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Flloods Badly and Stalls when Engine Warms Up

It was 1950 or something when I posted the message below. I took the advice given and, finally, today started the truck. It didn't help.

The problem - stated more clearly and precisely than below - is that when the engine is cold, it starts quickly and runs not too bad (slightly rough). After about 4 - 8 minutes of idling, both TBIs spit 4 - 5 times the normal amount of gas and the engine stalls.

I spent a lot of time cleaning the coolant sensor connector, but everything remains the same.

Is there a diagnosis procedure?

> 1987 C20 4-wheel drive > > > > Problem more or less is: > > > > Can only be started - occasionally - with gas peddle fully depressed > > > > Flooding badly. > > > > On rare occasions - less and less frequent - runs OK. Exclusively or > > almost exclusively only if from cold start. > > > > Once from a cold or nearly cold start with air filter off, ran perfectly for > > about 20 seconds then saw both "injectors" suddenly increase fuel spray > > by about 5 times normal amount. Engine stalled as typical. > > > > Anyone have and experience or ideas? > > > > Just about everybody with the early TBI systems will eventually run into > this. The coolant sensor connector corrodes, making the ECM think it's > 40 below outside. The sensor is next to the thermostat housing, and will > have a yellow and a black wire into the connector. Pull the connector > off and clean it very well.
Reply to
Al Smith
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Stupid question, I know, but did you replace the sensor or just clean the connections? If the sensor is bad and going to ground or to open, it will either starve or flood your vehicle.

Sam

Reply to
GaWd

My guess is 02 sensor. Looks like when it switches into closed loop and realies heavily on the 02 sensor signal it's flooding out.

Doc

Reply to
"Doc"

Ehhh, retract my last statement, could be CTS or the 02, could also be fuel pressure regulator.

Doc

Reply to
"Doc"

Quite certain the sensor was a coolant tenp sensor.

However, I have no idea if that is the problem.

I don't know how much computing power this thing has, but I don't see any reason it couldn't be the engine control unit (if it has one) Could be something wrong with the temp sensor, the connection to the temp sensor, the wires connecting the temp senor to whatever it connects to or almost anything else.

Reply to
Al Smith

No, I just cleaned the connection. Is there a way to test the sensor.

Is it an off/on sensor, change resistance with temperatur, or what?

Reply to
Al Smith

Resistance changes with temp. As temp increases, resistance decreases.

Doc

Reply to
"Doc"

Try unplugging the sensor you think is the problem. The computer will go into "limp in mode" and run farely well. If you found the problem, it will run better.......Remember it might not idle well and generally run not so good, but if you got the right one it wont flood out.....

Reply to
Scott M

Uhhhh, wrong. It'll only go into limp home mode if the ECM detects a catastrophic failure. Unplugging a sensor is juts gunna f**k with the ECM and is NOT a diagnostic method.

Doc

Reply to
"Doc"

Could you define what "f**k with" exactly means.

What will the engine do if the coolant sensor is unplugged?

Reply to
Al Smith

Exclusively

If you unplug the CTS while she is running, the ECM will "see" an infinite amount of resistance on the signal which indicates a super low temperature. She'll then start DUMPING gas into the engine, the RPM's will pop up to 1700 or so at idle, and the SES light will come on and set the code for CTS sensor fault.

Doc

Reply to
"Doc"

temperature.

So then what happens?.....after the light comes on and the CTS code sets? Does the computer not set a pre-determend value to that circuit? I have found bad map sensors easily this way. Come to think of it, flooding engine, his problem could be the map sensor. p.s. dont plug anything in while running.

Reply to
Scott M

What is the resistance for a normally warm engine?

What if I ran the thing until it stalled, unplugged the sensor and put a resistor of the right size across the plug?

Or, what is the right resistance at temperature? I can just measure it at the terminal.

How can I get this thing diagnosed?

Reply to
Al Smith

Engine cold, unplugged temp sensor for TBI system Ran poorly as usual when cold. Smoothed out as usual. Ran smoothly for about twice as long as before. Shut off the engine.

Problem, I think, solved.

Reply to
Al Smith

Drive it around for a while with the sensor unplugged, see how it does. Youll have to stare at the CEL but big deal. Sounds like you may have found the problem. If it does good, replace the sensor. If you buy a book it will tell you what the resistance should be at diff temps. You might be able to find the info online. But, it sounds like you found the problem anyway. GL

Reply to
Scott M

194 degrees = 240 ohms. 158 degrees = 458 ohms 122 degrees= 972 ohms 76 degrees = 2795 ohms

HTH,

Doc

Reply to
"Doc"

"Doc"in the message above gave the R values. I had a strong indication this morning that that was the problem when I measured the resistance and instead of getting one number, it drifted upwards. The number I got was about 980 k and drifted up to over 1 meg at about 70 degrees.

The sensor can't be that expensive.I'll just buy one

What is a good book for this thing?

Reply to
Al Smith

Sensor is under 20 bucks. Haynes or Chiltons are ok, Factory service manual is the best but is expensive.

Doc

>
Reply to
"Doc"

I have installed a new ignition module and it started right up. But still seems to be loading up spewing smoke like it getting to much gas. The longer it runs (after like 2min) it wont rev up right. It starts to cough and chug then quit. Now it wont start again. I pulled 3 plugs and all were fouled. Could mine have this bad temp sensor I read about? My next move today is to replace the plugs and put new plug wires and look for that temp sensor. I don't under stand when I have changed ignition module twice now the engine starts up and runs for a few minutes and dies. Then it will not start again. Do you think the module goes bad each time.

Reply to
flogg55

Reply to
Tim Long

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