EA82T Injectors Not Firing

[Tycho]

1985 Turbo Sedan (early MPFI)

 

Freshly rebuilt EA82T

 

Car cranks

Plugs spark

Fuel pump and pressure are good

Fuel injectors don't click

Plugs are dry after cranking

 

I took an injector off and bench tested it. Soon as I put 12v across it it clicks open, then clicks shut when I remove voltage.

 

Hooked up a noid light and cranked. No triggering on the injectors. Both sides of the injector plug sit at +12v the whole time.

 

Mutlimeter'd the wiring harness. Continuity all the way to the ECU.

 

It would seem the injector drivers are dead. Any other suggestions? Insufficient grounding?

 

I took the ECU apart. The injector drivers don't appear to have physically smoked out, tho they may still be dead.

 

I'm really want to get this thing on the road to see if it blows up as quickly as all the other EA82Ts out there. Then I can just rid myself of it. But I can't blow it up unless I get it started first!

[john in KY]

Had an 85 XT once with the exact same problem. Problem turned out to be a bad ground wire that attached to one of the intake manifold bolts on the passenger side of the engine.

 

Hooked up a noid light and cranked. No triggering on the injectors. Both sides of the injector plug sit at +12v the whole time.

 

This doesn't seem right. One side should have 12v but not both. For some reason voltage is being "backfed" from the ECU. I would unplug the ECU and determine which two wires are from the injector circuit. (The injectors are fired in pairs so the 4 wires from the individual injectors somewhere between the injectors and ECU become two wires.) If my multimeter shows these two wires are hot then that tells me there is a short somewhere between the injectors and ECU. If the wires aren't hot then the problem I would think is a short inside the ECU.

[Gloyale]

Hooked up a noid light and cranked. No triggering on the injectors. Both sides of the injector plug sit at +12v the whole time.

 

 

He was measuring with the plugs hooked up to the injector. the injector passes the voltage through....that's normal for there to be voltage on both sides when it's hooked to the injector.

 

 

tycho, test voltage on each connector with it unhooked from the injector.

 

Also....it's be a good Idea to ohm out each injector and make sure it isn't shorted.

 

Also, are you gettting any codes? Checked all fuses for the ECU?

 

Have you tested for a pulse on the injector wires at the ECU? that would help determine if the problem is in the ECU or the Circuit.

[Gloyale]

Here's a diagrahm I did showing the faulty crimp splices in teh XT harness. this is for an 88 so the wiring is late style, a bit different than yours.....but you can see the idea.

Do you have an 85 FSM available?

Edited August 11, 2010 by Gloyale

[rpholz]

should have 12v to them from the fusable links then ground at the computer. i just completely redid the wiring on my 89 XT due to the hack job the PO did:banghead:

[Tycho]

tycho, test voltage on each connector with it unhooked from the injector.

 

Also....it's be a good Idea to ohm out each injector and make sure it isn't shorted.

 

Also, are you gettting any codes? Checked all fuses for the ECU?

 

Have you tested for a pulse on the injector wires at the ECU? that would help determine if the problem is in the ECU or the Circuit.

 

Ah hah! I checked with the injector unplugged ... but not with all injectors unplugged. The second one of the pair was passing voltage through. I'll disconnect all of em and try that again. In theory two shorted injectors could steal all the current from the other two.

 

I'm not getting a check engine light, I have checked all the fuses, I have NOT checked for a pulse at the ECU.

 

Will try some of that stuff tonight.

[Tycho]

Well it wasn't the other injectors being plugged in, or ground (tho cleaning them did make the starter a lot more snappy).

 

I checked the codes again.

11: Crank Angle Sensor (no ref pulse)

14: Fuel Injectors #1 and #2 (abnormal output)

 

I also have a mystery wire. Black wire with a yellow stripe and a 1 pin "flat" connector (white/clear). It comes out of the ignitor harness with the wires that go to the coil. Goes to the knock control unit on the passenger side of the harness. WTH does the connector on the driver's side go to?

[Cougar]

I think error code 11, caused by a bad CAS sensor, will cause the trouble you are having. Have you pursued that problem? You may need to replace the CAS sensor. First make sure you are getting proper voltage to it.

 

I assume you seeing near battery voltage on the connections to the ECU for the injectors. This is a good sign as the voltage should be high when the injectors aren't turned on. When the ECU turns on the injector with a pulse the voltage then go low on the lead to the injector.

 

Make sure the fusible links are ok along with fuses 5, 11, and 12.

[Gloyale]

I think error code 11, caused by a bad CAS sensor, will cause the trouble you are having. Have you pursued that problem? You may need to replace the CAS sensor. First make sure you are getting proper voltage to it.

 

There is no CAS on the early MPFI. They use a conventional electronic ignition distributor, not the optical CAS style like later models.

 

Injector firing is triggered by a simple tach signal.

 

Are you getting a tach signal at the ECU?

[Tycho]

Brilliant. Checked the tach signal (which was white going into the ECU, not Yellow like the diagrams say) and it was very low amplitude. Checked coil- while cranking and it was a strong signal. Means I had some wiring wrong.

 

The tach wire is black where it comes out by the coil, so I had it on coil+ with all the other black wires, thus giving a super weak tach signal. Moved it to coil- and the injectors started squirting ... but the tach readout on the dash went wiggy. Grounded that mystery wire (goes from the disty to the knock control unit on the other side of the engine bay) and the tach readout stabilized and I still got fuel + spark.

 

Screwed with the timing a bit (advanced) and got it to ignite some fuel. MAF/intake stuff is all off/disconnected, but if I cranked it with the throttle all the way open it would start and sputter along at 600 RPM or so. Need to check my dist. timing again I'd say.

 

Thanks for the troubleshooting tips. If the harness were anything close to properly color coded this'd be a lot easier! Never remember this much nonsense on my SPFI '90 Loyale.

[Gloyale]

I think you are looking at diagrahms for the wrong years.

 

I looked up codes in the 86 FSM. yesterday.

 

Code 11 is "no ignition pulse"

 

And code 14 is MAF.

 

injector code is like 42 or something high like that, and it's only one code...not paired like later years.

 

I'll bet even the 86 FSM may have wrong colors for your 85, as alot of stuff was wonky in those old ones.

 

wish i still had a working scanner. I could scan you the 85 and 86 FSMs'

 

Anyhow....glad you got it figured out.

[Tycho]

That's probably it. I was looking at diagrams for "1985 EA82T" in a Chilton's (far cry from a FSM) and an '87 FSM scanned code page I had downloaded some time ago. Thanks for the additional info. Was still getting Code 14 and all the injectors are working fine ... but the MAF isn't plugged in (now that makes sense). Figured 'pre '88 would be good enough, but these cars seemingly have about the most variation of any "mass produced" car ever.

 

Anyway, thanks again. Time to overheat it and blow a headgasket or two

 

Should be 100% up and running this weekend, and if not ... I'll splice the harness and put my EM4F on there and be done with this '80s EFI stuff (this is how I dealt with a 1985 Toyota with almost as many broken vac lines as broken wires).