I just purchased a 91 190E 2.3 which runs good but is hard to start. I have ordered a cd but I thought someone may have had this problem. I bought this from a guy who buys cars to fix up and sell to supplement his income. He knows nothing about it's history. Odo shows 113K but I think it has a lot more miles than that. He did a valve job (had bent valves), new chain, and put in a used auto tranny. The car is hard to start whether hot or cold. It starts fastest if I move the gas pedal down a little bit, maybe 1/4 inch, but misses badly until I get the revs above 1000, then runs smooth from then on until I turn it off. When I restarted after filling with gas on the way home it started up normal. If I went inside and used the mens room and got a drink it's the hard start time again. This seems to be the pattern time wise. I drove it about 1000 miles home and got 28.2 MPG at 70 MPH. Any ideas? Thanks.

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85 300 SD ~ 115K
82 500 SEC Euro ??K
78 450SL 164K

A couple of different things come to mind. It sounds as if your engine is flooding while it sits. The injectors could be leaking down when sitting putting more fuel into the engine that it can burn on startup. Another possibility is the fuel distributor plunger is leaking fuel into the intake manifold as it sits. When dealing with a hard start issue it is a good idea to check rest pressure as a failing accumulator could cause starting issues as well as a failed fuel pump check valve. I'd start by checking the fuel pressure as it sits, it should hold around 40 psi. If that pans out then check the fuel dist for fuel leaking into the manifold and have the injectors bench tested to see if they hold their rest pressure.

Thanks for the reply. If fuel was leaking into the manifold wouldn't there be some black smoke at startup? None is seen from the driver's seat but tomorrow I'll get the wife to start it while I look at the tail pipe. I'll get a pressure guage and hook it up where ever I can tie into fittings.

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85 300 SD ~ 115K
82 500 SEC Euro ??K
78 450SL 164K

You won't necessarily get black smoke but it is possible. Often there will be a puff of blue smoke from the extra fuel washing oil from the cylinder walls. The best place to tie into the fuel system is the feed line going into the fuel distributor but without a good gauge set with lots of fittings it may be hard to tie in.

My 86 was hard to start when hot, and it ended up stalling as well when it got hotter outside. Turned out to be the accumulator was allowing the fuel pressure to leak back to the tank through the small drain hose on the accumulator.

I tested the bad accumulator theory by blocking off the return so fuel could not return to the tank, and the car ran much better. For me, this was the easiest test since it did not require the purchase of a CIS fuel pressure gauge set (normal fuel pressure gauges don't work for CIS). Or maybe you can find someone to borrow the gauge set from.

I attached a drawing of how I plugged the accumulator and return hose temporarily. I don't recommend leaving the plug in place, it could eventually leak. Use high pressure fuel injection hose since it will be seeing 70-80psi I believe. I used a few pieces of aluminum rod that fit the hose inner diameter and clamped it with hose clamps.

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Thanks bbarcher, I'll try that.

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85 300 SD ~ 115K
82 500 SEC Euro ??K
78 450SL 164K