1980 FJ40 2F… Dying Under Braking (1 Viewer)

[ASO544]

I’ll recheck the timing again tonight. The butterflies seemed to be closed fully after cycling the linkage. The idle mixture screw is currently 2 turns out from the bottom.

Also some pics of the carb …. Maybe needing a rebuild.

 

[pb4ugo]

I wouldn't rebuild it yet. Check the dist timing. Set timing to your liking, check vacuum. Try to to adjust idle mixture. 2 turns is probably close.

 

[ASO544]

Ok… I still can’t get to the BB or TDC mark by turning the dizzy… it dies right as the BB comes into the window.

I set the advance on the light to 7*… remove and plug the VA, started her up and turned the dizzy clockwise… just as the BB comes into view the engines sputters and dies … couldn’t even get close to the TDC mark.

Now if I set the dizzy where the engine runs strong and stays idling (950 rpms was the lowest I could get it) and just use the advance on the gun it took 27-29 * to get the TDC mark lined up with the pointer.

There if definitely something odd going on… if I just set the dizzy by ear and idle…. It drives strong and runs great but it’s way off of the 7* BTDC.

 

[charliemeyer007]

There you go "tuned by ear". Perhaps at some time in the past the cam gear was changed and put in one tooth off - you could tune by ear for that.

In the summer I run the timing up to where its almost going out the window, don't try that in the winter or it will kick back and take out the starter.

 

[45Dougal]

Could try increase the idle by 500rpm and see how the timing looks

 

[pb4ugo]

Ok… I still can’t get to the BB or TDC mark by turning the dizzy… it dies right as the BB comes into the window.

I set the advance on the light to 7*… remove and plug the VA, started her up and turned the dizzy clockwise… just as the BB comes into view the engines sputters and dies … couldn’t even get close to the TDC mark.

Now if I set the dizzy where the engine runs strong and stays idling (950 rpms was the lowest I could get it) and just use the advance on the gun it took 27-29 * to get the TDC mark lined up with the pointer.

There if definitely something odd going on… if I just set the dizzy by ear and idle…. It drives strong and runs great but it’s way off of the 7* BTDC.

Thats odd. What's the timing, vacuum and idle rpm when set by ear? If it starts pinging retard the timing a bit.

 

[ASO544]

Even when set by ear where it drives strong the Idle won’t go below 1000 rpm without starting to cut off.

The vaccum is 14-16 at idle from the intake manifold

The timing is 27-29 degrees from TDC but I’m betting that at the 1000 rpm the mechanical advance is probably kicking in and skewing the timing off. My carb seems to be an issue not allowing me to get the idle in the 650 range it needs to be .

One a side note… I cleaned up the intake vaccum ports and did locate an exhaust leak by the #4 cylinder. Gaskets on order!!!

 

[procomsignathid]

So, perhaps not-related, but your fuel return line from the carb seems to be disconnected:

Also, if you take a look at the top of the carb when the engine is idling, do you see fuel spitting out of the venturi in the main barrel (the one closest to the engine / right above the idle mix screw). That has been an indicator to me that I had a clogged idle circuit. On that point, do you have any reason to believe that there would be something nasty in the fuel tank (moisture, rust, anything else), and how does your fuel filter look? The low vacuum / can't get it to idle low both could point at the idle circuit.

 

[dmaddox]

Idle circuit issue or vacuum leak still present is where I'd start. Does applying the choke allow it to idle better? If yes, idle circuit issue. If not, vacuum leak. Chasing timing when you have underlying issues with the carb/vacuum will drive you nuts.

 

[Tigerstripe40]

Having read through this thread, I did not see, but it sounds like the brake booster was replaced in the relatively recent past.
Have you checked for burnt valves?
A bad brake booster can cause the engine to run lean, esp the 5 and 6 cylinder, and burn the valves. It might be worth while to get a leak down tester and pressurize those cylinders and check.

 

[cruisermatt]

Ok… I still can’t get to the BB or TDC mark by turning the dizzy… it dies right as the BB comes into the window.

I set the advance on the light to 7*… remove and plug the VA, started her up and turned the dizzy clockwise… just as the BB comes into view the engines sputters and dies … couldn’t even get close to the TDC mark.

Now if I set the dizzy where the engine runs strong and stays idling (950 rpms was the lowest I could get it) and just use the advance on the gun it took 27-29 * to get the TDC mark lined up with the pointer.

There if definitely something odd going on… if I just set the dizzy by ear and idle…. It drives strong and runs great but it’s way off of the 7* BTDC.

This is probably a big part of your issue... it sounds like you are using your timing light wrong.
Your timing light has do idea what the actual TDC of your engine is, it flashed based on the actual pulse from the distributor, not based on TDC.

Set your timing light to 0*. It should flash at the same time as the BB meets the pointer in the timing window. This is your base timing of 7*. If you wanted 10*, you would set your timing light to 3* and then adjust the distributor counter-clockwise 3* which would advance the ignition timing 3*. Start with the base 7-degrees though.

From there, it should idle. Then you need to know:
1. maxiumum vaccum you can acheive at idle.
2. engine compression numbers would be a great info.
3. is the valve lash set properly.

commonly the distributor shaft bushings can be worn and cause really inconsistent idle timing. But I wouldn't throw a distributor at it just yet. I still would want to know why somone replaced a electronic 79/80 distrubtor with an oilder points unit.
Additonally: have you checked the point gap? are the point surfaces clean?

 

[ASO544]

Matt… I jump on those things this weekend. As for the dizzy … can’t tell you why the original was replaced.

As for the timing light and it use…. If i set the light to zero with no advance on the gun, VA unhooked and plugged, and the light hooked to the #1 plug wire. … with the truck warmed up and idling( although high cause it won’t idle down past 1k without dying) ….when it flashes there is nothing in the window. If I turn the dizzy to the right slowly, once the BB just starts to show in the bottom of the window the engine sputters and dies.

 

[cruisermatt]

Stupid question : you have the timing light on the #1 spark plug wire, right?

and you have 100% confirmed that you don’t have any vacuum leaks?

 

[ASO544]

Yes…. The plug wire closest to the radiator.

 

[ASO544]

Yes…. The plug wire closest to the radiator.

View attachment 3946797

 

[dmaddox]

I know this is frustrating - hang in there. To the previous question. If you disconnect the vacuum line to the brake booster, and plug it on the manifold....get the truck idling and then take some carb/brake cleaner and spray around the manifolds where they bolt to the head, base of the carb, and so on....does the RPM change at any point? If so, you've found a vacuum leak....if not.....I still think there's an issue with either your idle circuit or idle solenoid (just because its clicking, it may not be operational).

As to why your distributor has been changed? Mystery - but usual suspects are either bad coil/igniter pack over the years...or I've even seen some trucks robbed for their electronic ignitions and earlier, more common distributors put in.

 

[ASO544]

Sorry… double post

 

[pb4ugo]

It's like Deja vu all over again.

 

[procomsignathid]

If you can get it to idle, I would stop chasing the timing for now and clear the carb/vacuum leaks as problem areas.

 

[bhsdriller]

Matt… I jump on those things this weekend. As for the dizzy … can’t tell you why the original was replaced.

As for the timing light and it use…. If i set the light to zero with no advance on the gun, VA unhooked and plugged, and the light hooked to the #1 plug wire. … with the truck warmed up and idling( although high cause it won’t idle down past 1k without dying) ….when it flashes there is nothing in the window. If I turn the dizzy to the right slowly, once the BB just starts to show in the bottom of the window the engine sputters and dies.

Can you adjust the idle RPM up so when you do get the BB to show it will stay running?

You say sputters and dies, as you're turning the distributor does the rpm drop to where it's too low than dies?