|
|
|
1991 240
On the hot days here in Iowa it's necessary to use the gas pedal liberally to keep it from quitting upon starting... after research here I suspected a leaking cold start valve - too much fuel causing an extra-rich mixture. So, I unplugged the cold start valve electrical connector and now it starts fine.
My question is, is there anything I might have overlooked that I should check before I spend $150 on a used cold start valve? (New valves are apparently unavailable also.) On one occasion (before I unplugged the cold start valve) the check engine light came on and gave the error codes for air mass meter and oxygen sensor. I put a different AMM in and reset the codes, but the starting problem continued until I unplugged the cold start valve.
So right now it starts fine, but I wonder if it might be potentially harmful to drive it with the cold start valve electric connection unplugged?
I'll throw this in there too - the car tends to run cool, instead of the temp gauge right in the middle it's usually well below that. I'll try a new thermostat soon, but I wonder if the cool running temperature could indicate a chronic rich mixture from a faulty cold start valve.
Thanks!
|
|
-
|
|
|
One easy check is to check your air cleaner. In our 744 TI, the foam lining of the air filter disintegrated and clogged the air filter.
|
|
-
|
|
|
My impression is that the CSI is not really needed by the LH2.4 system. The ECU maintains engine revs/idle with the other injectors. Not sure, but I may have even removed it from my sister's '89 245.
--
1980 245 Canadian B21A with SU carb, M46 trans, 3:31 dif, in Brampton, Ont.
|
|
-
|
|
If you unplug the CSV and the rich condition abates (or changes in any way in August) replacing it will only be a waste of money and effort. The fact it is being turned on is the problem, and its response won't change if you replace it.
What turns it on is the computer's calculation of engine coolant temperature, and it should not turn it on until the temperature is below freezing. So, the fault is in the computer's determination of temperature, or more likely the sensor in the head or its wiring. If the sensor is open circuit, it will ask the computer to deliver full choke (in FI speak, long duration on the injectors) as well as turn on that valve you want to replace.
Meanwhile, before you figure out what is wrong with the ECT sensor, there's no downside to disconnecting the CSV. In fact, do it, so you don't continue to contaminate your oil with fuel. Then fix the sensor (or ECU or wiring) and change the oil as soon as you're done. Watch the temp gauge and see if the needle now runs where it should -- that measurement is separately made by the gauge sensor -- then determine whether you think the coolant thermostat is running open.
--
Art Benstein near Baltimore
Show me a piano falling down a mine shaft, and I'll show you A-flat minor.
|
|
-
|
|
|
Thank you so much for the reply! It was very helpful.
To clarify, which temperature sensor in the engine sends the information to the computer to alter the mixture on cold days - the sensor with one spade, or the sensor with two spades and a Bosch connector with spring release? I'm assuming of course it's the two-spade sensor, however, at one of the most popular parts websites the product terminology is somewhat confusing, but the pictures clearly show the quantity of spades. (The website lists the single spade sensor as "Engine Coolant Temperature Sensor" 460191OE, but I believe this is the gauge sender.)
I believe the sensor part number that I need to investigate is 1346030, it has two spades, and the Bosch connector.
Thank you!
|
|
-
|
|
|
Yes, the sensor the computer uses is the two-pin sensor with a black body, not the easy to access single-spade sensor used for the gauge. The parts sites all have problems with nomenclature.
You can get to this ECT using a 19mm deep socket and 10" 3/8"-drive extension after taking the AMM plumbing out, saving the work of removing the intake manifold and gasket, if you're at all comfortable with blind wrenching. By that, I mean you look at it with a flashlight and mirror, and then reach in with tools.
There are ways to confirm the sensor or its connector/wiring are the problem before replacement. Are you interested?
--
Art Benstein near Baltimore
Time flies like an arrow. Fruit flies like a banana.
|
|
-
|
|
|
Thank you!
What is the method for testing the functionality of this sensor and its wiring? I'd prefer to confirm it is the problem before I attempt to replace it.
|
|
-
|
|
|
The idea is to measure what the computer sees from the sensor. The simplest way is to turn the car off, and measure the resistance of the sensor from the computer's connector, and compare that resistance to a table with resistance values versus temperature.
A better way is to measure it with the car on, backprobing the input to the computer with a voltmeter, watching the voltage change from a high value to a low as the engine warms up, checking the operation under all temperature/vibration combinations you can create.
An introduction to this can be found in the 7/9 FAQ which applies quite well to the 240 in this instance: https://www.brickboard.com/FAQ/700-900/EngineSensors.htm#DiagnosingECTFailures
I say it is worth the trouble to learn. Besides, it is nice and comfortable compared to attempting anything similar under the intake manifold. Many times the connection is just poor, so fooling around under the manifold could drive you batty with both good and bad results.
--
Art Benstein near Baltimore
What's the definition of a will? It's a dead giveaway.
|
|
-
|
|
|
Using the instructions at the link you provided
https://www.brickboard.com/FAQ/700-900/EngineSensors.htm#DiagnosingECTFailures
the temperature sensor passed all tests with both voltage and ohms. Including warm-up conditions (I watched the ohms and voltage decrease in value, within range of values at link), I also unplugged the sensor to check wiring, and that test passed.
I wonder if this indicates possibly bad cold start valve or ECU... I'll keep investigating. It still starts much easier with the cold start valve unplugged.
|
|
-
|
|
|
Of course, it could be the ECU, with a defect that isn't commonly reported, or a pinched wire in the engine wiring harness, but what it absolutely cannot be is the CSV. There's no way in Iowa the CSV should be getting opened (activated) in August. Disconnecting the electrical plug merely keeps it from being activated.
--
Art Benstein near Baltimore
He often broke into song because he couldn't find the key.
|
|
-
|
|
|
Thanks again - I'll try these tests and eventually post a follow up after I get this sorted.
|
|
|
|
|
