Strange Random Stalling

[JBeau]

I have a strange situation I am not really able to diagnose. The car in question is a 1978 124 with an 1800 engine, 32 ADFA carb and upgraded electronic ignition.

During a short trip (but enough time to get the engine up to normal operating temp), if I stop for a few minutes and restart the car, the engine will idle low and then stall while driving shortly afterwards. Sometimes I am able to restart it immediately, but other times I need to wait until the engine cools more completely. At no point does the temperature needle read above 190, and there are no other signs of overheating. Additionally, the temp seems to read in the 150-170 range after the initial restart (before the stall). Here are the things I've looked at so far:

Fuel system - I have removed the fuel lines and blown air through them (both directions) as well as removed the sending unit in the tank and cleaned the pickup tube and made sure there was no debris in the screen. I have also verified that the mechanical fuel pump is functioning properly.

Carb/choke adjustment -- The choke is not closed when this is happening, so there should be enough air in the mixture. I have also cleaned the jets and made sure that fuel was getting from the pump to the carb. I have adjusted the mixture and idle speed according to the Weber/Redline directions and the advice I have found here.

Ignition -- The car has been upgraded with electronic ignition (Marelli originally, replaced with the Vick Auto distributor and a new coil from Summit Racing). There was some corrosion on the wire leading from the coil to the distributor and in the top of the coil, which I thought was odd. I plan on replacing the plug wires soon, I just haven't gotten to it yet. Plugs are about a year old, with about 4000 miles on them. I haven't yet pulled them to take a look.

There is not really any pattern to the phenomena except that the weather has been in the upper 60s-low 70s (spring and fall), the stops have been 10-15 minutes in duration and I have (mostly) been able to get it restarted within about half an hour. I'm not very experienced (this is the only car I've ever worked on), so I am not sure what I should be looking up to get to a solution. I've tried to include all the relevant details here, but please let me know if I have missed something.

Thanks in advance to anyone who has some advice!

[18Fiatsandcounting]

There are many things that could be causing the issue, but I'd start with the automatic choke. If the engine is not fully warmed up, and you shut it off, when you restart it, the engine may still be somewhat cold and need a bit more choke.

The other potential cause is that the engine is flooding. If you experience the problem again, try holding the gas pedal to the floor as you crank it (don't pump it), and see if it starts easier. Once started, rev it up to 2000 for a few seconds to "let things clear out."

The other thought I have is that this may be kinda normal for a 45 year old car. They don't behave like modern cars, and so sometimes they get a little finicky until totally warmed up and happy. I would think you'd be OK when the temps are in the 60s and 70s, though.

-Bryan

[JBeau]

Thanks for the ideas.

The situation happens after I have run the engine for a while (at least half an hour) and gotten up to normal operating temp, and then it stalls with the indicator in the 150-170 range. It could be that the gauge is off (likely), and the choke closes somewhat. However the last time it happened, I removed the air cleaner immediately and it looked as though the choke plates were wide open. I will check the overall adjustment, though, that's not a bad idea.

I hadn't really considered flooding, but I will try to remember that if the situation occurs again (panic sets in for a moment, so no guarantees). Thanks for the advice.

Since I posted, I pulled the ignition coil off to clean out the rest of the corrosion. It seems the sleeve in the top of the coil that contacts the wire to the distributor had basically disintegrated and the wire was only contacting the screw set in the bottom of the coil. (Not sure that explanation makes sense, but it's the best I can do.) I'm not sure what would cause that, but I suspect it would make for a weak spark, that could cause this kind of scenario. I have a new coil on the way, I hope that helps.

I hope it isn't just a quirk of an old car. While I like an adventure, the idea of getting randomly stranded is a little much for me on a day to day basis.

Thanks again.

[18Fiatsandcounting]

Since I posted, I pulled the ignition coil off to clean out the rest of the corrosion. It seems the sleeve in the top of the coil that contacts the wire to the distributor had basically disintegrated and the wire was only contacting the screw set in the bottom of the coil. (Not sure that explanation makes sense, but it's the best I can do.) I'm not sure what would cause that, but I suspect it would make for a weak spark, that could cause this kind of scenario. I have a new coil on the way, I hope that helps.

Given this new information, I agree with you that replacing the coil is a good idea. A weak spark could be the issue, and coil performance drops off as things get hot. Old condensers (those "cylinders" on the outside of the distributor) can also start failing if they get hot. In your case, if the central coil wire (the large one to the distributor) had a bad connection, the arcing across the contacts can literally corrode away the connectors over the years.

Could you share what your new coil is? Some coils require a ballast resistor, and some don't. Some coil manufacturers provide this information, but not always.

The other thing about a '78 ignition system is that it had the dreaded dual points setup. It was meant to help with meeting emission requirements, but it can be problematic. In a nutshell, there is one set of points for cold running and one for hot, and if both aren't adjusted properly, there can be ignition issues as the engine heats up and cools down.

-Bryan

[JBeau]

The new coil is a direct replacement for what I installed last time, an Accel 8145Acc "Super Stock" coil from Summit Racing. It does not require a ballast resistor. The ignition system had been updated from points to electronic by a PO, and this coil had the proper resistance and output. I don't recall why I chose it otherwise over either the Marelli or Bosch coils, but it likely was cost or availability at the time. Less affordable the more I need to buy, though...

I'll make sure that the connection is solid, and check it every time I have the hood open for something. That way I can at least see if my theory is correct. If there is arcing inside the coil connection, I'll figure out what I can do to fix that. Either way, it's one more thing off the list of possible causes.

Thanks again for all the help.

[HappyHog]

I think it could be your electronic iginiation control module.

I converted my 74 from dual points to electronic distributer and Summit coil similar to you. This car hadn't ran in 20 years prior so I was trying to work my way through it without sinking a fortune in parts all at once. I knew I needed to replace the plug wires, but was deferring that until later after I got other things worked out. Well, long story short - I burned up the ignitition control module.

When it first started going out, it would run good up to temperature and then just die. It would start right back - and since I was taking short test-drive trips at the time, it would get me back to the house. Then one day when I was running it in the driveway (luckily it happened in the driveway) it quit and wouldn't start back. I blamed the coil at first - replaced it and the plug wires and I had the same thing - no start. Then I remembered I had an extra distributer from my old dirt track racing days with a GM electronic ignition module that looked identical to the one I got with my electronic ignition set up for the Fiat. Slapped it in and it worked and haven't had a problem with the ignition since then. Other problems, yes - but not with the ignition!

Hope this helps!

Happy

[JBeau]

Thanks for the responses. Here's an update:

I think I might be having a fuel starvation/vapor lock issue of some kind. After replacing the ignition coil and plug wires, the stalling situation repeated itself, requiring a tow home (yay, roadside assistance and short trips!), since I wasn't able to get it restarted, even about an hour later. The next morning I went out to move the car down the driveway to work on it and it fired right up lie nothing had happened. I futzed for a bit, but things have been busy and rainy (and cold) here since then, putting a pause on the work.

In futzing, I noticed a fuel leak from the inlet barb on the carb (32 ADFA), not from the hose. I looked here about what I should do to deal with that, but it also got me thinking about other points that air could be leaking into the system. I also found a couple of Youtube videos from "Uncle Tony's Garage" that discussed a similar situation. Based on those, I purchased a venting fuel filter, which I need to decide how to plumb into the system after I look over the rest of the fuel lines for clogs (especially in the vent line) and cracks or leaks that could be drawing air in.

That's the plan for now, as soon as it is not raining when I am home with time to wrench. Thanks again for all the advice, and anyone else who has some ideas about this, please feel free to share!

[TheBender]

I had a similar situation quite a while back. When you refill fuel does the gas cap have a suction/hissing sound when you remove? Also, have you checked the fuel return line?

[JBeau]

I had a similar situation quite a while back. When you refill fuel does the gas cap have a suction/hissing sound when you remove? Also, have you checked the fuel return line?

I haven't noticed any suction when I pull the gas cap, but that's another thought. The vent line might be blocked, which could contribute to the issue. I'll definitely check that out.

When I had the problem initially, I blew air through the fuel supply and return lines, but it could be that something clogged them since then.

[JBeau]

Just a (hopefully) final update to this issue.

I replaced all of the fuel hoses (supply and return) from the tank to the engine bay and discovered some pinhole leaks in the hard lines, which I replaced as well. Realized in that process that the vent line was simply hanging under the car, so I identified and reconnected it to the hard line running with the rear brake lines down the transmission tunnel and to the charcoal canister.

So far, this seems to have dealt with my intermittent stalling after a stop issue. I was able to use the car to run errands yesterday (similar weather conditions to normal issue) and made it home just fine. Not only that, the overall performance seems to be better, as though the engine is getting enough fuel, although I realize that I am likely making that up in order to boost my confidence in my repair.

I have yet to change the fuel filter, I will hold onto it in case I need to. I would prefer not to have to plumb into the system any further, but we'll see what happens.

Thanks again to everyone who provided some advice and guidance.

[davefrancisco]

I'm having a similar issue, but only occurs when i have about 1/2 tank of gas. Driving along fine, then loss of power followed by a stall. Starts right up, goes for a short distance, stalls again. Repeats until you find more fuel..

I looked in the tank and it seems fairly clean, also added a fuel additive to absorb any water.

I swapped the electric fuel pump and filter and will be putting a new sending unit in as well.

Carb was rebuilt a few months ago, so don't expect any issues there. New fuel lines were put in about 1 year ago.

Anything else I should consider?

Thanks

Dave

[18Fiatsandcounting]

Anything else I should consider?

The first step is to loosen the gas cap a bit and see if the problem goes away. If it does, then it's a problem with building up vacuum in the tank, and fuel pumps will struggle to pull enough fuel under these conditions. If loosening the gas cap solves the problem, you have 2 choices:

Poor Man's Choice: Just leave the gas cap slightly loose all the time.
Man with sufficient time on his hand's Choice: Figure out what is blocking the air intake bleed to the gas tank.

Choose wisely.

-Bryan

[davefrancisco]

Seems like the issue is now resolved. I replaced the sending unit and replaced the fuel lines feeding the electric fuel pump. I also noticed some fuel weeping from the fuel input at the carb. Bad clamp was that issue.

I have been driving the car a lot over the weekend and down to a 1/4 tank without any issues. And on top, the fuel gauge works again.

I guess the real test will be filling up the tank and running it to empty. I would assume the vacuum condition would be more easily created if there was a small amount of air in the tank.

As always thanks for the help

Dave