Stalls once it warmed up - 305

[Shugalou]

Hi guys,

As expected my first ride with my family left me stranded - I gotta get their confidence back ha.

Everything seems fine until about 20 minutes of driving and then I can feel it start to miss and stutter...at the same time I notice the oil pressure begins to drop and return drop and return. After it dies I can restart but as soon as I put it into gear it dies.

I originally thought it was the coil but figured it wouldn't start if hot and expanded. I spoke to a speed shop and they said it could be a carb issue...if it's running too rich it's fine when cold but once heated up it could be flooding it out.

I'm thinking carb myself but would love to hear from the experts.

Thanks

[Dead Parrot]

Electric or mechanical oil gauge? Thinking maybe you are getting an intermittent electrical issue that is causing voltage to your distributor and gauges to fluctuate. Low voltage = weak spark = poor engine power.

If you have a vacuum advance, is it on ported or manifold?

Gas tank vent working properly? Next time it dies, loosen the cap. A bunch of sucking noise means bad vent.

Fuel filter nearing end of useful life.

Low probability is some kind of vapor lock.

[Shugalou]

Parrot thanks for the response.

I'll have to inspect the electrical...I know there are a couple of loose wires under the dash as they came loose while doing the brakes...not sure if there is something in that or not.

Vacuum advance is a new term to me I'm going to have to learn what this is before I can answer that.

I'll try the gas cap test -that would be an easy fix and could explain it...never thought of that one...even though I read about that for my snoblower/

Fuel filter is new...it's a cheap inline plastic filter but I can see it working.

I just tried to start it after about of month of sitting and after two tries of not working I noticed the fuel line is leaking onto the floor. This is first time I noticed this but I wonder if this could also be the culprit. I'll be installing new fuel hose in the next hour hopefully.

[chrismoore701]

Follow your fuel line and be sure it is away from all heat sources including your radiator hose. Heat equals vapor lock

[Shugalou]

Hmmm well this looks like it close to a heat source. I just replaced this today after it started leaking and I did as the previous owner had it thinking it worked for him. It attaches to the original hard line goes behind the alternator and up and out.

Is there a better way to route this?

Parrot I haven't had a chance to look into your suggestions yet but I will over the next little bit.

Thanks for the input guys

[chrismoore701]

Is your fuel line touching your heater hose to the left of the pic? And is your filter on backwards?

[Shugalou]

Fuel line is in correct - tocarb - pointing to carb.

No the line isn't touching the heater hose.

[Shugalou]

Parrot - You've given me something to think about with the electrical...I haven't confirmed it yet but I'm pretty sure it's an electrical Oil Gauge as it's factory.

[TrybalRage]

Choke not operating properly?
Someone leave the original filter in the carb and it's dirty?

[Shugalou]

Trybal,

Good guess with the filter but I have already checked in there and the bonehead left the spring and metal cap in there with no filter...It has all been removed and an inline filter is now in place.

Choke? Hmmm I'll have to find out how to test that one.

[Shugalou]

Parrot - it's a ported vacuum advance - what are your thoughts on this? If the carb is in need of a rebuild (the truck has been neglected by the previous owner) could this cause problems?

[cadillac_al]

It sounds like it needs a different ignition curve. Ported vacuum is almost never better than manifold vacuum. You should switch to manifold vacuum and reset the timing and idle speed. You can play with the timing a bit, usually 10-16 initial will get you in the ballpark, hopefully no more than 36 total.

[Shugalou]

Cadilac, I had read the same thing about manifold vacuum. These older systems are new to me so I'm learning as I go. I'll have to do some research on setting timing.

[Dead Parrot]

There are several threads on ported vs manifold on this forum, some of those link to other sites and have very good write ups on the topic.

I switched mine several years ago after reading some of the write ups and have been pleased with the results. Better idle and part throttle response.

Make sure the advance vacuum pot is still working.

Another thing to check is the suction line(s) from the tank to the metal line or from the switch valve to metal line if you have dual tanks. When those start failing, they can cause intermittent fuel flow issues. Same for suction line just before the fuel pump.

[Shugalou]

Parrot - Yeah I think will attempt to switch once I get a timing light.

To test the Vacuum pot I need to hook up something - like a bleeder and see that it holds pressure correct?

Suction lines are new to me - I'll have to investigate that - is there any visibile signs other than the obvious fuel leaking out of them - rusted corroded.

[Dead Parrot]

If you have a timing light, vacuum pot check is easy. Note timing with pot disconnected. Connect pot to manifold vacuum. Timing should advance 12+ degrees if pot good. If no advance, pot bad or distributor advance frozen in place.

Suction side lines will allow air in rather then fuel out.

[Shugalou]

Parrot thanks - I picked up a timing light last night so I will try to test soon.

I will have t et under the truck and locate the suction lines so I have a better understanding on how they work.

Thanks for the info

[Shugalou]

ChrisMoore.

You were right the fuel line was touching the hose, I think I will bend a new line away from the heat and see if this cures the problem.

[truckin 79]

Since you have a clear plastic fuel filter you should be able to tell of gas is getting to filter/carb. If in doubt pour some fuel in carb and see if it starts. I would also check the ignition control module. It sounds like it is getting hot and shutting down. Get a cheap spark plug tester from parts store(10.00) and when it dies check to see if you still have spark. Good luck

[Shugalou]

Truckin great advice, I will check the fuel filter the next time it happens (I have since shortened the fuel line to keep it from touching anything).

I also picked up that spark tester great little gadget for 10 bucks. I'm guessing with this tool you can drive around with it attached and once it starts acting up
pull over and pop the hood and see if the light isn't flashing as much due to weak spark.

I'm hoping to get some more testing done this week.

[barry1982]

Usually the ignition control module is a "go-no go situation. Have had several go... and my truck would not start again until I changed the module. Had a 78 miss /run rough when it warmed up. Changed coil, module no luck. Finally figured it out, it turned out to be the little metal tab on the rotor. The rivets that hold the tab to the plastic body loosened up. With the engine cold, plastic contracted, and ran fine. Once warm, plastic expanded causing the tab to move. New rotor.... and it ran fine.

[Shugalou]

Hi Barry, thanks for that suggestion, I have changed the Cap and Rotor already...that was first thought. I was also thinking about replacing the module and coil (and matching them) but I want to check a few more things to see if it's a spark issue.

I'm going to check my timing and see if that might be it...I'm also going to grab a vacuum gauge to see what it's pulling.

[Shugalou]

I have read up about ported vs manifold and snapped a pict of my current setup. I want to go manifold but it doesn't look like many available ports down by the base plate. I have one (highlighted in the picture) but it looks a bit high.

I know I can test when I have it running to see if it sucks which I'll try later today if I get a chance.

[Shugalou]

OK guys finally have an update.

Timed it to 8-9 BTC before this when I unplugged vacuum on carb it would want to die. After adjusting timing it ran smoother. I did the timing with the vacuum line unplugged.

I also was able to get the engine to react to the adjustment screws passenger side mostly not much action with the drivers side...but progress I suppose.

I adjusted idle down to about 800 and in drive it goes to 500 but every now and then it goes back to about 1,000 - when I punch it a few times it comes back down. Much quieter than before feels like it's gonna die at a stop.

Here's the question
When I brought it back home it died in the driveway while in drive...I was able to start up and move again but wondering if anyone has any suggestions? Play with idle screws some more? Raise idle?

Thanks guys - feel like I'm getting close and learning how this things works is a great feeling of accomplishment.

[Shugalou]

OK guys I want to update the progress.

After learning more about how the choke operates I have trouble shooted it down to the electric coil not working. I replaced the coil and now the choke plate opens as it supposed to. I have yet to take it out for a test ride but I am excited to see if there is a difference since this hasn't run right since I've owned it.

Trybal - You were correct with your guess. I keg of beer to you my friend.

Thank you everyone for your suggestions...I'm sure I'm not out of the woods yet but I feel closer.