924Board.org

[Ian89C4]

Ladies and gents and everyone who has helped me,

I am still having F/A mixture problems even with all of the things that people have suggested on this great forum. I have tried everything that everyone has said, but was not honest at the forefront and I could have solved (or at least minimized) this issues off the bat if I had done very simple tests.

So...today I decided to test actual fuel delivery. I pulled off the return line to test the fuel pump flow rate..and it was well over the 750cc in 30 seconds. So all good there.

Then I decided to test injector delivery rate. The manual said to check flow rate to 100cc and all should be right on or extremely close....below are the results from the tests:

Test #1


Disregard color, there was a small amount of water in each jar as that is how I set the 100cc level (black tic mark). It was also extremely humid adn the fuel was cold.
So...#4 was the only good injector, but they all leaked as soon as there was pressure put against them...so bad anyways.

But, for due diligence I traded the #4 injector out with the #3 (the lowest level) to make sure that it was not the distributor.

Here is the result:


The injectors are crap!!

I tried one more test with one of the 80-81 injectors on the #4, but apparently the injector was clogged (it was new when I put it in, but I probably got something in it or in the line when I pulled it to replace it with the pre 80 injectors). I was trying to check fuel flow rate differences between the two different types of injectors, but was obviously not able to.

As mechanical things require persuasion sometimes, when I tapped on the injectors (minus the 80-81 injector) they decided to start spewing out more fuel. I used spewing deliberately because that is what they did, there was not real atomization, just fuel coming out a nasty angles in streams.


So...I would have to venture a guess that this is the majority of my problem. Although they started working better after taping, there is no way that that will work...probably why they would be good for a few laps, and then the engine would run very lean....

Dan...you have an order on your site for new injectors...

Again, sorry to all who have offered up very good advice!
_________________
Ian Edgerly
North Carolina

Current:
1981 924 SCCA/ChampCar Weissach Race Car ("Serenity")
1987 924S ChampCar Endurance Car ("Der Weg")
1980 924 Euro ("Wahala")

[ideola]

This is one of the PITA tests to do, but very eye opening once you do. In my experience, old injectors almost always have wide variances in flow rates. This is also one of the reasons I run a bottle of Techron thru all of my cars once per season.

When you get the new injectors, I strongly advise re-doing the test. Don't assume that there isn't also a problem at the fuel distributor!
_________________
erstwhile owner of just about every 924 variant ever made

[joewest]

Definitely redo the test once new injectors are installed as Dan had suggested. At least for piece of mind....
_________________
'79 924 Supercharged / Track Prepared
'80 931 Daily Driver - Sold
"The number of posts in my profile may represent the number of times I have screwed something up...and admitted it here."