Cylinder not contributing ..

[justin_b31]

1993 Explorer (pushrod?) is failing emissions. Shop figures out that cylinder 6 is not contributing.

Their testing:
spark test
compression @110
pull ignition wire from each cylinder, one at a time, to determine power loss
swapped ignition wire to 6 (don't know which one)

Based on the diagnostics, cylinder 6 has fuel delivery problem. Asked them about regulator and their response was that, because 5 was good, 6 should be fine too ...

Now I have the throttle body and fuel rail out.

At the FPR I applied 15 (psi?) vacuum with a mighty-vac tool. Vacuum held for 5 or so minutes. Can I assume this is the extent of the testing? Replacement suggestions?

Injector 6 came out next and I rigged an injector tester. Here is a video of the injector.

Is this injector reusable? It appears to be the same spray pattern as another injector. Or should I just replace it just in case?

And what of the other injectors? Any advice about replacing the whole lot if I replace the one?

Thanks!

 

[Roadrunner777]

I think I got from your notes that a spark test was done on this cylinder and they got spark.

Air? Check.
Fuel? Maybe.
Spark? Check.
Compression? Check.

I wonder if the driving circuit for that injector is bad, or maybe bad wiring between. I'm just throwing stuff out there.

I like the video, it has a mythbuster's feel to it.

 

[justin_b31]

that's correct. They did a spark test by swapping the ignition wire with another cylinder. That said, I did a spark test at the plug by holding the wire in close proximity to the plug.

Having bought the plugs earlier this week I'm going with the "spark is good" thought.

Speaking of injector firing, I forgot to mention that I attached a noid and it blinked pretty fast.

So, does the injector in the video seem to be okay then? I'm trying to compare its pattern with other videos and pictures -some injectors have this nice conical shape whereas these injectors are more like 4 streams of fluid

 

[Facimeor]

The injector looks fine to me. Nice test rig. I have a similiar setup that I used an old fuel pump and pressure regulator to feed a constant supply of fuel to the injector. Then I run a 50/50 mix of seafoam and gasoline through my injectors. My spray pattern results are typical of what you have there.

get a cheap spark tester from napa or autozone. Its just like an adjustable spark plug that lest you dial in the gap. Use that to check to make sure you have a nice hot blue spark at factory gap. Maybe a combination of weak spark and low compression?


Edit: still looking for a definate answer on the compression numbers. 110 still seems low to me. You might want to see what the others are at for comparison.
Edit 2: yeah what the next poster said.

 

[pauley]

when i tested the compression on my engine (with a dead cylinder) i had 135psi at 5 cylinders and 115psi at the dead cylinder you may want to check the cylinders next to it just to see what they put out. if all cylinders are at 115 then it will most likely be fine but if the other two are substantially higher it will cause a miss condition. my issue ended up being a bad head gasket. just a fyi. hope you find your issue.

 

[Roadrunner777]

Patterns - There are a couple of different nozzle styles out there, a single centered nozzle and a 4 orifice nozzle. Anyway, your pattern looks as good as any pattern I have seen.

I have other thoughts that really are not very practical. I might swap the injector to another cylinder and see if the problem follows it. I think some parts stores can test computers, maybe I would do that just to rule it in or out. I got nothing.

 

[justin_b31]

thanks for the replies all! I appreciate the feedback

Guess I will run out and grab a compression tester and see where to go next

 

[Robert Nick]

Make sure you remove all the Spark Plugs and Block the Throttle Chamber Butterfly Open during the Compression Test. At my former employer we would test Injectors that way except we used Mineral Spirits because it has the same Specific Gravity as Gasoline. I once built a 555 Timer Circuit that would drive all the injectors at the same Duty-Cycle during warranty part testing. I agree with Roadrunner. Swap the Injector to a different location and see what happens. The Spray Pattern looks good to me.

 

[That-Guy]

I just went through this on my 94 xlt (it was 2 days ago), I'm 90% sure its the fuel injector. Now why it's clogged, it could just be faulty, but I suggest replacing the egr valve $50, and don't use the commercial cleaners. They have a 50% success rate, 50% of the time they ruin them all. It costed me $35 for a new injector, $15 for upper intake manifold/fuel rail gaskets and I broke the $80 egr pipe in the process. Runs like a champ again, I drove 50,000 miles on 5 cylinders.

The low compression suggest a blown head gasket or valve. You can replace a head gasket for $1000 or use $25 BARS LEAKS brand radiator stop leak. Put it directly in your radiator and make sure to run the motor for a few hours or it can freeze in places you dont want it too.

 

[Facimeor]

^^ no offense man, but suggesting a pour in headgasket rememdy makes me question your mechanical knowledge enough that it negates the rest of your advice completely. And why replace a working EGR for no good reason?

 

[Turdle]

Now to make sure the ECM is sending the signal to the injector. Both sides will be 12v, one will drop low with the signal. You can rent a "noid light" to check for the signal.



If your truck has egr -it will be a "sequential fire" ignition system. There could be an open in the circuit between the ECM and injector.

If it is a non egr 93, it will be a batch fire injection system. If there is an open in the circuit it would be in the injector harness right where the #6 injector wire is spliced into the injector harness, as each side is a common line-all 3 injectors are wired in parallel.

 

[justin_b31]

I'm certain this is a non-EGR version -it should (judging by the pictures) come out by the oil dipstick

Noid light did work when tested so I'm pretty sure the signal is okay.

Other than this, I haven't gotten to work on it lately. The battery was stone-cold dead and needed a charging. No cranking no compression -although I guess I *could* have manually cranked the engine

Also need the weather to let up too

 

[justin_b31]

Finally got compression done on that bank.
Cylinder- compression
#6- 112
#5- 100
#4- 110

So, i think that this indicates a sealed head gasket.

 

[That-Guy]

^^ no offense man, but suggesting a pour in headgasket rememdy makes me question your mechanical knowledge enough that it negates the rest of your advice completely. And why replace a working EGR for no good reason?

Just because of my opinion on pour in sealer, my advice is wrong? I recently talked to a mechanic with 30 years experience who recommended the same thing. I recommended a new EGR because it might be working, but not to its full potential.

 

[Roadrunner777]

Finally got compression done on that bank.
Cylinder- compression
#6- 112
#5- 100
#4- 110

So, i think that this indicates a sealed head gasket.

Not bad numbers. I barely remember how it was supposed to go, but I think acceptable is something like 10% lowest to highest, you're good enough for my book. And #6 is where you diagnosed the issue, which is the highest.

My suggestion... I don't really have one. I like your injector test. But, I don't know if it 100% reflects running conditions. If you have total faith in your test, then swap the injector to another cylinder and reassemble.

There are differences, your test was solid on, the system pulses it. Maybe it fails with a pulse, or vibration, or something else more subtle. I am not a fuel system expert. I am only pointing out the logic. Maybe the best path is to replace the injector anyway and reassemble. If the problem goes away then you are done. If not, then you can at least say the injector is good.

I am trying to understand the ignition test. They pulled the wire, no change in engine, so that indicated the cylinder. I got that. Did anyone then check to see that spark actually existed on that wire? You say they swapped it. But, do you know for sure that you have spark at this cylinder? The line of thinking says someone did, but I don't want to assume this because it would explain sooo much if it did not actually have spark and someone missed it. Maybe you could add some detail on what was done there.

 

[justin_b31]

Spark, yes i did several variations os spark testing.
1- unplug wire at ignition module, start truck, and carefully move plug near module. At about 2" distance a visual spark is seen.
2- same test only performed at the spark plug. Because of cylinder 3's location, it was skipped

I dont know how thw shop performed the test.

[Update]
discovered a dark fluid coming from vac line of FPR. Replaced on the thoery that, with the fuel return between cylinders 5 & 6, there was a possibility that pressure was bad and fuel returned before hitting injector six - path of least resistance.

[synopsis]
Didn't fix my problem

@roadrunner
This knucklehead forgot to verify where i was installing the suspect injector.. Not exactly the smartest thing i've done. The "good" news is that cylinder six seems to be firing great, add/remove spark and engine does seem to lose/regain power.

That said, i did consider the possibility that an injector is still a solenoid and solenoids do have in-between where they work sometimes and sometimes not.

And it does seem the missing moved to another cylinder..

Will stay posted after replacing the whole lot of injectors

 

[Nomad767]

Try another ECM? I had an injector issue with my Mustang once. After just about strangling everyone that told me I had a blown head gasket, while I said it was just pouring fuel down the cylinder, I replaced the ecm on the deduction that it was holding my injector open constantly. No prob after that, except for the "unplugging" of the cat.

Maybe you are having an issue with signal loss to the injectors due to the ecm? My experince with injectors is that they all keep 12v available to the injector, just awaiting ground closure from ecm. Okay...I assume you already covered that since going back over I must have missed turdles post.

Maybe you have trash in the rail and it has moved to block another injector from you having it off and re installing?

 

[justin_b31]

I got a junk-yard injector and installed with no change..

HIGHSpeed Test Idle Test
HC CO% CO2% RPM HC CO% CO2%
846 .48 14.8 2585 1819 .04 15.0

The shop graciously has not charged for the 8 retests beyond the initial and the numbers are pretty much the same.

If I am not mistaken, high HC and low CO indicates unburnt fuel so it really made sense to replace the injector.

I think that this leaves me with the ECU.

Regarding the ECU, mine is identified as BAT1 -injector batch fire.

does anyone know of a way to test these without going out and buying? THere's a ton on ebay but I really don't want to buy the wrong one either. Checked Cardone and can't find info how to look up ECUs

 

[justin_b31]

Tried another ecm. Rockauto had one on closeout for seventy bucks. Engine seems unchanged to me, have not yet had emissins retested.

The only thing left is the maf and the right-side. Since the original diagnosis pointed me to cylinder six, i am now wondering if that was incorrect.

 

[Facimeor]

I personally think you just have low compression leading to poor combustion. 100psi is right at the threshold of rebuild time.