chaseincats

The pcv valve is new but I’ll have him check that

Hi guys, My friend's 75 280 has always made this strange hissing from the intake: https://youtu.be/mjrzNhHvXL4. Any ideas what this could be? We took off the cone filter and when we did we could hear it from the afm, so we took off the afm, and could hear it through the throttlebody, when we took off the throttlebody the sound stopped (kept the engine running by pulling the temp sensor cable and left the tps switch in to run rich enough for it to not die). We've checked multiple times for vacuum leaks using both a smoker and a can of starter fluid on the manifold and there are no leaks. We also tried 2 other throttlebodies and both make that noise. I've never heard if this issue - has anyone encountered it? -chase

That shouldn't be ok though I'd think, right? Guessing it's at least a sign of it needing to be replaced sooner rather than later, no?

Hi guys, I was driving my 78 today and the car died while driving. I pulled over, checked for spark, pulled the oil pressure switch to force the pump on and nothing. I have a manual trigger for the cold start valve and when I did it, the car tried to start but after the fuel rail was cleared of fuel, that trick no longer worked. Eventually, after playing around with it further by pulling the fuel pressure regulator hose it started. I then put everything back the way it was and it continued to run a little rough but smoothed out leading me to believe the stuff I did under the hood didn't change anything. The rest of the trip went fine and it ran great including another hour-home drive. The pump is at least 7 years old (the amount of time I've owned the car) and that could be dying (or dirty) but a strange thing I noticed is during the short trip in which it died (after driving for 45 minutes), the starter sounded different, almost like it was struggling to turn. After the car died, for all subsequent cranks after that, the starter sounded perfectly normal. I know these are two different problems but I'm curious if any of you have any ideas as to why both happened on the same trip (the car died about 3 minutes after that starting cranking issue). The battery is really strong (per the volt gauge) so it shouldn't be that. Any ideas? -chase

Gotcha - thanks all!

Disconnecting the blue wire from the ignition box worked. Should we leave the other wires connected or remove the box in full? All wires except the blue are still connected and the car runs with the tach.

That's odd. Nope, standard L-jet is connected.

Gotcha - I'll give it a shot and let you know tomorrow if it works.

Wouldn't that disable the blue wire or would that just allow the tach to work without interference?

Hold on...what other module? I thought the transistor ignition box was in the passenger footwell. Is this something else? EDIT: fuse box not fusible links lol sorry, brain fart. Why would the car run with both connected but the tach wire being the final straw? Is disconnecting it as simple as unplugging the box or are there other wiring changes I'd need to do for that to work?

The tach adapter is used for an "erratic tach" only it seems. Since the tach isn't working at all and is killing the car I don't think we'd need that. I'll give the wire colors a look this weekend and report back. Regarding the blue wire, it's on there in the FSM for '75 tho:

I thought those were rivets but apparently they just stripped all the screws - great

If we can figure out how to open these things we absolutely would haha

I plugged in a different AFM without play in the arm and the problem went away. I was able to see the richness/leanness change due to the play in the swing assembly on my air fuel gauge. You can tune the car using an air fuel gauge by changing the tension in the AFM's spring after confirming your water temperature sensor is working properly. There was a thread on here with a very long adventure learning how to tune my car with that method.

Sorry if I'm not explaining this properly. If you open your afm cover you will see an assembly that turns right to left. The wiper arm is connected to a counter weight that is mounted to a pipe that goes laterally through the housing to which the flap inside the afm is connected. There is play in that entire assembly regardless of how tight you crank the black gear controlling the tension spring. I'm assuming inside the unit (on the side opposite the circuit board (toward the radiator) there is a bushing on which the rod pivots which is probably dead. I'm asking if there is a way to access and replace that bushing. I hope that makes more sense!

Any place specifically you know that would buy it? Beats sitting in my garage collecting dust.

Finally got a chance to check and it's losing spark.

Sorry, I meant the entire arm assembly as a unit (arm, weight, flap - that entire assembly has some forward/back (open/close of the flap) play.

Question for you - my friend's AFM's arm is loose in that you can wiggle it back and forth about a millimeter or two. Tuning the car with an AFM is obviously impossible since the resistor arm isn't getting consistent results. I'm guessing there's a bushing in there somewhere that went bad. Can these be opened up, and if so, are the bushings available?

I changed my motor to the kia one a few years ago and immediately noticed a difference in terms of fuse consumption. I went from changing them every couple weeks to every couple of months.

So the resistance created by the resistor in the fan case does not move backwards into the fuse?

I was under the impression that the fastest fan speed setting was the best for the car since it wouldn't be using the resistor in the big fan case under the dash (I dont remember what its called).

Sorry to bring this back up but did you ever find out what was causing this Dave? My fuse is getting pretty toasty too.

It isn’t, I’m guessing that’s part of the crane system.

We ended up cleaning the terminals on the dropping resistor and now the car idles really well. After the fact, we measured all of the injectors through the ECU connector and they all ready ~10.5v. I checked the dropping resistor power wires, the main power wire was battery voltage and the one on the top left was around 10.5v (same as the injectors). Not sure if that's how its supposed to be, but now it's idling well.