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Old 11-03-2002, 11:49 AM
Posts: n/a

I've seen a few items that mess the minds of people who work on these fussy systems.

1. The injectors can look ok when tested exactly as described in the test procedures and still be worthless. Are you using an exhaust gas analyzer in conjunction with the mA readings at the EHA? Have you ever tried a comparison of the idle speed change caused by individual cylinder shorting? IF all compression numbers are relatively equal, the combination of these things can lead to at least an indication of whether the problem is related to the whole system, or the system is trying to compensate for one (or more) weak spots. For example, any injector that isn't getting the fuel atomized correctly leaves unburned fuel in its related cylinder, which affects the lambda, causing it to lean out the system.
Are you getting the same quantity of fuel through each injector? IF you make asetup like I have, that uses a known good fuel distributor, EHA, and pressure regulator as a test system, you can check both output pattern and quantity, something the CD doesn't give you. Run all 4 injectors at once, letting them spray into individual plastic ( clear is very helpful ) containers. Do a 20 - 30 second run with approximately idle deflection and measure the fuel. Then do the same at a mid and full throttle setting. THey should be within 10% of each other at any setting. IF not, try changing them among the 4 output lines to verify the problem is not upstream. Using this method lets you observe the injector pattern as part of the system, not just on a test stand.

2. Wiring issues: Check both input and output values at both ends of the wiring harness. If you're electrically inclined, you may be able to convert the various values from volts to amps and vice versa. Between these you may find, as I did, that corrosion and age had reduced the number of connected strands from the normal 8 -15 to 2 or 3: enough to get a reading, but not enough to carry the load.

3. Low cold idle generally means not enough fuel or not enough air, assuming mechanical and electrical issues are resolved. Make a fabricated idle air bypass, plugging the inlet hole and connecting the fabricated unit to the output. With a regulated air source ( compressed air with a control valve ) start the engine and vary the amount of air you let into the system. IF idle increases with more air, the fuel side is probably ok, and your problem is in the air inlet and management of to intake system. IF it decreases, the fuel side is likely the problem. IF there is no effect, take the adapter that gets the air into the intake manifold apart and clean it so all orifices are open and try again.

4. Uncalibrated timing light, or incorrect selection of timing marks or timing mark indicator. Consumer reports did a check a few years ago and found timing lights varied by up to 10 degrees. What would a change of 10 degrees mean to your system?

5. Leaky high voltage wires. Cold, wet engines are most susceptible to high voltage leaks. Big leaks can be seen in full darkness. Smaller leaks are harder to find.

6. One last thing: did you ever get a load of bad fuel, or do you know if that ever happened? Though the filters are pretty efficient, you can get enough stuff through to mess up the distributor, even plugging the littel filter cones.

7. Finally, try purposely enriching the mixture, so the mA readings at the EHA indicate the system trying to lean out the mixture. Start with about a 4mA change and check the effect.

8. If you're brave, and can visually examine the computer circuit board, use a 3x or more magnifier and look for cold or fractured solder joints. These can be repaired.
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