E21 Cold start problems
Subject: Cold
start problems
Sent: 31/08/04 09:33
From: Jeroen jeroen@bmwe21.net
Posted on bmwe21.net forum
Posted on the bmwe21.net forum by Rob in Sydney:
11/22/03 03:35
If the cold engine takes some time to start, but when it finally starts it is
running well, on 6 cylinders and at enough RPM's: Most likely the cold start
injector (an extra fuel injector mounted underneath the intake plenum) fails.
This
injector is switched on by the 'thermo time switch' which is fitted on the
thermostat housing, next to the temp sender for the instrument cluster. I
believe the switch with the 2 wires connected is the thermo time switch.
This
switch gives power for max 8 seconds (to the cold start injector) if it detects
a low coolant temperature.
The cold
start injector then injects extra fuel (delivered by a black fuel line coming
from the Warm Up Regulator) to help the engine start.
You can
check if the TTS switches (switch can be dead or connections corroded). If so,
you can pull the CSI to see if it delivers any fuel. Use a can to prevent
spillage or fire hazard. Before pulling the CSI, order a new o-ring for it at
the dealer because it is likely to have been sitting there untouched for all
its life so the o-ring will be worn.
Rgds,
Jeroen
Addendum 31-08-04:
I’m
working on a complete story on the mechanical Bosch K-Jetronic fuel injection system
as used in the 318i, 320i and 323i. But just some fuel related starting
problems:
·
Engine is hard to start and when the
engine finally runs idle is at 400 rpm or even less. If you press the
accelerator the engine dies. In that case the Warm Up Regulator (WUR) which is
supposed to deliver the extra fuel for a rich cold start, fails. Replace.
·
Engine starts but runs 1500+ RPM or
engine starts but doesn’t stay on at idle. In that case the Auxiliary Air Valve
(AAV) is stuck. BMW used electrically operated versions (check if is has power,
if the valve moves freely, can be adjusted but only slightly) and a mechanical
version that works on coolant temp and a wax element (can be cleaned and
adjusted). The mechanical version is now replaced by a self adjusting one but I
prefer the old version.
More detailed info to follow!
Jeroen