'74 FJ40 won't idle. Need Colletive MUD brain!

[Spike Strip]

This started when I rebuilt my carb. Truck was running ok before, but would occasionally diesel, and would occasionally stumble and have a rough idle.

I though it was carb rebuild time:

https://forum.ih8mud.com/threads/how-do-i-fix-a-warped-carb-air-horn.851676/

After the rebuild, I was unable to get the truck to idle without the choke fully engaged and after reading many threads, it seemed like a warped air horn, as shown in linked thread. After weeks of trying and not being able to get the truck to idle, in my exasperation, I broke into the secret vault and installed a NOS '74 Calif Spec Aisan carb. Yes, brand spankin' new --

AND still the truck would not idle unless the choke was fully on. Same as with other carb.

Checked multiple times:

Fuel level in sight-glass is spot on in the middle. Was with both carbs.

Idle solenoid is working on both carbs. Audible 'Click-Click'. Tried to run with 12V connected directly to solenoid, Still no idle without full choke. Checked engine fuse, ok, and also checked if there was power to the idle solenoid in 'engine run' condition'. Ok.

Checked extensively for Vacuum leaks with both Carb cleaner and injecting smoke (cigar) into intake manifold and no leaks that I can see - Engine pulls 15-16 Hg steady vacuum at idle with choke fully on.

Looking into carb venturi during running, it seems as though too much fuel is metering, but I really don't know what proper metering should look like. When I manually move the choke butterfly open, engine will slowly stall.

Things I have done, for no particular reason other than I was at the 'try anything' stage:

1. Checked spark, kind of orange, so New Coil/ w/ new external resistor. Still orange.
   
2. New Distributor condenser (Dizzy is new non-USA vac advance unit - points look good)
   
3. New OEM Fuel Pump
4. New OE Fuel Filter
5. Removed and cleaned Fuel return lines.
6. Checked Evap system for blockages or pressure build up.

I have not done:

• Check compression - because there are no empirical signs of bad head gasket or compression loss. Coolant is clean and good. Oil clean.

I suppose it's possible that both carbs could have Idle-Circuit issues, but ... ?

So any other suggestions of where to look would be GREATLY appreciated. I'm out of ideas.

Thank you...

 

[Bambi Girl]

Hi
Have you checked your points Dwell ? Here in the land down under equals 41.
Next check your timing for us it's 7 deg BTDC
If you get these right it's something else you can rule out.
Cheers


...via IH8MUD app

 

[edwjmcgrath]

At the risk of pointing out something obvious...You need to remove the plastic cover on the carb.
That said, if it only runs with the choke on, with a new carb, you very likely have a vacuum leak.
I'd give up smoking, for health reasons and take up carb cleaner (over cigar smoke) for finding vacuum leaks.

 

[Spike Strip]

Bambi, thanks - I have not checked the Dwell nor timing and I should have just to rule out. Will report back.

@edwjmcgrath - well, I was waiting for the first wise-guy to point out the carb cover - Just on there to keep the wind-borne crap out and to cap for the smoke test for vacuum leaks - Checked and triple checked for the Vacuum leaks and can find nothing, as that what I was leaning toward, too. Used both carb spray and injected smoke... Vacuum gauge is a little low, but steady.... I don't smoke, but just bought a back of Swisher Sweets for the test! Man, no one sells tobacco anymore - Had to find some crummy Russian-owned liquor shack that still sold 'em!

 

[ErikinSC]

REPLACE POINTS AND CONDENSOR. Check points gap. Reset your carb settings - idle speed, idle mixture, etc.

 

[77wagon]

When I was fully choking mine to get it to run, it was poring gas into engine. You might want check your oil and make sure it doesn't smell like gas. In the end it was junk in the fuel. No matter how many times I cleaned or rebuilt the carb it just clogged up again. I had to replace all fuel lines and tank. Just my problems, might not be yours.

 

[MT2000]

I had a reman carb doing the same thing. I rebuilt is and found that the gasket on the stopper for the pump discharge weight.

 

[Pin_Head]

You haven't found the vacuum leak yet. 15 inches is too low and it explains the symptoms. Check the brake booster and check for manifold cracks.

 

[Solace in Solitude]

I can't tell... is there an open port, to the left of the idle mixture screw, on the valve cover side of your new carb?

 

[sggoat]

about 20

Bambi, thanks - I have not checked the Dwell nor timing and I should have just to rule out. Will report back.

@edwjmcgrath - well, I was waiting for the first wise-guy to point out the carb cover - Just on there to keep the wind-borne crap out and to cap for the smoke test for vacuum leaks - Checked and triple checked for the Vacuum leaks and can find nothing, as that what I was leaning toward, too. Used both carb spray and injected smoke... Vacuum gauge is a little low, but steady.... I don't smoke, but just bought a back of Swisher Sweets for the test! Man, no one sells tobacco anymore - Had to find some crummy Russian-owned liquor shack that still sold 'em!

I would not depend on the dwell alone. It has a habit of being way advanced for the actual points timing(could be as far as .035 point gap). Stick with the timing marks on the flywheel-7 degrees BTDC is the spec--point gap is a squished matchbook cover(if you still have one of those-about .020-(spec is .018)--this is only if you haven't found the vac leak yet---
BTW, I've never seen a carb with that vertical banjo fitting--what year is it from?

 

[Spike Strip]

Carb is a 73-74 Calif-spec w/egr. AFAIK only ones that have the fuel return pressure relief valve in the banjo fitting.

No open port in the carb - what you see is the machining plug.

I'll check the points and dwell and gap tomorrow.

If there's a Vacuum leak, it's a bugger. No cracks in the intake- I looked all over the intake with a mirror and strong light, also checked extensively when the carb was removed. Headers so I can see the underside of intake where the carb bolts down and no crack there. . Checked the booster and even capped off the manifold vac port to the booster to make sure. Still no idle without choke. I've sprayed as much carb cleaner as is safe around where int/exh bolts to cylinder head, and the base of the carb, with no change to the RPM - but it may be running so rich on full choke that the spray won't affect engine RPM ?

 

[Pin_Head]

Make sure that the centrifugal advance is not stuck.

I still think it is a vacuum leak, but if so, you should be able to make it run by increasing the idle speed so it runs of the main jets instead of using the choke.

 

[unklwedy]

You might want to remove solenoid and make sure plunger is retracting.

 

[Searcher356]

When you say "dieseling," I assume that you mean after shutoff. That can be a symptom of too much timing advance. Checking timing is a good idea.
As Pin Head suggests, make sure the centrifugal advance is free.
Regarding the brake booster, a way to check that is to pump the brake pedal several times with the engine off, until the pedal finds its new "unassisted" pedal location - should be higher than normal. Then, while keeping firm pressure on the pedal, start the engine. As the vacuum builds, the pedal should depress further. If it doesn't, then you have a faulty booster, and that could be your vacuum leak.

 

[Adrift]

When I had the exact same symptoms with my 77 2F it was a vacuum leak.

 

[MoCoNative]

Any time I had this problem, either the capped EGR was cracked, or the PCV line to the base of the carb had cracked, which led to a massive vacuum leak. Sorry I don't have anything for yours, install looks good. Try PinHeads advice, the full choke will mask the leak.

 

[FJ40Jim]

Make sure the idle mix screw is backed way out, like 4-5 turns.

What kind of distributor is in it?

 

[Spike Strip]

I started with Idle mix screw backed out 4 turns, but will try more.

Dissy is new Toyota (less than 500 miles) Non-USA vac advance 19100-61080. Just checked mechanical advance. OK. Dwell about 44*. Timing 7* OE plug wires. Checked dissy cap for cracks, arching, anything funky with rotor. All looks good.

..

 

[FJ40Jim]

Safety alert: In that last pic, the throttle return spring is not helping. It will actually try to pull the throttle open.

When fuel (gumout spray carb cleaner) is sprayed in the top of the carb, does the idle improve? Can the idle be stabilized by repeated squirts in the top of the carb?

 

[Spike Strip]

Carb spray down top of carb will improve idle and keep engine running - repeated squirts will stabilize idle - this is with me manually pushing the choke butterfly open; engine dies too quickly for me to push choke knob in and grab a can of spray and squirt.

Thank you for the throttle spring alert... But I don't see any other attachment points? Previous carb was set up same way... Best to leave off ?