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1990 Escort - random no start
01-24-2012, 12:23 AM
A friend of a friend has a 1990 Escort 1.9L automatic with a TBI setup. It has a random no-start condition that only seems to act up when its cold outside (below 20 F). I've only seen it act up once with minimal testing equipment, so I'm digging for answers.
The injector fires normally and flooring the pedal goes into clear-flood mode as it should. It has spark, but sounds out of time. It will attempt to fire unless the pedal is floored long enough to take fuel away. Starting fluid in addition to the fuel makes minimal difference, but results in intake backfires when you stop cranking. After a random amount of cranking, it will eventually fire and then the issue goes away completely. Once it fired, I was able to shut it down and restart it indefinitely with no hesitation. While running, it shown no signs of being out of time, vacuum leaks, etc. I have very little experience with the EEC system, but friends suggest a TFI module. A weak or mistimed spark seems to be the cause, but I'd like a second opinion. I shook and moved every wire I could find and checked the TFI pins for corrosion - no change.
01-24-2012, 06:49 AM
By "TFI module" are you referring to the ignition module? If so, the ignition modules tend to act up when hot rather than cold. That's not to say they never act up when cold, but since you mention it acts like it wants to start and is sparking, just out of time, I don't think that's the problem. Before condemning the ignition module, I'd put a spark tester in series with one of the plug wires and see if the spark is consistent. If so, I really doubt the module is the issue.
My primary suspect would be the engine coolant temperature sensor (not the sending unit for the gauge). It may be dumping too much or too little fuel in to the engine depending on if it is telling the PCM the engine is warmer or colder than it really is.
Of course you should also check fuel pressure and understand when the last time is that the car had a tune up (spark plugs, plug wires, fuel filter, etc.). Also make sure the battery is fully charged before trying to start the car. A weak battery can wreak havoc on the signals interpreted by the PCM.
01-24-2012, 06:21 PM
I'm referring to the ignition module on the side of the distributor. Everything I've read about them says that they generally fail when hot, which is not the case with this car. Spark seemed a bit weak, as it would jump the .020" setting on my spark tester, but not the .040" setting. Testing was done at the distributor tower for a random cylinder. When it sparked, it was a clean blue color.
I have no idea when the car was tuned up last. I suggested a full tune up as the first step, since it seems to need one anyway (along with a timing belt). If it continues to act up after that, I will give the CTS a look. The diagrams in Mitchell show that the ECM only has a few inputs (CTS, O2S, MAP, TFI), so tracking it down shouldn't be too difficult if I can catch it when I have some tools.
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