no start; 1988 carb. dist wire to ecu showing resistance

[katscan]

The blue orange wire, unpluged from the ignition module, going to the computer is showing resistance value to ground. Shouldn't it be infinite.Do i have a bad Ecu? Car was running fine and then just died while driving. has to be electrical.....have new icm(control module) coil is fine; weak spark with distributor out of car and turning by hand. install distributor and have no spark when engine turns....Any things to focus on....I have the dash out now, btw..

[bravekozak]

The blue orange wire goes to the

[bravekozak]

barometric sensor and ECA. When you drive to Denver, the timing needs to be increased for fuel efficiency.

[katscan]

so; do you think it is an eca output wire or eca input wire? I'm guessing ignition output. Thanks

[tooldude]

Not being familiar with your car, If I was there troubleshooting it, here are some things I would check; that the fusible link terminals are clean, especially the main, & the links are not blown; with the key on engine off, lights on, blower on high, wipers on, that the battery voltage across the posts is equal to the voltage taken at the ign. coil positive terminal; that the timing belt is intact; that no vacuum hose is off or open; that compression is good.

[Movin]

I wonder what the voltage to the ignition is while cranking the engine ?

[tooldude]

I wonder what the voltage to the ignition is while cranking the engine ?

I was wondering the same thing, but I once had a voltmeter ruined while probing the coil terminals as the spark traveled down the tower to the voltmeter probe (engine running). I'm unsure why that happened, but until I can be sure that won't happen again, I'm not going to do that or recommend it to anyone. I'm thinking the above will pull enough amps through the ign switch to show any significant voltage drop there and reveal an undercharged or weak battery if he has at least a voltmeter to work with. Correct or no? I didn't mention any possibilities about fuel as one has to start somewhere. Also katscan, I mention for you or anyone not familiar with this, you should not be measuring resistance through the computer's solid state circuitry unless you know it's safe. The ohmmeter can supply enough current to damage any very sensitive components.

[Movin]

Hopefully that was a digital meter..I looked at my 88 and found the wire and the connector shown in the diagram. I unplugged the connector and my ohm meter on the 20K scales shows a path to ground. The side going inside the disty shows open. I plugged it back in. The car started and ran as usual. I unplugged the connector while idling and the timing retarded and the idle slowed somewhat. It sounded like about 5 degrees of timing change. I plugged it back in and timing and idle returned to normal. I live high enough to trigger the baro switch. Those of you not so close to the stars should see no difference. I would see a large drop in fuel economy with this wire open. If one were to ground this circuit you should have a broader advance curve. It could be wired to be a regular fuel - race fuel switched circuit.

Another fun thing about a festy, any other ideas?

This circuit can not cause a no start unless it gets shorted to power. Do not do that!!

[katscan]

any chance for me; could you probe the disconnected wire . measuring the end going to the ecu; I am getting 12volts to battery neg post with ign inthe on position. Would like to know what you have. Thanks.

[Movin]

any chance for me; could you probe the disconnected wire . measuring the end going to the ecu; I am getting 12volts to battery neg post with ign inthe on position. Would like to know what you have. Thanks.

In that scenario I have 0 volts. But I am high enough to throw the barometric switch which is wired in series to the disty. When I check there I have 10.8 volts coming from my ECM. I have the same zero going to to the disty. I think I will go back out and try some more tests..

[Movin]

Running I still have about 2 volts less than battery at the barometric switch. I tried disconnecting and connecting it and I tried to blow in the port to see if it would pull the battery voltage down or send battery to the disty. I could not force it to switch.

I hooked into the stock O2 sensor. At a steady speed I averaged .35 volts. I unhooked the baroswitch from the disty. I heard the immediate timing change. I held the rpm steady and shortly the O2 went from .35 up to .45. I plugged it back in and it went back down. I repeated a few times just to make sure this is consistent..it is.

If you are at a lower altitude you should see the same voltage on both sides of the baro.

electrically something is missing from this ...where does the ground reading come from ?

[Movin]

Okay, I looked at the prints again and the power comes from the computer with key on or running. With the key off the computer is the ground present in the blue wire with orange stripe. Running there is voltage to the disty and baro. The baro at some altitude is just a switch to ground. It will pull the voltage supplied by the computer to ground.

At high altitude it leans the mix and advances the timing. It probably delays and reduces gas vapor from the cannister to the intake manifold. It may change when idle speed solenoids kick in. In california cars it may turn off or delay the egr. The timing part must be controlled by the ignition module as unplugging it but leaving the baro plugged in changes timing. The rest is by the computer and depends on the baro to switch.

[william]

you say you have spark from disty when turning by hand but none when motor is turning, is the timing belt good?

[katscan]

thanks movin for the info. My car starts if I unplug the left yellow plug on my ecu. Plug it back in and it wont start. i don't have a wire diagram. I do know that when I unplug that left ecu plug; the bouncing on my tach stops. If everything is plugged up; I can disconnect the blue orange wire at the dizzy and the bouncing stops. I am stumped. The car starts and runs if I keep giving it gas. Let off the gas and it dies.

So, you said with the car on; you read 10volts at that blue /orange wire at the dizzy? That makes me feel better; don't want to think my ecu was bad yet.

[katscan]

I have 12 volts with car on; not running; that 12volts is coming from ecu; Does that mean it is bad? I now think you said you have 0 volts at the blue/orange connector disconnected from dizzy with car on; not running. That is different than what I have and trust me; I have gone over every ground in the car.