Gave up on quadrajet electric choke today...

Status
Not open for further replies.
L

leroyd92

Joined
Jan 21, 2014
Messages
606
Location
AZ
I have 3 motors that have the Rochester electric choke system. 2 quadrajet, 1 mercarb.

I recently tried to add an electric choke to my 454 RV qjet and I just couldn't win.

After 30 seconds, the choke blade opens up 1/2 way, and the motor falls flat on it's face. Add more tension to the electric choke, and it bellows black smoke out the exhaust. Any less tension, it dies sooner.

I adjusted the idle mixture screws with a vacuum gauge. The RV runs fantastic when it's warmed up.


So to end this nonsense, I rigged up an manual choke today. Now the RV starts and idles great.


I don't know what I did wrong, but I couldn't fight this one any longer. We want to use the RV and I'm tired of fouling plug trying to start it.


I might continue my adventure when the RV sits during the 120° days, but it's on the back burner right now.

Does anyone have suggestions? I'm not new to qjets in the least, but this one has me stumped
 
Sounds like maybe it needs to open a little more slowly, I bet the addition of a resistor will make it open slower. I've always been a manual choke fan myself, automatic ones seemed to be troublesome at times for me too. Seems like the ones mounted on a heat riser in a manifold exhaust passage worked the best-they would open faster when it was hot out, & slower when it was cold.
 
FiTech EFI to the rescue! Carburetors suck. If I ever buy another carburetor Square Body Chevy it's gonna get the EFI conversion. I've sold two already because of carburetor issues nobody could figure out.
 
Mine had the hot air choke thing on it. It gave me a couple issues, but nothing like this electric one.
 
The electric choke is grounded to the carb body. Make sure you remove the paper gasket between the choke and body.
I am assuming you are talking about a conversion kit...
 
Originally Posted by JeffKeryk
The electric choke is grounded to the carb body. Make sure you remove the paper gasket between the choke and body.
I am assuming you are talking about a conversion kit...

Yep, it's grounded, and it works great, but I couldn't get it to work on this application...
 
The 454 in my pickup has an oil pressure switch in line to the choke heater as well as a vacuum choke pull off. The cover has notches or serations that allows the cover to be moved in small increments. What type of choke was on the caeb originally?
 
Originally Posted by bullwinkle
Sounds like maybe it needs to open a little more slowly, I bet the addition of a resistor will make it open slower...
I agree. That's exactly what I did when I had to replace the choke heater on my Mazda, and the only junkyard one I could find that fit heated too fast.
 
It sounds to me like you did not have a "vacuum break" hooked up.

it is VITAL - it cannot be left out of the equation.
 
Every engine I have ever built or helped friends upgrade we have put Holley 650 double pumpers on them and removed the manual choke. A properly tuned and matched carburetor to the engine shouldnt need any choke. Literally give it 2 little pumps and turn the key and it fires off in 2-5 seconds. The square bore holley carburetor is the best upgrade anyone can do for a engine. There is a reason why people who have had quadrajets then upgrade to double pumpers call them "quadrajunks".
My 434 has a 950 double pumper from pro systems with a 4 corner idle system and I have never heard of people adjusting air fuel mixture screws with a vacuum guage..... all air fuel adjustments should be made by "tuning by ear". Same thing we do for small engines that run phenomenal when I get done with them.
 
All of the quality technicians that could work on a carburetor and diagnose them long ago retired.

Me personally, I would not drive a car today (unless a classic car) that had a carburetor. No way at all would my daily driver, or long distance (RV) vehicle have a carburetor on it.
 
Originally Posted by Jmoney7269
Every engine I have ever built or helped friends upgrade we have put Holley 650 double pumpers on them and removed the manual choke. A properly tuned and matched carburetor to the engine shouldnt need any choke. Literally give it 2 little pumps and turn the key and it fires off in 2-5 seconds. The square bore holley carburetor is the best upgrade anyone can do for a engine. There is a reason why people who have had quadrajets then upgrade to double pumpers call them "quadrajunks".
My 434 has a 950 double pumper from pro systems with a 4 corner idle system and I have never heard of people adjusting air fuel mixture screws with a vacuum guage..... all air fuel adjustments should be made by "tuning by ear". Same thing we do for small engines that run phenomenal when I get done with them.


Quite a bit of misinformation here. Engines tuned currently do need a choke to assist with cold startup. Big difference between a street strip or race setup and a carb on a RV or truck.

The Q-jet is one of the very best carbs at accurately metering fuel across a wide RPM and load scale, it has WAY more fine adjustments available than a standard Holley carb, metering rods for extremely fine fuel control, lean cruise adjustments, in a word it's excellent.

So let's get this straight, since you've never heard of tuning idle mixture with a vacuum gauge, it's wrong, but doing it "by ear " is correct? Using vacuum is a perfectly acceptable way to tune idle mixture.

A well tuned Q-jet can out perform a Holley on a street driven vehicle in numerous ways, part throttle precise metering, outstanding throttle response due to the small primary bores, lean cruise adjustments for cruise mileage, increased load enrichment sensitivity over the Holley which just uses a fixed enrichment where the Q-jet is a curve as the metering rods withdraw, air door secondary on the Q-jet prevents lean bog when transitioning from primary to secondary circuits.

I'm not bashing the Holley here, I own multiple, but it's not fair nor is it accurate to say as a blanket statement that the Holley is ALWAYS an improvement over the Q-jet because it's just flat not true, they each have their place.
 
Originally Posted by bubbatime
All of the quality technicians that could work on a carburetor and diagnose them long ago retired.

Me personally, I would not drive a car today (unless a classic car) that had a carburetor. No way at all would my daily driver, or long distance (RV) vehicle have a carburetor on it.


Its not for everyone I suppose.

I haven't touched the boat qjet in 11 years.
I cleaned the c10 carb 3 years ago.

And my 2 motorcycles haven't had the carbs cleaned in the last 8 years.


So I have the upmost faith in carbs.

Fuel pumps, rubber hoses, electrical stuff, and things off that can leave you stranded worry me the most
 
For the QJet automatic choke to work properly, a choke pull-off, like the one pictured in the post by Linctex, is necessary. It opens the choke plate partially as the engine starts and develops vacuum. The amount the choke pulls open is set by an adjustable link that connects to the pull-off diaphragm. The pull off on your QJet was probably adjusted to open too far making the warm up too lean.
 
Status
Not open for further replies.

Similar threads

M
1995 25hp Johnson 2 stroke J25EEOA rough at idle and in gear
Replies
13
Views
740
97prizm
B
Need a Toyota guru 1MZFE Hesitation
2
Replies
26
Views
1K
GMBoy
eljefino
84 w250 idle peters out... float adjustment?
Replies
9
Views
609
eljefino
mrbreezeet1
2001 Grand Prix SE High Idle and late shifting too! {Must have taken a fit, It's OK now}
2
Replies
30
Views
1K
mrbreezeet1
Number_35
2005 Hyundai Santa Fe - troubling symptoms, easy fix
Replies
5
Views
527
Propflux01
Back
Top