fittings into the IP and out of the IP can leak. All banjo > fittings are supposed to have an aluminum ring under the bolt head and > under the fitting. Absence of any aluminum seal ring can allow air in > the lines. > > There is a check valve on the backside of the IP at the exit line > banjo fitting. It is possible somebody removed this. When it is very > quiet, you can hear the check valve operating when you pump the hand > primer pump. > > > Do you have a rising oil level? It is possible, but very rare, for > the IP shaft to leak fuel into the crankcase. > > > >> I checked/replaced all connections and hoses and cannot determine >> where anything is leaking. Everything is dry and clean. I can >> actually see the fuel level in the clear filter level drop. I >> appears to be draining toward the spin on filter. Is there check >> valve somewhere that is allowing the fuel to drain back when it is >> hot. Is the injection pump going bad? I am getting so frustrated. >> Anyone within 200 miles of Whitehall, MI that has knowledge of how to >> fix the issue? I would be willing to travel to solve this. >> Thanks, >> Mike >> On Jun 11, 2010, at 3:21 PM, John Reames wrote: >> >>> Check to see if your vent line is plugged... Either fighting to pull >>> the filler cap or hearing air go in. >>> >>> I had an 84 sd that was taking on air until I blew out the vent >>> line... >>> >>> -- >>> John W Reames >>> jwrea...@comcast.net >>> Home: +14106646986 >>> Mobile: +14437915905 >>> >>> On Jun 11, 2010, at 14:05, Dieselhead <126die...@gmail.com> wrote: >>> >>>> A stream of bubbles in the clear filter only indicates an air leak >>>> in the suction line. An air leak after the clear filter, in lines, >>>> transfer pump, filter, IP, or return lines do not indicate by >>>> bubbles in the clear filter. You can use the presence or absence >>>> of bubbles to focus your efforts before, or after the prefilter. >>>> If the hoses are old, OFTEN, there are multiple air leaks. If the >>>> hoses are all less than 2-3 years old, it is likely to be a clamp >>>> that is not tight. >>>> >>>> It is a good idea to change all the fuel hoses every 5 years or so. >>>> (yes the original hoses lasted 10-20 years.) I have not had MB >>>> replacements last that long. FLAPS hose is usually good for 5 >>>> years. >>>> >>>> I only use OE or OEM radiator hoses. They are still noticeably >>>> better than any third party hoses. >>>> >>>>> Also note that the hand priming pump only moves fuel into the >>>>> injection pump, NOT out the injection lines to the injectors. You >>>>> operate the priming pump about 50 to 70 times to prime the >>>>> injection pump; you will know that it is primed when the noise >>>>> changes and the pump action firms up. >>>>> >>>>> How does the car run once you get it started? Can you reach top >>>>> speed or does it lose power at highway speeds? Watch the clear >>>>> in- line filter >>>>> - is there a stream of bubbles entering? >>>>> >>>>> -Max >>>>> >>>>> -----Original Message----- >>>>> From: mercedes-boun...@okiebenz.com >>>>> [mailto:mercedes-boun...@okiebenz.com] On Behalf Of Dieselhead >>>>> Sent: Friday, June 11, 2010 12:58 PM >>>>> To: Mercedes Discussion List >>>>> Subject: Re: [MBZ] Hard start problem returns >>>>> >>>>> Try bleeding the fuel system at the filter (Top bolt, or line >>>>> out) while >>>>> you pump the primer. It sounds like air is getting into the fuel >>>>> system somewhere. A leak at the filter can cause a leak. Bad >>>>> copper seals in the delivery valves can cause problems. >>>>> >>> >>> _______________________________________ >>> 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 > > > _______________________________________ > 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 _______________________________________ 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
