1979-1993 & 94 Conv [Subscribe to Daily Digest] |
Sean,
I'm sorry the thermoswitch wires trick/test didn't help. Did you leave the switch's wires shorted together for a long time, like during the whole warmup period? (I didn't know if I made that part of the procedure clear-- just touching them together for a moment isn't what I meant). If that's no help...
I would try John's suggestion, too.
The cold start injector is sometimes known as the "fifth injector," and it might be fouling up things. It is electronically controlled--unlike the other four. This electronic control is accomplished by the vacuum "impulse" switch (two wires attach to it and both are brown, I think) and also by ANOTHER thermoswitch (they're everywhere on these CIS cars!!!) and the Transient Enrichment relay. This impulse switch is located (on my '84S) on a little bracket bolted to the fuel filter, near the radiator coolant tank on the (US) driver's side of the engine compartment. The t-switch is screwed into the top of the engine block between the fuel injectors for cylinders #2 and #3. The Transient Enrichment relay is located in the little auxilliary relay box on the driver's side, screwed to the fender.
The vacuum impulse switch is designed to sense certain changes in vacuum (large drops in vacuum, to be precise), as in when you accelerate. It creates a circuit across its terminals during this instant of vacuum drop, creating a path for current to flow to the cold start injector. The thermoswitch limits the injector operation to when the engine is "cold," below 110°F. The relay times out the whole process about 120 seconds after startup, if the t-switch doesn't reach 110°F before that.
It's called a "cold start injector" because the injector fires repeatedly during cold start cranking and up to three seconds after the engine RPMs rise above a certain level (400 RPM?). After that, it acts as needed to supply extra fuel for acceleration. Fuel tends to condense on cylinder walls and in the intake manifold when the engine is cold, so that's why this injector is used during warmup--the "transient" period from cold to hot when it needs fuel "enrichment," thus the relay's name.
One test in which it's easy to see if the cold start injector's controls are working is to connect a test light across the injector plug's terminals (wiring unplugged from injector--be careful with the clip, which must be pried up on the sides to remove plug--don't lose it!). I use a test light sold for the Bosch EFI systems at AutoZone here in North Carolina, which ends in two little pins and fits right into the plugs of the cold start injector (and also those of LH system fuel injectors).
Start car. If light flashes/stays lit while cranking, OK. Light should go out after cranking. Jab the gas pedal. Each jab should cause light to flash momentarily. Light will only flash once per sudden throttle opening and will not stay lit if pedal is held down constantly.
After 2-3 minutes, jabbing the gas should result in no light from the test lamp. If it still lights up when jabbing the pedal after five minutes, there's a problem with the electronic controls (the Transient Enrichment relay).
If the test lamp stops lighting up after 5 minutes, you might want to take the cold start injector off the throttle body to see if it's squirting gas despite the electronic controls telling it to be "off." The two Phillips head screws which attach the injector to the intake manifold are seated quite firmly, but you can remove them easily by using an impact driver WITH THE PROPER SIZED BIT! (I ruined one screw by trying to use a simple Phillips head screwdriver which was slightly small for the screw.)
After you get the injector out, you place a piece of duct tape over the injector hole and its two screw holes to keep air from entering and creating a HUGE vacuum leak. Place the injector in a small pan or bottle that is gasoline resistant. Then, start the car.
** SKIP THIS PARAGRAPH IF ENGINE WARM. The injector should squirt continually while cranking IF ENGINE IS COLD. After that, it only squirts gas upon acceleration (well, this is a stationary test, so whenever you jab the gas pedal).
If it NEVER STOPS, even after five minutes, then you need to do some troubleshooting: either the injector is stuck open through some physical obstruction or its electronic controls are telling it to stay open when it shouldn't (not the latter if it squirts gas when unplugged!).
I hope this isn't too convoluted and that it offers some understanding and help for you. I'm no CIS expert (or even a mechanic at all), but I knew how frustrated I was when I was learning the 900's CIS system.
--Micah in NC
posted by 67.35.160...
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