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Cold start issues with MFI, Start Valve suspected


Ensign

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Hello,

I have been having problems with cold starting on my ’72 tii. The car has to be cranked much longer than usual, but runs fine once started and it starts fine when warm.  However it does show signs of running rich. I decided to run tests on the temperature/time switch, starting valve and timer box as described by Mike Macartney in the BMW ’02 Restoration Guide.

I first checked to make sure that the connections to the temperature/time switch and starting valve were not reversed, and they were not.

Unfortunately the testing did not produce the results outlined in the book and I became suspicious of the starting valve and began running other tests on it. Fuel would spray when the ignition was on, but before the starter was engaged, but perhaps more importantly, the starting valve would spray fuel with the ignition on, but with the wiring plug completely removed from the valve.

I am assuming that the normal position of the solenoid in the starting valve is closed, but this valve seems to operate as if the solenoid is stuck open. If the fuel pump is running, the starting valve sprays fuel. So my first question is: Should the starting valve spray fuel when the wiring/power to it has been disconnected? Second, if the starting valve is bad, is the only option a new valve or can these valves be serviced?

Thanks, as always, for your input.

Tony Garton

 

1972 2002tii

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1 hour ago, Ensign said:

Should the starting valve spray fuel when the wiring/power to it has been disconnected?

 

Second, if the starting valve is bad, is the only option a new valve or can these valves be serviced?

 

Thanks, as always, for your input.

Last I checked, if you disconnect the cold start valve wiring, valve should not be open and permit fuel spray.

 

A valve can be bad due to debris or plain old fashioned wear.  You ought to be able to hear the valve engage "click" when connected and disconnected  to a 12v source.  I would suggest removing the valve and examining closely.  You might be able to fix, even for the short term, by spraying with carb cleaner (E.g., Berrymans or Gumout) to remove possible unwanted fuel deposits.  Can't see where it would hurt anything.

 

Another thought.  If the weather permits (i.e., if it is warm enough) and you don't mind some poor "cold" engine performance, simply plug the incoming fuel line and leave everything else connected.  Certainly not needed except for cold starting.  (Your mileage and battery life may vary in cold climates.)

Edited by avoirdupois
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8 minutes ago, avoirdupois said:

Another thought.  If the weather permits (i.e., if it is warm enough) and you don't mind some poor "cold" engine performance, simply plug the incoming fuel line and leave everything else connected.  Certainly not needed except for cold starting.  (Your mileage and battery life may vary in cold climates.)

Thanks, I like this idea.

(I did listen for the "click" of the solenoid, but did not hear anything.)

Tony Garton

 

1972 2002tii

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I have been searching the internet for the cold start valve. Bav Auto lists the Bosch #0280170010 as verified to fit my vehicle. Their price is $514.95.

FCPeuro.com lists the same Bosch part for a Volvo 142, 144 & 145. Their price is $168.59.

Tony Garton

 

1972 2002tii

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I ordered a new cold start valve and, while I wait for delivery, I plugged the fuel line going to the existing valve, as suggested by avoirdupois.

Cold starting was difficult (it’s been in the 40s overnight and daytime highs only in the 50s), but once started, the engine ran fine. I was curious as the old cold start valve was spraying fuel 100% of the time. (My gas mileage should show some improvement)

When the new cold start valve arrived, I installed it and ran some of the diagnostic tests again.

The thermotime switch is definitely bad and I thought the timer box was bad too until I discovered that it wasn’t getting any power. I lifted the fuse box and the green wire that provides power to the timer box was just hanging there. I couldn’t believe it! I connected the wire to fuse #11 and re-tested the timer box with positive results.

Now, with the faulty thermotime switch, I am only getting a 1 – second squirt from the cold start valve with each crank of the starter. Without an operating thermotime switch, the timer box thinks the engine is warm and tells the cold start valve to provide only a quick spray of fuel. Using short, multiple cranks, cold starting is not too bad. Warm and hot starting is fast.

I have a used thermotime switch and it tests fine. However the “head” of the old switch is much larger than the existing switch so I am not sure if it is correct for my car. Below is a picture of the used, good switch. If someone has a known correct one, outside of their car, I would be curious to know how it compares to the one pictured here.

5930bd40aa563_thermotimeswitch.thumb.JPG.fca0a4c399043e7b6dd5c27623843488.JPG

 

Tony Garton

 

1972 2002tii

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14 hours ago, Ensign said:

I am only getting a 1 – second squirt from the cold start valve with each crank of the starter.

 

You were saying that your weather is creating 40-50F temperatures.  The following excerpt from the KF injection manual says:

5931886ab8bce_Thermo-timeswitchgraph.thumb.jpg.262d5b265fb471f71b491eb5f915ec27.jpg

 

It sounds like it's working.

73 Inka Tii #2762958

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1 hour ago, PaulTWinterton said:

You were saying that your weather is creating 40-50F temperatures.  The following excerpt from the KF injection manual says:

Thank you Paul.

I am getting the default, one second squirt, regardless of temperature, but I understood that to be a function of the timer box, not the thermotime switch. The thermotime switch should tell the time box to extend the duration of the injection when the temp is below 35 degrees C.

I used a test lamp from the positive battery terminal to terminal W on the thermotime switch. According to Mike Macartney's book, the test lamp should light with a cold engine. My switch does not cause the test lamp to light, but my used switch does. Macartney has another test for the thermotime switch and mine failed that one as well.

Tony Garton

 

1972 2002tii

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