Why is no info available for the SEFI diagnostic test?

[Dash Riprock]

Im going through pages and pages of Google returns looking for some direction on this.

I was running the KOER test on a Ranger for a friend. I entered the SEFI test and at it's conclusion was presented with codes "1" and "4". Is this code "14", or does it simply mean cylinder 1 & 4 failed?

Do I automatically have these injectors replaced or cleaned?

Considering the wealth of info out there on the OBD systems, I find it odd I cant find anything on this seemingly simple test.

Anyone got any clues?

 

[Dash Riprock]

I think I should correct myself a bit. I understand that although some places call it a SEFI test, it is not a test of the injectors in isolation. Rather it is known more accurately as the Cylinder Balance Test, and any indication is simply a statement that one or more cylinders are weaker/stronger than the others. It simply uses the injectors as a means of testing this.

So my outcome of the test on this Ranger probably indicates that Cylinders 1 & 4 are weaker in relation to the others. Obviously a compression check is in order before starting to go for the injectors themselves.

Feel free to add to my knowledge!

 

[MrShorty]

From Mitchell for a '95 Explorer

CYLINDER BALANCE TEST
This test helps identify a weak or non-contributing cylinder
in engines with SFI fuel systems. PCM shuts off fuel supply to each
injector and measures RPM drop. It computes variation between
cylinders and identifies weak ones.
This test mode is entered from KOER SELF-TEST after all codes
have been displayed. Within 2 minutes after codes have been displayed,
lightly depress throttle (a 2-3 degree throttle angle is required, not
a wide open throttle). After a brief stabilizing period, PCM will
activate test procedure.
Test will be repeated if throttle is depressed within 2
minutes of final code output. During second and third test sequences,
percentage of allowable variation between cylinders is reduced.
Service codes displayed during this test identify weak or non-contributing cylinder. See CYLINDER BALANCE TEST DIAGNOSTIC TROUBLE
CODES table.
If Code 90 is displayed during this test, system has passed
test. If Code 77 is displayed, repeat cylinder balance test. If
throttle is moved during this test, Code 77 will appear, indicating
test is not complete. Repeat cylinder balance test. Total test time is
about 3 minutes.
CYLINDER BALANCE TEST DIAGNOSTIC TROUBLE CODES TABLE

Code Application
90 .................................................... Pass
10 .......................................... Cylinder No. 1
20 .......................................... Cylinder No. 2
30 .......................................... Cylinder No. 3
40 .......................................... Cylinder No. 4
50 .......................................... Cylinder No. 5
60 .......................................... Cylinder No. 6
70 .......................................... Cylinder No. 7
80 .......................................... Cylinder No. 8
77 .................................................. Retest

I have no first hand experience with this test, so I can't comment any further. As I understand it, x0 is how some scanners will interpret single digit codes, so I expect if you're doing this with just a voltmeter or CEL as your output device, you will just see a single digit to represent each cylinder. Thus, I would guess that the computer is interpreting cylinders 1 and 4 as weak.

As you say, the next step would be a compression check. Don't forget to check the spark plugs/wires.

I agree, there doesn't seem to be a lot of information out there about this particular self-test. I invite you to share your experience with this test so we may all benefit.

 

[Dash Riprock]

Thanks Mr. Shorty. Ill definitely update this thread as I learn more.

I am only using the CEL light so, as you stated, that is why I only get single digit codes.

I did find the following on a Mustang site that confirms the ability of the test to lower the pass/fail criteria for subsequent tests. I assume this would allow one to get a read on how severe the cylinder was failing:

At this point you can optionally run the SEFI or Cylinder Balance test. If you have an '87 or later, lightly tap the throttle (it only takes a small movement) WOT), and release it. Owners of '86s will have to go WOT briefly. After a little while, the EEC-IV will begin cutting the injector to each cylinder in turn, and looking for a drop in RPM. If there is no drop associated with any individual cylinder, then there is some problem there (that may or may not be related to the injection system- you could have a valve problem, or a fouled plug, or a shop towel stuck in the intake runner, and get the same effect). This test takes about 90 seconds. If a cylinder is found by this test to be weak, a single-digit code will be flashed telling you which one (1-8). If all is well, the code will be 9. If it gives you a 77, it got confused (perhaps you bumped the throttle) and you need to start over and rerun the test.'87 and later cars can then rerun the SEFI test after it finished, again by just tickling the throttle (saves having to go back through the whole KOER test). It also relaxes the criteria for "fail" with each retest, so if one cylinder fails the first time but passes the second, it's only a little weak- whereas if it fails 3 times in a row, it's profoundly dead. Those of us with '86s have to go back to Square 1 to rerun, and we don't get this progression of thresholds to help us troubleshoot.