1988 300te m103 - very hard to start

[thehast]

Hi,

I own a 1988 300te with a m103 and it is very hard to start. I bought the car about 4 months ago and despite everything I do the problem seems to have gotten worse. The thing is, it will always start eventually, but I might have to crank it for 20 seconds. When the engine finally does start it usually isn't running on all cylinders until I give it some gas, then it runs just fine. It has no idle issues or power problems, it actually runs very well, it is just very hard to start.

I am fairly sure it is a fuel pressure problem as it is worst after sitting for more than about 15 minutes. If you turn it off and on again after running for a bit, it starts quickly. At first I thought it could be a fuel pump problem because I could hear the fuel pumps whining and they sounded like they were on their last legs. I replaced the fuel pumps and the problem persisted. I was then sure that it must be leaky injectors, so I replaced all the injectors. The problem still persists. Note that I don't really mind throwing parts at the problem because all of these parts were beyond their service life.

The list of things I have already replaced is as follows:
both fuel pumps and check valves
fuel filter
all injectors
OVP relay
fuel pump relay

things I am about to replace:
distributor cap and rotor
spark plugs
O2 sensor

Note that while this happens on "cold starts" it's summertime in Texas and it's 100+ degrees F.

Does anyone have any idea what my problem might be?