Hot start issues

[200two]

Hi everyone, new issue showed up and it’s driving me crazy. I have a 74 non-tii with 38/38 weber carb, electric fuel pump.
 

Car ran decently well for the past few months since I’ve had it (late winter - spring). Then, went on a trip and let it sit for a while, came back a week ago and it has a super rough idle, and trouble starting and has an intense gas smell. Took it for a drive and the car stalled out multiple times. If I got to a red light it would die immediately. Push start only worked part of the times it stalled out but eventually got it started to get home. 
 

Thought it may be a spark issue so I took out the spark plugs, tested them and they all are okay, changed them to a new set while I was there since I had some extras and these were completely black. Checked the coil, distributer, distributor rotor, and those all seemed okay as well, battery is fine also, started sounds fine. Ran the car again, checked the newly installed plugs to see if they were black, and they come out black with soot. Seems like I’m running rich. I don’t think its a spark issue.

 

Few days later tried again and found gas boiling in the carb, and at one point even dumping out of the carb after starting it and letting it sit. I’ll add a video below. Took out the carb made sure the float was okay (carb is basically brand new). I also have the spacer under the carb. Admittedly when I put it back, I haven’t been able to adjust it properly yet since the car runs poorly already. Also changed the fuel filter since it’s simple enough.

Car still runs super rough and after driving if I turn it off and try to turn it back on 5-10 mins later it won’t start. Basically have to let it sit a while and start it again.

 

Searched the forums, most people say it’s probably vapor lock but I’m suspicious because I don’t have a mechanical fuel pump and seems like it’s less common with electric? Last I checked, the fuel lines are all away from heat sources but I can double check that anyways. Any other ideas?

 

 

Edited August 13 by 200two

[Stevenc22]

Check the needle valve. It might be clogged and not shutting off fuel to the float bowl which then overpours everywhere.

 

With the car cold, turn on the ignition but don't start the car. You should hear the electric fuel pump turn on and start pumping. Leave it pumping and then go inspect the carb. You should not see any signs of fuel anywhere because the needle valve should be closed and stopping fuel from entering the float bowl. If you do see fuel over flowing or leaking, the needle valve is definitely clogged and not closing.

 

You may also want to check you have the right electric fuel pump. Only very specific low pressure pumps are suitable for the weber. Most generic pumps are way too much pressure and can cause these kinds of problems.

[TobyB]

+1 for a clogged float valve.  

 

After that, a failed float.

 

Setting the float level is a measurement between the sealing surface of the 

carb top and the bottom of the float.  There are different dimensions for

brass or plastic, and I don't recall them off the top of my head for the 38.

 

I DID remember the URL- https://www.lainefamily.com/images/WeberTuningManual.pdf

 

t

 

[Son of Marty]

Your float has sunk or is sinking. 

[Mike Self]

Having had two floats (one brass, one plastic) on two different carbs (one Solex, one Weber) go down with all hands, I can attest they do sink.  Just don't do what a (supposedly) professional mechanic did to a friend's brass float--tried to solder up the crack...with a propane torch.  When the float exploded from the gas vapors still inside, it burned off his eyebrows and eyelashes--he was lucky not to be blinded.

 

One other thing to check:  that electric pump's output pressure.  Webers seem to like 1.75 psi and many electric pumps put out something around 3-4 psi.  You can buy an inexpensive pressure regulator to install upstream of the carb to take care of that.  Or just reinstall the mechanical pump.  They last (almost) forever, give the correct pressure and take little maintenance to function properly.  Keep the electric pump--on a switch--to prime the system after sitting.

 

mike

[Son of Marty]

If you have a brass float  you can shake it and if it feels colder as you do it has fuel in it, Mikes friend with no eyebrows even if he did reseal the float it would be heavier due to the added solder and not do it's job the way it was intended. Foam floats need to be weighed, or at least compared to a new one, to see if the fuel has soaked in to it. Plus one on a fuel regulator for your system along with a inertia switch to shut off the pump in a accident. 10 bucks on amazon.

Edited August 13 by Son of Marty

[VWScott]

+2 on checking fuel pressure. Everything else could be spot on with too much fuel pressure the scenario you describe could happen.

[VWScott]

4 minutes ago, Son of Marty said:

If you have a brass float  you can shake it and if it feels colder as you do it has fuel in it, Mikes friend with no eyebrows even if he did reseal the float it would be heavier due to the added solder and not do it's job the way it was intended. Foam floats need to be weighed, or at least compared to a new one, to see if the fuel has soaked in to it. Plus one on a fuel regulator for your system along with a inertia switch to shut off the pump in a accident. 10 bucks on amazon.

I used the dummy charge light on the dash and I tapped into it at the diagnostic port.When the car sees the light the electric fuel pump wont work(through a standard relay). I put a priming switch in the center console to act as a bypass in case the relay fails and can use as a prime function after long time sitting to save starter and battery. I've used this same method on VWs for years and works well plus it uses a standard Bosch type relay(dirt cheap)

[200two]

Thanks everyone, will give each of these a shot when I’m back at the car, this is super helpful. I’ll post my findings once I have some updates. I remember that have a plastic float from previously taking it apart. Might be a dumb question but what’s a good way to test if a plastic float is sinking? Just see if it’s filled up with liquid? I attached a photo of the carb and float below from my previous attempt.
 

As a side note I only noticed the flooded carb like in that video on two occasions. The other few times the car didn’t start until I let it sit for a while, but the carb wasn’t filled up with gas.

[200two]

I did see that the previous owner had installed a fuel regulator forgot to mention that. To be honest I have not touched it since I got it, I assumed (maybe stupidly) it’s on the correct setting. @Son of Marty

View recent photos.heic

[VWScott]

Just weight the float and compare to standard.

It's possible carb wasn't full of fuel because a good bit of it spilled over to intake because of fuel pressure and/ or float issues 

[VWScott]

1 minute ago, 200two said:

I did see that the previous owner had installed a fuel regulator forgot to mention that. To be honest I have not touched it since I got it, I assumed (maybe stupidly) it’s on the correct setting. @Son of Marty

View recent photos.heic 210.45 kB · 0 downloads

Use an inline gauge to test fuel psi

[Son of Marty]

Yup a 1.5 psi is good as VWScott said it would be good to verify the setting with a gauge but yes weigh the float also just find a guy who grew up in the 60's or 70's they all seem to have a triple beam scale for some reason🤔

[Dick R]

The great responses that you've already received will no doubt solve your problem.  This is yet another example of the enormous collective wisdom generously shared on this site.

 

I just wanted to comment on the video you provided in your initial post.  I never saw gasoline actually boiling in the carb before.  It's amazing how vigorously it boils.   That video is a terrific reference proving that gas really does boil in the carb. 

[Stevenc22]

Don't assume anything the previous owner did is correct. I see lots of suspect things in the picture you posted.