Dieseling problem (1 Viewer)

[Captron]

Thanks Alex. Hope you are keeping warm!
It does make sense to set the timing to the bb as would be done with a stock carb. The spark is in the same place. Cylinder is the same. It's just this crazy old MAF sheet of paper says 12-14 btdc.

 

[WILLD420]

Vacuum blew off because gas vapors were in cap. Search the threads, there are reasons for your problems. If you are carboned up, treat with seafoam etc. Plugs might be too hot heat range as well.

 

[Captron]

OK will do. I will also take Alex's advice and try to use 7* BTDC as a baseline (or whatever is closest and runs well).
Thanks!

 

[Captron]

I set timing to bb. Single vac into distributor. Quart of marvel mystery oil into carburator. Turned idle mixture screws out a quarter turn. It still diesels.
Before trying a colder plug I want to keep adjusting the idle mixture screws. It idled up when I turned out the screw closest to me. I think this means that it wasn't at the ideal setting.

 

[morganism]

Check the pcv valve is working, if blowing off vac hoses, that should be venting back into intake. Do you have a charcoal canister setup? They can plug, try switching the hoses, see if it helps.

 

[martyjayFJ62]

I think you may have an issue completely unrelated to both the carby or the timing / distributor.
I had VERY bad dieseling on my FJ62 even after replacing all 6 spark plugs (the PO plugs were absolutely ancient and growing rust).

But even with new spark plugs the car dieseled horribly, sometimes taking 15 seconds to die with a backfire after I turned the key off, this would be much worse when the engine was hot. I thought at first it was the carby leaking extra fuel into the hot engine after shutdown, but it wasn't.

I'm betting you have the same issue.

THE PROBLEM (cause of dieseling):

Carbon build up inside the piston cylinders. My car was a 1989 build and the engine had been treated like s***, as such it had a massive amount of carbon build up inside the ignition chambers, as I drove and the engine got very hot, this carbon would act like a spark and keep the engine running even after I switched off.

THE SOLUTION

Run small amounts of water through your carby intake. The water turns to steam inside the engine which gradually blows the carbon out of the cylinders. If your car is dieseling this means there is a LOT of carbon built up, so you may have to give your engine this treatment for several days in a row.
It might seem scary or stupid but just follow these steps, it works:
- Start the car, get it idling for about 10 minutes until the engine block is very hot.
- Get a spray bottle filled with water and a little bit of dish washing liquid, set the spray to a stream not a mist.
- Take off the top cover for the carby, so you can see down to the butterfly valve (down into the intake manifold)
- Spray in a few jets of water (never dump a big amount of water at once) keep spraying in water until you hear the engine begin to lower in rpm and nearly stall, then stop spraying let the engine go back to normal.
- Repeat this process about 10 times with the engine speed at idle
- Now using the throttle cable set the car to high rpms and spray more water in
- stop spraying water and for about 5 seconds redline the cars RPMs
- if you have bad carbon buildup you will see a huge cloud of black smoke come out the exhaust when you redline the rpms
- repeat this whole process until you have no more black smoke coming from the exhaust during the water sprays (this may take several times over several days)
- ensure you let the engine stay hot idling for another 5 minutes after you have finished adding water (to make sure you evaporate all water left in the engine intake system)

Let me know how it goes.

 

[Captron]

Check the pcv valve. Do you have a charcoal canister setup? They can plug, try switching the hoses, see if it helps.

Thanks I'll look into pcv function. The canister is there but I honestly don't know if it is actually hooked up. Do you mean switching around the hoses going into/out of canister? Is this to switch direction of air flow?

 

[Captron]

I have a feeling carbon is my problem as well. My dieseling only goes for a few seconds so not anything as dramatic as what you are talking about! I'm a bit hesitant about adding soap with the steam cleaning but I'll give it a shot. It was dark out when I did the mmo treatment so I couldn't see the color of the smoke. Previous sea foam treatment I did had all white smoke if I remember correctly.

 

[Captron]

My engine is definitely running too hot. fix this and my dieseling will go away. I think.

 

[morganism]

Yup, the canister valves have a known sticking problem. Spray in some wd40, and switch the purge and return valves for a week or so. Keep an eye on gas cap pressure too.

If it isn't the carbon build up alluded above ( a real issue with the 2F), it could be burned valve seats with that stuck pcv valve allowing positive crankcase pressure to force in fresh vapor. Try the spray, but would do compression checks on cyls before and after, see if it changes. Leak down is called for too.

 

[Captron]

Thanks. These are good suggestions for me to follow up on. I did a quick look at my canister this morning and found where one of the lines ends:

 

[Captron]

I have a feeling this is not a Toyota design feature.

 

[Captron]

I found that my water pump belt was ridiculously loose. I adjusted it tighter and now there is less of that screaming sound when I rapidly open up the throttle. Not none; just much better. I haven't done a full highway test but it seems to be running cooler around town.

 

[Captron]

I still hear this slight tweet bird sound like a bearing going bad so I went through each of the pulleys to see what condition their condition was in. I have an air pump where the smog pump was. It currently isn't working in that the pully stops turning when I engage the pump with it's electric switch. However, when not engaged, the pully spins freely as it should. I did notice that the shaft must be out round as the pulley sort of wobbles as I spin it around. The power steering pulley is stiff and doesn't spin freely but does not have any "gritty" feel or grind. Perhaps it is normal for the ps pump to give resistance on the pully. I did find a bit of rough grittiness to the small pulley that sits just below A/C compressor. I think this small pulley it meant to keep belt on when AC kicks on. Overall no major problems that need immediate addressing. I would like to try and salvage the air pump at some point but it looks like i would need to remove PS pump to get access to it.

 

[Captron]

For the compression test, do I need to cut fuel off? The fsm doesn't mention it and the threads I've looked at don't either.

 

[Captron]

I used vise grips on the fuel line leading to the carb to restrict fuel coming in. I pulled the plugs and they are very dark. Cylinder 4 was the worst, cylinder 6 looked pretty descent. I will back off the carb's idle adjustment screw a little.

 

[Captron]

Number 6 plug:

 

[Captron]

I also found 6 plug was only hand tight. I wonder if this it a sign of dieseling in this cylinder or me being a dumbass and not tightening down the last plug when I changed them. I also checked the gap on all:
#1: 0.031
#2: 0.031
#3: 0.031
#4: 0.029
#5: 0.029
#6: 0.035
That last one is surprising to me. I can't remember if spark plug temp has something to do gap size.

 

[Captron]

Compression test results dry:
#1: 155
#2: 144
#3: 149
#4: 155
#5: 140
#6: 155
I went back and retested #5 dry and 140 again. Then did wet and still 140. Valve needs adjust on this one perhaps? I don't have leak down equipment. I'm gonna buy new plugs after I read up on relationship between gap length and spark temp, sea foam and then repeat compression test.

 

[Captron]

I replaced the water pump belt with new Gates belt that should be oem size. It was incredibly difficult to get on but I was able to by having my brother spin the rear tire in fourth while I pushed, pulled and cussed at the belt. It is so tight that I can't get the adjustment bolt back but I tightened down the "hinge" bolt down pretty good and the compressor is not moving around. I haven't had the chance to test on a long hwy trip yet but it runs good around town.