hard starting m603 engine - PeachParts Mercedes-Benz Forum

oso · #1 08-07-2008, 09:51 AM

After changing fuel filters my perfectly starting engine developed a habit of not wanting to turn over on the first try. IEventually it gets going but it takes some persuasion with a starter. Any ideas as to why?

redassag00 · #2 08-07-2008, 10:02 AM

Some more information would be really helpful....

I.e. year, make, model, mileage, known history, etc.

How are your glow plugs? And the wiring harness?

How long are you glowing your car for? I know on my OM603, I glow for 30 seconds at least in the winter, 15-20 in the summer, and it starts up just fine.

oso · #3 08-07-2008, 12:56 PM

right: '87 300TD, about 168000 miles, new glow plugs 3mo ago. Was starting perfectly before the filter change. Is it because not all of the air is gone from the system?

ctsoth · #4 08-07-2008, 01:07 PM

I doubt you suddenly developed glow issues at the magic moment of your filter change.

Examine the following facts:

1. Car started and ran fine with old filters.
2. Car hard starts with new filters.

I would think that the cause would be either a bad filter[s] or far more probable air in your fuel system. I suggest that you form an intimate relationship with your primer pump

Once the vehicle is started do you have a rough idle?

oso · #5 08-07-2008, 01:41 PM

Once it gets going it works fine. Only after it sits for a while it does not start like it should. And so I know - primer pump and sending pump are same thing different name?

Diesel Dan · #6 08-07-2008, 03:20 PM

Did you put oil on the rubber sealing gasket on the new filter? Is it tightened appropriately? Did you have to disturb any fuel lines when changing the filter? Any of these things could lead to an air leak that would not necessarily affect running of the car once started, but if it sits for a while the air leak can cause you to lose the fuel prime, and thus cause hard starting.

Your car doesn't have a primer pump. The older models had this device, which is used to manually pump fuel into the system to "prime" it. Unfortunately, the way your car is designed is to "prime" the system by cranking the starter. I usually disconnect the hose leading to the injection pump and use a hand operated suction pump to pull the fuel through, so it reduces the cranking time.

The "lift pump" is the mechanical pump that operates off a cam and pulls fuel from your fuel tank and sends it to the injection pump. I'm not sure what you mean by a "sending pump".

oso · #7 08-07-2008, 04:21 PM

OK- lift pump than... How do you check it for fuel pressure coming out?

Jetmugg · #8 08-07-2008, 04:32 PM

Was this a normally scheduled filter change, or were you changing filters due to clogging?

SteveM.

oso · #9 08-07-2008, 04:35 PM

I did it because I thought it may help with the lack of power, very sluggish take off.Symptoms still persist.

Diesel Dan · #10 08-08-2008, 12:01 AM

For sluggish performance do a search on this forum for "alda". That might be the problem. Or it could be any number of other things. I'm not sure of the best way to test fuel pressure other than with a pressure guage.

oso · #11 08-08-2008, 09:50 AM

Most posts I looked at addressed the line that goes from the back of the manifold to the switch-over valve and than to ALDA. My car ('87 300TD)has a vacuum line that goes off the side of the manifold to connect to the switch-over valve. I checked the line and the nipple- both look OK.

Diesel Dan · #12 08-08-2008, 10:43 AM

I have the same engine as yours. You can also adjust the ALDA, or some people remove it entirely. When I adjusted my ALDA, my off-the-line performance improved significantly. For more on this, you might search for "adjust alda" or "remove alda", etc.

LUVMBDiesels · #13 08-08-2008, 10:51 AM

Quote:

Originally Posted by Diesel Dan

I have the same engine as yours. You can also adjust the ALDA, or some people remove it entirely. When I adjusted my ALDA, my off-the-line performance improved significantly. For more on this, you might search for "adjust alda" or "remove alda", etc.

I took mine off and it made a world of difference