enigne stalls when secondaries are opened? - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

 
LinkBack Thread Tools Display Modes
post #1 of 12 (permalink) Old Nov 6th, 01, 11:43 AM Thread Starter
Senior Tech
 
Join Date: Jul 1999
Location: denver, co USA
Posts: 407
Post

I have a '67 with a 396. The car is restored back to stock condition. The motor has been rebuilt with about 800 miles on it. All igntion components have been replaced and also have about 800 miles on them. The carb is the original Q-Jet but it has NOT been rebuilt yet. The distributor is original but not rebuilt. Here is my question, the car starts great, idles great, runs great, no problem. But when I punch it and the secondaries open, it accelerates well until about 3500 rpm and then the motor just quits, almost like it's out of gas or there is a rev limiter. Then when I let off the gas, the engine comes to life and everything is fine. I am thinking 1) fuel pump 2)timing advance or distributor 3)carb. The points read dead-on 30 degrees. The timing is set at 8 degrees initial. Any suggestions on tests I could do or things to look for that might narrow it down? Thanks!
denverRS/SS is offline  
Sponsored Links
Advertisement
 
post #2 of 12 (permalink) Old Nov 6th, 01, 12:47 PM
Team Member
John
 
JohnZ's Avatar
 
Join Date: Sep 2000
Location: Washington, Michigan USA
Posts: 7,728
Post

Nearly-clogged fuel filter?

------------------
JohnZ
'69 Z28 Fathom Green
JohnZ is offline  
post #3 of 12 (permalink) Old Nov 7th, 01, 04:17 AM Thread Starter
Senior Tech
 
Join Date: Jul 1999
Location: denver, co USA
Posts: 407
Post

John, good thought, I would love it if this were the problem, easy and cheap. I will look at it tonight. I know there is a filter at the carb inlet and I think that is the only one.
What does a car act like if the fuel pump is going out? Does it just die all at once? What is the liklihood that the fuel pump isn't sending enough fuel to feed the carb when the secondaries open??
denverRS/SS is offline  
 
post #4 of 12 (permalink) Old Nov 7th, 01, 06:17 AM
Tech Team
 
Join Date: Jan 2000
Location: Santa Anna, TX USA
Posts: 55
Post

If I remember correctly, the quadrajet secondary fuel supply is supplied from two small holes at the back and bottom of the fuel bowl. If the carb has any trash in the bottom, it will pretty easily find its way to the supply holes, causing a lean condition when the secondaries are kicked in. Also, even tho the secondary throttle plates open when you "mash the gas", the air flow is actually controlled by the "flapper plates" at the top of the secondary bores. If the spring rate is not correctly adjusted, the plates will open too quickly, causing a severe bog, or not enough, giving less performance. A starting spot would be to hold the throttle open(engine off), and push the air valves open. They should gently return all the way to the closed position. If they do not, the spring tension probably needs to be adjusted.


------------------
David
68 SS Camaro (377CID, 11.633 @ 115mph)
72 Chevelle (350CID, 13.42 @ 99)
73 Nova Hatchback (under construction)
LoneStar68 is offline  
post #5 of 12 (permalink) Old Nov 7th, 01, 06:58 AM
Senior Tech
Mark
 
mbrekke's Avatar
 
Join Date: Aug 2000
Location: mid-Missouri
Posts: 2,182
Post

denver

I agree with John's fuel filter theory. It lets enough fuel through to keep it running, but is clogged enough to limit the gas supply when you open it up. Like you say, it's a cheap fix. My experience with bad pumps is they tend to kill the engine intermittantly at cruising speed (engine just stalls while driving) and then die all together. The stock pump is generally enough unless you build a monster engine and run it wide open.

Hope the $2 filter fixes the problem!

Mark
mbrekke is offline  
post #6 of 12 (permalink) Old Nov 7th, 01, 03:45 PM
SSuperman
Guest
 
Posts: n/a
Post

This might be a shot in the dark but it happen to me.....The person I bought my car from put the wrong carb base plate gasket, so every time I'd nail the gas, the secondaries would get hung up on the gaskets and the motor would flood out....
post #7 of 12 (permalink) Old Nov 7th, 01, 03:59 PM
Senior Tech
Bob
 
Join Date: Dec 2000
Location: Ct.
Posts: 1,142
Post

Check for rubber fuel line collapsing if you used more than several inches of it or if it is old. Check for kinks in fuel line. Is it possible to put the fuel filter in backwards at the base of the carb, this would kill the fuel flow.

------------------
Bob
Garnet Red 69/SS396/TH400/355 Posi
94 HD Dyna Wideglide
phel69 is offline  
post #8 of 12 (permalink) Old Nov 9th, 01, 06:47 PM
 
Join Date: Jun 2001
Posts: 142
Lightbulb

First place to start is testing fuel pressure. Tee off the line for a fuel pressure gauge (maybe your vacuum gauge will handle both)and run several feet of vacuum line to your gauge. Get the gauge in the car with you (preferably with a friend) and run the car the way you described. You should have 6-7 PSI at idle and not drop below 4PSI under full acceleration and through your shift point. If below 3.5 PSI, you have a fuel supply problem. If it stays above 4 PSI, you probably don't. Start looking at timing, including vaccuum advance.

------------------
67-327, 700r4 trans, 9:1 Comp XE268 Cam, Perf. RPM Intake. 750 Holley, Sportsman II Heads, Ceramic coated headers
Dans67 is offline  
post #9 of 12 (permalink) Old Nov 10th, 01, 02:19 PM
 
Join Date: Nov 2001
Location: newmarket
Posts: 28
Post

CHECK FOR ALL PROPER CARB ADJUSTMENTS
AND HOSES ......
IF THE CARB CAN GET THE RPM UP TO 3.500
THEN YOUR FUEL IS OBVIUOSLY THERE.
SECONDARY JETS WORKING
NOW THE SECONDARY FLAP NEEDS TO BE WIDE OPEN AT THAT POINT FOR MAX AIR DOWN STREAM
FOR PROPER ATOMIZATION OF FUEL..TO CHECK IT:
RUN THE CARB AT CURBSIDE .
BRING IT UP TO 3.500 RPM OR SO THEN WATCH FOR THE BOG ,THEN SRRAY AIR INTAKE CLEANER INTO IT AND WATCH ,IF IT CLEARS UP FUEL IS THE PROBLEM,IF NOT THEN ADVANCE TIMING ,TRY
AGAIN.
NOW THE PROBLEM COULD BE PLUGGED FUEL
FILTER,FUEL PUMP CHECK VALVE STICKING,
STICKING NEEDLE VALVE ,DIRTY
CARB PASSAGES,METERING RODS STICKING
LEAKING VACUUM SECONDARY,
IF STILL NFG GO FOR THE REBUILT CARB .
YOUR DIST IS SINGLE POINT ONLY ,
PRODUCES LOWER SPARK PLUG FIRING VOLTAGE AT HIGHER RPM`S
NOW WHAT ABOUT USING A CARB BASE PLATE
HEAT SHIELD PLATE TO REDUCE POSSIBLE
FUEL BOWLIND TEMP`S............
rennycal is offline  
post #10 of 12 (permalink) Old Nov 10th, 01, 08:54 PM
Senior Tech
 
Join Date: Oct 2001
Location: milw,wi,usa
Posts: 159
Post

Well you have enough carb answers which is great info so I'll add a different twist to this.I have seen the wire inside of distributor lose contact because the wire is starting to break from the breaker plate advancing and retarding.Just a thought.

[This message has been edited by sschevyfan (edited 11-11-2001).]
sschevyfan is offline  
post #11 of 12 (permalink) Old Nov 16th, 01, 06:00 AM Thread Starter
Senior Tech
 
Join Date: Jul 1999
Location: denver, co USA
Posts: 407
Post

Thanks to all for the replies, I have just got the car back from the body shop doing some adjustments and I will try to get to as many of these tests as possible. In a week or so, I hope to let you know what the problem is. Thanks again!
denverRS/SS is offline  
post #12 of 12 (permalink) Old Dec 16th, 01, 10:12 AM Thread Starter
Senior Tech
 
Join Date: Jul 1999
Location: denver, co USA
Posts: 407
Post

I solved the mystery this weekend. The secondaries were locked closed. The choke was not coming off all the way when warmed up and so the "lockout" that holds the secondaries closed would not come off. My car is the 396 with the choke that sits on top of the intake manifold. The choke linkage was binding, so the choke would not open entirely. If the choke is not all the way open, there is a cam called the "secondary lock out" that will hold the secondaries closed until the engine warms. Because the secondary throttle plates were locked closed all the time, when I would floor it, the carb would fill with gas, flood and kill the motor. I hope this maybe helps someone down the road and thanks to all for the suggestions. Now that the secondaries will open, any suggestions on avoiding speeding tickets
denverRS/SS is offline  
Sponsored Links
Advertisement
 
Reply

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Team Camaro Tech forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address.
NOTE we receive a lot of registrations with bad email addresses. IF you do not receive your confirmation email you will not be able to post. contact support and we will try and help.
Be sure you enter a valid email address and check your spam folder as well.



Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 
For the best viewing experience please update your browser to Google Chrome