No power without choke. 75 Fj40

Joined
Sep 17, 2022
Messages
19
Location
90804-4120
Idles great with or without choke. Spent time to adjust properly (idle mix, timing advanced, leak check . Has headers and inside manifold is welded. Boggs without choke and lacks power in 3rd gear or higher RPM. Seems to be affected after warming up more
Not de-smogged.
All the threads direct me to intake leak and I already resolved them. So does not seem to have any others but I know this is a classic sign of Intake leak.
Could the carb need rebuild? What about fuel starvation or similar?
Thanks in advance.
75 FJ40 stock
 
Joined
Sep 17, 2022
Messages
19
Location
90804-4120
I guess I could follow protocol better and make and introduction. I have followed IH8MUD since my 1986 4runner but now have a 75 FJ40 that bought in very poor shape. Some seals, new oil, adjustments, camo spray paint etc and now she is running. 1 single seat because I bought her without Interior and out s cheap seat in for testing.

I believe the carb needs a rebuild but am very effort and price conscience at this point. I have a 7 mile round trip to work and want to start driving this FJ couple days a week.
So far so good but powerless without choke -ICV is new and looks like power valve sprays well. . Idles great. Has electric fuel pump.
I feel that this is an issue with fuel starvation. But everyone online says vaccuum leaks. I am exper9eneced mechanic and have resolved the Initial leaks that had my idle poor.
Any direction would be great.
Thank you
 
Joined
Jul 28, 2006
Messages
297
Location
Hilo, Hawaii
Welcome! Pics of your engine bay and carb might help,

Why the electric fuel pump? Might not be keeping up with demand.
 
Joined
Jan 5, 2017
Messages
4,050
Location
Charlotte, NC & Alexandria, VA
2 things:
Overhauling (which almost everyone refers to as rebuilding) a carb isn't hard. Follow the FSM and take pictures. You need screwdrivers and cleaning solution/brushes. Me too: why the electric fuel pump? No way to tell from here if that's the problem, and since it's not OEM, the FSM isn't going to help you at all.

Having said that, spray carb cleaner (not the tree hugger kind, use the kind that burns) on the carb and manifold and see if the idle increases. If it does, you have a hole somewhere. Troubleshooting vacuum leaks is easy, remove one end of each one, one at a time, in turn until the idle changes. If it doesn't after you get through all the hoses, you don't have a vacuum leak.

None of the troubleshooting is going to be quick, although it is all pretty easy, you just need to resolve yourself that it's going to take time and be methodical, writing down what you do and observe as you go.

Good luck.
 
Joined
Sep 17, 2022
Messages
19
Location
90804-4120
Here are some picts and thanks for the feedback guys. I am grateful for this forum as it has already helped me get to this point
NOTES.
1 - truck had been sitting for years in the desert. I've been going though it a little over last couple years
2- fuel tank outlet was clogged and I cleaned out tank to get running. Will check again
3 - dont know my PO out in electric pump
4 - fuel filter is a bit dirty. Didnt replace yet ..Will replace
5- no intake leaks. I had them but believe I resolved them. Idle is great.
6- booster is disconnected and vacuum gauge on it.
7- pulls 19-20 psi vacuum at idle.
8 - seem to get good gas out of main jet when reving. Did oki rebuild and that helped get it running initial.
9- i removed smog pump belt

So my main question is the need to run with choke a symptom of need for carb rebuild and/or fuel supply issue? Like I said no I take leaks.

20220918_173540.jpg


20220918_173516.jpg


20220918_173511.jpg


20220918_173418.jpg


20220918_173357.jpg
 

Skreddy

SILVER Star
Joined
Feb 3, 2020
Messages
1,571
Location
Stanwood, WA
My thoughts: replace that fuel filter, check valve adjustment, check timing, replaced any rubber fuel and vacuum lines (and make sure they are going to the proper places). I bet that fuel filter may cure the issue. Revving in neutral is way different than rpm’s under driving load and that filter is probably clogged enough it can’t keep up with demand.
Also, where is the fuel level in the sight glass when idling (check again when sluggish) and is your electric fuel pump plumbed in-line with mechanical pump still in line as well? Simpler: is your mechanical pump still there and fuel running through it?
 
Joined
Jul 28, 2006
Messages
297
Location
Hilo, Hawaii
Maybe drain fuel tank.....blow out lines (see what comes out)..definitely replace the filter. Ponder buying an OEM mechanical fuel pump and ditch the electric. Keep plugging away...you'll get there.
 
Joined
Sep 17, 2022
Messages
19
Location
90804-4120
My thoughts: replace that fuel filter, check valve adjustment, check timing, replaced any rubber fuel and vacuum lines (and make sure they are going to the proper places). I bet that fuel filter may cure the issue. Revving in neutral is way different than rpm’s under driving load and that filter is probably clogged enough it can’t keep up with demand.
Also, where is the fuel level in the sight glass when idling (check again when sluggish) and is your electric fuel pump plumbed in-line with mechanical pump still in line as well? Simpler: is your mechanical pump still there and fuel running through it?
Hi! Yes, valve adjustment is good, timing good (i went through these already). the mechanical pump has been deleted and a plate covering the hole in the block.
def going the replace filter and see. then check tank lines again.
good idea to check float level after driving and sluggish like mentioned above. that would move the issue to fuel supply and not intake leak or main jet issue.
 
Joined
Jul 29, 2007
Messages
842
Location
Keene, Ca.
Really sounds like a vacuum leak to me.
 

Blue77FJ40

SILVER Star
Joined
Nov 30, 2004
Messages
2,662
Location
MD
It's hard to see if that carb has an idle solenoid, but if it does, did you check if it's functioning? Lots of posts on how to do this. Also, if the idle solenoid is present, check the o-ring for condition.
 
Joined
Sep 17, 2022
Messages
19
Location
90804-4120
So the issue was 2 fold.
1st, dirty fuel filter.
2nd... found my jets were 103/159 jets for high altitude. I'm supposed to run 140/220. Tested using the 159 in main position and ran luke a champ without choke!
I started another thread regarding the jets.
I like to end the thread with results when possible. Reading others issues has solved many of my problems all ready.
Thanks MUD!

20221005_212624.jpg


20221005_212405.jpg
 

Users who are viewing this thread

Top Bottom