Fuel problems on 389. - Pontiac GTO Forum
User Tag List

Reply
 
LinkBack Thread Tools Display Modes
post #1 of 25 (permalink) Old 09-01-2019, 01:46 PM Thread Starter
 
Join Date: Sep 2019
Location: Ohio
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Fuel problems on 389.

I just bought a 65 GTO with 398 engine. Seller said he always used 93 octane without ethanol. I put 9 gallons of Shell V power nitro+ in with the half full tank. 5 miles later engine started acting starved then as I reached my driveway it started popping and running rough. Never heard any pinging. Any idea what happened. Obviously it had something to do with the new gas.Thanks for any help you can offer.
jjminor is online now  
Sponsored Links
Advertisement
 
post #2 of 25 (permalink) Old 09-01-2019, 03:54 PM
 
Join Date: Jun 2019
Location: Middle Tennessee
Posts: 3
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Did the car set awhile. The problem can be many different things. I just purchased a 65 weeks back and it stopped pulling gas from tank. Long story short it had rust in it. I replaced it and sending unit along with rubber hoses and filter. I did have to clean carb out as well. First thing to do is pull filter out of carb. If its good work back to tank. If your good there look for a vacuum leak. PVC or brake booster hoses are a good starting point. Hope this helps. Good luck.
Casper is offline  
post #3 of 25 (permalink) Old 09-01-2019, 05:55 PM Thread Starter
 
Join Date: Sep 2019
Location: Ohio
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Seller filled tank six weeks ago and had used about half when I bought it. In line filter is clean as can be. The popping sounds were like mini backfires. Thanks for your input.
jjminor is online now  
 
post #4 of 25 (permalink) Old 09-02-2019, 10:38 AM
 
DNODennis's Avatar
 
Join Date: Jul 2017
Posts: 4
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Have you considered fuel boiling in the lines or in the float bowl? Vapor lock issues can make my brother's 64 Tri-Power GTO exhibit similar symptoms under the right conditions.
DNODennis is offline  
post #5 of 25 (permalink) Old 09-02-2019, 10:50 PM Thread Starter
 
Join Date: Sep 2019
Location: Ohio
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Fuel boiling? Never heard of that
jjminor is online now  
post #6 of 25 (permalink) Old 09-03-2019, 12:33 PM Thread Starter
 
Join Date: Sep 2019
Location: Ohio
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Update. I drained the gas tank and found nothing foreign in the fuel. I decided to try and start the engine to see if a cool engine made any difference. It started and immediately began coughing quite a bit and blowing mist back out of the carb at every cough. Could this be a timing issue with the 93 octane?
jjminor is online now  
post #7 of 25 (permalink) Old 09-03-2019, 12:34 PM Thread Starter
 
Join Date: Sep 2019
Location: Ohio
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
I am going to mix a few gallons of cam2 with fresh 93 and see if it runs better.
jjminor is online now  
post #8 of 25 (permalink) Old 09-04-2019, 05:50 PM Thread Starter
 
Join Date: Sep 2019
Location: Ohio
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Today I got all the fuel lines empty and air flowed freely thru all lines. I pushed compressed air thru the pickup into the gas tank. All good. Replaced the fuel hoses that I pulled loose to drain everything and put a mixture of 2 gallon of cam2 with 2 1/2 gal. of new 93 octane. Couldn't get the fuel pump to prime and pull fuel from rear to front. Car started but still backfired and wanted to quit running. I noticed that the clear plastic fuel filter was showing empty. Pulled the hose loose from carb and unhooked coil wire. Turned the motor over and saw fuel pumping in to my catch container. I am going to have the timing checked and maybe try a different number and see if that takes care of the problem. Any good ideas would be appreciated.
jjminor is online now  
post #9 of 25 (permalink) Old 09-04-2019, 06:08 PM Thread Starter
 
Join Date: Sep 2019
Location: Ohio
Posts: 14
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Started the motor again. It soon became a somewhat steady pop about 1 per second at idle speed. Shut it back off.
jjminor is online now  
post #10 of 25 (permalink) Old 09-04-2019, 08:26 PM
 
PontiacJim's Avatar
 
Join Date: Dec 2012
Location: Gastonia, NC - Born & raised in Connecticut - 31 years
Posts: 3,543
Mentioned: 1 Post(s)
Tagged: 1 Thread(s)
Quoted: 362 Post(s)
Garage
Quote:
Originally Posted by jjminor View Post
Started the motor again. It soon became a somewhat steady pop about 1 per second at idle speed. Shut it back off.
Could be a timing issue or even the timing chain.

Could be a crossed spark plug wire - causing a misfire.

However, could be a valve needing adjustment. One valve may be hanging open just enough to cause the popping back through the carb. Hopefully not a burned valve as a burned valve will also do this.
PontiacJim is online now  
Sponsored Links
Advertisement
 
Reply

  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Pontiac GTO Forum 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 for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 14 (3 members and 11 guests)
geeteeohguy, ralph7, RMTZ67
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