Popping Noise Cold/Accelerating

[Kilgore]

So the rig is running great...except for a loud popping noise coming from the fuse panel area. It happens when its cold and accelerating or if I hit the gas and open the throttle. Rig is a 10/75, desmogged and rebuilt motor. Electrical system is all stock but in good shape. The popping noise is accompanied by the smell of hot metal. What are your thoughts?

 

[Solace in Solitude]

Electricity arcing... find the short before you burn it down...

Could be in the area of the fuse panel... could be in the area of the ammeter (behind the gauge cluster)... there are several other harness connections behind the dash in that area (key switch branches off to steering column; DS front lights/horn branch off thru the firewall; etc.).

Bottom line... you have a hot wire touching metal... if its arcing enough to hear over acceleration, you should be able to find it by looking for burned marks on metal.

I would disconnect the battery and start looking closely, behind the fuse box and behind the cluster.

Good luck - you can do it!!

EDIT: You DO have a fusible link between your battery + and the harness on the PS fender well - right? If not, be sure you add one while you are fixing the short. @Coolerman has everything you need to install a fusible link.

 

[Kilgore]

Ok so a few things looking under the dash. Gauge wiring looks to be unmolested. The foul play looks like the PO had installed a 30 amp instead of a 15 amp for the tail lights. Thats not what I believe the culprit is. It looks like someone took a relay and went to a cheap aftermarket part. Thoughts?

 

[Michael B]

The silver "can" looks like a turn signal "flasher" for domestic vehicles. Definitely not Toyota.

 

[Kilgore]

No really familiar with relays but it doesnt seem like there are any new Toyota parts on the market. Im guessing these arent parts that wear very often?

 

[Solace in Solitude]

Part# 81980-30040 is the turn signal relay.

The yellow wires and the silver cylinder are not OEM...

I can't tell the wire colors that feed into the black tape and emerge as yellow wires... What color are they?

There's also some sort of connector in the tape end of the silver cylinder... What is that?

The black tape on the silver cylinder/yellow wires... Is that insulation coming out of that black tape?

I would pull the tape off and see what you can see...

Also, the harness, to the left of the yellow wires has some brown stuff on it... What's that?

I can't see where anything is arcing in that picture... Do your turn signals work? Especially the front DS?

The DS front lights/horn portion if the harness exit the cab, thru the firewall, above the clutch master cylinder... There should be a large firewall grommet in the firewall hole... The wires aren't arcing on the firewall, are they?

What does the metal around the fuse box look like? And how does the fuse box look?

These are old wires... I wouldn't want a 30 amp fuse in a 15 amp slot...

 

[Kilgore]

The brown stuff would be rust. The insulation is just mouse nest thats blown around the interior. Green wires that feed into the yellow. Turn signals work, lights work, gauges work. No signs of arcing on firewall that I could tell. The engine side of the firewall there is nothing there that looks like arcing either.

Do I need the emissions control box if I don't have any more emissions equipment?

 

[Kilgore]

Fuse box looks good, fuses look good. I took of the dash pad the other day and the wiper reach rods looked brand new. This cruiser looks great in some areas!

 

[Kilgore]

Update:

I have the blinkers using the correct relay now. They even make the tick tick they didn't make before! Don't believe this is the problem.

I also unplugged the "Emission Cont." box. This seems to have helped the problem 80%. It still makes the loud popping noise if I'm doing 40 in 4th and floor it. Overall it feels a little sluggish, like maybe something is sapping the spark?

Thoughts??

 

[Solace in Solitude]

So, the popping isn't as often, but still occurs on acceleration... Do you still smell 'hot metal' when it occurs?

I don't know why arcing would only occur on acceleration...

I don't know '75... On my '78, the dome light wire runs thru the windshield frame, to the roof top and back to the dome light, on the pillar... Do you have this dome light and does it work? Any sign of arcing around it?

Is your gas pedal linkage touching any wiring? Like... Floor it and short something out...

Same with the other pedals...

You say the gauges work... Including the ammeter?

I thought it was a loose bare wire, touching metal under certain conditions... Now, I'm thinking its metal being moved to touch a bare wire... Like the pedals, under the dash or the carb linkage under the hood.

If it really is arcing, you're just gonna have to look at every place that your wiring breaches metal... Holes in firewall... Springs around drivers footwell, etc.