I would like to know where the two check valves need to be installed in the fuel system on my 1989 190E 2.6. My car is really hard to start most of the time because I believe the fuel has leaked back to the tank or someplace else because the check valves are defective. Once the car starts, it runs great, so I don't think its the fuel pump. Thanks.

More than likely it's the fuel accumulator that's the problem. It will leak down fuel pressure like a check valve and in my experience that's always the problem.

the check valve screws into the fuel pump and the tubing then goes over the end of the checkvalve. In the middle of the fuelpump you see the copper washer, then the hexagonal part of the checkvalve, then another copper washer and then the tubing over it. Here is a picture of a 87 420 setup.

Attached Thumbnails

 

this would be the accumulator behind the filter on picture 1.

Attached Thumbnails

 

How does one test it? A well placed pressure gauge I presume (what rating? 0-100psi). Can the accumulator be bypassed temporarily to figure out the problem?

I was just visiting this forum from a friend with a 1988 300se that has a similar symptom (impossible to start in the morning) and was going to ask if the problem was in component that held pressure, because the car starts well during the day. It's only the first start in the morning that hurts.

-CTH

PS. Two fuel pumps? Why would a car have two fuel pumps.

__________________
- cth350@gmail.com
http://www.111lakeside.com/

Hi CTH,
there is a lot in the archives, so a search will give you a lot of info.
Pressure is normally measured at the fuel distributor in the engine comp., if my memory serves me right. For my 420, I believe its in the 60s psi area. The 2 pumps generate "system pressure" and excess fuel is sent back to the tank. Little differences in pressure are then used to fine-tune with the Electro-Hydraulic-Actuator or EHA. The check valves I guess help the pumps and the accumulator is supposed to keep the pressure up after the pumps stop. That's why Stan Pittman has his money on the accu.

190E2: When placing the car key in the position just before the start without starting, my pumps will run for about a second and built up the pressure. You might try this 2 or 3 times with your car and see if it starts better.
Good luck

RKruetzer,
Is that all new parts?? Looks incredibly good. I need to find a source for the rubber boots to cover the electrical connectors, mine are nearly non-existent. Beautiful pictures.

__________________
Earl McLain
'02 C230 Kompressor
'89 560 SEL "Frau BlueCar" (retired April 2004)

Thanks greenacres2,
yes, it was all new when I took the pictures. I first took pictures of the old pumps so I would get it all back together. One pump was loosing fuel right out of the electric connector and the whole cluster was 15 years old, though only 47,000 miles. As I planned to keep this car, I thought it best to replace both pumps, the filter, accumulator and the tubing/hoses. The tubing still could have been used and the rubber boots are actually original. I use Wurth rubber treatment, a glycerin product, to keep rubber in good shape. The only thing I couldn't replace was the hose coming down from the tank. I was afraid I might round that 21?mm nut, thats how much force I applied and it still didn't budge. The hose got my rubber treatment and I decided to take the chance.
This is how it looked before:

Attached Thumbnails

 

My 88 TE stumbles badly at start up (always when cold and sometimes when warm) and then smoothes out after 3-5 seconds. It fires right away. Can the accumulator be the culprit in this instance also? I have replaced the filter, wires, coil, rotor, dist. cap. etc.

EJC