Trouble starting a 92 190E 2.6
 

After this car finally starts, it runs and restarts just fine - it's the first start of the day that is so tough. A friend believes that it's the idle mixture screw (accessible from top of air cleaner). He says it has to be tweaked just right to get the car started and then readjusted after it warms up, making it wrong for the next time the car is cold.

The process is tweak screw, try to start, tweak screw, try to start, over and over for about 5 minutes till it finally kicks over. He is convinced it is matter of getting the screw just right. I am convinced it has nothing to do with the idle mixture screw, but is probably fuel pressure not building up quick enough.

Any ideas? What does it cost to replace the fuel pump? Online parts sellers indicate there are 2 fuel pumps required - is that right? Or maybe some cold start mechanism is off?

Thanks
Bobby

When the vehicle is running, center the CO/mixture screw in the middle of its run cycle so you know where a solid reference point is (turn it counter-clockwise till it just about dies, turn it clockwise till it just about dies, then adjust it in between).

Your vehicle cycles the pump for about 1 second when you turn the key to the "start" position; pumps can be a cause of no-start conditions, but if there's no pressure in the lines to start with, your care isn's going to start either, so you need to locate the cause for the system leak (one-way valve(s) on the pump(s), leaking injector pintle, leaking fuel distributor, bad accumulator/pressure damper, etc.). You can do it the easy way and throw in a bottle of Chevron Techron fuel injector cleaner into the gas to hopefully alleviate the problem; if this doesn't help, expect to be sourcing the car out to a tech that can do a fuel pressure test to check residual pressures and fuel run pressures. Feel free to prime the system on cold'start by cycling the ignition switch 3-4 times to build system pressure up.