Moparts
My car doesn't want to run when its hot
Posted By: fireeng
My car doesn't want to run when its hot - 08/08/13 12:04 AM
This is an update from a previous thread. I have a stock rebuilt 340 with electronic ignition and a harms built Thermoquad. The car starts up and runs mint for about 35-40 minutes after that it does not want to idle. I had it out yesterday and at the thirty minute mark I was in a parking lot and the car was running mint. I was able to stop and go into reverse and start and stop several times with no issues. 5 minutes later on my way home the idle starting getting rough. I limped to my driveway and tried checking a few things. Choke was wide open at this point. I covered the choke with my hand and the car wanted to stall out. (no vacuum leak??). I tried adjusting the mixtures screws a little and it seemed as though they were already in the best spot. The temp gauge is showing a normal operating temp but after fiddling with those few things the car now does not want to idle at all. It will start right back up but seemed as though it was now loading up. When I give it gas it spudders and wants to bog out, some smoke is present in the exhaust and when it does stall, I can see a mist of gas pop up through carb. It did back fire at one point and blew of one of the vacuum caps on my brake booster. I let it cool and took out a few spark plugs, 4 of them looked a little golden brown and the others look good, just metallic with no carbon build up and no excess smell of gas. I let the car sit overnight and this morning it ran the same, perfect for the first 40 minutes, then rougher a rougher until it was just bogging out.
Let me also disclose that I am by no means even a backyard mechanic. I am trying to learn as I go and trying to try a few things before I can get the car to a real mechanic.
Posted By: RapidRobert
Re: My car doesn't want to run when its hot - 08/08/13 12:40 AM
Could you pull up the original thread so we can see what's been done so far?
Posted By: fireeng
Re: My car doesn't want to run when its hot - 08/08/13 12:47 AM
Robert, If you remember we were focused on vapor lock, but I'm thinking that's not it because the car will start back up after it stalls.
https://board.moparts.org/ubbthreads/show...e=5#Post7785169
Posted By: RapidRobert
Re: My car doesn't want to run when its hot - 08/08/13 12:51 AM
Thank you. I remembered some of it. Deals like this I wish I could be there in person
Posted By: fireeng
Re: My car doesn't want to run when its hot - 08/08/13 01:35 AM
Quote:
Thank you. I remembered some of it. Deals like this I wish I could be there in person
I know, the list of "could be's" at this point is a long one.
I talked to my mechanic that works on my daily drivers and our mechanic at work and one of them is going to give it a look at next week when I get back from vacation.
Posted By: rapom
Re: My car doesn't want to run when its hot - 08/08/13 01:06 PM
Could be your pickup coil in the distributer going bad. They can act up when they get warm, but usually they just shut down when they get hot. Also could be coil. Still sounds like a vapor lock issue though. Maybe you could run with your hood off and see if the problem goes away.
If you have a good cooling system I would install a 165 degree thermostat. Might keep you cool enough to eliminate whatever problem you have.
Posted By: Paul_Fancsali
Re: My car doesn't want to run when its hot - 08/08/13 02:05 PM
The fuel is a problem now if you are in reform gas area. Myself I would change coil first and then pickup plate in dist. If you have a spare control box that would help. I had a 73 Cuda 340 that did the same thing it was the control box.
Posted By: DAYCLONA
Re: My car doesn't want to run when its hot - 08/08/13 05:31 PM
Scott,
I'm just going to throw this out there, because I had a similar problems years ago when I changed out the gas cap on my Challenger, I but a non vented cap on it, unknowingly, and the car would start to run ragged after 20-30 minutes, let it sit and what I thought was cooling off, it would restart and run fine for another 20-30 minutes...well it turned out I was starving the pump for fuel because of a vacumm/suction lock in the tank, I getting some fuel but not enough...could this be your issue?, perhaps a cap, or flip cap added during your resto?, or perhaps a vent/emission line not open, deleted, plugged, plumbed wrong during the resto?...if this might be the case, try running the car with no gas cap to see if the condition prevails,...sometimes it's the simplest things, or things we do to ourselves
Mike
Posted By: fireeng
Re: My car doesn't want to run when its hot - 08/08/13 07:58 PM
Quote:
Scott,
I'm just going to throw this out there, because I had a similar problems years ago when I changed out the gas cap on my Challenger, I but a non vented cap on it, unknowingly, and the car would start to run ragged after 20-30 minutes, let it sit and what I thought was cooling off, it would restart and run fine for another 20-30 minutes...well it turned out I was starving the pump for fuel because of a vacumm/suction lock in the tank, I getting some fuel but not enough...could this be your issue?, perhaps a cap, or flip cap added during your resto?, or perhaps a vent/emission line not open, deleted, plugged, plumbed wrong during the resto?...if this might be the case, try running the car with no gas cap to see if the condition prevails,...sometimes it's the simplest things, or things we do to ourselves
Mike
Thanks Mike, I will try this first as there is no expense or waiting involved. I also ordered a new control box as I don't think it will hurt to have a spare on hand if that's not the problem.
Posted By: fireeng
Re: My car doesn't want to run when its hot - 08/21/13 08:44 PM
I tried running the car with no gas cap. It still did the same thing. It ran fine for 35 minutes then wants to stall out.
I changed the control box to a chrome unit and I am hoping to run it for an hour tonight.
Posted By: 68goldfish
Re: My car doesn't want to run when its hot - 08/21/13 08:57 PM
Had the same problem. Ran fine for about 30 min, and would die. I had a rotted filter in the tank. It would plug up and starve fuel. Later the tank debris would fall off the filter and it would run fine another 30 min. Check your fuel tank! Good luck!
Posted By: fireeng
Re: My car doesn't want to run when its hot - 08/22/13 12:21 AM
Quote:
Had the same problem. Ran fine for about 30 min, and would die. I had a rotted filter in the tank. It would plug up and starve fuel. Later the tank debris would fall off the filter and it would run fine another 30 min. Check your fuel tank! Good luck!
Brand new fuel tank in the restoration. Just 600 miles on the car. Thanks for the idea though.
Posted By: Challenger 1
Re: My car doesn't want to run when its hot - 08/22/13 12:45 AM
How hot is the motor when it starts acting up?
And are the heat riser passages open or blocked?
Posted By: ahy
Re: My car doesn't want to run when its hot - 08/22/13 01:08 AM
Can you put a "T" on the carb fuel line and rig up a fuel pressure gauge? Tie strapped to the cowl outside the passenger compartment works. Hook it up and run and watch. If it is vapor lock, debris in the tank or basically any fuel delivery problem you will see it drop before it stalls. Ideal is probably 5-7 psi and it should still run ok in the 3-4 range, at least at moderate load.
I'll add you have probably been all over the fuel lines but an older line can get soft from alcohol and get sucked shut by the pump. It will run for a while and quit. When it stalls, the suction is relieved and it may open up enough to run a little more. I had that problem on a PU.
Posted By: fireeng
Re: My car doesn't want to run when its hot - 08/22/13 12:46 PM
Quote:
How hot is the motor when it starts acting up?
And are the heat riser passages open or blocked?
Not exactly sure on the operating temp when it starts to act up. It shows normal on the dash gauge. Heat riser is removed.
Didn't get a chance to run her yesterday and it looks like rain today but hopefully I can sneak a ride in before it gets wet out.
Posted By: Challenger 1
Re: My car doesn't want to run when its hot - 08/22/13 01:14 PM
Quote:
Quote:
Had the same problem. Ran fine for about 30 min, and would die. I had a rotted filter in the tank. It would plug up and starve fuel. Later the tank debris would fall off the filter and it would run fine another 30 min. Check your fuel tank! Good luck!
Brand new fuel tank in the restoration. Just 600 miles on the car. Thanks for the idea though.
Is the pickup and strainer new? I'd do what was suggested and hook up a tempory fuel pressure gauge and see if it's vapor locking.
Bragging...I drove my 340 in Vegas a couple weeks ago and it was 100+ degrees.
Posted By: fireeng
Re: My car doesn't want to run when its hot - 08/23/13 07:26 PM
Got to run the car today with the chrome box. No change, car ran fine for 45 minutes then it will stall if it stays at idle for any extended period. My driveway is a bit of a hill and in order to back it in today after the 45 minutes I had to hold the gas and the brake in order to keep it from stalling out. Coil next I guess??? Not really sure how to put in the fuel line pressure gauge on my own.
Here is what the temp gauge said when it started acting up.
Posted By: JohnRR
Re: My car doesn't want to run when its hot - 08/23/13 08:30 PM
Do you have a points distributor ? A timing light ? when it starts acting up like that have someone in the car keep it running and look at the timing light , if it's missing then you will see it , could be the coil , could be the pickup in the distributor or ...
But I would think if it was heat affecting ignition components wouldn't it make the car miss and fart at ANY RPM and not just idle ?
Posted By: WO23Coronet
Re: My car doesn't want to run when its hot - 08/23/13 09:18 PM
You mentioned it starts to act up at idle, what's happens if you put it to the wood?
Posted By: fireeng
Re: My car doesn't want to run when its hot - 08/23/13 09:47 PM
Quote:
You mentioned it starts to act up at idle, what's happens if you put it to the wood?
Its seems to be able to drive if I give it some fuel but I do seem to think there is a bog or sputter present when it starts to run crappy. Those issues don't seem to be there when it first starts up and is running good.
I have a mopar electronic ignition conversion on it with the chrome box now. It still has the same coil that was on it with the points distributor. (I think that is my old 318 coil but I'm not 100% sure)
Posted By: DAYCLONA
Re: My car doesn't want to run when its hot - 08/24/13 12:22 AM
Quote:
Quote:
You mentioned it starts to act up at idle, what's happens if you put it to the wood?
Its seems to be able to drive if I give it some fuel but I do seem to think there is a bog or sputter present when it starts to run crappy. Those issues don't seem to be there when it first starts up and is running good.
I have a mopar electronic ignition conversion on it with the chrome box now. It still has the same coil that was on it with the points distributor. (I think that is my old 318 coil but I'm not 100% sure)
IMHO.....time to swap the carb out, even if you have to use an adapter plate just to mount a known "good" running carb, rather than chase ghosts, I'd think if it was ignition oriented it would rear it's head from the initial start up and running senario.....eliminate the thermobog from the picture
Mike
Posted By: Supercuda
Re: My car doesn't want to run when its hot - 08/24/13 02:08 AM
Had a coil that would quit when it got hot. Let it cool off and it would work. Not exactly the same issue you have though.
Posted By: Dodgem
Re: My car doesn't want to run when its hot - 08/24/13 02:09 PM
Have you tried adjusting the carb idle when it's hot??
sounds like a rich idle condition. floats to high?
carb good and idle screws set exactly the same amount of turns out??
enough idle advance in the dizzy??
Posted By: 540DUSTER
Re: My car doesn't want to run when its hot - 08/24/13 11:02 PM
see what the fuel pressure is when acting up?You might be blowing the seats off the float.
Posted By: TJP
Re: My car doesn't want to run when its hot - 08/24/13 11:23 PM
Quote:
Not really sure how to put in the fuel line pressure gauge on my own.
just tee it into the line as close to the carb as possible . Your condition sounds a lot like vapor lock as the others have said.
if you are running 10% ethanol based fuel it is known to cause these exact symptoms in older vehiclesdue to its lower boiling point . I have seen several cases come through the shop. A few of the vehicles had see through filters and as the condition started happening the level of fuel in the filter would decrease substantially.
Another thing I have had cause it is parts store fuel pumps that are putting out 11-13.5 PSI. I tried several different brands and they were all the same. Switched to an edelbrock and the problem vaporized ( pun intended) So we are Currently using edlebrocks exclusively( Pricey) and have not had any further issues.
I would agree with the others, time to check the fuel pressure cold and hot.
Posted By: fireeng
Re: My car doesn't want to run when its hot - 08/25/13 04:33 PM
Guys, thanks for all your ideas and input. I am getting a real mechanic to look at it next weekend.
Just a question on vapor lock, I always thought with vapor lock the car would not start back up when that is happening. My car will start back up, it just doesn't want to idle.
My carb is new this season, built by HARMS, but never adjusted for my car. I am hoping all this is due to some tuning issues in the carb.
My mechanic has my TQ that I used last season. He was looking at it to get familiar with them. (he was a GM guy back in his hot rod days). The car ran ok with that carb on it last season, once we adjusted the metering rods as high up as they would go. Before doing that the carb would bog out off the line. I had just finished the resto last season and only drove the car for more then 30 minutes once last year, that time it ran ok. I am going to get that carb back and throw it on to see if it will run longer then 45 minutes. Then I will know for sure if it's in the carb or not.
Posted By: TJP
Re: My car doesn't want to run when its hot - 08/25/13 07:36 PM
Our vapor lock examples would re start but run very poorly.
The fuel pressure ones usually came in on a hook
Posted By: Dodge-N-Shelby
Re: My car doesn't want to run when its hot - 09/04/13 01:52 PM
Maybe I missed it in another thread, but did you ever figure out what was causing the problems with your car? I had replied to your first thread when this all started as I was having a similar problem with my 65 Newport. I am now happily running the original points distributor in mine. My electronic conversion is on the bench waiting until I have winter down time to trouble shoot it.
Posted By: roe
Re: My car doesn't want to run when its hot - 09/06/13 11:38 AM
I had similar issues before with a 318 with stock points ignition. I ended up swapping in a new parts house dizzy and a new coil at the same time and the problem went away. It had to be either the pickup coil on the dizzy or the coil. Cant say which because I replaced them both at the same time.
Second time I had something similar happening with my current 360, it was a combination of things and I could watch my see through filter start to run dry. And I still dont have it completely fixed, but Id say its about 70% improvement. I had an aluminum intake with no spacer between the carb, so I added a 1/2" 4 hole phenolic spacer. My dizzy wasnt tuned to my combo, which had my timing retarded causing me to run hotter than optimal, so I sent it out to Don at FBO. I replaced my worn/clogged brass radiator for a champion aluminum and installed twin electric fans from an OEM V6 (just preference over mechanical, and I dont remember the car, I just scrounged a JY). I installed a good in-line fuel pressure regulator, and I did a bunch of tuning to my carb with the help of guys here and a lot of reading.
I think the two biggest things that helped my vapor lock were not having my timing so retarded and not having my carb so lean. Eddy 1406's are rediculously lean OOTB. Then I would say the spacer was the next most beneficial.
Still on my to do list are to switch to a eddy fuel pump, and replace my intake manifold gasket and install some metal block off plates for the heat cross over.
Maybe all of these will give you some places to look.
roe
Posted By: fireeng
Re: My car doesn't want to run when its hot - 09/06/13 08:41 PM
Quote:
Maybe I missed it in another thread, but did you ever figure out what was causing the problems with your car? I had replied to your first thread when this all started as I was having a similar problem with my 65 Newport. I am now happily running the original points distributor in mine. My electronic conversion is on the bench waiting until I have winter down time to trouble shoot it.
I still have not gotten to the root of the problem yet. I just got my old TQ back that was on the car last year. I replaced that carb with one from HARMS because the car was not warming properly, but I have now been educated and think that may have just been a choke linkage issue. So I hope to correct that and run my old TQ. I am going to put that one back on and see if the problem goes away. The car ran ok last season after it warmed up with that carb, but I didn't take it on any long drives because the resto was fresh and I was staying close to home. I want to try to rule out weather or not the problem is coming from the carb before I start changing more ignition parts. I hope to do the carb swap one night this weekend.
Posted By: fireeng
Re: My car doesn't want to run when its hot - 09/09/13 03:56 AM
Well it seems my problem is in the Carb. I put my old TQ back on and ran the car for 50 minutes with no stalling, no rough idle. Car was running just as good 50 minutes in as it was when I first started it up.
Now to figure out what is wrong with my "nice looking TQ"......
.jpg "7844825-IMG_1830(640x478).jpg")
Posted By: DAYCLONA
Re: My car doesn't want to run when its hot - 09/09/13 04:24 AM
Scott,
If your sure it's the rebuilt carb, and confirmed it's not an installation/set-up tuning issue...send the carb back to HARMS for a look'se...Thermoquads can be "touchy" when rebuilding or tuning DAMHIK
...but are awesome performers when properly set-up
Mike
Posted By: fireeng
Re: My car doesn't want to run when its hot - 09/09/13 10:25 PM
Quote:
Scott,
If your sure it's the rebuilt carb, and confirmed it's not an installation/set-up tuning issue...send the carb back to HARMS for a look'se...Thermoquads can be "touchy" when rebuilding or tuning DAMHIK
...but are awesome performers when properly set-up
Mike
Thanks Mike,
I've been talking to Scott at HARMS and I have a friend here who is going to check the float level and try to help me set it up before I send it back to the left coast.
For now all is good with my old one (just don't peak under the air cleaner cause she ain't pretty)
Posted By: mopa
Re: My car doesn't want to run when its hot - 09/14/13 02:10 PM
Any updates on the carb issue. I have 71 thermoquad that I thought of trying to rebuild myself and would like to avoid any problems.