Stall in Warm Weather - Fixed

[Mike Murrell]

Vehicle description in signature below.

On 3 separate occasions, car would start bucking/stalling at highway speed after having driven 15mi-20mi and only in warm-to-hot weather. If I let up on the accelerator pedal engine would die. Car would not restart until engine had cooled down. Usually took 30 min to an hr. before vehicle would restart.

After the 1st occurrence and some cool down, engine speed would vascillate while idling, then die. After the 2nd occurrence, the fuel pump relays pins in the MAS were jumpered and still no start(pins 1 & 2). The MAS was changed last yr. During the 3rd failure, I was finally in a position to listen to the pump with a mechanics stethescope while another turned the ign. switch on. No priming was taking place at the pump.

Pump is a single unit model - Pierburg. Since this pump was the factory original along with all associated fuel delivery items(minus the filter), the following items were replaced:

fuel pump - stayed with Pierburg
fuel pump check valve cap nut
fuel accumulator - Bosch
fuel accumulator to elbow hose - dealer item - 5.5 mm hose - 12" long
fuel filter - Bosch
fuel tank screen(filter) - OE
fuel tank screen o-ring - OE
large fuel tank hose - goes to pump inlet - OE
small fuel tank hose -return - OE
fuel line from pump to elbow - approx. 2 3/8" long - OE

fuel line from filter outlet was reused - replaced about a yr. ago.

After replacing these parts, vehicle was driven 120 mi. in near 90F heat. No stalling occurred during this drive.

Referenced doc on 126 CD for repair instructions. If you do not have an MB CD, reference the following WEB site:

http://mb.braingears.com/

Car was first backed up on to ramps to elevate rear section.

Removed pump, filter; accumulator as a unit since all parts were being replaced. Four 8mm mounting screws hold this assembly on.

19mm offset loosened fuel tank return line at tank. 22mm open end stubby loosened feeder fuel line at tank. Baum 46mm loosened fuel tank screen at tank. All were fairly snug

Tank is drained when the feeder fuel line that connects to the pump is removed. Best to first try and drive car to near empty. Drove 'til low fuel warning light came on and then some and drained approx. 2.5 gals. of fuel.

Now it's time to fix the A/C & air distribution problems.

Onward.