Re: [diesel_mercedes] Here's a good one for you guys

On 6/19/2011 9:12 PM, diyernh wrote:

I was thinking a leak in the fuel line, letting in air.  As the tank level drops, a higher vacuum is needed to lift the fuel.   This would cause the surging.  I would figure the lift pump would be more steady.

This is NOT from experience with Mercedes, just other vehicles.  I ended up stranded when my fuel filter leaked air in my duramax.  It doesn't take much of a leak to pull in enough air to kill the engine.

You might want to take a gander at the fuel lines while you are under there.

Carl


On 6/19/2011 8:16 PM, john public wrote:

I have had this same problem with my 83 SD; for me it was a hanging vacuum shut off valve. Essentially, the shut-off was  remaining partially closed, reducing fuel flow, starving the engine and preventing higher speed operation. I too, thought it was a bad pump, but as soon as  I disconnected the shut off solenoid, and removed it altogether, the problem disappeared; after replacing it with a new unit, no more problem.  --- On Sun, 6/19/11, Mark Atkins <mratkins@embarqmail.com> wrote: From: Mark Atkins <mratkins@embarqmail.com> Subject: Re: [diesel_mercedes] Here's a good one for you guys To: diesel_mercedes@yahoogroups.com Date: Sunday, June 19, 2011, 7:07 PM You likely hit it. Thanks, Mark On 6/19/2011 5:32 PM, Nate Rector wrote: Yes pump warm and not pumping good. --- On Sun, 6/19/11, Mark Atkins <mratkins@embarqmail.com> wrote: From: Mark Atkins <mratkins@embarqmail.com> Subject: Re: [diesel_mercedes] Here's a good one for you guys To: diesel_mercedes@yahoogroups.com Date: Sunday, June 19, 2011, 5:01 PM Thanks, Nate. I suspected it but the problem is worse as the car warms up. It runs pretty well for the first 20-25 miles. Would that support the lift pump theory? Mark On 6/19/2011 3:41 PM, Nate Rector wrote: sounds like a lift pump is almost gone. --- On Sun, 6/19/11, Mark Atkins <mratkins@embarqmail.com> wrote: From: Mark Atkins <mratkins@embarqmail.com> Subject: [diesel_mercedes] Here's a good one for you guys To: diesel_mercedes@yahoogroups.com Date: Sunday, June 19, 2011, 3:29 PM My friend has an '85 300SD with about 210K miles. He bought it a year, or so, ago and has had a recurring problem that is driving us crazy. We went on an 800 mile round trip "adventure" this weekend that allows me to share the problem accurately. Shortly after he bought the car he went on a trip and experienced a loss of power which reduced the top speed to ~45 mph. He returned home and changed the fuel filters thinking that was the problem. Since we have taken a few 400 mile round trips in the car and it would lose power intermittently but never limit the speed to less than about 60 mph. He discovered that topping the fuel off seemed to help with the problem, however, the problem has occurred more and more frequently as time has passed. This weekend the problem was so bad that any overpass the car would lose power and speed would drop to 40-45 mph and a couple of large bridges it would only top them at 15-20 mph. Top speed on level ground (I-10 in southern LA and Texas) was 40-45 mph the entire return trip. That, my friends, SUCKS! One bridge in LA and one over the Houston ship channel, on the return trip, the speedo would barely indicate movement (as confirmed by our sight!). Houston to New Orleans is usually a 6 hour trip, each way, but we spent 10.5 hours getting there and 12.5-13 returning. Unacceptable! We have checked the fuel system from the tank strainer to the injector pump and it is not plugged. The car surges at WOT similar to a "hit and miss" type engine (see YouTube for example). I suspect the problem is the injector pump but do not know of a way to troubleshoot it. The car is otherwise a beautiful example of a vintage SD and has been well cared for it's entire life. Any suggestions? Thanks, Mark in Texas -- -- --

I also had a similar problem with a Dodge van.  The fuel pickup came out the top of the tank, but there was an internal air/fuel leak on the pickup tube in the tank.. Everything was fine with a full tank.  After that it went downhill. The PO had added an electric fuel pump which more or less solved the problem until I redid the engine and eliminated the electric pump.