200FT Hard cold start. Pulls like a train when warm.

[Danders]

Hello all.

I've been nudged in your direction by a friendly chap at my local dealership. Maybe in sharing my story it might prompt some new ideas.

Ive done a fair amount of work so far, mostly suggested from other posts on this forum (thanks for that) but I'm still plagued with a cold start issues.

The problem - Will sit on the starter for minutes (!) stumbling and firing on one or two cylinders. Eventually it will catch and sit at a lumpy idle before warming slightly then purring like a kitten. I imagine in this time its hitting closed loop and sorting out the fuelling.

Some more notes;

- no fault codes
- has been going on through several tanks of fuel
- warm restart is fine
- had complete new (Bosch) ignition system from coil to plug (no improvement)
- checked fuel pressure regulator by reading rich-lean voltage swing on lambda when applying mityvac to the FPR vac line
- fuel pressure reg doesn't leak through vac line
- checked for air leaks on all vac lines
- fixed poor engine earth
- throttle position switch is adjusted properly at idle
- checked engine coolant temp resistance at cold and hot on back of ECU plug
- tried mate's ECU (LH jetronic 2.4)
- tried mate's MAF
- tried mates fuel pump relay
- new crank position sensor
- can smell fuel and have spark
- timing appears good
- injectors don't appear to leak
- starts on the button when warm


If anyone has any hints or can re-kindle my love for this car then please drop a reply!

Regards.

Andy

[mocambique-amazone]

Head gasket ?
good luck Andy, Kay

[Danders]

Hi there Kay, nice idea. I should borescope before my cold start maybe and check for oil. I've been putting this off as I have no mayonnaise under the oil filler cap or smoke after fuelcut
Thinking along those lines, though, could be valve stem seals? ...on several cylinders?
Thanks!

[Laird Scooby]

Add 2L of methylated spirits to no more than 1/4 tank of fuel. Don't be tempted to add a 500ml bottle to see if it has any effect, it doesn't work that way and just wastes the small bottle. Also the small bottles are £3.50-4.00 so not economical to buy.

I use this one from Toolstation :

https://www.toolstation.com/shop/Pai...+Spirit/p99550

Also don't be tempted to add more fuel, 1/4 tank is the maximum as it's all about the concentration which needs to be about 10% for the best results.

Here's how it works and what i'm fairly sure the problem is as you've seemingly exhausted most, if not all possibilities.

It sounds like you've got either contaminated fuel or condensation in your tank Andy - this is much more common than you'd think!
Water (whether as part of contaminated fuel or just plain condensation) is heavier than petrol so will always sink to the bottom of the tank. The fuel pump pick-up is also at the bottom of the tank. The fuel return is immediately above the pick-up point.

Once you've got it started, the returning fuel will stir up the water laying on the bottom of the tank so that there is more "neat" petrol getting to the pump so the car runs as it should. It takes some time for the water to settle down on the bottom of the tank so this is why the problem shows up more when it's cold. You may in bad cases get a few misfires when it's warm.

The meths doesn't mix with the water but forms an emulsion which is then burned off as the emulsion does mix with the petrol.

It has to be worth a try, if nothing else it will eliminate condensation in the fuel as a possible cause.

For the record, valve guide seals won't cause the problem you've got.

[TonyS9]

What car and year?

Early 940s had a cold start injector, later ones just used software map. B200FT sounds early to me.

Check all injectors by disconnecting in turn and comparing engine change.

Did you definitely check the coolant temp sensor (easy to confuse with the gauge sensor).

Does sound like a cold start system problem, so I'd double check temp sensor and search for cold start injector (under throttle body i think).

[Laird Scooby]

Originally Posted by Danders

- tried mate's ECU (LH jetronic 2.4)

If anyone has any hints or can re-kindle my love for this car then please drop a reply!

Regards.

Andy

Originally Posted by TonyS9

What car and year?

Early 940s had a cold start injector, later ones just used software map. B200FT sounds early to me.

Check all injectors by disconnecting in turn and comparing engine change.

Did you definitely check the coolant temp sensor (easy to confuse with the gauge sensor).

Does sound like a cold start system problem, so I'd double check temp sensor and search for cold start injector (under throttle body i think).

If it's LH2.4 Tony, that would make it a later one surely?

Andy, didn't notice originally about the closed-loop comment - that won't apply under cold conditions as the Lambda sensor needs to warm up before it starts giving an output - even the heated version need to warm up before they work! As such, closed-loop doesn't come into play until the engine is warm and if it runs as nice as you say when it's hot, i'd say the CTS is functioning as intended, especially if you've confirmed the resistance cold and hot.

[TonyS9]

Found an old post of mine where I thought the LH2.4 never had cold start, bob12 replied with:

"Jun 22nd, 2014, 14:02
LH2.4.2 has the cold start injector, but it was done away with by 'improved' electronics in LH2.4.4"

[Danders]

Hi all. Thanks for your time. I'll add some methylated spirits. I see what you're getting at. Fingers crossed. I should also drop some 'fuel' into a clear bottle from under the car - maybe I'll see the petrol floating. I like this idea as it does kick out plenty of condensation when its does finally start.

Last night I did some more checks - I dead-ended my main pump into a pressure gauge - it holds 9bar so I'm happy with the delivery pressure and the non-return valve.

Car is 1992 2.0 Wentworth.

Yep def coolant temp sensor pins 13 to 5.

..and gotcha regarding closed loop - my thoughts was it was running way too rich open loop (cold) then as it warms and goes closed loop the lambda was trimming off the excess.

[Danders]

Originally Posted by TonyS9

Found an old post of mine where I thought the LH2.4 never had cold start, bob12 replied with:

"Jun 22nd, 2014, 14:02
LH2.4.2 has the cold start injector, but it was done away with by 'improved' electronics in LH2.4.4"

..yep, no cold start injector in mine. Guess that means i have improved electronics!

[Laird Scooby]

Originally Posted by TonyS9

Found an old post of mine where I thought the LH2.4 never had cold start, bob12 replied with:

"Jun 22nd, 2014, 14:02
LH2.4.2 has the cold start injector, but it was done away with by 'improved' electronics in LH2.4.4"

Talk about retrogressive progress!

I know my 1988 LH2.2 equipped 760 doesn't have a cold start injector, all done by increasing the injection time. More logical in many ways than having an arbitrary cold start injector that operates for 8 seconds on a thermo-time switch (original idea on the D-Jetronic many moons ago) and quite possibly works on a similar idea on the LH2.4.4 although probably under ECU control.

Originally Posted by Danders

Hi all. Thanks for your time. I'll add some methylated spirits. I see what you're getting at. Fingers crossed. I should also drop some 'fuel' into a clear bottle from under the car - maybe I'll see the petrol floating. I like this idea as it does kick out plenty of condensation when its does finally start.

Last night I did some more checks - I dead-ended my main pump into a pressure gauge - it holds 9bar so I'm happy with the delivery pressure and the non-return valve.

Car is 1992 2.0 Wentworth.

Yep def coolant temp sensor pins 13 to 5.

..and gotcha regarding closed loop - my thoughts was it was running way too rich open loop (cold) then as it warms and goes closed loop the lambda was trimming off the excess.

Best way of getting some petrol is to disconnect the fuel return, add an extension hose to it for safety and direct it into a fuel can then (try to) start the engine. Let it run a short while (if it will) until you have enough of a fuel sample. Do this before getting the car started from cold to get as much of the "settled" fuel sample as possible.

Decant it into a clear container/bottle/jar or whatever and put it somewhere to settle overnight.

If water is present then it should be fairly obvious. You might need a fairly big sample though because the fuel lines will be full of the "neater" petrol from the previous run and the water will have settled in the tank. It's this that gets pumped through when the system primes to get up to pressure first thing.