#5 not firing right

[Walt Fricke]

Well, not necessarily wet, as with gasoline. Not sure.

I did check (and recheck) the sensor gap. About 0.013, which is within spec.

The Wintec allows me to look at the voltages from the TPS, MAP, and MAT in real time (also "engine temp," which means water in those cars. I don't use this, as oil is too slow to warm, and CHT I am told is too fast for what basically is a warmup circuit). Nothing special there, other than that they are working, and I have given the TEC reasonable values for them. I can look at injector on and off time. It dithers around some, which might mean something.

I can add a WEGO - have a bung on each side for a separate O2 device, but haven't hooked that up, because I can't see what that will tell me, other than that left side is AF something, and I assume right side will be different with a hole not firing. Maybe if leaner, would mean no gas, and richer, no spark? But what does raw gas do to the O2 reading?

The Tec3r will act as a WEGO monitor, and for street use you can even have the sensor adjust things automatically. Not a good idea for a race motor, I am told. In many ways, tuning race motors for EFI is a lot simpler, as you only really care about WOT, and don't have to adjust cell by cell.

Plus I'm PB Blasting the right side bung plug so I can get it out.

I've thought of a scope. I have an ancient rack mount one stored away. Large and heavy. And I've never used it for automotive stuff. What would I be sensing? Where would I hook it up? What would I be looking for? Inductive clamp for each spark wire? I'm thinking those old nice six or eight traces displayed were for the coil wire on a distributor system? Or did they have six or eight clamps and inputs and were separate channels?

[Lapkritis]

The effect of a no spark, fuel present condition is actually lean on the wideband. Seems backwards when you first think about it.

While WOT is important for race, you can also tune part throttle to keep things running clean and not fouling while also taking out much of the cold blooded nature of the engine. May systems will incorporate an RPM/TPS cutoff where lambda compensation is deactivated to allow for safe WOT/heavy load operation. Many of these systems do not recognize specific cylinder misfire so if a hole loses spark the ecu trims all 6 to compensate. You then end up with a rough running pig rich 5cyl.

[WERK I]

Good morning Walt,
I think a scope would be useful in determining the relationship of the injector firing and the plug firing. If your scope is dual trace, which most are, you can put one probe on the DC voltage firing the injector coil and the other probe clamped on #5 ignition lead. If your ignition probe is a high tension lead you could actually read the amount of voltage firing the plug. A clamp type probe will only show you a spike of unknown voltage, but that is still useful. The scope will give you a time relationship of the events to one another.

Does the engine run like a six cylinder with one dead cylinder or is it running just barely, sometimes sounding like a 3 cylinder, then a 5, then a 6, then ........?

When you had the timing light clamped on the ignition lead, you mentioned the light was dancing around somewhat. Do you think it was #5 erratically firing at those times?

IMHO, I really think your engine is mechanically fine, but there's a wiring/electronic gremlin in the Tec3r. Have you spoke to Richard Clewett on this matter? He is an absolute wizard on these systems.

[Walt Fricke]

Other than a scope, and talking with Richard Clewett, I am rapidly running out of ideas.

It mostly runs like a 5 cylinder. I can try to persuade myself that the #2, while clearly firing, maybe isn't running as well as 1,3,4 and 6. But that's based on IR gun on exhaust sometimes showing the temp a bit lower than the other four. However, because there is a hose clamp around the header about an inch below the flange at the port (holds the EGT probe in), the insulating effect of that clamp could account for this. The greatly reduced temps on #5, which also has a hose clamp and EGT probe, really tell the tale. Plus the plugs - all but #5 are, if anything, a bit sooty rich (not so much so that the tailpipes (stingers, really) for either side are sooty). All #5 shows is a slight film of oil, which seems reasonable to me given that the cylinder is pumping but not firing to burn any of that off, and not enough to prevent sparking.

Jon at Electromotive couldn't think of anything having to do with the TEC3r system itself which would cause one cylinder out of six not to fire.

James Bricken recounted a situation he encountered where there was just enough amperage or voltage or general oomph for one injector of a paired set to fire, but not the other. Simple to test: pull the plug on the good injector and see if the recalcitrant one fires. I did this. Engine slowed down to act like a 4 cylinder engine.

In case there was some hidden defect in the wiring, I pulled all the injector plugs off, but a lot of tie wraps, and put the right bank plugs on the left bank injectors, and vice versa.

Guess what - aaaargh, #5 still dead.

I'm toying with putting carbs back on to see if there is some hidden mechanical issue no one has put a finger on.

[Lapkritis]

If it's still waking up with carb clean/brake clean into the throat them it's certainly fuel related. I would replace that fuel injector (carry a spare or two for a race car isn't a terrible idea anyway). Make sure the injectors all match part#. Are they high impedance or low? Was the set purchased together? If low, does tec3 require resistor installation in the harness?

There are collector screens in the top of injectors where the fuel enters that may collect debris that makes it through the filter. Invert it, tap it out and check for debris. Could be blocking fuel flow.

Cycle the pump with the feed line off then injector and confirm the flow in that line is clear.


Issue is here somewhere, you'll find it.

[WERK I]

Hi Walt,
Could you tell us a little about the crankshaft differences between the 2.8 LS and the 2.8 SS?

Have you clamped the timing light on cylinder #1 and get an idea what your initial timing is at idle?

If you're thinking of putting the carbs back on........
You could also swap ITB banks and see if the problem migrates over to Cylinder #2.

[RClewett]

Walt,

This thread was brought to my attention. Check your ECU connector and verify that all the terminals are making a good connection. This is under TEC Tips on our web site.

Inconsistent sensor values can be caused by poor terminal connections. We have seen instances where the terminals in the gray and white connectors have been spread open, causing a poor connection to the ECU. Carefully check each terminal with a .040 diameter pin. When the pin is carefully inserted into the terminal, there must be tension on the pin. If there is no tension, carefully remove the red terminal lock on the ECU connector. This procedure is in the TEC3r manual. With the terminal lock removed, all the terminals are in clear view. Each terminal has 3 fingers that make contact with the ECU connector terminals. With a pointed object, carefully push each of the 3 fingers to the center of all the terminals. Replace the red terminal lock, making certain that each terminal is fully seated in the connector. Verify that each terminal has tension on a .040 diameter pin. Don't neglect to visually check each sensor and injector terminals as well. We have seen a number of the sensor terminals which have been damaged, causing false readings.

It says for inconsistent sensor readings but also applies to outputs such as coils and injectors.

Regards,

Richard

[Walt Fricke]

A 2.8 LS is 92x70.4 (Porsche's 2.8 RSR's dimensions). A SS is 95x66 - about one cc larger.

Using a timing light on a waste spark motor is a bit tricky, as you get one per rev. And my crank pulley doesn't have any convenient marks at around 14 degrees advance. I have tried different advance settings in the programming, and they do move the idle RPM around some, but have no effect on the problem child.

I've swapped connectors bank to bank. Swapping the ITB units is problematic, as they would swap ends, so the linkage wouldn't fit. I could probably figure out how to get the MAT and TPS sensor leads lengthened.

Compared to carburetors, the ITBs are (or seem to be) so simple that it is hard to see what could go wrong. There are only two internal passages - the idle air bleed, and the vacuum drilling. These are older model ITBs, with a single throttle shaft on each bank, so the butterflies all have to (and do) open together.

Richard - thank you for the suggestion. I had read (reread, actually) the tips from your helpful website to see if something suggested itself. Until I started to troubleshoot this problem, the white connector had been in place and untouched for three years now (gray one too, for that matter). I did pull the white connector to do continuity checks on the injector ground wiring, and later futzing with firmware. The fundamental theoretical problem is why the same injector driver pin which serves two injectors would only work for one. Especially since that injector has been swapped around with no change.

I'm going to pull the fuel rails and all the injectors, and inspect all the passages, and swap injectors bank for bank. I can't imagine finding a dead fly larva blocking #5 somewhere where swapping 4 and 5 previously wouldn't have revealed or dislodged, but there has to be something.

[RClewett]

Walt,
You are correct with phased sequential or batch fire and swapping wires from side to side both ignition and fuel, would have exposed an electrical problem. Have you tried replacing the plugs. If it is specific to #5 there will be something, plugs, fuel or compression. One thing I've learned well over the years is to assume nothing. It's the simple things that will get you.

Richard

[WERK I]

Originally Posted by Walt Fricke

A 2.8 LS is 92x70.4 (Porsche's 2.8 RSR's dimensions). A SS is 95x66 - about one cc larger.

Walt & Richard,
According to Walt's info above, are the Clewett 60-1 pulley's interchangeable? Do different vintage cranks have different pulley key offsets?

The only thing left to do is ohm-out every pin on the connectors as Richard suggested. Makes sense; both engines were running before the Tec3r components were removed from one and applied to the other.
I may eat these words, but IT IS NOT A MECHANICAL PROBLEM. Not unless you stuffed a rag down #5's ports to protect the mechanicals.

[HawgRyder]

A good contact cleaner might help with electrical faults.
I use Stablilant 22 on all connections (learned in the military).
It is mandatory on all connectors on aircraft....you can't afford to have an intermittant while in combat!
Bob

[Walt Fricke]

Richard - I replaced the plugs on the right side early on. No joy. Today I pulled the right side injectors and inspected the fuel rail. Clean as a whistle, though I ran a bristle brush through it anyway. No hard shell beetle stuck in the center hole or the like. Now the #6 injector is in the #5position when I get around to starting it again.

I don't know how to get at the filter on the injectors, nor do I have a test rig (other than the ITBs and fuel rails themselves) to check things. Doesn't look like I can easily backflush (standard Bosch pintle injectors), but I squirted brake cleaner into the inlet end, and let it flush back out just in case and because I had them out.

I discovered that the brown color of the body of these Bosch injectors is paint, and a paint my carb cleaner dissolved. But one mottled appearing injector isn't going to hurt. I sprayed their male connector prongs with a contact cleaner. Since I have the former left side (aka the working side) connectors on the right side now, I'm not sure what good spraying the female parts on the plugs is going to do, but I can try that too.

Next is pulling the right lower valve cover to see if anything is amiss in there, and to check exhaust valve spring pressures (no high hopes for any of this, given how much of it I was able to check through the intake valve cover side, though).

In addition to the "why does one side work but not the other of paired functions" conundrum, I have checked the resistance of the plug wires involved, and of the injector wires, including back to the ECU connector output pin. Nothing amiss that I could tell with my ohm meter.

But ultimately something simple is going to have to come out of hiding.

[Walt Fricke]

Well, nothing amiss to be seen under the lower valve cover. That's an official Wil Ferch valve spring qualitative tester. #5 and #4 exhausts both equally stiff to the push, as one would expect. There is a bit of excess copper anti-seize on the headbolt by the #5 lower spark plug, but that's not unusual. You can see why it would be very hard for me to get the plug wires on the wrong plugs.

[Lapkritis]

Any chance to start since moving the injector? I have my eye on that guy.

[WERK I]

Lapkritis,
I think Walt already tried that.


Walt,
I just got over the very same problem with the turbo. There was a serious misfire/no fire on one the the cylinders. I immediately went to the plugs to check they were all properly snapped on the plug terminals. Got to #5 topside and found the plug connector loose on the plug. Tried to snap it back on to no avail. Pulled the plug off the Electromotive to inspect, nothing obvious. Pulled the plug out and found the terminal of the plug had snapped off! The rest of the plug was pulled out of the plug wire connector. I had found something wrong, but not what was causing my misfire. It's a twin-plug, so even if 5A does not fire, 5B does.
The plug 5A looked pretty fouled, so I decided to pull all the plugs. Everyone of them was carbon-fouled, badly. It must have been bad gas when I filled the tank last November and treated it with Sta-Bil. Winterized in this manner for the last 15 years and never gotten bit by it. Well, 12 new plugs and a bottle of Techron later, everything is back to normal.

Wish I could come up with something that would get you out of the dilemma your in Walt. Trying to think of something in the Tec3r that would pertain only to cylinder #5. Have you clamped on the timing light to plug wire 5A and then 5B with engine running to see if they are getting high voltage to fire the plugs?
Got get this narrowed down between fuel and ignition somehow. Hang in there.

[Walt Fricke]

I did clamp the timing light on 5A and B, and it flashed the same on them as it did on the numerous other wires I clamped it on. Because it is not a dialback, I can't really tell how spot on the firing is, or compare it with any other cylinders in terms of timing.

[WERK I]

I suppose #2 injector electrical connector could not be swapped for #5 and vice versa?

That fact you're getting ignition to #5 kind of rules out ignition. Even if it were off, timing-wise, you would probably get some sort of backfire up thru the throttle body.

Could it be a broken lead/bad crimp on the injector or the ECU?

[Lapkritis]

The brake clean response has me thinking either injector or driver.

[HawgRyder]

Andrew...if you are thinking that the brake clean adds combustibles to the chamber to get the correct fuel/air ratio...I agree.
Walt...I know this is left field...is it possible that the feed to #5 injector is somehow partially plugged?
Perhaps the joint in the fuel rail is restricting the flow to that one injector.
If it's a "T" junction...maybe the tail of the "T" has slipped too far into the main rail.
Bob

[johnman001]

What is the leakdown on #5?