Help with hard-starting Aisin carb after rebuild.

[GJCruiser]

I have searched and read all I can about cold and hot hard starting issues but I still need help. After completing a recent carb rebuild, I am experiencing poor cold start (second concern--fuel is draining out of bowl overnight) and poor hot start conditions. The cold start can be solved by cranking until the bowl refills so my primary concern is that the 40 won't restart by cranking alone after shutting off when warmed up. I need to shoot a spray of starting fluid into the primary side of the carb and then it fires instantly.

Back story: This is a 9/76 Aisin carb that Jim C. rebuilt for me around twenty years ago. It has always run and started perfectly until recently. Hot starts were always quick w/o any pedal assistance. The 40 sat on the Gulf Coast for about six years with only about 100 miles put on it the entire time (start and run around the block until hot). Moved the 40 back to CO to discover a no start condition caused by fuel tank rusting out and filling with rust chunks. Replaced fuel tank and soft lines with new and rebuilt carb by following Pin Heads excellent videos. I had followed his videos one other time on a different carb with excellent success.

The 40 is stock with a professionally rebuilt 2F about 15,000 miles ago. Exceptions to bone stock are a Davis DUI distributor and wires and there is no carb fan. I have never had a carb fan and have never experienced vapor lock or fuel boiling from the bowl. After filling the bowl from sitting overnight, fuel level is otherwise midline in the sight glass. Manual choke operates per factory spec via normal operation. I can observe accelerator pump sending healthy stream into carb when actuated. I have tried the "pedal to the floor" with no pumping of the accelerator method and also pumping it w/o success. Once started with the help of starting fluid, the vehicle runs strong, smooth, accelerates well, and will easily drive at 65-70 mph. I'm not well versed on troubleshooting the various circuits of the carb and would appreciate any guidance. Thank you.

 

[GJCruiser]

Any ideas who I may contact?

 

[charliemeyer007]

So have you made sure the fuel pump is providing fuel constantly not intermittently - You could add in an switched electric fuel pump to provide priming, I run one all the time. Cost like $10 and last 10 years.

I have a Rochester carb. I turn the key on - listen to electric fuel clicking - when it slows way down, I step on the gas pedal to the floor, then pull out the choke knob full (sets the high idle position), take my foot off the gas pedal and then crank the engine. It will start almost instantly. After like a minute I need to push the choke in say 1/3 or it will load up. I keep pushing in the choke a little every few minutes. When the engine is showing warm on the gauge and the heater is blowing at least warm air, then the fluid heat riser is working and I can turn off the choke.

Way back in the 90's I use a modified propane torch with a hose in to the air filter horn to provide priming. Open the valve, wait 30 seconds and hit the key, Even at 35 below it would bark to life, and I would pull the choke and turn off the torch

Carb work isn't for everybody. Cleaning out tiny passages is a PIA. Then there are little details like noticing the ring cut in the mixture screws taper by some ham fisted gorilla torquing down the screw - but you don't see the damage to the seat even tho they replaced the screw.

Doesn't Mark's Off Road do carbs?

 

[Pighead]

I am experiencing poor cold start and poor hot start conditions.

So, you have trouble starting it? Is there a time when it starts easily? If you fill the carb bowl before a cold start does it start better? Is the fuel level midway in the glass before your hot starts? What's it timed at? Last time you adjusted the valves? How many volts does your coil get when cranking?Sometime, mine likes a little choke when warm, just for a second, to start.
Pics of your carb and engine and stuff would be nice.

 

[anothernz45]

Engines over here had no smog gear on them but later ones did have evaporative recapture thing on back of cab.

 

[LAMBCRUSHER]

might be siphoning fuel out of the bowl due to a clogged air passage from the bowl. Cold start = cranks till bowl fills, then it fires. Hot start = fuel has siphoned into the manifold and effectively floods engine. Just a guess. I was told long ago to do an Okie Rebuild. It can't possible hurt. (unless you use a bare hand to choke it out and it backfires...) When asked how to do this, I was told to start the car with the air cleaner top removed, and run it on high idle. then choke out the carb with a piece of cardboard, or welding gloved hand. It should speed up for a tiny fraction then sputter out and die. This pulls bits out of places they shouldn't be. Sometimes anyway. You can also do this to check for intake or big vacuum leaks - if it doesn't die, you have unmetered air entering.

Its been quite a while since I've done one, or explained it, so you may want to search the topic. I can't recall straight off if you want the choke closed or open.

from this thread: FJ-60 OEM carb goes dry - https://forum.ih8mud.com/threads/fj-60-oem-carb-goes-dry.7422/#post-63014

 

[GJCruiser]

.

Some photos and some test results. Note the fuel level is at the center of the sight glass. There is a "bubble" in the upper left of the sight glass that has been there forever.

For the last few days I have been cold starting in the morning then hot starting throughout the day to gain experience. Three straight days w/o failure made me think that the only component not changed was the fuel pump. I guessed maybe the pump passed some crap into the rebuilt carb causing the problems which I incorrectly assumed had vanished. The fuel level was always mid-way in the sight glass.

This morning before I started it, I noted the fuel level was very low in the sight glass. The vehicle did cold start but harder than the previous days. It would not hard start- crank forever, but no start. STRANGE MISUNDERSTOOD OBSERVANCE- When it refused to start, I pulled the choke completely out and she started. I did have to push the choke off immediately. That I don't understand.

I performed the "Okie" rebuild. Engine revved only for a split second before dying. The vehicle then started poorly and ran horribly. I had to actively feather the accelerator to keep it running while it surged. That eventually passed and normal running conditions returned. I performed Okie rebuild several more times from a high idle. Vehicle ran great and hot started. I always wait about three minutes to try a hot start. I needed to take the 40 for gas and wanted to be sure it would restart away from home.

Filled her at the gas station and it did not start. Crank forever. Pulled choke out and it restarted. Pushed choke in and drove home great. After sitting about five minutes, it did restart. But when I try to immediately restart after turning off, it will not start. Pulling choke out will aid in starting.

I will look tomorrow morning to see if Okie rebuild allows fuel to stay in bowl overnight. I don't believe fuel pump is still sending crap but I could be wrong. Still not a confident hot restart and don't know why choke would help with hot starting (unnecessary rich condition) if plugged vents are allowing nozzle discharge into manifold also creating rich condition. I did follow Pin Heads excellent videos when rebuilding to include running nichrome wire through what passages I found.

Thanks.

 

[GJCruiser]

Went to garage after the 20 minutes or so that it took to write above post. "Ticked" the key and fired right up. Turned off and attempted to restart. No start, crank all day, fuel mid way in sight glass. Pull choke out and restarts. School me please. Thank you.

 

[charliemeyer007]

Pulling the choke out increases the vacuum - that allows for more pull on fuel threw the passages. After its running fuel has momentum to continue threw the passages. My guess your wire didn't clear the passages completely - cholesterol build up in the artery inhibits blood flow. I need to do my Rochester for the first time ever. Back in the 90's I had to free up the leather pump cup in the accelerator pump. Other than that I haven't really fooled with it since I got the rig in 82. Every 5 years or so a good spray down with carb cleaner inside and out. I did buy a heated ultra-sonic cleaner and a gallon of carb cleaner juice for it.

 

[Skreddy]

Do you push the pedal before trying to start it or just crank until it starts? In my 60 series, I give it 1 full pedal pump, pull choke, turn key to start. If it’s hot, no pump first but sometimes give it a pump as it’s turning over.

 

[charliemeyer007]

The procedure for my Rochester is as follows. Switch on key, listen to electric fuel pump clicking - when the rate of clicking slows way down - the bowl is fuel. Push the gas pedal to the floor, and pull out the choke knob full out (sets the fast idle) take foot off the gas. Put tranny in neutral, engage the starter. It will usually fire right up. Push choke knob in part way or it will load up really quickly. After a few minutes, tap the gas pedal quickly to release the fast idle. Depends on how cold it is, if the block heater was plugged in... how long I let it just idle. Have a liquid heat riser to help because of the header. Keep pushing the choke knob in slowly. Its about 1/2 mile to the county road - I usually just let it idle there in first. By this time I can feel heat coming out of both heaters.

 

[cstav86]

If your tank was rusted out, likely your hard lines were rusted too and slowly leaching crap into your fuel system, at least that was the case for my 40. I would bypass the metal lines with rubber and likely replace your fuel filter again.