Car won't start after warmed up Options

[Hammy]

This is continued from the NARP board a while back. I'm still having the problem so I'm posting here

This is a carbed (dual Weber) 1.7

It happens like this:

I drive the car around town, gets up to full temp, stop at a store to go in real quick, come back out a couple minutes later and turn her over...
Crank, crank, crank, crank. Doesn't fire up

This happens sometimes, and then sometimes it doesn't happen, just fires right up. (IMG:style_emoticons/default/confused24.gif) Also, the car starts fine and easily when the engine is cold.


I can't tell if it's fuel related.
I don't know if it's getting too much fuel when trying to start?
I usually turn the engine over, and step the pedal down half way and it fires up. When this no start problem happens, no matter what I do with the gas pedal it doesn't fire. Sometimes I can get it to fire by holding the pedal down all the way and cranking forever and it'll start and run at like 100rpm, really slow like a tractor. I usually try and lightly tap the pedal to get it going strong, sometimes that'll work and sometimes it'll die.


Then I can't tell if it's not getting enough fuel when trying to start -
Because If I turn the engine over and don't touch the gas at all, it won't start. I normally have to push the gas down half way for a normal start.

Or is it ignition related? Could incorrect timing cause it to do this? Dying battery? Engine seems to turn over fine. I have 12.4 volts across the battery posts with the engine off.

Or Vapor lock? My fuel pump is just below the hell hole.

Also, I've checked for any pinched fuel hose/lines and can't find any. I wouldn't think it was that because once the engine gets started again, it runs perfectly fine. I'm just scared to turn it off.

Any help MUCH appreciated. This is killing me.

[904svo]

Put a pressure gauge in line with the carb's, the pressure should between 3-5 lbs
if it more then put a pressure regulator in line and set it for 4-5lbs. There may a
chance that your pressure is higher that 8lbs, the fuel is going past the neddle
and seat assemble and flooding out the engine.

Thats my first guess.

[Hammy]

Put a pressure gauge in line with the carb's, the pressure should between 3-5 lbs
if it more then put a pressure regulator in line and set it for 4-5lbs. There may a
chance that your pressure is higher that 8lbs, the fuel is going past the neddle
and seat assemble and flooding out the engine.

Thats my first guess.

That's a good guess. Never thought about fuel pressure. Where can I get a pressure gauge? Does it matter what kind I get or are they all the same?

I DO have a pressure regulator in line before the carbs. It's this kind from CB performance. I don't know if it's good though, it came in the car when I bought it. No telling how old it is. Can these things go bad?

[914Sixer]

What about the old fashion vapor lock?

[John]

How long has it been since you rebuilt those carbs?

What fuel pump do you have located under the hell hole?

When we ran a carbed car, we had the fuel pump up front, lower than the bottom of the gas tank.

Do you have a heater valve in the area of the fuel pump?

[LowGT]

My 74 did that, you could actually see the carbs dribble fuel when you shut it off. Fuel pressure was fine at 3.5ish psi, I think the carbs were just worn out.

[Twystd1]

Well.

Since the car does run and does start most of the time.

That (probably) rules out a bunch of things.

As far as having enough fuel... I bet you do.

Since you have carbs, and they have a built in reservoir (Bowl).
That pretty much rules out a fuel pump issue. As the car will start without the fuel line even hooked up to the carbs if the bowls are full.

So for the moment. Lets rule out the fuel pump.

You did say that you start the car with a half throttle snap. That makes sense. That pushes the accelerator pump on the carbs and pumps fuel into the combustion chamber to start the engine. I do that to on some cars.

So my guess is the same as some of the other fellas......

That is .. When you park the car and turn it off. The ambient heat from the engine is percolating into the carbs... And they are dripping fuel down the intake manifold and into the combustion chamber. And your spark plugs are getting wet from the RICH fuel mixture.. And VOILA.... The dam car won't start.
Cause it is FLOODED...!!!!

I B guessing that a good puff of smoke comes out of the exhaust when this happens and it eventually starts.... Correct?????

Try this next time to see if our theory is right. Next time it happens.

Try this starting technique.

Car won't start after a run. Floor the pedal... YUP.. I said floor it. This does two things.
1) The carbs pumps more fuel into the combustion chamber (bad)
2) Now the combustion chamber can get more air to change the fuel/air ratio to a much more lean condition. Then the little bugger should start. Just don't forget to take your foot off the peddle when it fires up. (IMG:style_emoticons/default/happy11.gif)
Ya see... With the throttle wide open. The carb will dam near STOP sending fuel down into the engine. Thats because the speed of the air going pass the transition ports will be so slow from the open butterfly's (creating less vacuum) . The carbs will send very little (if any) fuel on down into the heads. (We want that to happen)


Assuming this all works. (It might) You know know your carbs have the infamous "Slits drip"

Which simply means you need to rebuild and blueprint your carbs as best you can.

I think you have dual 32s... Am I right????? (cause I forget eveybody's setup)

ALSO: Like one of the other fellas said. If you have "Slits drip" (IMG:style_emoticons/default/blink.gif) in your carbs.

You can handily pull off your air cleaners when this happens. And look down the venturi. You will see what looks like raw fuel slightly dripping down the carb throat.

It only takes a little bit to flood an engine and make it hard to start....

Anyway... Thats my .02 worth.

Regards,

PS... Never ask me why they call it "Slits drip"... You don't want to know.

I can tell you it originated from the following.... (IMG:style_emoticons/default/sheeplove.gif) (IMG:style_emoticons/default/sheeplove.gif) (IMG:style_emoticons/default/sheeplove.gif)

C

[SirAndy]

sounds like fouled plugs ....

check the carbs for leaking fuel into the runners ...
(IMG:style_emoticons/default/wink.gif) Andy

[Hammy]

I do have a heater valve right near the pump, but it's hooked up to the heater hose and going into the long. Maybe it popped off? I'll have to check. I also don't have my passenger side J heater tube capped off.

Clayton, they're dual 40's. I don't know the look of the exhaust when I finally get it to start because I'm usually so damn happy I don't think to look (IMG:style_emoticons/default/biggrin.gif)

Also, putting the pedal to the floor and holding it there is usually the way I've gotten it to start when it won't start. In fact I think that's the only way I've gotten it to start. But I'm usually cranking it over and over and finally it'll fire up and run real lumpy and slow. So I know pedal held to the floor HAS worked to get it started. I can't remember if it's been that way every time though.


Now for a real stupid question, where's the venturi? I know the basics of carbs but I don't know where all the stuff is yet.....

[SirAndy]

Also, putting the pedal to the floor and holding it there is usually the way I've gotten it to start when it won't start. In fact I think that's the only way I've gotten it to start.

still sounds like fouled plugs, flooded engine and leaking carbs .... (IMG:style_emoticons/default/biggrin.gif)

[Hammy]

Also, putting the pedal to the floor and holding it there is usually the way I've gotten it to start when it won't start. In fact I think that's the only way I've gotten it to start.

still sounds like fouled plugs, flooded engine and leaking carbs .... (IMG:style_emoticons/default/biggrin.gif)

Yes.... I know (IMG:style_emoticons/default/smile.gif)

How much is a carb rebuild gonna hit me?

[Twystd1]

YUP...

You just clarified what Andy, LowGT, John and myself have suggested.

Your carbs B dripping the "Slits Drip"...

You need to rebuild em. Or have them done professionally.

Depends on how much bucks you have. If'n you have bank.

You send em to Art Thraen at ACE.

If you have have short dollars.

You bust out the manual and buy the rebuild kits and do it yourself.

ALSO: Anything that is making extra heat into your engine compartment needs to be FIXED.
I see some guys with the heater tube openings in the engine sheet metal exposed (open). This allows heat to come up into the engine compartment creating lost performance, engine over heating and carbs burrbling fuel.

Just like yours.........

So if thats an issue... FIX IT.......

OK... "Where is the venturi?" was your question.....

If'n you pull off your air cleaner on one side. You will see 2 holes that the air flows down into the intake manifold. (And takes fuel with it)
As you look down inside of the carbs. you will see 2 venturis. These look like aluminum rocket nozzles in effect.

These help straighten out the air flow. AND they dictate the size of the opening of the carb. As these can be bought in different sizes.

These are UNDERNEATH the air cleaner base plate... Not above.
(Above the air cleaner base are called velocity stacks)

GO TO the CB PERFORMANCE or the REDLINE Carbsweb site's and look up the Web 40s details.

You will see what I am talking about... or by the time I finish writing this Aaron will already have posted a pic of said venturis

They hav e schematics for you to look at .

What else ya need sir???

C

[bondo]

I rebuilt those carbs right before I sold the engine to Hammy, so they shouldn't need rebuilding. They could need cleaning out and adjusting, as webers are pretty darn sensitive to crud intrusion. I meticulously set the float levels, but who knows, maybe they got out of whack?

(I rebuilt them with a full overhaul kit which included new floats, springs, needle valves and adjustment screws)

[bondo]

Oh, and I know Hammy has the haynes weber book, because I gave it to him with the engine. (IMG:style_emoticons/default/smile.gif)

[Twystd1]

If the carbs were just rebuilt.. And they work great except for this starting issue.

That probably mean the carbs ARE getting heat soaked.

What kind of gaskets do you have between the intake manifolds and the heads? Paper? Plastic?

The good ones can be gotten from Jakes site. (I think)
They are better at insulating the intake tract than paper gaskets or even the standard plastic spacers.

What kind of holes do you have in your sheet metal that might let heat into the engine compartment?

AND... Were these carbs sent in the mail???

I am really reaching here.... (remote possibility)
If so.. the floats could of changed their settings and fuel is sitting higher in the bowl and it's venting from the heat sink issue down the intake manifold.

This MIGHT exacerbate the issue...

If they were working perfectly. A float height change is probably not the case.
(Long shot but possible)

Just food for thought...

AND... You will have to find out if your fuel pressure is at 3.5LBS or a bit less.

READ your weber manual I just found out you have one...!!!!!!!!!
And read the part about FUEL PRESSURE. These carbs ONLY work well in a very narrow pressure range.

If your pressure is too high. This also could be part of the issue.

Me thinks your fuel pressure is probably pretty close as apparently it runs fine most of the time except when restarting a hot engine.

Nonetheless... You have to know what your fuel pressure is or you might be fighting a never ending battle.

You can go to most any aftermarket VW shop. They typically have a little T and a small gauge that you can T the gauge into of the fuel line going to the first carb. I take the cheap plastic gauges out after testing as they can be a fire issue. The higher end liquid filled gauges I leave in the engine compartment as a permanent fixture.

Just for clarity, And so I am not talking out my ass on suppositions.
(been doing that a lot lately)

ARE THERE ANY MORE SYMPTOMS THAT YOU SHOULD TELL US ABOUT?

DOES the engine run great except for this issue?

Spill the beans bro... Cause there might be better data for us to give you...

Cheers,

C

[Twystd1]

It ain't terminal... Just giterdone...!!!!!

C

[Hammy]

Thanks Royce. didn't remember you rebuilt the carbs yourself. That's good news. I think.

I've read a little bit through the Haynes weber manual and also have the Tomlison tech manual.

Clayton, I've got the stock gaskets. Got em from PP.
Carbs weren't in the mail. I did have them off the engine for quite a few months though.
Only holes I can think of in the tin right now is just the stock CHT hole. Been meaning to plug it up but not sure with what. I also have the pass. side j tube completely uncapped. Driver's side is capped. Not sure what to cap off the passenger side with. I think I've read using a spray paint cap or something? Anyways, that uncapped J tube is probably DUMPING hot exhaust air right on or near the pass. carb.

As for anything else I can think is wrong, remember my other thread from a little while back? About how the passenger side carb butterflies aren't closing fully for some reason. Mech. adjusted them as best as possible but still couldn't get them to close fully. So the engine will idle at 1200-1400 from time to time.
But it was fine when I first got the engine and carbs from Royce. Idled right in at 800. In fact the engine fired right up with little effort first or second try after install.
It was something I did when messing with stuff. Maybe I bent the throttle shaft or something?

It's also hesitant under 2500, then it takes off and pulls strong.
That ^ and I think the timing is off a bit cause it runs a little warmer than I'd like.

[Twystd1]

It is probably running warmer due to the J Tube not being plugged...

FIX IT..... NOW.......... (please)

If the carb ain't closing all the way... You either have a linkage issue..

Or the butterfly (throttle blade) is sitting cocked in the carb base and not allowing the blade to close all the way. Or the throttle blade shaft is binding somewhere in it's bore.

Either way... You need to find out whats up and fix it.

I think "Engman" makes some block off plates for the J tube... Look him up in the vendor section and see if he has a remedy for that. Or simply fix your heater.

NOTE: After driving your car for twenty minutes or so. Pull over and pop your engine lid. Touch the carb bodywith your pinky. If it is so hot you are burning your finger. It's too dam hot. Usually carbs are relatively warm... NOT HOT..!!!!

They will get hotter if you wait a few minutes. (engine heat rising)

And if you burn your finger on it.... Well........ Thats your fault. I didn't say you had to try this..... (IMG:style_emoticons/default/idea.gif) (IMG:style_emoticons/default/cool_shades.gif) (IMG:style_emoticons/default/alfred.gif)

YOU will have to figure it out. Don't send me the doctor bill like Aaron did. (IMG:style_emoticons/default/agree.gif)

NOTE 1: If you are really running it hard and pull over and check the carb body. It might even be cold to the touch.

NOTE 2. If you let sit and idle for ten minutes and try to touch the carb base... you better have a bandaid ready. Capiche?

Note 3: On an alcohol fuel race car. The carb will sometimes have ice on it when run hard........ no kidding.

Let us know what transpires on this... Okydoke?????

Hot carbs = BAD.

OH... And check your timing.

BUT FIRST.......
If using points. Check your your dwell with a dwell meter or re-set your points with a feeler gauge. I use a dwell meter only on points. Much more accurate.
(no feeler gauge for this guy if I can help it on used points)

BECAUSE YOU CAN'T SET CARBS CORRECTLY WITHOUT THE VALVES, POINTS AND TIMING BEING DEAD ON WITH NO INTAKE LEAKS.

Else your chasing your carb tuning forever......... Just wasting time.

Have I beat this to death enough?????

Cheers brother,

C

[DBCooper]

Heat will also affect an already weak coil or condenser. One other thing, I see you're in Mo-town, is it foggy? Old carbon cored ignition wires will work fine in a dry environment but suddenly develop a lot of extra resistance when it turns humid, making it harder to start. That usually happens overnight, but it's worth checking. As Clayton says, no sense in trying to adjust carbs until everything else is in proper tune. And get some phenolic fuel-injection spacers for the carbs. It will keep them cooler.

[mudfoot76]

If the carb ain't closing all the way... You either have a linkage issue..

Awhile back, I had a similar problem that turned out to be a linkage issue. Car would not idle, but ran OK as long as the throttle was more than 50% open. On one side, a tiny screw had come loose slightly and messed up all the alignments.