Apologize for the long read but I tried to cover everything. Need some trouble shooting input on my roadster, the one in my avatar. Awhile back, last year, I was trying to figure out why there was such a sticky spot when letting the clutch out. Took it into a shop and after pulling the transmission twice it was determined that the clutch fork was tweaked. Well that was repaired and it works just fine. While it was in the shop I was told it would be a good idea to install a fuse block because everything was straight wired with no fuses. So that was done. Was told the roadster was ready to be picked up. Picked it up drove it and got on the freeway and it just dies. Started it up and got it going but everytime I left off the throttle it would die. Limped back to the shop. Got a call a couple days later and they determined it was a bad coil. The coil was replaced and the shop was nice enough to deliver it to me, about a 15 minute trip. Took it out for a drive and after about 10 minutes of driving come up to a stop light let off the throttle and it dies. Again limped home. Called the shop and told them the same thing was happening again. I checked the coil and the new one has the same symptoms as the one that was replaced. I just don't think it was the coil in the first place. Now the thing about the whole situation is the car ran just fine when I took it into the shop for the clutch repair. When I bought it I drove it home, about 20 miles, with no problems. Drove it to Midnight Mass and back, no problems. Picked it up from the shop, problems started. I was also able to replicate the problem while the car was sitting in the garage. I started it up and let it run for about 10-15 minutes then it starts crapping out. Was able to replicate the symptoms with the car just sitting in the garage running. In the garage when it started dying I checked the glass fuel bowl, full. It has an electric fuel pump. I'm thinking it has something to do with the fuse block that was installed. Been trying to get the shop to take the car back but I'm being told that there is no room for it and they only have one mechanic working.
It could be the car is slowly starving for fuel . bad ground or power supply to fuel pump ? When it stalks does it fire “ right back up” or is there a bit of a delay ? over heated ignition part ? Points and condenser ? Pertronix ? Other ?? cools be a bad or loose ground wire , possibly .
The last part replaced is the most likely suspect, but check all. I suspect something is getting hot and breaking down. The other common runs then dies is a fuel starvation, but that's rare to replicate sitting in the shop. I'm a big fan of infrared temp guns, but modern stuff uses cameras to monitor temps. I know there are stand alone units and some can work using your phone plus accessories. As @VANDENPLAS mentions, a lot of ills can be traced to grounds.
Loosen up your gas cap and drive it around the block or a tad further and see if that continues. Unless you have a separate vent system these old rigs take vented gas caps and if you have one that isn't letting air in the tank to take place of the gas or isn't letting enough in the car will starve for gas or act like it ran out of gas. I'm not apposed to the concept that something electrical is getting overheated real quick and acting up though.
That's valid advise, but I've never seen one pull a vacuum after 10 minutes at idle. It's usually 15-20 minutes of driving (more fuel used).
It has the same gas tank and gas cap on it from when I bought it. The only problem I had was the sticky spot with the clutch. The only thing I can think of is something went south when the new fuse block was installed.
Ooooo Mmmmnnn. What a mess. It’s probably not the clutch. Ok, it sounds electrical. Something is getting hot. This could be a nightmare. Who knows how this car is wired? Do you have a schematic of the harness? It sounds like you had a very “rudimentary” wiring system that worked and they were going to help you out. This may be a case of stacking poo-poo on top of poo-poo. I don’t know. The hard way which may be the only way is tracing every wire one by one. The chef’s kiss of this problem would be if all the wires were the same color.
Look for a wire that may be getting pulled by the clutch pedal action, you may even have a pinched wire.
I'm going a simple suggestion route that happened to me..... Change the fuel filter ( on the fuel hose to the carb ?) as even though the fuel bowl was full, if there is a booger in the line it moves and blocks fuel flow. What Carburetor is on it ? Here's one fellas miss. Old style with the internal Carb carbon thimble type ? If so - change it. Depending on how long it has been sitting prior to you owning it, if it's been a long time not running- just sitting , how old the Carb is - and what fuel they ran ( ethanol type) could have corroded the inside of the carb / floats. I've seen it. Let me know if I was right and win the prize.
Change that too, sometimes a micro carbon crack is there you really don't see unless you look at it real close. Resistors and fuel filters are cheap enough to try first anyway.
Had an electric choke that once warmed up would ground itself and shut the ignition off as it was hooked to the same circuit. Just an idea
Yup, easiest test to do. Bypass the electrical work you had done with direct power to the pump and ignition, start it up and watch for trouble. If there are no problems then you have an electrical problem. If it still happens then you need to look elsewhere (distributor, carb, etc.).
I'm wondering how old the gas is. Doesn't sound like you have driven the car very much. Old gas causes problems. We are guessing what ignition system is on the car, and what condition it is in. Bad points or a bad condenser (or a bad point replacement set up) could cause a problem. An improperly adjusted carb could do the same thing. Could be as simple as the idle speed set too low. I would start here. The plugged up gas vent is legitimate also, an easy test is to pop the gas cap off and do an hour long test. If the problem goes away, you know what it was, if it still dies, you know that is not the problem. Then go here. I'm standing in line with the guys that tell you to run a power straight to the coil to bypass the "new" wiring, and a power wire to connect directly to the fuel pump will eliminate any wiring issues the "fix it" wire job may be causing. You only need to run the test wires for about an hour, that would be 3x as long as it currently runs. You will know by then if the problem still exists with the "new" wiring bypassed. After these two simple tests, we can figure out which direction to go. Your problem is not likely a plugged exhaust, they would cause more problems at higher rpm, your issue is at idle, and the ride runs well at higher rpm.
Just for grins, change out the condenser. It's the only ignition part, that I can think of, that goes south when it gets warm.
While installing a fuse block it might have been necessary to disturb some of the wiring somewhere it's not easily seen. Things might have gotten jostled around enough to have loosened a connection. And while pulling the transmission and clutch they might have failed to reattach a ground cable, or two. If you're still leaning toward an ignition problem try reinstalling your original coil if it's still available and see if the issue is still there. Or soak a couple shop rags in cold water and wrap them around the lower canister part of the coil. Go for a drive and see if keeping the coil cooled down offers an improvement.
Somewhat left field, but do checkck if a breaker has been installed somewhere that's tripping out and then quickly resetting. Unlikely, but you never know! Chris
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