#5 not firing right

[Lapkritis]

How are you doing on this Walt?

[WERK I]

Yes, I'm curious too.

Hope you and your family are doing ok and the Colorado fires are no where near you.

[Walt Fricke]

I've been off in Michigan at Parade, then visiting family along the way home.

Leakdown on #4 was 4%, and on #5 3.75%, all in both cases through the rings. Don't place much reliance on those absolute leakdown numbers - the two gauges don't quite zero the same to start with, etc. But nothing obvious there.

To add another test to the injector wiring, I swapped the right side wiring and plugs to the left side and vice versa. No joy.

Since the #5 is the middle injector, the end fittings on the fuel rail can't affect it in any obvious mechanical way. I pulled the rail and end fittings for inspection and a bristle brush, though there was nothing in there for it to brush. Each fuel rail is fed from its front end, and at its rear end each goes over to the fuel pressure regulator and return line. If this were an entirely new setup, especially if the fuel rails were at all asymmetric side to side, I'd wonder if there is some kind of standing wave action going on, but neither are the case and I don't think anything like that could happen anyway.

I've been thinking about what is different here, other than the fact that I rebuilt the motor without making any changes to its features.

One thing which is different is that the ITBs were attached to the motor which blew up the #6 piston. This sent oil and aluminum bits all over, including up the intake, out the intake stack into the air filter, and some aluminum and oil from all this made its way into the #5. This meant the #5 as well as the #6 ITB were a bit oily. So I'm going to swab the #5 (though I think I did this before reattaching the ITBs, and besides it didn't affect the #6). There really isn't any where in the ITB for debris to hide, much less cause trouble with lighting the fire.

We'll see if this, plus swapping yet another injector into #5 position, do any good.

[Discseven]

I did not have time to read the whole thread so perhaps this has already been stated...

This is cable leading to #6. Assumption is it chaffed on the air filter box above it. This cut fuel off to 6. #5 is in same area so same could happen.

[Walt Fricke]

Karl - thank you for pondering my plight.

I think your picture shows the cabling for the injectors on a 3.2 stock motor? I have aftermarket EFI on a race motor, with very little stock about it.

As it happens, I have checked (and rechecked) the injector wiring, and even swapped it side for side, and the wiring is good. And when tested the injector in the #5 position squirts fuel.

Which is what makes this so frustrating.

Swapping around injectors yet another time made no difference.

Yesterday I repeated, at greater length, the effect of squirting brake cleaner into the #5 intake. It caused that cylinder to fire for a while - doing it enough caused the EGT for that cylinder to rise to where it should be compared with the one for #2. But the effect of this wears off quickly, and firing stops.

I had pondered whether it was possible for a head to lack a battery ground connection. In addition to the many physical reasons why grounding the case must ground the heads, this pretty much proves that the plugs are firing.

I pulled the ITBs off the manifold, and squirted each injector on the right side into a pan. I didn't have something really suitable for gathering the squirted gasoline and measuring it, but it looked like all sprayed a roughly identical amount, as they should. I could see the gasoline spray out of #5. At cranking speed not much fuel is sprayed anyway, but it is there.

I also squirted carb cleaner through the only relevant orifice on the #5 ITB - the idle air bleed passage. It wasn't blocked (didn't think even if it was that would matter, but grasping at straws).

I rechecked the compression on #5. Previously, with a friend's tester, got 130 psi. With mine, and the engine pretty warm and the butterflies all propped wide open on that side, got 145 psi. I don't think that is high enough to prevent the plugs from sparking, or otherwise affect combustion.

With the engine idling nicely on five cylinders, I pulled each injector plug in sequence. For each cylinder except #5, the engine slowed a bit and ran a bit less smoothly (as one would expect).

So still no closer to figuring this out than before.

Got spark, got fuel, injectors fire, nothing wrong with plugs or wires. Hard to find it is something in the ECU or programming, because that is hard wired to ground (which energizes the injectors, which have 12V positive applied to them all the time when the ECU has power) the 2 and 5 with a single grounding transistor or other electronic switch. If wiring was bad, switching the 2 and 5 injector leads would have moved the problem, but it didn't. If the ECU or software had a problem, both 2 and 5 should have the same problem with fuel getting in to be lit off by the spark. But they don't.

Sending the ECU off to Electromotive for testing seems in the cards even if the most likely result of that is a statement that it is working fine.

At that point, I'll have to try the "back to carbs" approach to see if something mechanical neither I nor anyone else has suspected is causing this problem.

[Lapkritis]

Walt, the injector must be dropping out once the engine is no longer cranking. The carb or brake cleaner is simply supplementing the fuel supply missing from the injector. Is there a two step limiter setting that was accidentally enabled? I've seen that before...

[HawgRyder]

Idea way out in left field...
Is it possible that one of the cam lobes for #5 (probably the intake) is damaged?
Along that same line...what if the valve were sticking...not likely seeing the compression is good.
But if the lobe were worn...you could have this effect.
The reason I ask...I had a cam tear off a lobe in less than 10 minutes of running time once...it "doorknobbed" very nicely.
Bob

[pete911]

If it runs close to normal while you are spraying brake cleaner into it then ignition and compression are fine. Somehow that cylinder isn't getting fuel.

Pete

[Walt Fricke]

Fuel certainly seems at the heart of it.

I've looked at those cam lobes. Intake moves the rocker up and down like it should. Ditto exhaust.

I'll check my rev limiter settings, as there are several options. And to make sure I'm not on some kind of staged (one squirting for low RPM, and another chiming in for higher RPM) setting. However, with the injectors twined - each fires once per revolution, I'd need to be on a sequential injection setting to have one thing happen with 2, and another with 5. There is provision for individual cylinder trims, but that's only for sequential injection, which calls for a cam sensor, and I don't have one or use those features, so I don't know how it would know how to deal with just one cylinder. Plus for sequential you have to wire up the injectors differently, using three extra outputs (which are currently unused) from the ECU.

Keep those notions coming. Getting a cylinder to fire has been around for 120 or so years.

[HawgRyder]

Walt...are these the same cams as before rebuild?
Also...#5 is the last cylinder to fire...is there some reason that the charge might dissipate before the plug gets around to sparking?
If the injectors all squirt at the beginning of the cycle (#1) then #5 might have less of a charge by the time the plug fires.
I remember trying to tune the Can-Am engines way back...and the stack lengths were a nightmare to get right...had everything to do with
charge "float" in the stacks...if you got them wrong...one or more cylinders would run lean.
Grasping at straws here.
Bob

[nocarrier]

How is the fuel pressure?

[docrodg]

Intriguing. While there are many on here with more knowledge than me I was wondering if this may be a bad injector only when hot, kinda like starter heat soak. It is a coil actuated device, and resistance increases with heat...

[HawgRyder]

I believe Walt has swapped the #2 with #5 to eliminate that.
Bob

[piggdekk]

what about borrowing a set of carbs?

[Eagledriver]

Forgive the questions if they are not helpful, I don't have much experience with electronic injectors. How does the injector get it's ground? I know you checked the cylinder ground for the spark but what about the injector ground. Does it have a wire or ground to the rail? Maybe it loses it's ground when the engine is running somehow.

-Andy

[Lapkritis]

They all get constant 12v from the key on circuit and the ecu switches the ground on and off to open the injector.

[Walt Fricke]

Same cams. This was a quickie rebuild - bearings, valve job, reset spring heights due to valve job (actually, I didn't measure spring heights on teardown), new cylinder base washers just because old ones looked a bit too crushed for my taste, and put back together.

I rerouted the right side injector wiring farther away from the plug wires, but that didn't help. I used actual starting fluid (ether?) when running it. Squirting it into the working intakes caused the idling ending to slow a bit! But into #5, same old thing - engine picked up, EGT picked up, my hand behind the exhaust felt more even pulses. Then back to no fire in #5. The #5 exhaust runner was hotter the farther away from the port it got! That has to be due to it getting next to the other runners, and picking up heat from them.

#5 has failed to fire when it had the #5, the #4, and the #6 injector in it. And #4 and 6 have worked fine no matter which injector is installed.

Redid leakdowns and compressions on the right bank. All were very close to each other. And I keep checking exhaust runner temperatures on the left bank, especially #2, just to confirm that that side is working right.

I have a set of Weber 46s. I can plug those in while the ECU is off to Electromotive for them to see if the ground which serves both 2 and 5 can somehow make 5 go bad without affecting 2.

But first I'm going to see if I can run alternate wires from the ECU injector output for 2/5 to the #5 injector without cutting any wires. And from the common positive to #5. Since swapping the loom didn't change anything, I don't hold out much hope.

[Jeff Alton]

Walt,

Are you sure the #5 injector is firing? You can use a noid light to test. Or if your ecu has the ablility (may good ones do) to see if the injector fires? You should hear it, or hear a change if you pull the connector during the test. Or use a stethescope. You can even use a 9v battery and a spare injector connector to test the actual injector while still connected to your fuel supply.

If it is gettig fuel and not firing you should see a pretty wet plug. If you pull a plug after running it and it is dry, then you are not getting fuel. With a stethescope and the motor running you should be able to tell if the injector is firing. If it is, pull it and run the engine with that injector spraying (or not) into a cup. I would not waste time putting carbs on as a test. Have you tried plugging the injector connector for the other cylinder that fires at the same time a #5 onto the #5 injector to see if the problem switches banks??

This should be straight forward if the injector is known to be good.

If you are sure you have spark (at the correct time) and have compression that really only leaves fuel......

I suspect that wiring or ECU is to blame assuming your injector and fuel supply is good....

[HawgRyder]

Walt...my reasoning...
You have swapped the injector and found out in is NOT the injector itself.
You have swapped #2 with #5 wiring...same result...no change.
To my brain...that just leaves fuel delivery to the injector....or...something in the cylinder itself.
You have checked cam action...compression...and numbers look OK.
It has to be the fuel to the injector....is it possible to rig a different fuel manifold (temporary) ?
If you eliminate all the possibles...the last (and probably crazy one) is going to be the problem.
Bob

[Walt Fricke]

I couldn't figure out how you get a post to appear in italics, so I'll wing it. Jeff Alton asks:

*Are you sure the #5 injector is firing? You can use a noid light to test. Or if your ecu has the ablility (may good ones do) to see if the injector fires? You should hear it, or hear a change if you pull the connector during the test. Or use a stethoscope. You can even use a 9v battery and a spare injector connector to test the actual injector while still connected to your fuel supply.

--USED A NOID - bought a 12V led, which I believe is all NOID is? Flashed. First time I had the issue I used the stethoscope (actually, borrowed a friend's piece of small tubing, as I was at his house trying to get it going out in the country) to listen to all injectors. All clicked. Pulling the #5 connector makes no change in engine running. I have a spare connector, but why wouldn't I just use 12V? However, this sounds good and I'll do it. Timing of the injection pulses (one of which comes 180 cam degrees out of phase with the other anyway) shouldn't be critical, at least at idle. No worse than me spraying starter fluid in.

*If it is getting fuel and not firing you should see a pretty wet plug. If you pull a plug after running it and it is dry, then you are not getting fuel. With a stethoscope and the motor running you should be able to tell if the injector is firing. If it is, pull it and run the engine with that injector spraying (or not) into a cup. I would not waste time putting carbs on as a test. Have you tried plugging the injector connector for the other cylinder that fires at the same time a #5 onto the #5 injector to see if the problem switches banks??

--PLUG IS DRY. I can't pull injector and make it spray, as it requires the fuel rail, and something to hold it in the rail. However, I have opened the butterflies and spun the motor with no ignition - injector seems to spray. All three I have tried, which work on the other cylinders. I had carefully checked the wiring for continuity, and finally swapped the looms over from one side to the other - just called for snipping a few zip ties. Made zero difference! To deal with the need for fuel rail to test injectors, I just removed the entire throttle body assembly from the manifolds, and had them squirt into pans. Seemed about equal.

*This should be straight forward if the injector is known to be good.

--AGREED, but it doesn't seem to be.

*If you are sure you have spark (at the correct time) and have compression that really only leaves fuel......

--AGREED, but spark for #2 is spark for #5 in a waste spark DFU. 2 works, so timing for 5 must be OK. I've swapped terminals, and tried other plug wires without success. And putting a timing light clamp on the #5 wires shows flashes when engine running (on the other 5), just as it does for the other holes. Plus the fact that the hole fires when I spray a combustible fluid in says spark is at least sparking.

*I suspect that wiring or ECU is to blame assuming your injector and fuel supply is good....

--REASONABLE SUSPICIONS, but why would the ECU fire (by grounding) the #2 but not the #5, which uses the same ground - separate supply wires from a panel external to the ECU to each injector, but the ground wires are connected for each pair - come together in the middle - and a single wire goes to the ECU, which dictates when and for how long it is grounded. If one of the two wires from the injector plug were bad, swapping sides should have made a difference. But it doesn't. James Bricken suggested I pull the 2 to see if the 5 would then fire (he'd run across something like that), but that didn't work either. Which is why I am thinking of carbs.