Capacitor on firewall?

[68isgreat]

Hello, newbie here. I've got a crusy 68 short narrow stepside with the original 250 six, and I'm going to try to get it running. The tags say '98, so it appears it has been sitting since then. There's a small capacitor coming out of the wire loom and screwed into the firewall above the wire junction block. What is that for? Is it just a radio noise capacitor? It does have the original AM radio. Not sure if I should replace it or not. It's old and rusty.

Also, separate question. The engine turns over but isn't getting spark, so I'm replacing pretty much everything, and staying with points and coil for now, until I get it usable. While replacing the coil, I see that the yellow wire from the coil was spliced to the thick white fabric shielded resistor wire from the firewall, and then another 20ga yellow wire goes from there down to the starter. Doesn't that negate the point of the large resistor wire? Should I extend the large resistor wire down to the starter by itself, and then run a separate yellow wire back to the coil? Or am I supposed to run the large resistor wire straight to the coil, and a separate yellow wire from coil to starter?

Thanks! Pic below of the crusty old engine in question.

[kwmech]

That is what we call a ground strap. Very much needed

[68isgreat]

Originally Posted by kwmech

That is what we call a ground strap. Very much needed

Thanks. I was actually referring to a small round capacitor up near the drivers side firewall junction block, not the grounding strap. I'll post a pic of it to make that more clear. That grounding strap was hanging loose too, btw. I re-attached it.

[68isgreat]

Here's the capacitor:

[RichardJ]

.................................................................................................... ..........
..............................................................


>>I see that the yellow wire from the coil was spliced to the thick white fabric shielded resistor wire from the firewall, and then another 20ga yellow wire goes from there down to the starter.<<

That is actually a bulkhead connector on the firewall.
12 volts from the ignition switch, connects to that side of the resistance wire(cloth covered) at the bulkhead connector. The yellow wire(copper) connecting the resistance wire(nichrome) to the coil is as the factory did it. This is the ignition "run" circuit.
The wire going down to the starter solenoid is the "start" only, by-pass circuit.

Un-rap that non-factory tape at the bulkhead connector and see what that non-factory capacitor (at that location) is connected to.

Nichrome wire does not solder, so crimp connectors have to be very clean.
With the key "ON" there should be 12 volts at the resistance wire, at the bulkhead connector.

There will be 12 V at the other end of the resistance wire and at the coil if the points are "open" when you are measuring. Take the diist cap off and place a strip of paper between the point contacts or turn the engine till the points "OPEN".

[Rich72C10]

Originally Posted by 68isgreat

Here's the capacitor:

That photo is crazy big - the forums have attachments and then using something to put in focus on the area you are talking about is useful too [like I did with Snagit].

[68isgreat]

Thank you. I'll re-size my photos and mark them in the future.

[truckster]

It's a flux capacitor. Get her up to 88 MPH and see what happens...

[jabborabbo]

Originally Posted by truckster

It's a flux capacitor. Get her up to 88 MPH and see what happens...

I’m embarrassed to admit it took me a couple of seconds….

[Steeveedee]

That is for radio interference suppression. You can ignore it as far as the ignition system goes.

[54blackhornet]

I would caution while attempting to remove that thermostat housing ? Carb looks good. How about some more photos of the vehicles. We love photos..good luck and keep us updated ok.

[68isgreat]

Originally Posted by truckster

It's a flux capacitor. Get her up to 88 MPH and see what happens...

McFly! LOL

[68isgreat]

Originally Posted by Steeveedee

That is for radio interference suppression. You can ignore it as far as the ignition system goes.

Thanks! That's what I thought, but wasn't sure. I'm replacing everything tertiary, in the hopes that it runs good once I get everything replaced. New battery, cables, starter, coil, distributor/wires/plugs, new alternator, voltage regulator, fuses, oil change/filter, fuel pump, steel fuel line, and even a new carb. The main throttle valve on the Rochester was rusted in place, and I had to remove the throttle body to get it unstuck, and clean/lube it. After putting it back together, some gas seeps out at the gaskets. It needs rebuilding, so I'll get it running with the new carb, and rebuild the old one later. Engine oil looks good, 4 speed trans works great, even the brakes work, appears to be a solid unit, just needs TLC. I figure once I get it running well, I can always sell the 250 six later and upgrade. Or not. My '70 had a six banger and I liked it fine. Can't wait to hear it run after sitting for 25 years. All my parts should be here this weekend. I'm like a kid with fun new rusty toy!

[68isgreat]

Here's what she looks like now after I had it brought home. I have replacement doors, hood, front fenders, new rocker panels and cab corners. The rear stepside fenders are in great shape actually, no rust, but the bed is rusted out and bowed out inside. It was a farm truck. I bet it hauled everything back in the day. I'll have to get a replacement bed for it down the road. For now I'm going to focus on the engine, then strip the front down and work on brakes (will probably convert to disc) clean up the frame, then work front to back to the cab/ welding in new metal, etc., and then the bed. I don't have a shop, just a carport, so I have to be strategic about it. Wish I could get it done tomorrow. I really want to drive it!

[68isgreat]

Originally Posted by 54blackhornet

I would caution while attempting to remove that thermostat housing ? Carb looks good. How about some more photos of the vehicles. We love photos..good luck and keep us updated ok.

What specifically should I be careful with? Someone recently put new antifreeze and new radiator and radiator cap on it, so I'm wondering if the thermostat was done also. Guess I won't know until I take it off. I cut the heater hoses and am just doing a bypass for now. The heater core leaked fluid, so I'll need to replace it.

[68isgreat]

I'm going to have the original bench seat re-covered, so I can drive around with my dog. He really likes the truck already!

[roger0080]

Check the SPID on the glovebox door, if it is still there, and still readable, a radio suppression option would be listed as 9632 RADIO SUPPRESSION UNIT or something like that. Otherwise as Richard suggests, unwrap it a bit and see if you can trace it back to something.

[54blackhornet]

I only mentioned that because the bolts look pretty rusted. They are known to snap off if they have not been removed in decades. I would start soaking them in PB Blaster daily and give them a slight tap afterwards. I did this for weeks while working on other projects. Every time I walked by I gave them a bit of PB then a tap. I eventually got them out. Use a good quality anti seeze on reassembly.

[68isgreat]

Great tips, thank you. I'm hoping to get it started this weekend after my replacement parts arrive. Fingers crossed!

[54blackhornet]

Love the picture of your dog in the front seat ! My lab Simon loved going for rides in my GMC. Unfortunately I lost him to diabetes in 2020. Take yours for drives often, they love it and you will never regret the experience..Jack

['68OrangeSunshine]

It might have been for a CB radio too. The capacitor would suppress ignition noise.

[68isgreat]

Since it has the original AM radio in it, I'm hoping it might still work. I don't listen to the radio much anyway, so I don't need a fancy stereo, and it would really be a cool old school vibe if the original radio works. If it doesn't, can they be fixed or re-built?

[54blackhornet]

Yes they can ! Bluetooth is a nice upgrade. Do a search on AM radio restoration.