2F '84 FJ60 Hesitation, anyone interested in helping me diagnose? (1 Viewer)

[DieselFJ]

All, I've been fighting this hesitation since I got it back on the road after years of sitting, '96 was the last time it was registered.

Symotoms: Hesitation when engine is colder, get less noticeable when warm, but still definitely there. Feels like someone has a tow strap hooked up and is hitting the brakes causing drag. I would say it was in the primary circuit of the carb since once I get into the secondary there seems to be no hesitation at all. If the choke is slightly pulled it will help mitigate the issue. One other symptom, on really cold days the cold start doesn't seem to operate correctly, it will start up fine, but will slowly die unless the gas pedal is feathered a bit then it will operate as normal.

Completed engine/drivetrain work to get it back to road worthy: I've gone through all the emissions systems, PCV, EGR, Decel Fuel cut etc... double checked all the vacuum lines for correct location and breaks. vacuums good, no intake leaks, verified intake manifold is cracked, replaced PCV and verified PCV circuit is working, rebuilt carb, replaced plugs, wires, cap and rotor, good air cleaner, new Cat and exhaust. Compression is good on all cylinders, valves adjusted. New clutch, rebuilt H55F and T-Case.

All work has been completed by myself via Toyota manuals per specs. I started doing diesel swaps in my LandCrusiers a few years back so I haven't dug into a 2F for quite a while. I've rebuilt my share of 2F's engine/carbs etc... so I am very familiar with about every aspect of these motors, but this one has me stumped for now, what am I missing?

All suggestions are welcome!!! (I'll eventually find it given enough time, but I'm lacking the time right now so hoping to utilize this resource to help clear this up a little quicker, it is a daily driver)

Possibilities: Thinking maybe it's a distributor/Advance issue, although it seems to be functioning as expected and timing is set without issue. Carburetor issue??? (possibly, but the rebuild went great with no issues, and this isn't my first build, not saying I didn't miss something since I haven't been into a carb for a while but once in it it was like riding a bike.)

 

[salvage60]

Guessing it is part of the emissions system. There are a few functions that can leak vacuum at certain engine temperatures, they connect to the two BSVC valves. The hardest thing to test is the EGR as you can not confirm its not leaking without removing it but you test the rest of the system.

 

[Pighead]

What is your timing set at now?

 

[DieselFJ]

Guessing it is part of the emissions system. There are a few functions that can leak vacuum at certain engine temperatures, they connect to the two BSVC valves. The hardest thing to test is the EGR as you can not confirm its not leaking without removing it but you test the rest of the system.

Thanks, I've replaced one BVSV's and verified functionality of the other. I did actually remove the EGR to verify the functionality. It was clean and working as expected. I have heard of the EGR cooler coming apart inside and clogging the EGR, but this issue wasn't evident when everything was apart.

Scott

 

[DieselFJ]

What is your timing set at now?

7degrees BTDC @ 650RPM

 

[Mark W]

set your timing to 13 degrees btdc.

Simple stuff first. Have you verified that the acel pump is working properly?

Mark...

 

[Pighead]

7degrees BTDC @ 650RPM

Right. I don't know about all that emission stuff, but my early 2F ( with a 60 dizzy) would stumble and hesitate, especially when cold until I advanced the timing.
I also replaced the advance mechanism due to a bad diaphragm and replaced the advance weight springs but advancing past 7 was a big help.
Put a vacuum gauge to your intake manifold, advance timing to best vacuum, back it off a bit and see how it drives.

 

[DieselFJ]

set your timing to 13 degrees btdc.

Simple stuff first. Have you verified that the acel pump is working properly?

Mark...

Verified today that the pump was set to 9.5mm and that it had a good stream pattern. I'll have to get a new timing light to set outside of the flywheel indicator, I'll do that this weekend and report back. My daughter took the 60 up to school this evening, she'd driving it until I get her 55 painted and back on the road.

 

[Mark W]

Verified today that the pump was set to 9.5mm and that it had a good spray pattern. I'll have to get a new timing light to set outside of the flywheel indicator, I'll do that this weekend and report back. My daughter took the 60 up to school today, she'd driving it until I get her 55 painted and back on the road.

The "pattern" should not be a spray. It should look like a stream from a squirt gun. if it is anything other than that, the orifice is partially obstructed and it is not getting a sufficient charge of fuel. Not saying that is is your only problem, but if you have a spray of gas when the pump is actuated... it is one of your problems.

You can set the timing to 13btdc with a standard timing light. Just use the lower edge of the window as your timing mark, instead of the pointer.


Mark...

 

[DieselFJ]

The "pattern" should not be a spray. It should look like a stream from a squirt gun. if it is anything other than that, the orifice is partially obstructed and it is not getting a sufficient charge of fuel. Not saying that is is your only problem, but if you have a spray of gas when the pump is actuated... it is one of your problems.

You can set the timing to 13btdc with a standard timing light. Just use the lower edge of the window as your timing mark, instead of the pointer.


Mark...

Sorry, said spray, but meant to say stream of fuel, I'll edit the post. I didn't realize the lower edge of the window was 13degrees, thanks for that info! I'll get that adjusted on Saturday when it's back home and report back.

Scott

 

[salvage60]

set your timing to 13 degrees btdc.

Interesting, I have never run more than 9 but am smog legal other than disabling the EGR and that has it's own issues.

 

[DieselFJ]

Interesting, I have never run more than 9 but am smog legal other than disabling the EGR and that has it's own issues.

I’ve wondered that as well, all my other 2F’s have ran good at 7degrees, why or what has changed in this 2F that needs the 13degrees? I’m smog legal as well with all components functioning.

 

[Mark W]

I’ve wondered that as well, all my other 2F’s have ran good at 7degrees, why or what has changed in this 2F that needs the 13degrees? I’m smog legal as well with all components functioning.

It may run good, but it does not run as good as it could. The 2Fs were sent out of the factory with no difference in this respect from the F engines of nearly 60 years ago... ready to run on Mexican Ditch Water if they had to. In the US of A in 2023, they don't need to. We have decent gasoline in these parts.

Those of us who have been tweaking stockish 2F engines and building hot rod 2F engines have been using 13btdc as a good starting point for the last 30 years or so. Noticeable difference in how the engine runs.

Mark...

 

[DieselFJ]

It may run good, but it does not run as good as it could. The 2Fs were sent out of the factory with no difference in this respect from the F engines of nearly 60 years ago... ready to run on Mexican Ditch Water if they had to. In the US of A in 2023, they don't need to. We have decent gasoline in these parts.

Those of us who have been tweaking stockish 2F engines and building hot rod 2F engines have been using 13btdc as a good starting point for the last 30 years or so. Noticeable difference in how the engine runs.

Mark...

With the change in timing do you run a higher octane fuel?

 

[OSS]

My guess:
Engine is starved of fuel.
Go through carburetor again.

If engine runs fine at WOT, that rules out any ignition problem.
Poor performance when cold : running too lean. Cold engine needs a richer mixture than a hot engine - which is why it runs better when it’s warmed up.

 

[g-man]

I know you said you checked the fuel decel cut but the symptoms you describe are classic fuel solenoid issues...ie herky jerky hesitation, stalls at idle, having to overcome with choke. Make sure the fuel solenoid is clicking when you turn the key to "on". This is a VERY COMMON problem and most always is the electrical connection at the green plug.

 

[DieselFJ]

I know you said you checked the fuel decel cut but the symptoms you describe are classic fuel solenoid issues...ie herky jerky hesitation, stalls at idle, having to overcome with choke. Make sure the fuel solenoid is clicking when you turn the key to "on". This is a VERY COMMON problem and most always is the electrical connection at the green plug.

I agree, and maybe I’m dealing with a couple different issues, but when I ran 12v directly to the solenoid and went on a test drive the hesitation was still there and I like your description “herky jerky” especially when cold is spot on.

I’m going to dive deeper into the decel fuel cut this weekend, maybe I’m missing something. BTW, it does idles perfectly and has good throttle response off the start.

 

[Mark W]

With the change in timing do you run a higher octane fuel?

Not unless you have done other changes, most specifically raising the compression ratio into the 9s.


Mark.

 

[g-man]

Are you hearing the single click at the fuel cut solenoid when you turn the key? Or when you directly connected 12v to it?

One other thing that causes a hesitation is the EGR modulator. Your EGR can be clean and functional but if the modulator is not delivering vacuum signal to the EGR it won't work when it's supposed to. Test for this by holding steady on the accelerator pedal in a certain RPM range roughly 1500 rpms to 2000 WHILE GOING DOWN THE ROAD. Don't test this with your choke or while idling at park. The hesitation will go away while excelerating hard through this rpm range or while above or below those rpms. There are tests in the emissions FSM to determine if the EGR modulator is bad. Also the check the EGR VSV. both the modulator and the vsv send vacuum signal to the egr to tell it to turn on and off while going down the road.

 

[g-man]

Also I didn't hear you say you checked the fuel lines. The fuel filter? Did you see if the fuel is 1/2 way up in the site window in the front of the carb? You can easliy disconnect the fuel line from the carb and have someone crank the motor and catch some fuel in a clear jar. Make sure to disconnect the coil line from the dizzy to prevent starting while you do this. You can check for obvious clogs and fuel quality here.