quick question about what sensor controls injector firing

[Movin]

Maybe somebody can get you the pin test for the relay
It can be tested with a test light.

[FestYboy]

dumb question, but i read the entire thread and no one mentioned the fuseable link....

as for signal, there are 2 pickups for the dizzy, the outer one (4 prong) is for spark and the INNER one (2 prong) is for injector pulse (batch fire system, 2 injectors fire at once 1&4 and 2&3) the also see 12v at all times, you should ALWAYS have power to the injectors with the key on. this info is true for '89 and '90+ cars.

[dueces]

Where would the fusable link be? would that cause the injectors to not have 12v? i havent been able to work on it but will get back to it in the morning.

john

[georgeb]

When you are checking voltage at the injector, are you probing the 2 pins or one pin and ground?

[dueces]

I tried each pin and grounded to the motor. i used the test light between the two pins

[FestYboy]

^ wth? no no no... first, the fuseable link is on the driver side strut tower marked EGI.
second, if you have the key on, you should see 12v on BOTH wires if the harness plug is still plugged into the injector. if you unplug the injector, you'll see 12v on just one wire. and you can't (won't) see any voltage if you test between the 2 wires... the test light needs to always be connected to battery ground. the injuctor ground is switched and not active unless cranking but DO NOT use a test light for that (draws too much current through the ECU).

[scitzz]

^ wth? no no no... first, the fuseable link is on the driver side strut tower marked EGI.
second, if you have the key on, you should see 12v on BOTH wires if the harness plug is still plugged into the injector. if you unplug the injector, you'll see 12v on just one wire. and you can't (won't) see any voltage if you test between the 2 wires... the test light needs to always be connected to battery ground. the injuctor ground is switched and not active unless cranking but DO NOT use a test light for that (draws too much current through the ECU).

Unless he was using the noid light...

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[dueces]

I checked each wire on the connector with it not connected to the injector. neither showed 12v.

[dueces]

Ok, Today I checked the actual voltage at the injectors. and with the pigtail disconnected, I get around .5V on BOTH leads. A buddy ripped the ECU out and opened it up to see if anything looked bad, said it looked good, so we plugged it back in. As he was checking the voltage at the injector, I disconnected the ecu and it went to 6V at the injector, which I have no idea what that means, but it seems to me that there would be a problem in the ECU, right? I am pretty much hopeless when it comes to diagnosing electrical....

[FestYboy]

ecu does not control voltage to the injectors, just the ground.

so, what voltage do you have at the EGI fuseable link?

[dueces]

the full 12v

[FestYboy]

ok so you're looking for corrosion along the power wire to the injectors (or a break/bent pin etc). start back tracking from the harness until you see 12v.

[dueces]

Ok, i think ive found it. when i put the fuseable link back in, it did read 12v on both terminals. Then today i started working toward the injectors from there and came to the relay. there was a 4pin pigtail to the relay and on the fuseable link side it had 12v, but .4v on the relay side. messed with that and got a better connection, and now had 12v going to the relay. tried to start it, got nothing, checked the injector for 12v, nope... well traced it back to the fuseable link again. So now im either going to get another link or i will make a jumper to see if i do infact get 12v at the injector

[Bert]

I don't wish your kind of electrical problems on anybody. Probably a lot of abandoned cars out there with similar convoluted issues that thoroughly confounded every hasty mechanic.

Oh to be able to go back to the days of a single wire to the coil and every thing was hunky dory when there was 12V, points that opened and closed, a carburetor and a mechanical fuel pump.

[dueces]

Lol yeah i can do a lot of it myself, but when i dont know where to start i get frustrated and in over my head.

Well the car is running now, but i have no runnings lights, ha ha. up by the ecu under the dash there are some corroded wires that im pretty sure contol just that....

Thank you guys for all the help!

John