EFI relay unplugged

[240260280z]

Take resistive measurements of the water temperature sensor in the morning before starting. It should be the about the same as the ambient temperature.

Take another measurement after the engine is up to operational temperature.

[rcb280z]

Ok, thanks Blue. Will do those tests in the am before work and post results.

[240260280z]

fyi:

[TABLE=width: 500]

<tbody>[TR]

[TD]°C

[/TD]

[TD]°F[/TD]

[TD]Resistance[/TD]

[/TR]

[TR]

[TD]-30[/TD]

[TD]-22[/TD]

[TD]20,300 Ω to 33, 000 Ω[/TD]

[/TR]

[TR]

[TD]-10

[/TD]

[TD]-14[/TD]

[TD]7,600 Ω to 10,800 Ω[/TD]

[/TR]

[TR]

[TD]+10[/TD]

[TD]50[/TD]

[TD]3,250 Ω to 4,150 Ω[/TD]

[/TR]

[TR]

[TD]+20[/TD]

[TD]68[/TD]

[TD]2,250 Ω to 2,750 Ω[/TD]

[/TR]

[TR]

[TD]+50[/TD]

[TD]122[/TD]

[TD]740 Ω to 940 Ω[/TD]

[/TR]

[TR]

[TD]+80[/TD]

[TD]176[/TD]

[TD]290 Ω to 360Ω (325Ω is typical for an L28 engine at operational temp.)

[/TD]

[/TR]

</tbody>[/TABLE]

(crappy content management software for this site removes "spaces" so the table above looks screwy... it looks perfect when editing however)

Identifying the water temperature sensor

Schematic showing temp sensor pig-tail connections.

Edited January 26, 2012 by Blue

[240260280z]

This drawing shows what the EFI system does for any engine temp and rpm (x axis of graph).

For your cold starts, everything on the left side of the graph is significant up to the x point of "Water Temp 158F 70C"

All of the start enrichments are driven by the ECU except:

1. Cold Start Valve Increment (Which is driven by thermotime switch and the ecu) It fires only when cranking and only when the water temp is below 60F to 70F. After about 12sec of cranking, it no longer sprays.

2.Correction by Cooling Water Temperature (Which is driven by Water Temp. Sensor and ecu)

3.Correction by Intake Air Temperature (Which is driven by Air Temp. Sensor in AFM and ecu)

My initial guess from your symptoms is water temp circuit.

Edited January 26, 2012 by Blue

[rcb280z]

Blue, thanks for all the info! I agree regarding cold start circuit. Unfortunately I just discovered a dead ohm meter. Have to get 9 volt battery after work and proceed with tests tomorrow morning. Post results then.

[rcb280z]

Ok, here is an update I guess. I got a battery from my neighbor and tested the water temp sensor. I hope you can follow this Blue. As i have said before I do not understand my way around an ohm meter like I wish I did. I set the meter to 20k because I didn't get a reading on 200 or 2000 and with both leads, one lead on one pin and the other lead on the other pin my reading was 2.96 with garage temp at 61 degrees. Did I perform this test correctly?

Edited January 26, 2012 by rcb280z
forgot some info

[SteveJ]

That reading sounds right. It would be 2,960 Ohms.

[rcb280z]

Thanks SteveJ. I guess that means I go back to the drawing board.

[240260280z]

Sorry I have been travelling all day.

OK that is step one done.

Now measure at the ECU Connector at the driver's foot pedal (pins 13 and 49). It should read approximately the same resistance as at the sensor.

Disconnect the battery -neg or +pos terminal before disconnecting at the ECU.

[rcb280z]

Blue, please don't apologize. I will try to get this done before I travel out of town tomorrow. I will take my laptop with me to post the results. I am going to my brothers to teach him how to rebuild the rear end in his mustang. Mechanics I do fine. Electrical I get by. It is time to take some classes I think. You are never too old to learn. I did this test a couple weeks ago but should have written the results down because I can't remember what they were. Anyway, thanks again.

[SteveJ]

Phil is Canadian. It's in his nature to apologize whether or not there is a reason. I even saw a news story about that on CBC when I was doing some work near Toronto.

[240260280z]

I am sorry I am Canadian