Engine riddle

[chef]

Just an update, I believe it's a howell programing problem. Now that i can drive it, when it is cold and operating in closed loop, I can stand on it and do brake burns without it dying. As soon as it warms up it falls on it's face. I pinched off the return line to up the fuel pressure to 15lbs, no change. I wonder what they will recomend next?

[tufcj]

EFI systems are in OPEN loop when cold. They only drop into CLOSED loop when everything is up to operating temp. In CLOSED loop, the mixture is being controlled by the O2 sensor. 15 PSI is normal for a GM throttle body. I think 13-16 PSI is the recommended range.

2 things I found with my Howell system. They weren't real clear on the purple wire they suggest hooking to the starter solenoid. It should be on the STARTER side of the solenoid (not the battery side), and only energized when the key is turned. This is for start enrichment, if it's powered all the time, you'll get WAAAAAY too much fuel. Try running it with the wire disconnected.

The other thing is if you still have the AIR pump hooked up. When mine was hooked up, it blew so much cool air down the exhaust that if it idled more than 30 seconds, it cooled the O2 sensor enough to drop into open loop, again the mixture goes way rich. You can either unhook the AIR pump (under the PS pump), or buy a heated O2 sensor.

Bob
tufcj

[chef]

Sorry i mix up closed and open all the time. My grand wag has a starter relay, so I don't think that is it. No air pump. My o2 sensor is heated. We read the block learn numbers at various RPM's, recorded ox sensor voltage and map. It was running very rich. They are sending me a revised chip, we will see.

[tufcj]

Find the purple wire in the Howell harness. Make sure it's only powered when the key is in the "start" position, NOT in "run", NOT continuous 12V. That's the problem I had with mine.

Bob
tufcj

[chef]

I'll check thanks for your help

[chef]

Purple wire is attatched to the power only when in start position, wire.

[chef]

Well, the failures continue, received the new chip from Howell. No difference in the running of the vehicle. I also installed the tuner rt software in my laptop and got the ALDL to USB cable. The BLM are running better now mostly 118-126. Here is where I have a question. the O2 sensor appears to be not working, I get no reading on my Air/fuel ratio gauge, confirmed with my meter. The Tuner software is recording 1.3 Volts with little or no change, is this a default? I am going to replace my O2 sensor this week, although I have never seen an o2 sensor failure cause these conditions. I am at the end of my rope with this thing

[tufcj]

1.3 volts seems high. It should be zero when cold. Range of a good O2 sensor is usually 0 - 1.1 volts.

Something I had in my notes.

Testing O2 sensors on the workbench.

Use a high impedence DC voltmeter as above. Clamp the sensor in a vice, or use a pliers or vice-grip to hold it. Clamp your negative voltmeter lead to the case, and the positive to the output wire. Use a propane torch set to high and the inner blue flame tip to heat the fluted or perforated area of the sensor. You should see a DC voltage of at least 0.6 within 20 seconds. If not, most likely cause is open circuit internally or lead fouling. If OK so far, remove from flame. You should see a drop to under 0.1 volt within 4 seconds. If not likely silicone fouled. If still OK, heat for two full minutes and watch for drops in voltage. Sometimes, the internal connections will open up under heat. This is the same a loose wire and is a failure. If the sensor is OK at this point, and will switch from high to low quickly as you move the flame, the sensor is good. Bear in mind that good or bad is relative, with port fuel injection needing faster information than carburated systems. ANY O2 sensor that will generate 0.9 volts or more when heated, show 0.1 volts or less within one second of flame removal, AND pass the two minute heat test is good regardless of age. When replacing a sensor, don't miss the opportunity to use the test above on the replacement. This will calibrate your evaluation skills and save you money in the future. There is almost always *no* benefit in replacing an oxygen sensor that will pass the test in the first line of this paragraph.

Bob
tufcj

[chef]

Getting closer, O2 sensor failed in such a way it was sending 12 volts to the ECM signal wire causing the computer to try to lean out the mixture. After it was replaced the BLM numbers went way rich, 148-172 any ideas how it could get this lean? Howell thought the ECM may have fried so I tried my buds who has the same system with my chipset, no difference. Is it possible my 360 breathes this well, and just needs a richer chip? I am leaning towards an internal vacuum leak. Opinions?

[chef]

Well after speaking with Troy at Howell, he thinks there "AMC HO chip" is just not enough fuel for the motor I built. To try to prove his theory and take away any mechanical issues, such as too long of a pushrod or internal vacuum leak, I took a spare temp sensor, plugged it into the harness and tied it away from the engine to see if it was possible to richen it up enough (to emulate cold start and a rich mixture). Sure enough the Air/ fuel ratio guage is reading stoich most of the time. Took it for a drive no more stumble or hesitation. I'll plug the laptop in today and confirm.
Thanks again guys