I had a 300SEL that had a bad plunger seal on the fuel distributor. Dang thing sucked fuel, but ran OK. Not fun to replace, but not a major undertaking, either. Made a significant difference in fuel consumption once it was replaced.
-D > On Mar 2, 2023, at 6:05 PM, Peter Frederick via Mercedes > <mercedes@okiebenz.com> wrote: > > Most likely leak point is the check valve in the fuel pump (the anti-return > valve, German is a strange language). Second wear point on a W116 is likely > to be the plunger seal in the fuel distributor. this can also cause hard > starts hot by flooding the engine as the fuel drips out with the engine off > until the accumulator is empty. > > The accumulator is a can in the fuel line, looks like a filter but isn’t. > Just a diaphram and spring, holds approx 100mL of fuel I think, maybe 150. > It’s there to prevent vapor lock on hard starts. > > Next most likely is leaking fuel nozzles, if you have not changed them do so. > > > You can also have a bad pressure regulator valve that leaks back into the > tank. > > I’m getting ready to dig into the KE-Jet on the wagon, it goes way rich, > probably because the 35 year old oxygen sensor is shot. Stays in limp mode, > and its a real pain because occasionally it will work and lean the engine out > to the point it stalls. > > >> On Mar 2, 2023, at 4:48 PM, Kaleb Striplin via Mercedes >> <mercedes@okiebenz.com> wrote: >> >> I am actually sort of having fun playing with the CIS and learning all about >> it. After spending a lot of time jacking around with the HF fuel gauge set >> and not getting accurate readings, I spent $130 on the correct test set that >> I picked up on ebay. Within minutes I am starting to narrow down the issue. >> I am running thru the tests that are spelled out in a training doc I found >> on w116.org that tells you which tests to run based on what the issue is. >> Test 3 tests the system pressure. This is done with the engine off, turn >> key on with valve closed on the gauge mine is dead on. Next test is testing >> static pressure. For this test, you open gauge, turn key on for about 30 >> seconds to fill the accumulator, then turn off. It says pressure is >> supposed to be 2.8bar. Since there is not a range, I assume it must be >> exact? While the pump is running it only shows .5 bar. After key is turned >> off, pressure builds up but mine only gets to about 2.5 bar. The test then >> says within 30 minutes it can leak down to 2.5 bar, so .3 bar leak off. >> After about 8 minutes mine has lost about .4 bar. So, this is the first >> issue to correct. >> >> Items it says to check for leaks are the cold start valve (done, it is not >> leaking), fuel pump non return valve (where is this?), accumulator for >> leaking diagram (is this the deal back by the pump?), pressure compensating >> valve (not sure where this is either), FD for internal leaking around >> control plunger or o-rings of metering sleeve. >> >> I will be digging into this further but this is just a quick check of the >> system so far. Without throwing parts at the thing, which if these items it >> a most likely cause? I figured somebody that has dealt with CIS a lot would >> run into some common issues. >> >> >> >> _______________________________________ >> http://www.okiebenz.com >> >> To search list archives http://www.okiebenz.com/archive/ >> >> To Unsubscribe or change delivery options go to: >> http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com >> > > > _______________________________________ > http://www.okiebenz.com > > To search list archives http://www.okiebenz.com/archive/ > > To Unsubscribe or change delivery options go to: > http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com > _______________________________________ http://www.okiebenz.com To search list archives http://www.okiebenz.com/archive/ To Unsubscribe or change delivery options go to: http://mail.okiebenz.com/mailman/listinfo/mercedes_okiebenz.com
