Adjusting Air / Fuel Mixture |
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Adjusting Air / Fuel Mixture |
sjhenry1075 |
Jun 22 2021, 08:29 AM
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#1
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Member Group: Members Posts: 269 Joined: 22-July 12 From: Stevensville, MD Member No.: 14,709 Region Association: North East States |
Hey everyone, please excuse my lack of knowledge on this subject, but I have a question regarding air / fuel mixture adjustment on my 71 1.7 with stock D-jet. I posted this question on Facebook but wanted to try here as well.
Back story: my car will only idle and drive when both vacuum lines are disconnected from the distributor. When connected (I used a diagram found on 914world so I know they aren't flipped) the car barely idles when cold or warm, and it is almost undriveable; it surges, bucks, and hesitates. If I remove both vacuum lines from the distributor it idles and runs great. From what I understand from the replies on FaceBook, this could be an air/fuel mixture issue, but how is that adjusted with for the 71? Is there a certain procedure for this? Thanks in Advance for any assistance you can provide! For those going to PA for the Northeast gathering, I'm looking forward to meeting you! |
JamesM |
Jun 22 2021, 11:56 AM
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#2
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Senior Member Group: Members Posts: 1,958 Joined: 6-April 06 From: Kearns, UT Member No.: 5,834 Region Association: Intermountain Region |
Back story: my car will only idle and drive when both vacuum lines are disconnected from the distributor. When connected (I used a diagram found on 914world so I know they aren't flipped) the car barely idles when cold or warm, and it is almost undriveable; it surges, bucks, and hesitates. If I remove both vacuum lines from the distributor it idles and runs great. From what I understand from the replies on FaceBook, this could be an air/fuel mixture issue, but how is that adjusted with for the 71? Is there a certain procedure for this? Have you checked your actual timing with a timing light yet? I dont recall if 71s 1.7s were plumbed the same but 72-73 1.7s the dizzy vac lines should ultimately retard timing at idle (the advance line should be ported vacuum and have no effect) so pulling your vac lines to the dizzy does 2 thing. 1. Allows slightly more air into the intake, 2. advances your timing at idle (but shouldn't have much effect at WOT) So while it is possible that the extra advance at idle is masking a fueling issue it seems unlikely. TBH probably 90% of the issues I have encountered with "d-jet" of the last 20 years eventually work out to being some issue with the distributor/timing. So, as stated by other posters check the basics (timing, fuel pressure, part numbers match, etc) and report back. What I wouldn't do is start out trying to "fix" the problem by "adjusting" d-jet components. for the most part they are not intended to be adjusted and are either good or bad. Identify the failed component first. |
sjhenry1075 |
Jun 22 2021, 12:12 PM
Post
#3
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Member Group: Members Posts: 269 Joined: 22-July 12 From: Stevensville, MD Member No.: 14,709 Region Association: North East States |
Back story: my car will only idle and drive when both vacuum lines are disconnected from the distributor. When connected (I used a diagram found on 914world so I know they aren't flipped) the car barely idles when cold or warm, and it is almost undriveable; it surges, bucks, and hesitates. If I remove both vacuum lines from the distributor it idles and runs great. From what I understand from the replies on FaceBook, this could be an air/fuel mixture issue, but how is that adjusted with for the 71? Is there a certain procedure for this? Have you checked your actual timing with a timing light yet? I dont recall if 71s 1.7s were plumbed the same but 72-73 1.7s the dizzy vac lines should ultimately retard timing at idle (the advance line should be ported vacuum and have no effect) so pulling your vac lines to the dizzy does 2 thing. 1. Allows slightly more air into the intake, 2. advances your timing at idle (but shouldn't have much effect at WOT) So while it is possible that the extra advance at idle is masking a fueling issue it seems unlikely. TBH probably 90% of the issues I have encountered with "d-jet" of the last 20 years eventually work out to being some issue with the distributor/timing. So, as stated by other posters check the basics (timing, fuel pressure, part numbers match, etc) and report back. What I wouldn't do is start out trying to "fix" the problem by "adjusting" d-jet components. for the most part they are not intended to be adjusted and are either good or bad. Identify the failed component first. I did set the timing using a timing light and procedures explained on Pelican. I will double check all parts/part numbers to make sure everything aligns. Thank you! |
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