Help! I'm Stymied!, Only firing on #3 and # 4 Options

[DipShit]

1.7 D-Jet

Engine was running just great until about two weeks ago, sigh. Now only fires on # 3 and # 4.

I have cleaned every connection including all grounds. And I mean cleaned them good! The elecrical appears to be just fine. I get a good noid light at both # 1 and # 2. The injectors have tested just fine as well (I'm getting about 7cc in 15 seconds). I have 40lbs of pressure the 1,2 rail. The spark plugs are getting juice and fire.

I have installed new points, cleaned the triggers (which shouldn't have mattered because of the sequence) and set the dwell. I'm a tad under at 44 degrees, but again shouldn't keep # 1 and # 2 from firing.

The timing has to be close as it runs really smooth for just two cylinders.

If I pull the power to injector 3 or 4, I get a real good drop and she will die. If I pull 1 or 2 - no change.

If I add propane to the intake, I get a good response in higher rpm.

I had originally traced to the Temp II sensor and it failed, so I replaced it. A new one seemed to be the fix, but only for a moment.

I have good fuel, spark and air -

(IMG:style_emoticons/default/WTF.gif)

I'm STYMIED (or just a REAL DIPSHIT)

[dr914@autoatlanta.com]

Valves too tight????

1.7 D-Jet

Engine was running just great until about two weeks ago, sigh. Now only fires on # 3 and # 4.

I have cleaned every connection including all grounds. And I mean cleaned them good! The elecrical appears to be just fine. I get a good noid light at both # 1 and # 2. The injectors have tested just fine as well (I'm getting about 7cc in 15 seconds). I have 40lbs of pressure the 1,2 rail. The spark plugs are getting juice and fire.

I have installed new points, cleaned the triggers (which shouldn't have mattered because of the sequence) and set the dwell. I'm a tad under at 44 degrees, but again shouldn't keep # 1 and # 2 from firing.

The timing has to be close as it runs really smooth for just two cylinders.

If I pull the power to injector 3 or 4, I get a real good drop and she will die. If I pull 1 or 2 - no change.

If I add propane to the intake, I get a good response in higher rpm.

I had originally traced to the Temp II sensor and it failed, so I replaced it. A new one seemed to be the fix, but only for a moment.

I have good fuel, spark and air -

(IMG:style_emoticons/default/WTF.gif)

I'm STYMIED (or just a REAL DIPSHIT)

[DipShit]

I figured I'd try to get the valves adjusted next week to be sure, but don't see how all of the sudden two valves would go out that bad when everything was just "peachy" prior to this.

I suppose anything is possible at this point.

Thanks for the suggestion!

[tod914]

29.4 for fuel pressure.

[DipShit]

29.4 for fuel pressure.

Typo - it was 30 not 40.

[thompson-mfr]

Slight Hijack:

I am having almost exactly the same problem.

Would love to hear some suggestions on this.

Went through the wiring as well and checked for breaks. Nothing.

Could this be the FI Brain?

[DipShit]

don't think it's the ECU as I have replaced with another with the exact same result!

[thompson-mfr]

don't think it's the ECU as I have replaced with another with the exact same result!

Good to know but I am running out of ideas, as it sounds like you are too.

[jt914-6]

Try cleaning the trigger points again. Remove them and pull a piece of paper through them.

[mike_the_man]

Are the plugs fouled? If it's getting the right amount of fuel flow at the injectors, you should be able to rule out the FI stuff. If it's getting good spark (you've tested plugs and wires?) then you should be able to rule out electrical stuff. All that leaves is air flow. Valves? Something blocking the intake? I'm not sure what else it could be...

Good luck!

[Dr Evil]

The injectors fire in batches of 2 ( 1&4, 2&3) so it is not the points. Pull the injectors on that bank and check the spray pattern. It is possible that you have some crap that clogged those two injectors. They are getting juice as per your noid test.

You need:

Spark - checked it and it was good, what do the plugs look like? Dark and sooty?

Noid check - good

Fuel from the injectors - 7cc/15min, but how was the spray pattern? Big drops?

Fuel pressure - checked good at 30psi

Propane is useless unless you are checking around things. Putting propane into the intake will give you a boost no matter what.


Compression - How is this?

The injector wires are not on the wrong injectors are they? Swapped 1 and 2?

[DipShit]

Plugs look really good. And the trigger points have been cleaned and recleaned.

I am leaning toward the valves, but just doesn't make sense to have TWO go at the same time when all was extremely well just prior.

Exasperating to say the least!

[thompson-mfr]

Try cleaning the trigger points again. Remove them and pull a piece of paper through them.

Sorry maybe a dumb question; what kind of paper are you referring too? Normal printer or 2000 wet sand paper???

[DipShit]

The injectors fire in batches of 2 ( 1&4, 2&3) so it is not the points. Pull the injectors on that bank and check the spray pattern. It is possible that you have some crap that clogged those two injectors. They are getting juice as per your noid test.

You need:

Spark - checked it and it was good, what do the plugs look like? Dark and sooty? THEY LOOKED CLEAN AND GOOD

Noid check - good - YEP

Fuel from the injectors - 7cc/15min, but how was the spray pattern? Big drops? GOOD SPRAY PATTERN AND FLOW

Fuel pressure - checked good at 30psi - YEP

Propane is useless unless you are checking around things. Putting propane into the intake will give you a boost no matter what.


Compression - How is this? - NEED TO CHECK BUT APPEARS GOOD! Had it running on all four briefly again last week when replacing Temp II

The injector wires are not on the wrong injectors are they? Swapped 1 and 2?

- NOPE, THEY ARE CORRECT. For shits and grins even tried 4 different injectors last night. I spent over 5 hours going through everything again, and again and racking my brain

[jt914-6]

When I had a FI four we would use regular paper. You could see the black left behind on the white paper. I would not use sand paper on them.

[Dr Evil]

Ya, valves, rings, and head studs are in the equation. Too bad the other, easier to fix stuff seems to be OK.

[DipShit]

When I had a FI four we would use regular paper. You could see the black left behind on the white paper. I would not use sand paper on them.

Used a match book cover and yes, wiped some black off and are real clean now. The trigger points fire apposed so this is been "cleared"

[Dr Evil]

The injectors fire in batches of 2 ( 1&4, 2&3) so it is not the points. Pull the injectors on that bank and check the spray pattern. It is possible that you have some crap that clogged those two injectors. They are getting juice as per your noid test.

You need:

Spark - checked it and it was good, what do the plugs look like? Dark and sooty? THEY LOOKED CLEAN AND GOOD

Noid check - good - YEP

Fuel from the injectors - 7cc/15min, but how was the spray pattern? Big drops? GOOD SPRAY PATTERN AND FLOW

Fuel pressure - checked good at 30psi - YEP

Propane is useless unless you are checking around things. Putting propane into the intake will give you a boost no matter what.


Compression - How is this? - NEED TO CHECK BUT APPEARS GOOD! Had it running on all four briefly again last week when replacing Temp II

The injector wires are not on the wrong injectors are they? Swapped 1 and 2?

- NOPE, THEY ARE CORRECT. For shits and grins even tried 4 different injectors last night. I spent over 5 hours going through everything again, and again and racking my brain

The only thing that is tied to both chambers are the head studs....but I am a pessimist. A compression check will show you what is up. The gauge is relatively cheap.

[DipShit]

Compression test and valves are next on my to do list, but I am very doubtful that either will change the outcome.

I've been told by a very wise Porsche Guru that eventually it will all boil down to the basics, so I really hope to be proven wrong in my thinking and that the valves are the problem.

[Dr Evil]

I would suspect the valves if they shared a common post that could be stripping out, but there are 2 separate posts for each bank of rockers. This is a puzzler.