No idle debug approach. (1 Viewer)

[cruiserb0b]

77 FJ40 (Kiwi) New Zealand, built with a 75 Motor - That's what's on the Build Plate.

I'm new to FJ's and F-motors, but have been around cars for a long time.

This one runs and drives. High idles OK at 1500; a little jumpy. Goes 45mph no problem, but refuses to idle below 1200. Aisan carb was filthy so temporary replaced it with a Partol (China I think), has the same problem. Vacuum pressure is around 16 and bounces +/- 2. Start to back off and when I hit 1200ish it dies out.

Plugged all vacuum lines, used Halomar sealer all the gaskets between the carb and manifold, tightened the manifold bolts. Same problem.

Used carb cleaner on all the seams, no real rpm change though tough-to-tell idling at 1500.

Started to look at timing........

Timing marks show in the window at cylinder #6, so it looks to be 180 out. However, I get no marks using a timing light when connected to cylinder #6, OR ANY OTHER. Vacuum advance works when I use a hand pump. The engine runs strong, so I'm inclined to let this go for now......

Next Steps?

1. I'm going to check compression and make sure it's not a bad valve. Then

2. Remove the manifold, reface it, and new gaskets.


Am I missing anything? Anything easy before I pull the manifolds?

Thanks in advance.


Bob

 

[1MOA]

is your idle solenoid working when you turn the key on? Also check the engine fuse and make sure it is good ( 2nd from the bottom) even if it looks good get another one and swap it out.

 

[middlecalf]

Get that timing baselined first.

 

[sggoat]

The idle sems to be the culprit--Don't think timing has anything to do with the prob-unless the valves are leaking-appears to be fuel/air related--you said you squirted carb cleaner(or such around the manifolds and did not see any idle changes--that indicates you may not have a major vac leak---however-the low idle vac number (16" -says you do--somewhere)-OR the . valves may be involved(as middlecalf said).--do the compression check----Your compression check is a good Idea--all cylinders need to be >120 psi--not optimum, but serviceable--can check it cold--that is the worst case--a real quick check is to start the engine, let it idle, then put your hand(gloved) over the exhaust pipe--if you feel the exhaust sucking your hand back against the tail pipe, you prob have a leaking exh valve--it COULD be as simple as a vlv adj--but when you think about this how did the adj get off? (takes a long time for the rockers to wear enough to cause this) -plus if this were the case you would have started to hear the clatter as the clearances opened up.--but this would not cause the varying vac numbers you are reporting(a burned valve(exh) will cause lowered vac numbers, but they would be steadly lowered--not fluctuating(I think--I have a vac t'shooting guide that was posted yrs ago in the forum-if I can find-will link it back to the original post-or you could search for Vac troubleshooting on the forum)----so the exh suck back would indicate a burned valve--this is a prob that might be involved, but I can't think of why it would impact the idle--that still tells me the fuel/air has something to do with the idle prob.
do a rebuild on the orig. Carb--follow the guide that Pin-Head posted on rebuilding a carb(can't go wrong here)-make sure gaskets are in good shape--(SMP makes a really good rebuild kit)--all parts EXCEPT for the ball check retainer clip--almost non-existent anymore--BUT Toyota still has them-for now-get em while you can!(Toyota South Atlanta parts dept--MUD member discount)

 

[pb4ugo]

I wouldn't tear anything apart until you ID the problem. You could see creating more problems if torn apart. It sounds like a vacuum or carb problem, but 1st confirm the dist is installed correctly and the timing is set to spec. The engine needs to baselined.

 

[Subterranean Nik]

Agree with @1MOA for a first step. Check that idle solenoid is getting power. Would think it’s the power to it that may be an issue (as two separate carbs are having the same issue).

Good luck, let us know what you find!

Some other things going on too as mentioned (with idle bouncing, etc…) but would get it to stay running at “normal” idle first.

Nik

 

[cruiserb0b]

THANKS FOLKS! Idle solenoid had no voltage the wire was cut. I connected it to +12V and my idle problems are solved for now. Drove her for about 45min today in crazy-ass warmth here in Massachusetts. Ran great.

What is the function of the idle solenoid? Does it open the vacuum? Cut the fuel? Why?

The electricals in this truck have had some significant tampering. Can anyone point me to a really good wiring schematic?

Thanks Again!

Bob

 

[edwjmcgrath]

THANKS FOLKS! Idle solenoid had no voltage the wire was cut. I connected it to +12V and my idle problems are solved for now. Drove her for about 45min today in crazy-ass warmth here in Massachusetts. Ran great.

What is the function of the idle solenoid? Does it open the vacuum? Cut the fuel? Why?

The electricals in this truck have had some significant tampering. Can anyone point me to a really good wiring schematic?

Thanks Again!

Bob

Cuts the fuel when you turn ignition off so it doesn’t run on.