This the first group of tests some of you may recognize from the FSM.  At the beginning of today, I flunked this thing BAD.  Spent a lot of time tracing down grounds/wiring issues and made some improvements. Results of before and after are:

• 1-1 (throttle valve)
  • Before: Fail, 2-3Mohm.  
  • After: Pass
• 1-2 (throttle valve open)
  • Before: Fail, open circuit
  • After: Pass
• 1-3 (AFM)
  • Before: 180 ohm, 180 ohm, 100 ohm
  • After: Same
• 1-4 (air temp sensor)
  • Before: 1.7 Kohm  (weird temp reading)
  • After: Pass, 2.3 Kohm
• 1-5 (water temp sensor)
  • Before: Fail, 8 Mohm
  • After: Pass, 2.3 Kohm
• 1-6 (air regulator)
  • Before: Fail, 27 Mohm
  • After: 61 ohm (?)
• 1-7: Pass
• 1-8: Pass
• 1-9: Pass
• 2-1: Pass
• 2-2: Pass
• 2-3: Pass

Where a "Pass" is a resistance of just a few ohms.  Even after "fixing" these wiring issues, still won't start.  Injectors still not pulsing while cranking.  I didn't have time to focus strictly on EFI wiring, but cleaned as many grounds as I could get my hands on.  Maybe drop resistors aren't supporting enough current, or issue at relay pins like Zed Head mentioned...

Well the biggie is the water temp sensor, at 8meg it would run big rich, the 2.3k must have been a cold engine (not run in a while, long enough to cool down). the air regulator must be the heater resistance. the water temp sensor should have made a huge diff.

One more possibility - bad or disconnected ground on EFI circuit.  It's been known to happen.  It's the wire at the negative terminal of the battery with the plastic connector.

Confirm power to the injectors.  While starting.

  On 10/21/2019 at 4:27 PM, Zed Head said:

One more possibility - bad or disconnected ground on EFI circuit.  It's been known to happen.  It's the wire at the negative terminal of the battery with the plastic connector.

Confirm power to the injectors.  While starting.

Interesting... The negative side of my battery only had one thick wire to it, nothing else.  It went straight to the big engine/transmission ground bolt (cleaned it up).  Maybe that plastic connector/wire is "grounded" somewhere else, or maybe it's just dangling back there somewhere.  Any ideas where that EFI ground comes from or where I should look?

Next time I'm with it, I'll definitely check power to the injectors during starting.

It's supposed to be attached to the firewall near the battery.  It looks like the one that goes to the positive terminal.  They sit close to each other and sometimes get switched by accident.

You don't show the ground test in your list.  Testing grounds is probably the most commonly overlooked test for automotive electrical problems.

  On 10/21/2019 at 5:21 PM, Zed Head said:

It's supposed to be attached to the firewall near the battery.  It looks like the one that goes to the positive terminal.  They sit close to each other and sometimes get switched by accident.

You don't show the ground test in your list.  Testing grounds is probably the most commonly overlooked test for automotive electrical problems.

Ahh, ok.  There was a random wire that was grounded to the firewall near the battery.  Had no idea what it was for, but cleaned it up anyway.

Can you elaborate on the ground test? Test 1-8 in the FSM passed and seemed to relate to the grounds to the ECU wiring harness.  But I'd love to have a more thorough test of the overall grounding.  Is there a detailed test in the FSM?

https://images.app.goo.gl/D7RiZctxWPzutAsL9

 

 

Edited October 21, 20195 yr by siteunseen

Yes.

Ah yeah, I did those.  It just didn't fit in my screenshot.  All of 1-8 tests passed with basically no resistance.

  On 10/21/2019 at 5:31 PM, siteunseen said:

https://images.app.goo.gl/D7RiZctxWPzutAsL9

Thanks siteunseen.  Hard to tell if there are multiple wires going to that firewall ground, I know I only had the one black wire.  

We're in the very common troubleshooting loop of "I already did that".  You're about at the point where you just have to understand how the system works.  The first few pages of the engine fuel chapter tell you what is supposed to happen.  The injectors open when the power is grounded, they stay open for a length of time that is determined by things like temperature and how far open the AFM vane is, etc.

Once you start thinking that way you'll have new ideas.  Seems like you've done a bunch already that you haven't described, and haven't done some of the things that have been suggested, like confirming power to the injectors during starting.  Good luck.

 

  On 10/21/2019 at 5:59 PM, S30Grit said:

Thanks siteunseen.  Hard to tell if there are multiple wires going to that firewall ground, I know I only had the one black wire.  

I'm sure it's just one and I've seen many that have melted the insulation off that wire.

Sand the firewall too under there.

Edited October 21, 20195 yr by siteunseen