Mal... I have the same problem. The posts and extended explantion of the parts involved in cold starting issues don't directly address the warm start problem however.... least-ways as I read & understand them.
The BBB also doesn't address warm starting problems either.
As I see it there are 3 possible temperature related starting issues...
Cold --- mine starts immediatly when cold.
Warm --- mine takes several cranks... like several seconds of cranking.
Hot --- mine starts great when hot (like yours, within less thant 1/2 hour of shutting down).
The discussion in my BBB relates to the relays, cold start magnates, thermo-timer, etc. being activated below 35C (95F) ('cold') vs above 35C (Not cold, but also not hot).
What I've tried to gleen from the BBB and the discussion teachings on this thread is specifically what's going on with the features designed for cold start conditions that are modified to the negative side (i.e. harder starting) when the engine's somewhere between cold and hot... i.e. warm.
A direct question is simply what does the cold starting features and adjustments have to do, if anything, with the warm starting syndrom problems? Is there any relation at all in fact? or are there other factors that are primary for the warm start problems?... and if so, what are the other primary factors that need to be adjusted or corrected to fix/solve warm starting problems without adversely affecting cold and hot starting conditions?
I'm thus far not at all pursuaded by anything I've read or understood that the cold start features adjustments and operation has to do with the warm start syndrom when the car starts perfectly well at cold and hot conditions.
I've seen only one post that makes some sense to me... a possible fuel delivery problem from the fuel pump... and that until the cooler fuel from the tank and line's from the tank are forced thru the lines to purge the injection pump of vapor bubbles having formed (a semi-vapor lock), there's a 'warm starting' difficulty.
Or perhaps this relates equally to the Cooling Water Thermostat at the injection pump (also referred to in this thread as the Warm Running Device or WRD).. so that it takes several turns of the crank to get cooler coolant to flow thru the Cooling Water Thermostat and move the tip to the 'cold' level... which would otherwise be reducing the amount of additinal fuel and air otherwise required for a cold start.... hence a 'warm' starting problem.
Either of these speculated conditions are potentially reasonable causes for the warm engine starting syndrome from my way of thinking.
What isn't clear, however, is what has to change to prevent or solve either of these issues if they are the actual cause?
Addrssing one of the above possibilities... that of the cooling water thermostat:
The cooling water thermostat (at the injection pump, aka the WRD) operates a "Corrector Assembly" within the Injector Pump housing. The purpose of the "Corrector Asm" is to adjust the amount of fuel & air enrichment to "correct" for both the following conditions ---
1) Engine cooling water temperatures (up to 60 or 68C depending on injector pump version) and
2) Atmospheric Pressure changes...i.e. altitude correction thru the anaroid compensators.
The Corrector Assembly is a mechanical system of levers and fulcrum positions within the Injector Pump housing which adjust valve positions to allow more / less air and fuel to enter the system according to the 'correct' fuel / air mixture required under various temperature and atmospheric pressure (altitude) conditions. The lever's are moved by the Thermostat's rod and/or the anaroid compensator's rod which extend into and link to the Corrector Assembly within the housing.
With respect to the cooling water temperature correction, one possibility is that the cooling water thermostat is behaving as if the engine's already hot... i.e. not forcing enrichment of the fuel & not allowing the additional air to enter the intake. According to the BBB, [ 07-10/12b, section d) Warming Up Mechanism ] the enrichment and additional air decreases with increasing cooling water temperature until it's supposed to cease enrichment completely at 60C (143F)in some injection pump models or 65-68C (149 - 155F) in others.
One scenario for the cooling water thermostat rod not behaving as designed such that the 'warm start syndrome' would occur is that
a. During driving, the hot cooling water temperature extends the thermostat's rod to the position which causes the enrichment correction assembly to cease to enrich (which is as it's supposed to do after the cooling wather reaches 60 - 68C).
b. After shutting off the hot engine, the cooling water starts cooling down... and cools below the temperture threshold at which the thermostat rod begins to retract.... the magnitude of rod's retraction which is supposed to be proportional to the cooling water temperature reduction below 60 - 68C.
c. However, if the rod's retraction magnitude isn't proportional to the reduction in cooling water temperature as it should or doesn't retract at all while the cooling water temperature is "warm"... i.e. warmer than a cold enough temperature to force the rod to fully retract,
d. Then, when the cooling water temperature get's cold enough however, the rod finally 'snaps' back to it's fully retracted and correct cold position. In other words the thermostat's rod becomes 'stuck' in an extended position as if the cooling water temperature were hot, and only fully retracts when the cooling water temperature get's cold enough to create enough force to overcome the 'sticking' rod.
e. This would let the cooling water thermostat operate properly when the engine was cold enough... and operate properly when the cooling water was over 60 - 68C and hence the engine starting conditon would be as designed when either hot or cold... but
f. At some intermediate "warm" temperatures, the rod is "stuck" in an intermediate position which
g. reduces the amount of enrichment of fuel and air delivered when trying to start a "warm" engine.... so that there's insufficient enrichment required for the actual cooling water temperature for which the starting condition is designed... and thus
h. At some warm intermediate temperatures between some "cold" temperture and "hot" temperature, the "warm start syndrome" occurs.
That's one possibility to explain how the cooling water thermostat's misoperation --- i.e. 'stuck' in intermediate position or even at the fully hot (greater than 60 - 68C cooling water temperature) position after shutting down the engine until the engine cooling water in the cooling water thermostat housing get's cold enough to let the spring force overcome the friction causing the 'sticking' rod condition.
The other possibility with the identical symptom but with a fully functional thermostat would require the "Corrector Assembly" within the Injector Pump housing to be defective... i.e. something sticking within the mechanical lever and fulcrum shifting linkages.
NOTE that the above Cooling Water Thermostat operation with the "Corrector Asm" as described in the BBB has no electrical connections and operates completely independant of the start mechanism described by the use of relay's, thermo-switches, or thermo-time switches, solenoids, etc.
The Cooling Water Thermostat and it's connection to the enrichment "Corrector Assembly" is designed to correct fuel/air mixtures according to engine's needs for proper operation AFTER the engine's been started. Because it's function is to correct mixtures when the engine's running up to cooling water temperatures of 60 - 68C, it's therefore also been referred to in this forum as the Warm Running Device or "WRD"... key word being "Running". It's actually the combination of the cooling water thermostat AND the "Corrector Assembly"... the corrector assembly being the actual Warm Running Device.... the cooling water thermostat is just an actuator input to the "Corrector Assembly" and together these items function as a Warm Running Device ... just in case anybody was as confused as I was with the BBB's description of things compared to the teaching posts unique names used for the same items in this thread. The combination of the Anaroid Compensator which is also linked directly to the "Corrector Assembly" could therefore similarly be referred to as the "Altitude Running Device" (ARD) I suppose.
I'll be looking for some free time this week-end to check whether my Cooling Water Thermostat is retracting proportionally with engine cooling water temperatures cooling down to "warm" or not.
If that's working as designed, I'll go into the Starting Mechanism's possibilities that can perhaps cause or effect the hard starting conditions related to a "warm" engine temperature...but which would still work properly under "cold" and "hot" engine conditions. uetaederl l
Longtooth
67 250SL US #113-043-10-002163
'02 SL500 Sport
