Vacuum issues ?????

[cruzersoul]

I have a 66 fj40 with the original F engine. I do not know how many miles the engine has on it. I installed a weber 32/36 carb with electric choke and I have a problem. When it idles it is getting a constant 20 HG which if I am correct is good. When I accelerate slowly it drops down to 15 HG but then shortly returns to 20 HG which I also think is ok. The problem that arrises is when I accelerate quickly, the vacuum drops dramitically to between 2-5 HG and the engine almost dies but then comes back and tops out at 20 HG. I noticed that when I spray carb cleaner around the adapters for the carb at the intake manifold while idling the RPM's drop down a little bit which makes me think that I have a vacuum leak at the carb. But I would like to know if there is anything else that could cause the problems that I am having.

-Cruzersoul-

 

[Mr. Toad]

Vacuum is supposed to drop when you open the throttle. When you floor it it should go down close to zero. The opposite is true when you close the throttle while the engine is spinning fast -- Try watching your vac gauge when you're doing 40 mph in third gear and then let off the gas.

So anyway, it sounds like the vacuum is fine, but there's not enough fuel in your mixture when you floor it. Check your carb's accelerator pump (if your non-Toyota carb has one), check for restrictions in the fuel line, and check whether your fuel pump is working right.

 

[cruzersoul]

How much psi is the fuel pump supposed to put out and how do I check this.

-Cruzersoul

 

[Mr. Toad]

It's not so much the PSIs as the volume. A mechanical pump delivers more fuel when the engine is spinning faster than it does at idle.

An answer from another thread:

The F engine manual mentions something like the pump should put out close to 2 liters in 1 minute at 1000 cam RPM (That's 2000 engine RPM, right?). At 3.4 to 4.8 PSI.
. . .
But it's usually the fuel filter.

 

[fireflyr]

Here's a cool link dealing with vacuum guages and readings:

TRS Magazine - Dealing with engine vacuum

When I set up my Weber 32/36 I remember reading that if you have your idle speed screw in more than one and a half turns it will cause vacuum problems. There are alot of references on the internet for setting up a Weber.

Table of Contents

Other Info Page

Good luck.

 

[Mtrunner]

How's your timing?

 

[Michael Hanson]

Carb.issues I think,fuel pump usually will give out at about 40-45 mph if its like all mine have done,it will buck and kick. Mike

 

[cruzersoul]

Timing should be good I will go ahead and check it again and let you know.

 

[65swb45]

How's your timing?

Fair question, but not likely to be an issue here. Hard to pull 20" of vacuum if the timing's that far off. More likely an accel pump issue.

Best

Mark A.

 

[cruzersoul]

I went ahead and checked my timing and it was off a few degrees but I don't think its was enough to affect anything. I went ahead and set my timing and it actually created another problem. When I accelerate quickly now the engine almost dies and backfires through the carb. How do I go about checking my accel pump

-Cruzersoul-

 

[cruzersoul]

Forget my last post. Timing is now set correctly and is not backfiring through the carb. I am still having a problem with the engine getting very sluggish under heavy acceleration. I did notice that once the engine is completely warmed up it doesnt seem to happen as often but I suppose I could just be imagining this. I would like to know if there is anyway of checking my accel pump. I am starting to think I should just go back to the oem carb. If there is anything else that anyone can think of to try please let me know. I am about ready to push my 40 off a bridge.

-Cruzersoul-

 

[Mr. Toad]

I don't know anything about your carb, but I know that on a stock carb, you can see a stream of fuel shooting into the carb throat when someone hits the gas pedal. If there is no stream then the accelerator pump isn't working. If it's a weak stream or a dribble, it's not working to the best of its ability.

Remember though -- if the engine isn't running, you don't have very many squirts before the fuel bowl goes empty. It won't squirt then either.

 

[cruzersoul]

Im starting to think that the carb is jetted wrong. I am just going to go back to the oem carburetor because the weber is a POS.