Hot Rod Forum banner

please help..... annoying warm start problem

5K views 21 replies 8 participants last post by  Steve B 
#1 ·
Hi all :) Great site!

Let me first start by saying I am a mechanic and hobbist for 20 years. More specificly I am a Engine Performance Specialist by trade.

Well........ I recently aquired a 67 Barracuda. Nice car and runs great but very difficult to start when warm. Here is the deal.....

Thing runs fantastic!

Cold starts are great and hot starts are great.

Problem is, it's a ***** getting started after sitting 10 to 30 minutes. Still plently warm, choke wide open, great spark, plently of
fuel............ just takes 10 to 15 cranks to get it to fire......... that's not right, something is wrong.

All my other carb V8 cars (GM) were tuned to perfection and fired right up at the tap of the flywheel. It's not like I haven't figured out how to start this specific beast yet (car personality thingy) because I'm past that stage, it's been 4 weeks and have tried everything.

What I have is.........

-late 60's early 70's 318
-12 to 15k on re-build
-10.5:1
-30 over
-mild street cam
-headers
-Edelbrock intake & carb
-new: (correct) plugs, wires, cap, rotor, quality points/condenser, balast resistor, oil, belts, bla bla bla.

-Dwell 30.5
-Timing correct
-carb in very good working order
-200 HC & 2% CO @ idle and half that at 2500 RPM

Has great spark while cranking warm but not starting..... WTF?

Here is where I'm at........

Possible heat soak problem:

Voltality of the fuel manufactured this time of year (winter) will vaporize under heat much quicker than summer fuel. Coolant stops flowing & fuel stops flowing after shut down. Fuel in the carb get very hot as engine temp starts
to rise. (no spacer plate to reduce heat) When you go to re-start fuel is vaporizing stightly out of accel pump, even more in intake, and next to nothing is left before it even gets to the combustion chamber.

Problem with this theory is if you have somebody give you a "test squirt" during cranking it seems to have no affect. And when it does eventually fire there is a slight indication of load-up, which indicated plently of fuel.

Possible valve lash problem:

Does the early 70's 318 have adjustable rockers? Hydrolic lifters? If so, and if not adjusted properly, when the engine gets hot the clearence is less, and will cause hard hot-starts. This was an issue with a Typhoon we built for over 500HP. But I seriously doubt that is the problem.

Possible fuel PSI or float adjustment:

Edlebrock specificly states you can have no more than 6 PSI. (5.5 optimum) I have not checked mine yet, but reguardless that would cause a "running" problem more than a starting problem. If I had too much PSI pushing fuel past needle & seat I would have idle problems. This car idles great with excellent burn. (200 HC & 2% CO)

I best educated guess at this point indicates there is too much fuel.

If you start it withing a couple minutes of shut down there is no problem. Has to sit at least 5 to 10 minutes. And will act the same after sitting 30 minutes.

This means there has to be time allowed for "something" to happen or a "rich condition" to take place.

Thinking maybe the fuel is overflowing and or dripping after shut down. But there isn't an overwhelming smell of fumes. And if you pull a plug after tring to start it they are dry.

Basicly......... it "acts" like a dripping carb when you look at the starting symptoms, but evidence shows the plugs are dry and when it eventually fires it's not struggling, blowing black smoke, or acting loaded up.

It would have to take an aweful lot of fuel in the intake & combustion chamber to prevent a perfectly tuned engine to struggle like that. But there is not an idication of that.

It's a very annoying problem.

Suggestions or ideas?

I'm running out of ideas.............
 
See less See more
#2 ·
The old Chryco coils were liquid filled and notorious for giving problems when hot, a Ford coil interchanges and does not have this problem.

I would check this first.
 
#3 ·
I live in California, and have been experiencing this EXACT problem with a 292 Ford Y-block engine equipped with an Autolite 2100 2 barrel. My thought process followed your pretty closely.

Then I tried removing the air cleaner lid, and starts after a "hot soak" were much improved. My thought is that winter fuel was volatilizing too readily. So as an experiment, I obtained an old air cleaner lid at the wrecking yard, and drilled two holes in the top to accomodate fuel line. I basically connected the hoses to the bowl vents and extended them through the lid. roblem "solved".

It sounds kind of Mickey Mouse, but it works. I plan to run the engine this way until summer, when I'll remove my vent entenders and see if the winter fuel really is the trouble.
 
#4 ·
"The old Chryco coils were liquid filled and notorious for giving problems when hot, a Ford coil interchanges and does not have this problem. I would check this first."<hr></blockquote>

Thanks... but the car has plently of spark and starts fine hot. Problem doesn't seem ignition related.

Thanks for the details SteveB. Interesting fix, but if that was the case my car would fire upon instant "squirt" of outside fuel.

What I mean is...... if a partner provides a additional fuel source while trying to start it under those conditions it doesn't help.

If my fuel were volatilizing, and my car wasn't starting warm because of it, then any "outside" source of fuel would cause the engine to fire instantly.

This has no effect. If anything it makes the condition worse, causing additional load-up, which shows a rich condition when it does start. Basicly symptoms of too much fuel.
 
#5 ·
I'm not suggesting that the fuel is evaporating so much that the bowl goes dry. I'm proposing that the vapors are building up in the air claener and intake manifold to the point where it makes the car moderately hard to start because of a rich condition.

I have had my carb apart a couple of times checking for a loose power valve or high float level etc., but it all checks out. The 2100 is about as simple as carbs get! When I look down the throat of the carb when the engine is hot, it looks dry as the Sahara down there.

Try removing the air claener lid next time the car is good and hot and see if it makes a difference.
 
#6 ·
"I'm not suggesting that the fuel is evaporating so much that the bowl goes dry. I'm proposing that the vapors are building up in the air claener and intake manifold to the point where it makes the car moderately hard to start because of a rich condition."<hr></blockquote>

Ok.... I gottcha.

I was thinking of it backwards. That would explain the 'extra outside fuel source test' only making it worse.

To be honest, it acts the same with the lid on or off.

Just an annoying problem that's got me frustrated.
 
#7 ·
I've had a similar problem in the past. Maybe your carb is leaking. What happins is after you turn off the motor, gas slowly leaks out of the carb into the intake manifold and after a few minutes it's the same as being flooded, but if you wait 20 minutes or so the leaked gas evaporates and the car starts just fine and if you were to crank it over after only a couple of minutes it starts right-up because it hasn't had a chance leak enough to flood out
 
#9 ·
Is it hard to start only after a waiting period following at least a 15-20 minute run on the freeway? Or will it also start hard after just being warmed up to operating temp? If it needs to get good and hot before it will do this, I would try the insulator gasket as mentioned above.

Also-I know the emissions are low, but how are the idle needles set? 1 to 1 1/2 turns out? Are they sensitive as they should be? I'm guessing you already know this, but if the idle needles must be turned in too far to idle right, you may have a leak (fuel source) feeding the engine.
 
#10 ·
Here's one that's a little out there,

Could you be experiencing fuel draining out the fuel lines while sitting?

I know that would/should be solved with a buddy and pouring raw fuel into the carb but maybe he's using to much and effectively flooding it.

What about cranking RPM? Fast enough to properly atomize fuel?

Try covering the ing. coil with a piece of sheet metal and see if that keeps the coil cool enough. Or just relocating it far enough away from engine heat.

Edelbrock carbs love to leak fuel below the throttle plates where it won't be seen. A sure sign the throttle body is cracked.

I would change carbs for a short while, Borrow one from a buddy or something and see if the problem is really in the carb.

I'm thinkin your gonna have to get out the test tools and follow thier recomendations. Scope, ing. analyzer pressure guage, temp gauge ect...
 
#11 ·
Thanks for all the feedback guys.....

Maybe your carb is leaking.<hr></blockquote>

That's pretty much where I'm at now with it.

Have you tried installing an insulator gasket between the intake and the carb?<hr></blockquote>

No, and was considering it because of how it was behaving. But was trying to avoid it because I have VERY little clearance left between the air cleaner and the hood. She practicly touches now, and didn't want to raise it at all.

Is it hard to start only after a waiting period following at least a 15-20 minute run on the freeway? Or will it also start hard after just being warmed up to operating temp?<hr></blockquote>

Don't have to drive it. Doesn't matter. All it has to be is at operating temp.

Could you be experiencing fuel draining out the fuel lines while sitting?<hr></blockquote>

Na, plently of fuel, pressure still in line, clear filter that you can visually see, accel pump works like a champ.

************** UPDATE *****************

Wanted to reply to your comments first.

New info!!! :)

Earlier today I decided to start it up and check it out some more. Been 2 weeks since I ran it, was due anyways. Stumbled across new evidence!

Did the usually start up, ran flawless from cold to hot, let it run a while, shut it down.

Let it sit about 10 minutes. When back to start it but before I did I decided to look down the carb for the 10th time just to make sure it wasn't nossle dripping or anything weird.

Usually the radio is on but this time it was quiet in the garage. When I looked down into it that's when I heard it. :D

Sounded like the pipes in your house when the toilet doesn't shut off all the way. I could hear the fuel gurgling. This means one of 2 things......

1) too hot, fuel is boiling, causing rich condition and hard to start

2) too much pressure in the fuel line after shut off forcing fuel past the needle & seat, causing rich condition and hard to start

If you had to guess, which one do you think it is and why?
 
#12 ·
Originally posted by 67cuda:
<strong>Thanks for all the feedback guys.....

************** UPDATE *****************

Sounded like the pipes in your house when the toilet doesn't shut off all the way. I could hear the fuel gurgling. This means one of 2 things......

1) too hot, fuel is boiling, causing rich condition and hard to start

If you had to guess, which one do you think it is and why?</strong><hr></blockquote>

This one gets my vote and is why I suggested installing an insulator between the intake manifold and the carb base. Good luck!
 
#13 ·
I find it hard to believe that the fuel is boiling in a carb this time of year during normal driving. I know I have driven cars in super hot weather hour after hour on the freeway, and have never had trouble like that.

So I think its time to check the float, needle and seat. Make sure the float doesn't have any fuel in it, which would make it slighty heavy.
 
#14 ·
Many thanks for the help guys!

Least got it narrowed down and isolated.

Plan on doing 160 stat, shroud, viscous fan & clutch. That should lower the temp some. Needs done anyways. If problem persists after that then I will consider a spacer plate.

I hear ya Steve. But remember that winter fuel has a higher voltality rate. So running at idle in a 60 degree garage really isn't a cold weather factor or condition. Will pull top of carb to check & adjust. Will also check fuel pressure to make sure it's under 6 PSI.

Thanks again, was much help talking it out.

If anything crazy happens or turns out to be something else, I'll post it. :)
 
#15 ·
Originally posted by 67cuda:
<strong>I hear ya Steve. But remember that winter fuel has a higher voltality rate. So running at idle in a 60 degree garage really isn't a cold weather factor or condition. Will pull top of carb to check & adjust. Will also check fuel pressure to make sure it's under 6 PSI.</strong><hr></blockquote>

I guess I'm still having trouble with the idea of fuel boiling off or volatilizing when the engine is merely warm. I could see it under conditions where the motor was good and hot though. How hot is it running anyway?? Anything under 190-195 and you should be OK-even after you shut down for awhile.

Be sure and post any new developments on this as I am still trying to figure my hot start trouble too. Those tubes stricking out of my air cleaner work, but they sure look weird! We may have to wait until summer to really figure it out.
Steve
 
#16 ·
Hey Steve, thanks for taking interest.

Well today was the first day I got to drive it since Christmas. SW PA weather and roads for January were horrible.

I find it hard to believe too, especially having owned many carb cars, all of which I ran in 90 degree humid weather and never had fuel boil.

But maybe it will help if I explain my problem more in detail.......

"I guess I'm still having trouble with the idea of fuel boiling off or volatilizing when the engine is merely warm."<hr></blockquote>

That's just it....... it's not warm it's very hot when this takes place. I should have been more specific in my original thread. That's my fault.

"I could see it under conditions where the motor was good and hot though. How hot is it running anyway"<hr></blockquote>

Here is the thing....... when running it's "normal" hot for that engine & era in my opinion. It has no shroud and a original bolt on death fan. So cooling at idle is not the greatest. I would guess she is running over 200.

Here is the important part...... when I shut that engine down at full operating temp, within the first 5 minutes of sitting it will start right up no problem. If you go listen to the carb you hear nothing.

At the 10 minute mark "things" start to take place. Coolant is not flowing any longer. Engine tempature is MUCH higher during this period than when it was running. (temp been rising for last 10 minutes) That is when the fumes are bad and you can hear the carb gurgling. Heater hoses are very hot to the touch.

As a matter of fact (this is scary) when I brought it home from work today, pulled it into the garage, shut it down. Took out the trash and a few things. Been about 10 minutes. I was standing next to the fender with the hood open. Fumes were pretty bad. Leaned over and listened, could hear the carb making noises. Stood there for a second thinking about the problem..... next thing I know my eyes start burning! I mean started slightly but then felt like somebody poured gas into my eyeballs! I couldn't believe it. Had to go rinse them out with water. And believe me, I work in a garage and on cars for a living. I am around gas fumes and other fumes often. So my eyes arn't virgin to this sort of thing. I was amazed.

I got my fan coming in the mail, calling about a shroud tomorrow, and hoping to get it all on with a 160 by the weekend. I'll keep ya posted. If you think of anything let me know. Thanks!
 
#17 ·
Although I think it's a good idea to upgrade your cooling system with a better fan & shroud, I'm not sure the 160* thermostat will help much. With 10.5:1 compression, that engine will want to run hotter than 160*. The only difference will be that the thermostat will open sooner. The engine will still run at the temp it wants to run at. I would install a temp gauge to see how hot it's running.

You have mentioened acouple of times that after 10 minutes or so you hear the carb gurgling. It seems to me the most likely explanation for this is that the fuel is indeed vaporizing from heat, which lowers the level in the float bowl enough to unseat the needle allowing more fuel in. Once the process starts, there may some "bouncing"(for lack of a better word) happening to the float-especially if the static fuel pressure is high.

1) Check the needle-seat-float system in the carb-you know what to look for.

2) Try to insulate that carb base from the manifold somehow- even if you have to try using two or three gaskets if you are really hurting for space. I don't have a space restriction, so I am probably going to try a 1" phenolic spacer for my heat soak troubles.

3) Check the fuel pressure-that's a simple test.

4) Are you still running on that same tank of gas since around Christmas? Maybe the fuel you bought back then was for some reason at the high end of the volatility range. Try a fill up at a different station.

I know where you are comming from on this- There HAS to be a logical expalnation RIGHT? RIGHT!
 
#18 ·
I have the same problem with my duster in the summer, going to try blocking the heat riser to intake man. with gaskets with block off plates.
I have electric fuel pump and it does not help.
It will run at 180 to 190 on real hot days but when it shuts off 230-240. will let you know after i do it
 
#19 ·
Just to add my two cents since, I have almost the same car (Pain in the butt trying parts and help). I was wondering when you explained your car, are you running full length headers? Where are they in association with the fuel lines. I installed a set of hooker super comp headers, that wrap around the frame and through the engine compartment. On the passenger side of the car the fuel line was going to damn near touch the headers so i rerouted the fuel line up the fire wall and on the fender well with a insulated wrap around it, but I am using a holley blue pump with a pressure regulator. I don't think that 200 degrees should cause that kind of problem for the carb. I wonder if the heat from the headers is warming your fuel lines and it is putting additional pressure on the carb from the expansion of the fuel in the lines? Just a thought!!!! Joel
 
#20 ·
Well...........

It's been a while since my last post and have done lots (actually all of the above) since that time.

Steve...... you still out there?

Just to re-cap, here is the problem:

Engine runs fantastic in all conditions, but when fully warmed up and you shut it off, after 10-20 minutes of sitting it will give you a slightly hard time starting. Basicly a hot start problem. It will start right up after you shut it off, it's only after it sits for 10-20 minutes.

There is a slight odor of fuel, and with your ear close to the carb in a quiet atmosphere, you can hear some gurgling or perculating.

It's a 67 318, 9.2:1, very mild cam, Edelbrock carb, Edelbrock intake, headers, mostly stock rebuild with 5000 miles.

Here is what I did to try and eliminate it:

- Upgraded cooling system to reduce tempature
1) Replaced 195 thermostat with a 180 high flow.
2) Replaced the original death-fan with a Mopar Performance clutch fan.
3) Added a fan shroud. (there was no shroud before)
- There is a very noticable difference in the temp now. (obviously) Runs much cooler.

- Upgraded fuel system
1) Replaced fuel fump with a stock 6 PSI Carter pump. The pump that was on the car was putting out 9.5 PSI (high-volume) and it specificly states that with an Edelbrock carb 6 PSI is maximum allowed pressure.
2) Added a heat insulator gasket between the carb and intake. (was just a paper thin gasket there before)
3) Replaced and relocated the fuel filter.
4) Replaced and rerouted the fuel lines.
5) Added insulation to the fuel lines on the intake manifold and along the body before the fuel pump where it passes by the headers.
6) Adjusted float level, and even reduced it some to be on the safe side.

- Upgraded the ignition system (might as well)
1) Replaced points, condenser, cap, rotor, wires, plugs, coil, balist resistor, and so on.

- Misc
1) Engine is tuned to perfection! I am VERY meticulous and a mechanic for a living. (Engine Performance Tech to be specific) Everything is in spec and the engine runs beautiful as you would expect under what's described above.

Well guess what???

With all the improvements listed above it is noticeably better..... BUT IT STILL FOOKING DOES IT!!! WTF???

<sigh>

Any final life rafts to be thrown my way?
 
#22 ·
If you are smelling fuel, it must be either percolating, leaking past the neeedle, or leaking internally. If leaking, the gurgling sound would be fuel entering the float bowl, but isn't it funny how these machines seem to defy logic? It sure sounds like you have addressed the issues we talked about before-and then some. Did you try disconnecting the fuel line after shut off? I can't remember. If not try that-it might give more clues regarding the carbs sensitivity to static fuel pressure. You might have to install a fuel pressure regulator

Is the carb new? Even if it is, if the hard starting is bad enough to bother you, I think it's time to try a different carb like a Holly or original Carter- but before you do, here is some stuff to think about and try.

The problem could be related to throttle blade position, or idle circuit. Are you running a PCV valve? If you are, and if it is either the wrong one or of a design that passes a lot of air at idle, you would have to compensate with a richer idle screw setting. After all, PCV's are just a controlled vacuum leak, and you may have to experiment with different PCV's to find the optimal one. I guess I'm thinking you may be dripping a little fuel out the screws with the engine off.

Where is your initial timing set at, and is the vacuum advance connected to manifold or a ported source? The reason I ask is that if you are running a bunch of advance (or not enough) the throttle plates could be either too far closed, or worse-too far open exposing the trasfer slots. Admittedly, both these conditions are likely to cause off idle flat spots and bogs(which you don't have) but after all we are reaching here a little right? I guess ideally you would be running about 8-12 degrees initial advance and the idle stop screw would be set one or so turns in for about a 600-700 rpm idle speed.

[ March 28, 2003: Message edited by: Steve B ]</p>
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top