38/38 DGAS vs 32/36DGAS

[Boaf 32]

Hi Gents,

I am having some "run-on" issues with my carb. I have a 72 FJ40 with a 38/38 DGAS on the truck.

1. After driving highway or local, shut off the motor.
2. The car seems to try and keep running, like gas is still flowing. I get the big Swooooosh noise after a turn on the crankshaft

What was done:

1. I re-set the dizzy and timing to 7 degrees on the Bead,
2. Set the idle to 650 and really smooth.
3. Reset the carb jets to all the way in and backed out to 1 1/2 turns.

The carb has been a challenge. When I got the car the adjustment jet on the divers side was broke off. Drilled out the jet with extractor and installed a new one. Ran good for a long time . So my question is, does anyone out there run a 32/36 DGAS on their 2F motor? What has been your experience with it? enough gas, power? I have a brand new one and wondering if I should install it.

Thanks,

Boaf

 

[charliemeyer007]

Dieseling in my experience is often carbon build up. Do a compression check. Give it an Italian tune up. More timing.

 

[Boaf 32]

Dieseling in my experience is often carbon build up. Do a compression check. Give it an Italian tune up. More timing.

Yep, I drive it once a week, and it sits maybe for 2 weeks. May have got really s***ty gas. Going to put in some 93 to clean it out. That can eliminate one possibility. Thanks

 

[JohnnyC]

Imho vacuum leak … whenever mine does it… it’s a vac leak

Check base gaskets on weber adapter plate as well as gaskets on carb

Btw Webers do like more advance … like 12-13

 

[70fj40]

I agree with johnnyc I have the 32/36 and runs very well. It takes some tuning and it will be a bit different from OEM carb/timing

 

[Boaf 32]

Imho vacuum leak … whenever mine does it… it’s a vac leak

Check base gaskets on weber adapter plate as well as gaskets on carb

Btw Webers do like more advance … like 12-13

Thanks, I will make sure the carb is snug. I may just go ahead and replace the gasket as well. I did reduce the passenger side mixture and will see haw that goes, It seemed to be delivering way too much fuel that I was able to see. Will check for leaks. Thanks @JohnnyC

Boaf

 

[rlong]

Related to Charlies comment in theory a potential foundational issue with “dieseling” is cylinder temp to high with some temps in the combustion chamber SO hot the continue to ignite fuel vapors. As long as it is rotating the cylinders will continue to “suck in fuel”. It’s right there in the name! (Although diesels have glow plugs). It does take a) your idle /throttle plate position to open or b) vacuum leak to allow air in, but your key does not shut off fuel just spark.

Fix idle, vacuum leaks etc. of course BUT your engine is telling you it is running too hot and trying to burn up its own valves!!

Combustion chamber temp CAN be a lean situation, so again this points to a vacuum leak, however it also and commonly happens when timing is too advanced or there is another ignition issue (say you put the wrong vacuum line on the vacuum advance! Understanding these is the solution.
1 confirm base timing
2 check thoroughly for vacuum leaks
3 if you have vacuum advance try running and driving without it
4 check head temps w IR temp gauge.
These will likely discover.. if not then your digging deeper.. but have eliminated 95% of causes.

 

[Boaf 32]

Related to Charlies comment in theory a potential foundational issue with “dieseling” is cylinder temp to high with some temps in the combustion chamber SO hot the continue to ignite fuel vapors. As long as it is rotating the cylinders will continue to “suck in fuel”. It’s right there in the name! (Although diesels have glow plugs). It does take a) your idle /throttle plate position to open or b) vacuum leak to allow air in, but your key does not shut off fuel just spark.

Fix idle, vacuum leaks etc. of course BUT your engine is telling you it is running too hot and trying to burn up its own valves!!

Combustion chamber temp CAN be a lean situation, so again this points to a vacuum leak, however it also and commonly happens when timing is too advanced or there is another ignition issue (say you put the wrong vacuum line on the vacuum advance! Understanding these is the solution.
1 confirm base timing Done
2 check thoroughly for vacuum leaks Done but always checking
3 if you have vacuum advance try running and driving without it
4 check head temps w IR temp gauge. Would need to get one
These will likely discover.. if not then your digging deeper.. but have eliminated 95% of causes.

Thanks @rlong, very methodical approach. What should the temps be in the cylinders? My temp gauge barely reads warm (just off the cold). This just started happening not to long ago.

I did find a bolt missing from the header collector, but no signs of exhaust gasses. Replaced the bolt. Checked carb bolts for tightness, all good there. I mentioned earlier that I reduced the passenger side mixture on the carb and see if that helps.

Boaf

 

[JohnnyC]

The bolts for the base adapter may be tight but it can still leak … if you have a multi piece adapter the connector bolts bottom out and need to be ground down in order for them to not bottom out

Use carb cleaner on base when truck is running to see if you have a vac leak

And you should be increasing the timing imho as well

Do you have a vac retard or vac advance dissy?

 

[Milkshake]

I had the same issues with my 2F with Weber 38. My main issue was the fuel being too hot, and vapors igniting on shutoff. I hadn't plumbed the fuel return line to the tank yet, and was just running a feed line. Once I plumbed the return, my fuel temps at the carb dropped significantly and I had no more issues.

 

[Boaf 32]

The bolts for the base adapter may be tight but it can still leak … if you have a multi piece adapter the connector bolts bottom out and need to be ground down in order for them to not bottom out

Use carb cleaner on base when truck is running to see if you have a vac leak

And you should be increasing the timing imho as well

Do you have a vac retard or vac advance dissy?

Thanks, @JohnnyC, I have a Vac Retard. I will spray tomorrow to confirm no leaks.

Any thoughts on the 32 / 36 DGAS? Appreciate it.

Bob

 

[60 40]

Are you still running a fuel cut solenoid like on a stock carb?

I remember getting dieseling (which I think is what you are describing as "run on") when I accidently disconnected my fuel cut solenoid.

Also the innernut says the Toyota fuel pump is too high pressure for a Weber carburetor so perhaps you need a fuel pressure regulator?

 

[JohnnyC]

Plug the vac retard and test to see if it still does it

The 32/36 is too small a carb … you’ll be throwing money away

 

[Boaf 32]

I had the same issues with my 2F with Weber 38. My main issue was the fuel being too hot, and vapors igniting on shutoff. I hadn't plumbed the fuel return line to the tank yet, and was just running a feed line. Once I plumbed the return, my fuel temps at the carb dropped significantly and I had no more issues.

Now this is interesting. I have no return line. I tried plumbing about 10 years ago and gave up. Do you have a return line diagram? Or even a drawing that runs into the tank or the supply line? I feel that is huge. My gas tank that I purchased from one of our popular LC Suppliers did not have a return and I thought that was the correct tank. Let me know and I am going to search the site as well. Temp gauge is very low, just above C so not baking (if the gauge is accurate). Been hot as SHi%$$ in FL this year.

Appreciate it @Milkshake

Boaf

 

[Milkshake]

My 40 is a 1971, and the motor is a desmogged 1984. I ran my return into the original metal lines that were still present on my firewall. I have a plastic tank with the same ports on the top as pictured.

 

[Boaf 32]

Thank you @Milkshake . On the Weber, the hose on the left of your picture is the return, correct? I have that blocked off.

Unfortunately, I boght the tank and it did not have a return and I never put it in.

Boaf

 

[BC40]

The 32/36 is too small a carb … you’ll be throwing money away

I don’t disagree on the bigger carb being better sized. He already owns the 32/36 so it could be a back up plan. May as well get the 38 on the truck sorted if he can tho

Yes to more timing. Then listen for pinging if you go too far.

Other part of original question. I run a much undersized progressive opening 32dir Weber on my 2f. Even smaller than the 32/36. It was a repurposed freebie to get up and running that stayed on the truck for the next 24years as it worked just fine. I’m sure I give up some at WOT but I try not to drive like that anyway. Mileage is bad enough as is. The little 32dir I have has the benefit of idle circuit fuel cut solenoid and manual choke, plus the small primary barrel is great for trail use near idle. And it was free. Sort of how I ended up running a gm HEI distributor for about as long.

 

[Boaf 32]

Update:

Hi All, I ordered carb gaskets and will replace then. It's been 13 years and many of that has been in FL heat. I recall having a previous issue like this but was a combination of issues. Sprayed carb cleaner (very little fluctuation 50 rpm? But noticed it).

Will keep everyone posted, I may grind down a thread to ensure it is not bottoming out.​

Also look into a fuel return. How to route it, that has to be determined as my Gas tank does not have a Fuel return.​

Thanks guys.

Boaf

 

[Boaf 32]

Are you still running a fuel cut solenoid like on a stock carb?

I remember getting dieseling (which I think is what you are describing as "run on") when I accidently disconnected my fuel cut solenoid.

Also the innernut says the Toyota fuel pump is too high pressure for a Weber carburetor so perhaps you need a fuel pressure regulator?

I did recall trying that with no luck. It could have been a bad regulator... Thanks @60 40

 

[Boaf 32]

I had the same issues with my 2F with Weber 38. My main issue was the fuel being too hot, and vapors igniting on shutoff. I hadn't plumbed the fuel return line to the tank yet, and was just running a feed line. Once I plumbed the return, my fuel temps at the carb dropped significantly and I had no more issues.

Hi @Milkshake ,

Can I run a fuel return line from my Weber to the supply line before the fuel pump? I do not have a return port in my fuel tank. Also, in your post, the return line is on the passenger side of the Weber, correct?

B

Post in thread '38/38 DGAS vs 32/36DGAS'

Jul 19, 2026

Thank you @Milkshake . On the Weber, the hose on the left of your picture is the return, correct? I have that blocked off.

Unfortunately, I boght the tank and it did not have a return and I never put it in.

Boaf

• Boaf 32

• 

Thanks,

Boaf