'97 3.9 with no spark
#32
Yep, you are correct sir. 5 volt supply comes from the PCM.
Learn somethin' new every day.
Of course, in hindsight, it DOES make sense, as the PCM will disengage the ASD relay if it doesn't see the engine turning after three seconds. If the crank sensor were part of that circuit, once the ASD was disengaged, the PCM would NEVER see the crank turning, as the crank sensor wouldn't have power either.
Learn somethin' new every day.
Of course, in hindsight, it DOES make sense, as the PCM will disengage the ASD relay if it doesn't see the engine turning after three seconds. If the crank sensor were part of that circuit, once the ASD was disengaged, the PCM would NEVER see the crank turning, as the crank sensor wouldn't have power either.
#33
#34
#35
Ok, pin 86 is hot with the ignition on on. I finally got the coil off after much fighting and cursing, and I'm thinking its not so good. It's cracked all over on the bottom, and the thin plates that go up the one side of it are all pulling away from each other and cracked as well. Primary resistance reads 1.5, but the secondary wouldn't stabilize to get a reading, just bounced all over. So, I'll order up a new one and hope.
#36
Ok, got the new coil, and now it starts only with the throttle on the floor, and it shrieks for 1/2 a minute or so. The plugs are soaked with fuel. So it's flooding hard. The only thing I can think of is that I had both the coolant temp and the intake air temp sensors off the manifold when I cleaned it in the varsol tank. I thought I put them back in there proper place, but maybe not, and it thinks the engine's way colder then it is? One sensor had one wire to it, and the other has two wires. One on either side of the thermo. Where does each belong? I think I have the single wire one on the passenger side.
#37
Doesn't matter, they both insert into the coolant passage that leads to the thermostat. The single wire feller is for the gauge in the dash, the two wire guy is what the PCM pays attention to for engine temp. Check and be sure it is plugged in good, and the connection is clean. Did you happen to use any sealant on the threads? That will sometimes cause some issues. (although, you wouldn't think it should matter with a two wire sensor......)
#38
Hmmmm, ok. I'll check into those in the morning. So then the ait sensor is the one on the passenger side near the top of the keg? If so, I remember that one had a good coating of oil crud on it. Can I clean it off with varsol or brake cleaner without wrecking it? Any other thoughts on why els it would flood so badly?
#39
IAT sensor is just a thermometer wire suspended in a cage, very easy to damage. I don't normally recommend autozone for electrical parts, but the IAT is a fairly simplistic design and they are significantly cheaper there than other places.
a bad coolant temp sensor can wreak havoc on your engine. I had one fail reading full hot, and the engine would detonate like nothing I've ever heard. Any amount of throttle off idlecaused massive ping.
Might want to verify TPS voltage and throttle position. It's best with a scanner, as it'll interpret how much throttle the PCM detects from the TPS. if you aren't at zero throttle at startup, you could be flooding the engine.
a bad coolant temp sensor can wreak havoc on your engine. I had one fail reading full hot, and the engine would detonate like nothing I've ever heard. Any amount of throttle off idlecaused massive ping.
Might want to verify TPS voltage and throttle position. It's best with a scanner, as it'll interpret how much throttle the PCM detects from the TPS. if you aren't at zero throttle at startup, you could be flooding the engine.
#40