heat soaked engine gets idle surge on restart. (1 Viewer)

[destin]

Hiya guys, new thread new problem.


on heat soaked restart does have the "boil off symptoms", fluctuating idle rpms / vacuum, like 550- 800 rpms, about 2 second cycles or so. These symtoms do not settle out if i let it idle i have to put some load on the engine and drive it for a block to sputter out whatever build up is happening, ( or likely over come some pressure or loss happening within the carb who knows )

lsit of new stuff btw

new tank
new sending unit
new gas cap
new lines
rebuilt carb ( sorted out the accelerator pump issue, jet pumps a nice stream now )
new points ( gapped at .0016, dwell/ cam angle at 43 degrees )
timing at 7 degrees before top dead center ( stock on the needle )

basically EVERYthing in the fuel system is new except for the carb.
Now i know old trucks get vapor lock, but I doubt every time you drive it for a half hour and let it sit and restart...

So I am think i need to find a working, 100 percent awesome, single barrel small window aisin carb with a idle solenoid cut off.

I mean unless you guys have a suggestion on how to fix this otherwise, it seems to be the only other link i can think off that might be the problem.

unless advancing the timing can solve this problem ( I doubt it )

i check the coolant it was a little low and filled it and tried to burp out any possible bubbles. i need get an overflow container for it and maybe a new cap to make sure that is 100 percent. but I do not think it is my cooling system...

This is getting beyond irritating, while it is all around better with the new fuel system, this problem HAS to have a fix.

Any input would be awesome!

Someone tell me they do not have my problem ( almost ) every time their engine gets heat soaked?

 

[Godwin]

Rig up an underhood fan to cool things down, I did this on my '77 and it helped. I used a fan from a FJ60, wired it with a relay and toggle switch so that when I shut off the engine I could run the fan some to cool off the carb.

 

[desertpat]

A fan will help to disperse heat.
Insulating the fuel line from the fuel pump to the carb is a very effective heat barrier to prevent fuel from vaporizing.

 

[destin]

yeah.. what drives me nuts is that it is only 80 degrees out... seems like it would not be so hot to cause this.

I am beginning to wonder if this is not my head gasket beginning to go out... ( had it happen once after rebuild of the motor )

I mean the idle surges as does the vacuum if you watch it.

1) so maybe compression drip down test or pressure test the system?

2) maybe the carb is just so warped and old it creates a pressure trap or becomes messed up when hot?

REALLY want to fix this once and for all.

 

[destin]

my neighbor said surging is usually a vacuum leak, said to mix soap and water in s spray bottle and hit around the carb and look for bubbles... bad idea?

so options would be

1) failing head gasket
2) some messed up carb or vacuum leak on carb internally / externally.
3) vapor lock

 

[gwalt584]

surge

Destin,
my 75 2f had a similiar problem after:
carb rebuild Jim C
exhaust / intake surface leveling.
new gaskets, new bolts and nuts for intake.
heat shield sent to Jim C when carb was rebuilt for new gasket and smoothing surface.
I found no leaks in the system, idles smooth when cold and got rough after restarts, happened anytime the outside temp was over say 75.
My point is that I thought I had done everything possible to solve the problem.
understand that doing all of that made it far better than it was originally.

The mod that helped the most was adding a carb fan to cool it.
I bought a FJ40 carb fan on ebay for 25 bucks, found a temp switch that activated at 175 degrees IIRC, bought a relay(normally off).

since my 75 was not originally equipped with a carb fan I did not have the brackets on the side vent to mount the fan. so I mounted it on the vender side.
I mounted the temp switch in the head where a switch for the emissions was mounted. (see the second picture the gold switch in the top of the head)
I rigged the realy to turn the fan off when the key switch is on.
The temp switch is wired to complete the circuit to the fan (ground) when the switch is above the switch temp setting.

On summer days, when I turn it off the fan comes on and runs for approximately 10 minutes. This past winter it would run for 8 minutes. it may cycle a couple of times after turning off the first time but usually the cycles are only a few minutes.

Oh, and I also added some insulation to the fuel line. it is wrapped in aluminum faced insulation wrap and then the foam you see in the picture. not sure how much that helped, but it did not hurt anything.

This mod helped more than anything in solving the carb heat rough idle problem.
Pictures are below

 

[destin]

what year carb fan would be best for a 1964? Does it matter?

I think i am gonna run a smoke test on my exhaust system and intake to be double sure.
Maybe pressurize the coolant system and check for leaks from the spark plugs as well to make sure the head gasket is good.

Failing that it might be a carb fan in my future.

 

[gwalt584]

carb fan

I really do not think it matters about the year, the carb fans like the one I used are all the same.
Gary

 

[destin]

I really do not think it matters about the year, the carb fans like the one I used are all the same.
Gary

and this immediately solved the problem for you?

Was you vapor lock / boil off symptoms like mine?

is,, idle would go up and down ( as vacuum obviously ) and it would only go away if you put the motor under load and drove it a block to work it out?

I just want to be sure I am not masking a problem, just want it fixed.

 

[gwalt584]

problem

my problem was directly related to engine heat. if I drove to the store parked and out for a few minutes when I returned and fired it up the temp gauge would be right above the first line. it would run rough, surge or lope and I would give it more throttle to increase the rpms, the temp would go down to just below the first mark on the temp gauge and idle smoother.(over several miles of driving)
Now I still see the temp gauge above the first mark after stopping but the restarts are easier and much smoother after restarts.
it helped mine. of course you have to understand all the other stuff I did first.
Gary

 

[destin]

right on.

i hear ya

taking it down to get a smoke test, JSUT to make sure it is not intake or exhaust leak ( doubt it, but want to verify )

i likely try to test for head gasket leaks too ( compression test, pressurize the coolant system and look for coolant coming out the plug holes )

I hit Jim up about a new clean single barrel carb, small glass solenoid shut off, but I have not heard back yet. could be my carb is just too warped and old too, dunno, could be just vapor heat problems too, hard to say.

ugh

 

[destin]

could this be because of the PCV valve on the PCV hose?

Could this be because of the oil filer neck cap does not seal tight as one might wish?
( PCV hose fits into the filler neck, so if there was air leaking into the filler neck cap, the PCV valve might not work properly?

jsut ideas here...

 

[destin]

As an experiment, I am going to also start running non ethanol gas for one month, during the hotest season, see if that sorts it or helps too.

hard to find non ethanol gas, this site seems to list a few in portland though.

Ethanol-free gas stations in the U.S. and Canada

 

[destin]

Question

Since my truck does not have an over flow canister ( trying to order one ) could this be introducing air into the coolant system causing it to run s***ty when hot or heat soaked? I have a new Toyota radiator cap coming too, old cap spring seemed a bit weak...

Thoughts?

Or do I just need a carb fan lol.

Still looking for a pristine single barrel carn with the idle shut of siliniod btw.

Thanks

 

[Tigerstripe40]

I had a similar problem with my FJ40 years back.
Rebuilt motor top to bottom. Jim C modified carb. IT would run great for a while, then if I shut it down, the motor would not restart.
Turns out it was the fuel pump (I don't see that you had mentioned that had been replaced).

My FJ40 runs like a top in 110 degree weather here in Salt Lake. No carb fan.

 

[destin]

Hmmm, mechanical fuel pump was replaced last year with a new one...

Has fuel at the glass so I think that is correct, unless the arm of the pump where it touches the cam needs lubed, but I am not sure that would sort it...

See 100 degrees and yours is running correct, wtf.

Do you have a coolant return canister?
What carb are you running ?
Oil bath air filter ?
Running ethonal fuel thre in Utah ?

 

[Tigerstripe40]

Hmmm, mechanical fuel pump was replaced last year with a new one...

Has fuel at the glass so I think that is correct, unless the arm of the pump where it touches the cam needs lubed, but I am not sure that would sort it...

See 100 degrees and yours is running correct, wtf.

Do you have a coolant return canister?
What carb are you running ?
Oil bath air filter ?
Running ethonal fuel thre in Utah ?

The motor oil in the crankcase should splash onto the cam lobe to lube things.
Yup. 100degrees, lights right off within 2 cranks of the motor.
I do have a coolant return canister.
Carb is a Jim C desmogged 2 barrel Aisin from 76.
Standard paper air filter (I have a 2F).
And we do have 10% ethanol fuels in Utardia (makes my fuel gluttony about 13mpgs).

 

[destin]

cool

ok update.

decided to replace:

radiator cap ( looked to be original lol ) with new 13psi cap.
added a cheap overflow and burped the system. ( will order OEM overflow later when CDan is back from vacation. )

Just wanted to eliminate the possibility of the system not getting fully pressurized, which could possibly cause the coolant to lower its boiling point... maybe making the engine heat soak at a higher temp on shut down...

See how that theory goes

going to pull the plugs later today when the new denso ones come in.
had 12,000 break in miles on the new motor, see how the plugs look...

maybe do a compression test and see how well the motor broke in ...



.

 

[destin]

ran it for an hour, check the temps with an infrared thermostat, 160-170 on the thermostat housing.

engine block around 190 - 220.

carb and fuel pump temps at about 120 F

seems correct yeah?

Coo

d

 

[DSRTRDR]

See 100 degrees and yours is running correct, wtf.

108 in Phoenix earlier this week and my 40 runs fine