Dr Chill

When car sits for more than 30 minutes, the starter has to crank 15 or 20 times before firing up the car. Initially this was intermittent, but now it's almost all the time. If restarted after only a short time, the car starts right up. No problem with rough idle or stalling. I suspected it had something to do with the cold start valve so I replaced the sender (temp sensing relay) and installed a new battery to no avail. This vehicle does not have a fuel check vakve as the fuel pump design was changed mid year to a pump that incorpoates a valve to eliminate check valve problems-at least that's what MB parts and service told me. I really want to fix this problem but not by the shotgun approach. Does anyone know of any common causes for this on this car? Thanks in advance for your consideration.

Dr Chill

Anyone?

bamberger_1

Most probably it is the back flow valve of the fuel pumps(s). It has ever been a somehow "integral" part of the pump assembly, but was never recommended in case of problems to replace it w/o replacing the pump. The thing is that the fuel pressure in the system drops quickly after the engine has been switch off, and it needs more crancking to get the fuel pumps running increasing the pressure. This failure is simple the locate if the mechanic can perform the fuel pressure test procedure. It will simply show wheter or not the pressure drops. I hasd the same problem, swapped the fuel pump incl. the back flow valve and all was fine again.

Dr Chill

I suspected the same also, so I took the cover off the fuel pump and filter and started the engine. After letting it run for a few minutes, I shut off the engine and immediately used a vicegrip to clamp off the fuel line between the pump and the filter. I figured this would prevent the fuel from draining back from the engine. When I unclamped the line 2 hours later, it still took a long time to start. Do you think this rules out the fuel pump?

bamberger_1

?? The question is how good the vice grip is preventing back flow. Can you hear the fuel pump(s) running (e few seconds) before the engine fires. (position 2 of the ignition key). I checked mine by just turning the key 3-4 times (not firing the engine) to get the fuel pressure up and the 5th time I started the engine and it worked pretty well then, since the system pressure built up high enough.
The better (unfortunately more eypensive) way to find out is to have some one meassure the fuel pressures before and after fuel distributor and towards the injectors.

hornbrod

I had the same problem, listened to Bamberger_1's advice, replaced the fuel pump (although I used a Pierburg); problem solved. Starts instantly in all temps now.

Don

Dr Chill

Well, before I could do anything, the car started running very roughly and then wouldn't rev past 2000 rpm. The ASR and check engine lights came on and I had to limp to the dealership maxing at 30 mph while pissing off many people behind me.

When I turn the key to position 2, there is a loud clanking noise from around the intake. The noise persists after starting the engine for about 10 seconds before it goes away.

Hopefully the dealer will figure it out in the morning as they are open on Saturday now.

Anyone care to guess before the truth will be known?

Dr Chill

Unfortunately it was a broken throttle slide which is also called the throttle actuator. The part was $925 and total bill $1403. When I started the car the next day, it still was hard to start and on the way back to the dealer the car began shaking as if ti was missing on one cylinder. Now I'm $500 more in the hole for a new ignition coil, fuel pressure regulator, and spark plugs. When will the bleeding stop?

Dr Chill

After appealing to their senses of pity, they dropped my bill to $290 due to the inconvenience of bringing the car back in and the fact that I'm a good friend of the sales manager.