Engine dies - I'm stumped

[Nelson]

My car runs as good as I would ever want it to run. That is true for only 15 or 20 minutes though. Then it suddenly runs very ragged and very soon just quits. At that time it will not restart and if it does it is just barely staying alive. Later in the day it will start and once again run great for a while. I have replaced the coil, the points, distributor cap, rotor and fuel pump. After each of these replacements the same scenario would be repeated. Today I pulled the plugs after it had died yesterday and they were carboned up. I cleaned up an older set of NGK BP6ES plugs and put them in. The engine started, with difficulty, and ran but was very rough and actually shaking. Yesterday when it died I checked both of the SU fuel bowls and they were full. I also used a spark tester at all of the plug wires at the plug end. They all had a good spark. The plug wires are Bosch and only several years old and look to be in excellent condition. This is driving me nuts!!! What am I overlooking as a cause for this?

 

[David_Doan]

compression?
pistons in carbs move free?
You said replaced the coil, the points, distributor cap, rotor....condenser?

 

[Nelson]

I haven't checked the compression or the carb pistons because when it runs it runs very well. My understanding with the condensor is that if it is bad it is that way all the time. Jeff at Advance Distributors ,who rebuilt my distributor after Elkhart Lake, told me that is the way the condensors fail. One of my drives was 14 miles and it ran fine until it suddenly went wonkus. If it were dead all the time this would be a lot easier to diagnose.

 

[drooartz]

Fuel tank clear? No gunk in there that could get stirred up?

Almost sounds heat related -- as soon as the engine is up to temp you have problems. I'd probably swap plug wires as well, just in case. Could be a little fault somewhere that happens when the wires get some heat into them. Other thought could be fuel and heat. I'm grasping here, just throwing a few random ideas out.

Fuel tank is vented properly? I've had motorcycles with a plugged tank vent that would fail to run -- pull the gas cap off and the problem went away immediately.

 

[59diamond]

This may be way out of line because I have already stated that I have no mechanical abilities. But I was having a lot of trouble getting my car to start. it turned out to be that my voltage regulator was not adjusted properly. I kept thinking it was the Generator, but after a very young guy adjusted my voltage regulator it has had no more problems.

 

[Nelson]

The gas tank was new several years ago and I also replaced the gas cap at that time. I guess I'll go ahead and replace the plug wires just to eliminate them as a possible cause. As I understand it hotter plugs are less likely to foul and mine were nasty looking. I had checked them recently and they were the proper color then. I tried to get BP5ES today but the local parts place doesn't stock them and found out that the NGK warehouse only has one in stock. They said to check back next Friday.

 

[Billm]

Nelson
Just for grins go ahead and change the condenser- it really sounds like a coil issue but condensers are cheap
BillM

 

[bthompson]

If I were to guess, I'd side with Drew: the gas tank is "oil-canning." The tank can't vent, and it starts holding a vacuum that fights against the fuel pump. Since the pump is only pushing 2psi, it doesn't take a lot of counter-pressure to overcome it. The longer it runs, the greater the vacuum, the less gas gets through, the leaner the mixture is, and the worse it runs as the plugs foul. Eventually, the vacuum counters the pump entirely, and the engine starves out.

 

[Nelson]

I can change the condensor easily enough but the only opening to the fuel tank is the gas cap. I don't know of any way to vent it. Could my "new" three year old cap have gone bad? Additionally, I opened both fuel bowls immediately after the engine died and they were both full to the top. I have two electric fuel pumps mounted at the gas tank and my problem has happened no matter which pump I had activated.

 

[Sarastro]

There should be some kind of a vent hole in the gas cap. Look at it closely.

This really doesn't sound like ignition to me. If it were, the car wouldn't run OK for a while and then start to misbehave. It sounds like vapor lock, fuel starvation, or something like that. You can check the tank venting simply by removing the gas cap when it starts to run rough.

Also, look into the carb throats and see if there is liquid fuel in the intake. You might have a stuck float valve and are getting raw fuel into the intake. That would be consistent with the carbon on the plugs.

 

[nomad]

There should be some kind of a vent hole in the gas cap. Look at it closely.



Also, look into the carb throats and see if there is liquid fuel in the intake. You might have a stuck float valve and are getting raw fuel into the intake. That would be consistent with the carbon on the plugs.

I'm going to guess with Steve on this one. Sticky float needle could be causing the car to suddenly load up and die. I've had similar symptom's. Have you checked a plug right after it happens to see if they are wet and smelling of gasoline?

Kurt.

 

[SaxMan]

I was thinking vapor lock. I had a 1983 Dodge 600 once upon a time that had that issue. Some brilliant engineer at Chrysler routed the fuel line right across the top of the transverse mounted engine (the wonderful 2.2 liter). You could hear the gasoline percolating in the tank. I eventually went to running Shell Super Unleaded as their fuels seemed to be the least susceptible to percolation. It worked.

The 600 was the biggest POS I ever owned. My parents gave it to me when I was in college. The 600 was like your standard K car, but had a longer wheelbase and was 400 pounds heavier. To call it a dog would be a very modest claim. I had Chevettes blowing me off the line.

 

[Guest]

The gas tank was new several years ago .

And my grandmother was once a baby. Drive it till it quits then pull the gas cap off and see what happens. Change the condenser too. Carry some carb cleaner with you and run it with the air cleaner off. When it quits, spray some juice down the carb throat and see if it runs. If it does, your problem is fuel, if not, ignition.

 

[Guest]

I'm going to guess with Steve on this one. Sticky float needle could be causing the car to suddenly load up and die. I've had similar symptom's. Have you checked a plug right after it happens to see if they are wet and smelling of gasoline?

Kurt.

I think he would know if it was cause he's already be complaining of fuel smell.

 

[JPSmit]

I can change the condensor easily enough but the only opening to the fuel tank is the gas cap. I don't know of any way to vent it. Could my "new" three year old cap have gone bad? Additionally, I opened both fuel bowls immediately after the engine died and they were both full to the top. I have two electric fuel pumps mounted at the gas tank and my problem has happened no matter which pump I had activated.

Nelson, take off the gas cap, get a plastic bag or saran wrap, cover the filler tube and attach with an elastic. Poke a hole in the plastic. Voila.

 

[Nelson]

I'm not sure if I can find a condensor locally but I'll give it a shot. Right now I can get the engine to run but it is very rough. I wouldn't be able to take it for a run to to see if anything else I try does any good for the dieing problem. Today I ordered a new set of leads for the dizzy cap but I suspect it will probably be a week before I have them. The filler tube cover sounds like a good idea for when I can get it to be driveable. I put in the higher heat range plugs today and lowered the float level in one of the carbs. Next I'm going to do a static timing check just to make sure something hasn't slipped. This is more of a problem than I had with my throwout bearing earlier this summer. At least with that I could immediately see the cause of my clutch slipping. What gets me with this problem is that I probably won't be certain I have found the cause except by driving the miles and sweating it out the entire time.

 

[smaceng]

How about a vacuum leak? Check the manifold and carb nuts.

 

[CaptRandy]

No hidden in line fuel filter? Filter inside the fuel pump?

 

[JPSmit]

I am actually wondering about these fouled plugs. I suspect there is a clue there.

Here is a quick summary https://www.ngksparkplugs.com/techinfo/spark_plugs/faq/faqfouled.asp

generally, too rich or too cold. so,

1. Assuming you haven't touched the carbs.
2. The Air filters are clean.
3. It is warmed up as much as possible

then it is electrical https://mgaguru.com/mgtech/ignition/ig106.htm

BTW this is the part https://www.ebay.com/itm/Beck-Arnle...Parts_Accessories&hash=item1e79fe9cdc&vxp=mtr looks like it is common enough that even Advance should have it.

 

[Nelson]

Those are great sites for information. Thank you. I just removed my condensor and checked it with my condensor tester. It read 0.2 mfd and showed no leakage so it seems to be OK. I had removed the dizzy so I checked the inside connections. I was able to start the engine after a few tries. It ran rough and as it started the front carb spit out some vapor. It was only for a moment. Then I checked the intake air flow on both carbs and found them to be the same. I'll buy another condensor but I'm not very hopeful that it is the cause of my rough running or engine dieing. I'm about to just put the car away and try to forget I own it.