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
