• Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Throwing a carb on EFI motor?

ZacSquatch

ZacSquatch

NAXJA Forum User
Location
Fairbanks, AK
Found a rig and want to see about taking the computer and EFI out and throwing a carb in... What all is involved in this? Can I just get a new intake manifold and call it good, or does the timing ect... need to to be changed?

Sure it may look like I'm going backwards here.. but nothing beats having just 2 wires to an engine and KISS.

Thanks
Zac
 
Depends on the motor. If it is a 4.0L then a new manifold and you will need to convert over to a distributor since the ignition is still computer controlled.

Carbs are a pain on rock crawlers. Extreme angles screw with the floats in the carbs and you tend to either flood out or starve the motor.
 
old_man said:
Depends on the motor. If it is a 4.0L then a new manifold and you will need to convert over to a distributor since the ignition is still computer controlled.

Carbs are a pain on rock crawlers. Extreme angles screw with the floats in the carbs and you tend to either flood out or starve the motor.
Click to expand...

x2, the issue seems more to do with not the carb and manifold, but how to control spark timimg.

zac, i dont know much about the 4.2 engine, but the 4.0 is based off that engine. may be able to use the 4.2 intake, carb, and distributor. maybe a bit more to that though.

good resource might clifford performance.
 
Was going to say... spark timing.

If you can find a local EE type, you might be able to get a custom replacement ECU that'll take the signal from the CPS and run just the ignition coil for you, but it'll take a lot of work and it's probably easier to build a new distributor with points + condenser.
 
The stock 4.2L distributor and coil setup will work. Do some research. All the 4.2L guys want to dump the carb and go EFI. Weber makes a nice carb setup but they are a touch spendy.
 
old_man said:
Do some research. All the 4.2L guys want to dump the carb and go EFI.
Click to expand...

X2.... I rode in a buddies 4.2 wrangler a few weeks ago with a carb motor and I got to say I wouldnt have one over a EFI motor. Any bad angle and it starved or flooded.

I agree that keeping it simple sounds good, but not counting the first couple of years EFI came out on cars how many problems do ya see now out of EFI?

wont the electric fuel pump be a issue also putting out higher pressure ?
 
Rmart30 said:
X2.... I rode in a buddies 4.2 wrangler a few weeks ago with a carb motor and I got to say I wouldnt have one over a EFI motor. Any bad angle and it starved or flooded.

I agree that keeping it simple sounds good, but not counting the first couple of years EFI came out on cars how many problems do ya see now out of EFI?

wont the electric fuel pump be a issue also putting out higher pressure ?
Click to expand...
(1) good info... I'd be thinking about this if I was considering a carb, but I hate all that crazy plumbing and fiddly bits involved, give me electronics any day :compwork:

(2) this is probably more driven by DFM (Design For Manufacturing, basically the "save number of assembly steps, reduce required precision of components, and reduce cost of components" mindset) and environmental/CAFE standards than anything else.

(3) great point. EFI fuel pumps push a lot more pressure, you'll want a fuel pressure regulator of some sort. TBI pumps are around 14-15psi iirc and MPFI ones are up into the 30s, 40s, or 50s, I will refrain from giving a number as I'm not sure exactly what it is.
 
Youll spend more making an injected motor carbed thatn it would cost to get the injection working right to begin with....that goes for the 2.5 and the 4.0. Theres only a couple electronic things that evr really go wrong on these motors, and theyre simple to fix.... keep it injected!
 
winkosmosis said:
KISS would be leaving well enough alone
Click to expand...

And we have a winner!

OP--good advice from all the others.

Buy a FSM and learn your system so you can work on it.
 
You must log in or register to reply here.

Similar threads

L
Manual to Auto transmission swap
Replies
9
Views
203
lvcanyoneer1
L
O
2000 XJ Failed Colorado Emissions high CO
2
Replies
27
Views
2K
Ken M
K
D
Chasing misfire and running out of variables.
2
Replies
21
Views
3K
deloxx
D
I
High idle, smells like gas, running out of things to replace
Replies
2
Views
2K
Inverhyt
I
S
Torque converter causing low rpm engine lope
Replies
2
Views
2K
lawsoncl
L
Back
Top