Adjusting Air / Fuel Mixture Options

[sjhenry1075]

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]

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]

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!

[JamesM]

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.

So per the book, timing is set/checked @3500 RPM with the vac lines disconnected.

Which of the 2 hoses kills the idle when it is attached?
Advance or retard?

Are you sure you are checking against the correct mark on the fan? Verify if the mark you are timing against on the fan is 27deg off the flywheel mark in the proper direction (this bit me more than once when i was new to 914s)

Edit: couple more questions
When the distributor hoses are connected and it is barely idling, could you describe the behavior?
Is the idle speed hunting?(indicating lean condition)
Is there a noticeable gas smell to the exhaust? (rich)
Does adjusting the air bypass on the throttle body make any difference?

[MDTerp]

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.

So per the book, timing is set/checked @3500 RPM with the vac lines disconnected.

Could setting the timing with the vac lines connected cause the poor running when hooked up?

I'm also going to the North East Gathering and trying to sort out a couple issues as well. Looks like I'm less than a hr away from you. I'm no expert but if I can lend a hand with anything I'd be happy to help.

[sjhenry1075]

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.

So per the book, timing is set/checked @3500 RPM with the vac lines disconnected.

Could setting the timing with the vac lines connected cause the poor running when hooked up?

I'm also going to the North East Gathering and trying to sort out a couple issues as well. Looks like I'm less than a hr away from you. I'm no expert but if I can lend a hand with anything I'd be happy to help.

I think if it were timing, wouldn't it be difficult to start? That's one thing, the car starts quicker than my Nissan Altima; as soon as I turn the key it fires up, both hot and cold.