Electrical 88 EEC Injectors batch firing ?

[Dustin 86GT]

I’m rescuing my 88 Notch and have a fully rebuilt engine and powertrain installed. Car ran 6 years ago when parked. I am having a very strange issue and looking for some ideas as I am not sure what to do next.

I have a weird issue where my injectors are batch firing on crank. It is an SD card with a good DA1 computer ( I have two and both are good and tested). I have following all the “crank no start” threads and everything checks out fine. I even pulled the rail off and zip tied the injectors and watched them all pulse together. They also don’t pulse long enough to actually move enough fuel to fire the engine. FP is where it should be etc. car will run on starting fluid fine and the PIp and TFI work as they should. Tried a spare good distributor and same issue was present.

I tested another spare injector harness and same issue. Tested continuity of individual grounding pins to the man eec connector and nothing weird was found. I’m at a loss…

Could I have an issue with my salt and pepper connection on the harness side leaking the grounding signal? I’ve checked all the grounds on the harness and computer and they are good.

Anyone ever had or seen this issue? I’ve read all I can find, including the Probst Ford EFI Bible and nothing makes sense anymore. Thoughts of what I can try next? Any ideas welcome. Thanks!

 

[AeroCoupe]

So when you say the ECU's test good do you mean you sent them off and a 3rd party tested them and said they were good? If you are concerned about the salt and pepper shakers leaking a ground signal just back probe them with a DVM and see if they have continuity.

 

[Dustin 86GT]

Thanks for the reply. I have a good ECU. Did some more testing last night and checked the shakers, and yes, I have continuity back to the ECU connector - nothing weird. Used a Noid light, and seems like I have a very weak and almost intermittent injector pulse, but I have 12V at all the injectors. The PIP appears to be good, as the spark is strong and my tach signal is present when trying to crank.

I will check all the grounds for the injector harness and ECU this evening, as it seems like I'm having an issue with the grounding signal strength. I suppose the PIP could be failing too, so I will check the continuity of the PIP signal wire to the ECU.

Anything else obvious I should be checking? I'm stumped...

 

[Mustang5L5]

How are you confirming that you are getting batch fire on crank? What about when it runs?

The ECU has a sticker on it which confirms which method of fueling it uses. Batch fire vehicles will say EFI and sequential will say SFI

A DA1 will say SFI-SD on it confirming its a sequential fuel injection setup.

There is a difference in injector harnesses between SFI and batch fire cars, however the differences would manifest at all times. In a sequential setup I believe it fires the wrong injectors in sequence. But nothing in the wiring would cause it to be batch fire only during crank and sefi when running, which is why i asked how you are confirming that both conditions exist.

 

[Dustin 86GT]

How are you confirming that you are getting batch fire on crank? What about when it runs?

The ECU has a sticker on it which confirms which method of fueling it uses. Batch fire vehicles will say EFI and sequential will say SFI

A DA1 will say SFI-SD on it confirming its a sequential fuel injection setup.

There is a difference in injector harnesses between SFI and batch fire cars, however the differences would manifest at all times. In a sequential setup I believe it fires the wrong injectors in sequence. But nothing in the wiring would cause it to be batch fire only during crank and sefi when running, which is why i asked how you are confirming that both conditions exist.

The reason I believed it was batch firing is that when I was testing the injector pulse with a spare good distributor and TFI, I could hear that all the injectors appeared to be "clicking" at the same time. When I plugged in a spare harness with a couple of injectors, it also seemed like the injectors were all firing continuously under signal from the PIP. However, I do have the correct SFI-SD ECU. However, when I pulled the rail and mounted the injectors above the intake and watched the video of the spray patterns under crank, it does appear that I am getting sequential firing of the injectors now. It is hard to tell as the spray pattern is very weak despite having 40psi of FP. It seems like I have a weak injector pulse overall, despite having 12V at each injector. The injectors have been checked and are good - fresh rebuilt and bench tested. I have other injectors I can try as well, but I really think I have a weak grounding signal to the injectors. Regardless of switching combinations of good TFI, PIP, and ECUs the problem remains and is consistent. It seems like the engine is not getting enough fuel to run, as it will run on starting fluid. Any suggestions?

 

[gkomo]

Could there be a clog/disruption in the fuel rail downstream of where you are taking the fuel pressure readings?

 

[Dustin 86GT]

Could there be a clog/disruption in the fuel rail downstream of where you are taking the fuel pressure readings?

Rail has been checked - good idea - but definitely not a plugged rail. Consistent issue with all injectors and there is good pressure to each injector.

 

[Dustin 86GT]

Spent a few more hours last night and have noticed my issue has changed a bit now. The injector signal strength has weakened to the point that a Noid light won't fire (just a glimmer of color in the bulb - and all injectors have >12v and ground connections are good). I also seemed to have lost signal to the coil, which is a new problem. I went and rechecked all the ground connections, and things tested fine. However, when I pulled the distributor to rotate it by hand to test for spark and injector pulse with KOEO, there was an obvious short from the distributor to the block. There is actually an arc that forms between the distributor body and whatever it touches. I had installed a new TFI, but now it seems like it could be an issue with the PIP sensor. I have one on order and will check things out as it really seems wrong that the distributor would be arching to the engine.

Has anyone ever experienced this kind of issue before?

 

[Flyboy60]

Sounds like you have a wire in the wrong place and maybe causing a high resistance short circuit. Check ALL your wires again... even fuses. Get a multimeter and go slowly and methodically leaving no wire untested.

 

[Dustin 86GT]

I thought it would be good to report back and close the loop on this thread. In the spirit of keeping forums alive, I hope this helps.

I ended up going back through the "crank no start" entire checklist again, reviewing all the steps. What I found is that indeed I was getting some very weak injector pulse, which I was able to diagnose by pulling the rail and injectors and observing the actual spray pattern. Yes, this is sketchy as hell, but allowed to actually see what was happening.

What I found was that indeed all the injectors were batch firing, but with very small amounts of fuel. I then put the system back together and tried another new noid light on an injector and could barely see the flicker of light.

I then checked every ground, every connection, tested every wiring lead, all sensors, and even the ignition wiring. The one item I could not test easily ended up being the culprit. Before I reveal, I want to share a bit more background. I have the Bentley Ford manual and service manuals, and another couple of Ford FI books, but none of the books directly have a workflow for the issue I was experiencing.

I then turned to Gemini AI and told it everything I was dealing with and used it for troubleshooting as well. In under an hour AI told me that if the MAP sensor fails in a specific way, it can lead the EEC to believe you are at 30,000 feet of altitude and will choke the injector pulse to a mere drip. In my case, I picked up a new MAP and plugged it in, and my problem was solved. I was shocked it was that simple a problem after all the work I had done to date. I suppose a MAF car wouldn't face the same fate since it has another sensor to determine air flow, but for an old SD system, the MAP is a key element to the EEC.

I made a quick YouTube video about it.

 

[gkomo]

Glad you got it sorted out.

I don't use AI much, but it has come in handy for helping with car issues/installation processes.