Carb fuel level in sight glass

waynehoc · Post by **waynehoc** » Sun Dec 03, 2006 8:54 am

So, in my continuing voyage of discovery doing all the mtce on my '87 2WD wagon, I happened to notice that the fuel level in the sight glass on the carb (see page FU-25 in the FSM) was at the very top of the visible glass area.

Resulted in way too much gas boiling off into the carb/air cleaner area during a hot soak when the engine was off for 20 minutes or more, with a nasty gas smell and slightly hard hot starting after a 20 minute or so hot soak.

Figured there must be a needle/seat/float problem so off to my local parts store for a carby kit c/w new float. On disassembly of both my carb and the carb from my parts car, I found the float setting in both cases close to the specs in the manual. I also set my new float to the same specs - to my surprise, the new float, set to specs, also allowed (what I thought) the fuel level to be exactly the same - way too high, with all the same hot soak/smell/starting problems.

Many carb top removals later, experimenting with float level settings to get the fuel level to be controlled at the (close to) exact center of the sight glass, I have ended up with a float setting (see pages FU-16 and FU-17 of the FSM) of about 5/64 higher than spec. The fuel level is now in the center of the sight glass at idle, engine warmed up, etc., as per the FSM.

Along the way, I have checked the fuel pump pressure and is fine - thought it might be too high, but is not the case. Also, the pump IS recirculating fuel back to the gas tank - with the engine running, and fully warmed up/hot, the fuel pump and suction & recirc lines are nice and cool.

I did a LOT of research on the Internet re correct fuel level for all types of carbs that have sight glasses, and all the info I found says fuel level at the center of the sight glass, so that is where I have the float set to contol the fuel level at, at idle.

Haven't noticed any performance problems either with the 'half way' level vs the 'full to the top' level of gas in the sight glass.

To try and minimize the hot soak problem I did a couple of simple things, based on what info I found on the Internet - re-routed the fuel line away from the engine, added a rudimentary heat shield between the engine and fuel pump (the fuel pump really heats up during a hot soak, and to a lesser degree while the engine is running), and added a 12-Volt PC fan on a timer that I now run during the hot soak period. The fan has made a HUGE difference in how much gas evaporates from the float bowl during hot soak - as long as the fan is running, virtually NO gas evaporates. However some gas still evaporates when the car is off during the entire day while I am at work, or overnight when the car is off. Total evaporation is very little now compared to before I installed, in particular, the fan.

Note that my wagon is a non-computer controlled Canadian 5-speed manual, and as such it does NOT have the evaporative emissions line from the float bowl to the charcoal canister that the computer-controlled wagons do. Evaporative emissions are simply contained within the closed air cleaner assembly.

A couple of pics of the mods

Typrus · Post by **Typrus** » Sun Dec 03, 2006 11:32 am

Why is a computer fan under there....?

waynehoc · Post by **waynehoc** » Sun Dec 03, 2006 3:33 pm

...and added a 12-Volt PC fan on a timer that I now run during the hot soak period. The fan has made a HUGE difference in how much gas evaporates from the float bowl during hot soak - as long as the fan is running, virtually NO gas evaporates.

I added the (PC) computer fan as an experiment, to see what effect it would have on minimizing hot soak fuel evaporation, and it works great!

Got the idea from Internet searches re hot soak problems. Apparently there were some older Fiats that had a terrible problem with heat under the hood, and actually came from the factory with a carb cooling fan. The guy who made the post said he'd added PC/computer fans to quite a few vehicles for heat control under the hood on carbed vehicles.

All I can say is that it works great in my case.

Prior to putting the fan under the hood, if I went into a store or whatever for 20 minutes or so, and came back out, the carb would be partly flooded from gas percolating/evaporating into the primary throat, and the hot start was not nice at all. Now I just turn on the fan (installed a timer low in the center of the dash) for the appropriate time I think I'll be away. When I come out and start 'er up, don't touch the gas pedal at all, and it starts right up to a nice normal idle. Not so pre-fan install - the @#&*&^%$#@ engine would run pretty ugly for a bit until things cooled off from the heat soak and got some cool gas into the carb.

Before I set the float to lower the fuel level in the float bowl (the level was originally right at the very top of the visible 'glass', well above vertical center), if I stopped the car after a hot soak and immediately pulled the top off the air cleaner, I could actually see gas being percolated out of the primary main venturi and dumping into the primary throat.

If I'm going into a movie, or parking for the day or night (say, at work, or at home for the night), I give the timer a full hour. Makes a BIG difference in the amount of fuel evaporated out of the float bowl.

Bottom line = less fuel evaporated from the float bowl and real nice hot starts.

Typrus · Post by **Typrus** » Sun Dec 03, 2006 3:44 pm

Huh.
Part of what might help would be that electric water pump. It claims to keep running for a while afterwards to minimize heat soak. Just a thought.

I had that issue before my rebuild, when she was running kind of rich. Not so much now.

Guess I missed that part of the post.

waynehoc · Post by **waynehoc** » Sun Dec 03, 2006 4:12 pm

In my case, wondering if I'm running a bit on the warm side. Have a near new double core rad, a rebuilt water pump and an OEM Toyota thermostat. Thermostat tests fine out of the car - starts opening at right around 180F as per FSM, etc. My temp gauge, when engine at operating temp, reads dead level with the zero rpm mark of the tach.

However, my rebuilt water pump has never stopped leaking at the seal from day one, and its been in there for six months or so. So I bought a new OEM Toyota water pump. Thought I was gettting a pump, but ended up with a complete water pump assembly.

Going to put it in late this month, and will post up some pics when I do.

When I got the new pump assembly and had a peek, I right away noticed two things.

One, the nub at the front of the pump where the pump pulley bolts on is a neat snug fit to the pulley. The 'rebuilt' has likely been shot blasted to clean up, and the same nub is lower and smaller diameter. Net result is that it is impossible to bolt the pump pulley to the pump and have decent alignment to the center/rotation of the pump. Pics to come will show this.

Second, the impeller of the rebuilt pump (also likely 'cleaned' by shot blasting) is not up to spec. More clearance from the water pump casing/housing and physically also looks to be worn down somewhat from the shot blasting treatment = more slippage that a new pump assembly. What this tells me is that a new pump should pump more liquid and more effectively/efficiently than a 'rebuilt'.

Just a theory at this point, but time will tell ...

Mac · Post by **Mac** » Mon Dec 04, 2006 12:55 am

hows the rad cap? I had to replace mine a few years ago, but next time i'll get a rad cap with a higher pressure, if i can find one with a higher pressure at crappy tire, otherwise i might go TRD.

I also noticed with my old engine, running 87 made it hot as hell, but now i run husky 90 octane, its the same cost as everyone elses 87 and makes my cars run great.

what i hate about our engines is the intake and exhaust manifolds are on the same side which makes the exhaust mani super heat the intake, i tried wraping it with regular old fiberglass, that worked fine on a lawnmower, but not so much for tercel.

Gasoline Fumes · Post by **Gasoline Fumes** » Mon Dec 04, 2006 2:30 am

Is that stupid flap in the exhaust manifold stuck in the "hot" position?

takza · Post by **takza** » Mon Dec 04, 2006 4:24 am

A lot of the mpg info says (among other things) to set the fuel level in the bowl lower than specs call for...it forces the air flowing thru the carb to draw the fuel futher up and into the carb...less spill over and more atomization.

Could be the OEM specs are a way to compensate for boil off?

The level in mine has always been at the middle or slightly below....and I do OK with mileage.

I don't have a problem with hot start (even with fuel heat)...but the fuel will manage to go somewhere after the car sits 3-4 days...takes a good while to get gas to the carb for it to start. It's not in the engine as raw gas.

Other things for mileage are to use a pressure reg to keep the pump pressure down to a minimum....and soldering the power valve shut.

Post by **ARCHINSTL** » Mon Dec 04, 2006 11:29 am

takza wrote:I don't have a problem with hot start (even with fuel heat)...but the fuel will manage to go somewhere after the car sits 3-4 days...takes a good while to get gas to the carb for it to start. It's not in the engine as raw gas.

Nor do I have the hot soak problem (172K miles, albeit w/reman carb) - and I would think that STL gets warmer than BC (mebbe the ambient has little to do with that, though).

I do have the same problem with the reluctance to immediately start as takza experiences. This was with the OE carb as well as the reman one. Never experienced this with a carbed car before; although I've never had a car with 172K miles before, either. While all gaskets/pump/lines have been renewed, I guess the gas just goes back into the vapor canister? ? ? Does this seem to be a prob with '80s Aisan-equipped Toyotas? Do you Weber guys have this as well?
Tom M.

waynehoc · Post by **waynehoc** » Mon Dec 04, 2006 10:24 pm

hows the rad cap?

Rad cap looks good, but I figured its only a few bucks to find out for sure, so got a new one on the way home from work today (crappy tire) and put it on after cool down. Took it for a long drive, but temp is still the same - temp indicator dead level with the zero line on the tach when engine fully warmed up.

What is the 'normal' spot for the temp indicator for everyone else?

waynehoc · Post by **waynehoc** » Mon Dec 04, 2006 10:28 pm

Is that stupid flap in the exhaust manifold stuck in the "hot" position?

Flap is working fine - I had that problem about a year ago (flap staying full open to hot air from the exhaust manifold - ran @%$#&^*% awful - turned out the HIC valve was no good. Got a good HIC from a local wrecker, which solved the problem.

waynehoc · Post by **waynehoc** » Mon Dec 04, 2006 10:41 pm

I also noticed with my old engine, running 87 made it hot as hell, but now i run husky 90 octane, its the same cost as everyone elses 87 and makes my cars run great.

What exactly do you notice with the Husky 90 in the tank compared to the 87 octane of others? Curious about any performance differences you might have noticed, and I assume from your post that cooler running is noticeable too? Also wondering about the fact that supposedly Husky and Mohawk use some ethanol in their gas, which might impact gas mileage by reducing economy slightly.

Am interested in any comments/observations you might have, etc.

I enjoy experimenting to try and tweak things, so am open to trying different gas if it sounds like a good idea. Have been a long time user of Petrocan, but recently switched to Chevron to see if there is any difference vs Petrocan.

takza · Post by **takza** » Tue Dec 05, 2006 6:23 am

waynehoc wrote: What is the 'normal' spot for the temp indicator for everyone else?

Mines an '83 with tach....I put a cheapo Stant in it....runs about in the middle of the gauge in summer...a little below that in winter.

Your temp sending unit might be off? Think I cleaned the connector on mine....was corroded and loose.

Mac · Post by **Mac** » Tue Dec 05, 2006 4:49 pm

waynehoc wrote:
I also noticed with my old engine, running 87 made it hot as hell, but now i run husky 90 octane, its the same cost as everyone elses 87 and makes my cars run great.
What exactly do you notice with the Husky 90 in the tank compared to the 87 octane of others? Curious about any performance differences you might have noticed, and I assume from your post that cooler running is noticeable too? Also wondering about the fact that supposedly Husky and Mohawk use some ethanol in their gas, which might impact gas mileage by reducing economy slightly.

Am interested in any comments/observations you might have, etc.

I notice a differance in power, I would say its because all that carbon build up in the engine bumps up compression a little bit. In the past I've found old cars usually respond quite well to using higher octane than new cars do. But the biggest differance I noticed was how much smoother the car runs on premium, even other people like my friends (and my brother who first tried running premium years ago). I noticed it was alot cooler under the hood when it was just parked after coming home from school or what have you.