Thread: 1947 Studebaker Truck w/Chevy 350 No Spark

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Hello,

I am new to this forum, but have been part of the Studebaker forum for years. I recently inherited a 1947 Studebaker M-5 Pickup. The reason why I am here, is that the Studebaker is equipped with the following:

- Small Block Chevy 350 crate engine (purchased and install around 1998)
- Mallory distributor (Model# 4748201)
- Mallory plug coil (Model# 29219)

Below is the sequence of events:

- Picked up the truck from the shop about a month and a half ago
- Truck had been in the shop for about 3 months getting new wiring
- Drove the truck home (about 5 miles) without incident
- Over the next four weeks the truck was started and driven around twice a week, about 3-5 miles each trip
- About two weeks ago I went to go start the truck and it was hard to start but started and idled for about 3 minutes before it died
- I decided to give it another crank and the engine started up again only to die about 3 minutes in.
- I figured that the truck might be low on gas so I went to go fill some gas cans.
- Filled up the tank, verified that I am getting gas to the carb and getting a healthy stream out of the jets
- Attempted to start truck, but would only crank
- Tested for spark and found that there was no fire
- Replaced inline ballast resistor, still no spark
- Tested coil resistance at both primary (1.9) and secondary (12,000) coils, seems to be within specifications
- Replaced coil anyway and attempted to start, but still no spark
- Tested ignition module inside distributor per this test: https://www.youtube.com/watch?v=PSiw4thM21k and module checks out
- Looked around for the obvious (loose connections, broken wires, etc.) and still can’t find anything
- When the ignition is turned to “ON” all gauges and accessories work that come off the ignition switch

Bare with me as I am not an expert when it comes to diagnosing electrical issues. I am looking for any other information anyone can provide here. Thank you, I appreciate your time.

Use your 4" hand grinder to grind down to bare metal at 3 locations that are close to each other under the hood, 1.any metal part on the motor, 2.the frame and 3.the firewall (just above where the passenger's feet would be). Use 2 ground straps (#2 welding cable or bigger) that are long enough to work. Bolt one end of one cable to the firewall with a through bolt and nut. Get inside the cab and hold the head of the bolt while your partner fastens the nut on the engine side of the firewall. The other end of that cable will be bolted to the frame rail in the same manner, together with the end of the second cable. Run the other end of the second cable to any metal part on the motor that could pass current to the engine block or cylinder heads. Make sure there is not paint or corrosion at the point where you will attach the end of the second cable. Secure the second cable end with bolt and nut (I like using star washers because they dig in). Now you have the body grounded to the the frame and the motor, the frame grounded to the motor and the body and the motor grounded to the frame and the body. Use RTV silicone to seal the connections so that moisture cannot rust them. Now that you have good grounding throughout the vehicle, go ahead with your testing.

Good grounds are the most missed components on any engine swap. NTFDAY will be along in a minute to orchestrate that for you.

.

If the truck was just re-wired.. verify that the shop did those connections for you.
If they didn't, you must. Grounds are the most important (and overlooked) part of the electrical system.

Put your jumper cable on the negetive batt. terminal and the other end on the eng and see if it starts

Thank you guys for your replies so far. I will take a look and verify. Stupid question: how would the vehicle run good, if these connections were not placed?

"IF" the ground circuit was broken or intermittent, it could run fine and then just stop when the circuit failed / resistance became to great

Guages are extremely sensitive to ground.
Since they work fine, and the engine cranks strong, ground wouldn't be my first thought. That said, extra grounds never hurt.

It looks as if the ignition is supposed to draw power through the ballast coil, and only gets full voltage at crank, that's interesting.

Anyway, chase the voltage.

Do you have full 12V to the ballast resistor?
Do you get full 12 V to coil during crank?

Check the voltage to ballast resistor with ground test lead on engine first, then with ground test lead on the negative terminal of battery. If voltage reads same, then grounds are good.

Test voltage at coil while cranking motor. Test as you did before, with ground lead first on block then at battery.

Another check you can try, is place negative lead on battery negative terminal, and positive lead on block, while cranking engine. If you see voltage then you have poor ground.

Okay, I have come back with some more information. I checked to see the following:

Ground straps: There is ground to engine, ground to frame, and ground to firewall. The connecting points all appear clean.
Checked rotor for burn mark: This seemed promising, but the wiring appeared to be in top order. No wear was present.

Again not being familiar with wiring, I turned the key on and measure voltage at the terminal of the ballast resistor that is connected to the ignition side and noticed that the voltage was at 4.73 volts. Shouldn't this be up around 12 volts? Or is this normal based on the last comment by DennyW? I was getting zero voltage on the other side of the ballast resistor that connects to the coil, but I was not cranking the engine at that point, the ignition was just turn to the "ON" position. Any thoughts?

I really like diagnostic threads on electrical stuff. Denny helped me out years ago with a old ford distributor these things can drive you nuts, but the more you learn in tracking down an issue, the better you understand the circuit for future problems. Thanks for this post.

Okay, so I went and worked on the truck and did the following:

Connected multi meter to ignition side of ballast resistor and engine ground.
Turned ignition on and read 11.95 volts.

Connected multi meter onto the ballast resistor terminals with ignition off and read
1.50 ohms resistance (resistor was warm from cranking engine earlier)

Found link here https://m.youtube.com/#/watch?v=PSiw4thM21k and tested coil by connecting multi meter to negative terminal on coil a to engine ground. With the ignition on the meter only read 1.6 volts, not 12 as mentioned. What does this mean, bad coil? I test primary and secondary windings on coil and they were good. Wire connections seem to check out as per diagram provided in previous post.

What was the voltage reading on the other side of the ballast resistor? I would suspect a bad ballast resistor.

Originally Posted by NTFDAY

What was the voltage reading on the other side of the ballast resistor? I would suspect a bad ballast resistor.

The reading was 6.24 volts on the side of the ballast resistor that goes to the positive side of the coil. This was with the key turned on but not cranking. With the engine cranking, the voltage reduces down to 4.30 volts.

Originally Posted by Stude47

The reading was 6.24 volts on the side of the ballast resistor that goes to the positive side of the coil. This was with the key turned on but not cranking. With the engine cranking, the voltage reduces down to 4.30 volts.

That sounds right. The ballast resistor is bypassed while the engine is cranking, it comes into the circuit when the engine is running. When you get it running you'll find the the voltage to be around 6 volts or so. If you have another coil handy swap it in place of the one you have. The primary resistance on most coils is 1.5 ohms or less and is hard without good equipment and since you have confirmed the ballast resistor is good and you're getting no spark out of the plugs that only leaves two things that can be wrong 1. the wire from the coil to the center of the dizzy cap or 2. a bad coil.

When cranking that side should have 12v back fed from wire that runs starter to coil-------You aren't getting proper volts -and you said your volt was 11.95 ??????? most batteries/charging systems will be nearer to 13-14 without any draw on them-------I think you have some serious resistant problems in battery cables/ posts/ clamps-----Its common that with age that the copper corrodes from the acidity around the battery end and also road trash stuff(road salt) underneath by the starter

Originally Posted by NTFDAY

That sounds right. The ballast resistor is bypassed while the engine is cranking, it comes into the circuit when the engine is running. When you get it running you'll find the the voltage to be around 6 volts or so. If you have another coil handy swap it in place of the one you have. The primary resistance on most coils is 1.5 ohms or less and is hard without good equipment and since you have confirmed the ballast resistor is good and you're getting no spark out of the plugs that only leaves two things that can be wrong 1. the wire from the coil to the center of the dizzy cap or 2. a bad coil.

I swapped out the coil with a new one that I purchased yesterday (2/19/17). Hooked it up and was still getting around 1.4 volts with ignition on, no cranking as before. Due to my lack of electrical experience, I don't understand why I have such a low voltage and not the 12 volts as indicated in the test: https://www.youtube.com/watch?v=PSiw4thM21k. I will see if I can chase down the wiring under the truck this weekend.