FI enrichment effects on idle and vacuum.

[siteunseen]

3 minutes ago, Dave WM said:

I have a pressure vessel that is used for flushing AC parts, I can use it with a regulated air pressure supply to supply fuel. Also have 6 injector plugs that I can wire up to activate. will use 6 separate vessels to capture flow to evaluate.

Take some pictures for us, you may have found a way to make it easier.

This was the easiest way for me to set the floats on my 240.  

 

[Chickenman]

Dave there is also an adjustable Air Bypass on the AFM of 75 and 76 models. May be hidden by a small plug. Lower right corner of the AFM. You can adjust your idle ADR with this. Makes quite a difference. 

I believe that the FSM says there is no adjustment. for Idle mixture. But that's not true. It's plugged only for Emissions purposes. 

 

[Dave WM]

I will look into that if the injector service does not resolve it. I just made two videos #1 with the miss and #2 looking much better. I have already confirmed its not a spark issue by using one of those spark gadgets, so I know its getting ignition. Compression was checked and ok as well. I can hear the injectors clicking away, so I presume its not an electrical issue to the injector coil, so by process of elimination I think it has to be something impeding the flow not as designed, presumably dirt or some other blockage.

[Dave WM]

 

 

[Zed Head]

I put all six of my injectors on a rail with a pump then filled 6 Coke bottles with fuel.  Battery power to the pump and the injectors, with a separate switch for both.  Scary because the fuel is partially vaporized as it squirts out, especially if you try later model injectors.  Have to be aware of the wind direction, sparks, and run-away paths.  Only good for wide open but will show clogs.  The set that came with my car were way out of balance.  But the engine still ran pretty well.

The idle air adjustment screw is a good idea.  Just make sure to keep track of the turns so you don't get lost wondering where your start point was.  But it will definitely have an effect.  The EFI systems were tuned for mid-1970's fuel so today's oxygenated blends probably won't idle the same, for sure.  I didn't feel bad about changing my settings at all.  It's hard to get the screwdriver head, straight blade, in the slot, but it is back there.  Use a mirror.  Backing out lets more air past the vane, so leaner, screwing in makes it richer.  It's an air passage.

My intake manifold is the non-EGR N42 type.  #1 is always lean, I've swapped several sets of injectors on to it, after flow-testing them to confirm that they're balanced.

[Captain Obvious]

I've never used a colortune so it was neat to see one in operation. Neat.

I can provide one potential answer about one thing... There is an "after start enrichment" that adds a little extra gas for a little bit after the starter stops spinning. Lasts maybe thirty seconds or so? I found and poked around with the section of the ECU that performs that task, and it tapers off over the first 30 seconds or so. That might be why you aren't seeing the misfire until a little bit after you start the engine. (For those of you that geek out about this kind of stuff... It involves PNP transistors, film caps, and high value resistors. In other words... Bosch analog voodoo.)

So about the colortune... On the video of #2. When you rev the engine and then release the throttle, I can see the bright blue ignition spark when the ignition spark is still occurring, but the mixture is too lean to ignite. The whole plug circle doesn't light up, but the narrow strip of the ignition spark gap still does.

But on the video of #1 when you rev it and then release the throttle, I can't see that same phenomenon. Is there a healthy spark during deceleration that I just can't see? I'm just making sure we're hunting a fuel problem and not anything possibly having to do with ignition.

[JSM]

7 hours ago, Dave WM said:

IIRC pulling the injectors requires removal of the fuel rail. As such it seems in the interest of science it would be a good opportunity to hookup a fuel supply at 30 psi and do my own flow test prior to professional cleaning. I am hoping to replicate the imbalance of 1&3 to confirm the colortune as a viable approach to diagnosing flow issues, esp at idle duty cycle rates.

I've got an injector pulser I made and an extra fuel pump if you need to borrow them. 

Edited August 29, 2017 by JSM

[Zed Head]

Another source of lean is a leak at the injector-manifold interface.  The o-ring (edit - actually o-shaped gasket).  You can test that with carb cleaner or starting fluid.  Both might remove paint though (they did on mine).  WD-40 might show something also or even plain old oil, in sealing up a vacuum leak.  Whatever way, a change in idle behavior is the clue.

Edited August 29, 2017 by Zed Head

[Dave WM]

9 hours ago, Zed Head said:

Another source of lean is a leak at the injector-manifold interface.  The o-ring (edit - actually o-shaped gasket).  You can test that with carb cleaner or starting fluid.  Both might remove paint though (they did on mine).  WD-40 might show something also or even plain old oil, in sealing up a vacuum leak.  Whatever way, a change in idle behavior is the clue.

ZH, I have some new o rings to install so that will be done.

Capt, maybe but I did check it with a spark tester (the kind that flashes) never had any indication of missing spark

JSM, thanks I will let you know.

At this point I am pretty much committed to pulling them for testing at least, and prob cleaning. I know I should flow check before I get cleaned will come down to how much time I have to mess with doing a setup. I presume the shop I take it to will do a flow test and give me the results, prob is I will not know if 1&3 were the problem.

[Captain Obvious]

Dave, I don't know if there was an ignition problem or not, but I was just pointing out something different on the two videos. Maybe it was just different indexing of the colortune when threaded into the two holes. Maybe on cylinder 2, the spark gap was on the visible side and hidden when installed in cylinder 1? There's a dark spot in the ring on cylinder 1 video. Maybe that's the shadow cast by the ground strap electrode strap? If that's the case, then the spark would be 180 degrees from that and would be hidden by the plug boot?

Would be neat to have two (or six!) colortunes installed at the same time for easier comparison in real time.

[Captain Obvious]

And about injector testing... I checked my injector balance a little while ago. I bought a pack of small plastic containers. I think it was an eight or twelve pack of containers from the dollar store. I used a small hole punch to cut a hole in the lid of six of them:

I weighed them empty to get the tare weight. Thankfully they were all the same (at least to the resolution and accuracy of my cheapo HF digital scale) at seven grams empty:

Numbered them up so I knew which was for each cylinder:

Disconnected the fuel rail from the head and thankfully there was enough flexibility to get the cups onto the ends of the injectors:

fired the injectors a bunch (I used a sig gen tied into the ignition system) and collected samples:

Weighed them up again and verified they were the same (again to the resolution and accuracy of my cheapo HF digital scale), so I'm happy:

[EuroDat]

Hey Captain,

That method looks firmiliar...

I found number 3 and 4 injectors were cloggeed using that method by lifting the fuel rail and making a simple container with masking tape for a lid.