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crazymanwally · Joined: 14 Feb 2003 Posts: 21 Location: zeeland, mi

My 735i has a problem starting after it has been turned off warm. It catches right away and actually starts for a split second and then dies. I usually just wait a half minute and try again and it sometimes works but sometimes it takes many tries. I'm sure my starter is not liking this. I've tried plugs, cap and rotor, valve adjustment, new intake boot and mass air flow, injector cleaner, different fuel, air filter, o2 sensor, new vacuum lines, and a new go fast chip in the DME. It still won't start easily when it's warmed up and it idles a little rough at all temps. My e30 has an idle enrichment valve and a few sensors to go with it. Does the 735i have some known problem that causes it to start hard when hot? Sensors to check? I don't have the $100 Bentley for the 7-series. Thanks. --Paul.

edjack · Joined: 04 Feb 2002 Posts: 3887 Location: San Jose, CA

I'd look for a bad ground on any ground wires that connect to the engine, especially on the intake plenum. Go over any other ground wires in the engine compartment. Actually remove the bolt holding the lug, and wire-brush the lug and the surface to which it mates.

It sounds to me like the injectors are not firing.

Nessy · Joined: 22 Nov 2004 Posts: 7 Location: Scotland

I have a similar problem. Why would any contacts be ok when cold and bad when warm?

KC Ron Carter · Posted: Tue Nov 23, 2004 8:27 pm Post subject: starting problem when warm

Fuel pump check valve.

I could replaced the fuel pump for $200 but I fixed the problem by putting in the fix from BMW for about $3.50,
part # "16 14 9 068 988"

Now the engine starts on first turn, hot or cold, overnight or after
standing for a while.

Diagnosis:

The check valve in the main fuel pump was leaking allowing the fuel injector rail residual pressure to bleed off resulting in formation of a huge fuel vapor bubble in the fuel rail and back down the fuel line toward the pump.

The extra cranking time was needed by the fuel pump to recompress and
eliminate the fuel vapor bubble in the line and repressurize the fuel injector rail.

Installation can be anywhere in the fuel pressure line but next to the main pressure pump is best.

It is a two screw clamp job.

Later,