1986 B2 2.9L - Fuel pump relay wiring issue

[Motech]

• CEL...typically it's a red light, and I don't see one. (bulb out?)

It's typically (by mandate) an amber light.

• I do see an "EMISS" light which comes on as the key reaches the "on" position, and briefly turns off as I rotate to the "start" position, when it lights again and stays lit. If this behavior is the same as CEL...then we also have a presumed good PIP signal.

If this is the CEL, and it lights up during cranking no-start, it indicates you are NOT getting PIP signal

 

[Jbrownjr]

Been a few weeks (travel and such), but back at it:

• Fuel pressure is good!
  • Since fuel pressure "seemed" (see next bullet) to be failing, we replaced the FPR (under warranty, thank you O'Reilly) yesterday.
  • Meanwhile I also discovered the Schrader adapter that came with the fuel pressure test kit had a loose pin (read: fell into my hand. O-ring seems to have gone missing.) O'Reilly just swapped me a good one today. After snugging up the connector(s) and turning the key, I was watching gas leak at the adapter until I applied Teflon tape. THEN pressure climbs within a few seconds to ~40 psi and stays there. While cranking it also stays strong (climbs just beyond 40 psi, but who's counting?)
• A good dose of starter fluid and she fires strong, but won't run. I'm without a helper today, so I can't confirm it'll run with just starter fluid, but this is progress!

I stumbled onto another thread with very similar symptoms which ended up being the computer, but as recommended above I can confirm that engine (EMISS) light does light in KOEO position, and stays lit during cranking. Now I'm still jumping the FP relay (lg/brn-to-battery-negative), and the pumps work as long as the key is on or in start. I'll address that later, but it's a symptom. So it appears we have spark and fuel pressure.

@Tiha - You mentioned "Could be a cam or crank sensor....After that we need to verify the injectors are firing."
Which do I test first, and how? (I did borrow a noid tester, but if it won't run, I'm wondering how I'd get them to fire and readout. During cranking, even if it won't start?

 

[L\Bronco]

Been a few weeks (travel and such), but back at it:

• Fuel pressure is good!
  • Since fuel pressure "seemed" (see next bullet) to be failing, we replaced the FPR (under warranty, thank you O'Reilly) yesterday.
  • Meanwhile I also discovered the Schrader adapter that came with the fuel pressure test kit had a loose pin (read: fell into my hand. O-ring seems to have gone missing.) O'Reilly just swapped me a good one today. After snugging up the connector(s) and turning the key, I was watching gas leak at the adapter until I applied Teflon tape. THEN pressure climbs within a few seconds to ~40 psi and stays there. While cranking it also stays strong (climbs just beyond 40 psi, but who's counting?)
• A good dose of starter fluid and she fires strong, but won't run. I'm without a helper today, so I can't confirm it'll run with just starter fluid, but this is progress!

I stumbled onto another thread with very similar symptoms which ended up being the computer, but as recommended above I can confirm that engine (EMISS) light does light in KOEO position, and stays lit during cranking. Now I'm still jumping the FP relay (lg/brn-to-battery-negative), and the pumps work as long as the key is on or in start. I'll address that later, but it's a symptom. So it appears we have spark and fuel pressure.

@Tiha - You mentioned "Could be a cam or crank sensor....After that we need to verify the injectors are firing."
Which do I test first, and how? (I did borrow a noid tester, but if it won't run, I'm wondering how I'd get them to fire and readout. During cranking, even if it won't start?

If you plug the noid light into an injector connector and it flashes while cranking, that means the PCM is trying to fire the injectors, and given that you have solid fuel pressure, the injectors would be at fault.
If it doesn't flash while cranking, check for 12V at the red wire on all of the injectors.
Hope that helps
Cheers

 

[Motech]

If it doesn't flash while cranking, check for 12V at the red wire on all of the injectors.
Hope that helps
Cheers

A step further...

If you have voltage at those injector leads @L\Bronco refers, and noid does not blink when cranking, check coil.

With test light hooked to battery negative, confirm KOEO power at both ignition coil terminals.

If good, switch test light clip over to battery positive, probe the dark green w/ yellow coil negative terminal and crank engine.

If no flash there, and no injector noid flash either, it's a triggering issue, likely PIP sensor.
You may get one flash when you turn key on, but ignore that. Should consistently flash when cranking.

 

[L\Bronco]

A step further...

If you have voltage at those injector leads @L\Bronco refers, and noid does not blink when cranking, check coil.

With test light hooked to battery negative, confirm KOEO power at both ignition coil terminals.

If good, switch test light clip over to battery positive, probe the dark green w/ yellow coil negative terminal and crank engine.

If no flash there, and no injector noid flash either, it's a triggering issue, likely PIP sensor.
You may get one flash when you turn key on, but ignore that. Should consistently flash when cranking.

Thats a good point Motech, but I believe he said it runs when he sprays starting fluid in the throttle body. It must have PIP.
Its a strange one.
cheers

 

[Motech]

Thats a good point Motech, but I believe he said it runs when he sprays starting fluid in the throttle body. It must have PIP.
Its a strange one.
cheers

My bad. Must've lost it in my head a page or two back.

I remember 25-30 years back struggling to grasp how perfectly good high pressure inline pump would fail to deliver fuel when low-pressure priming pump in tank failed.

Also, didn't those old systems eat pump electrical connectors for lunch? Been a while, but replacement units always included new, upgraded pigtail connectors we'd have to install as well.

 

[L\Bronco]

My bad. Must've lost it in my head a page or two back.

I remember 25-30 years back struggling to grasp how perfectly good high pressure inline pump would fail to deliver fuel when low-pressure priming pump in tank failed.

Also, didn't those old systems eat pump electrical connectors for lunch? Been a while, but replacement units always included new, upgraded pigtail connectors we'd have to install as well.

Yeah they did up here for sure. The way the vanes were mounted in the HP pump made them unable to draw much\any vacuum, so they could only pump from a full tank when the prime pump failed, they needed a little head pressure.

 

[Jbrownjr]

Good news!

With 40psi at the fuel rail, I moved on to the injectors - rather the injector connectors.
Noid light gets nothing when we crank. We tested all 6 and got nothing at all.
(The kit has a "Ford" light, but it's prongs don't seat into the slots. A GM light has slot pins and does seat well - if it matters)

I found the attached wiring diagram (attached), and I see the injector circuits, but the colors are off.

• At the injectors there's a black wire and either a brown or brown/black wire. Maybe it's "tan/blk" and "tan" - even though the drawing calls those out for the 2.3L? (We definitely have the 2.9L) Pulling the injector wiring harness, there is no resistance along any of the 3 circuits to all 6 injector connectors.
• The connector behind them is a 3-prong/wire: Dark Green, Red, Tan/Red. I get 12v at KOEO on the red wire. It looks like "Tan/Red" goes back to the computer (#59). I don't see any reference to the green wire.

1. What am I looking for in this gray connector? Voltage for each wire? (i.e. during starting attempts?)
2. If the injectors aren't firing, how did I get combustion when spraying starter fluid into the intake? (I'm just ignorant as to how the spark plugs firing and injectors firing work together to make it run?)

I think we're getting closer. This time hoping the testing tool (noid light) is not giving a false negative like the fuel tester was. The noid light kit did come plastic-sealed. (Brand new)

 

[L\Bronco]

Ok, sounds like progress.
First, your question, normally the injectors spray the fuel into the intake manifold and the spark plugs light the fuel at the right moment to creat combustion and the heat created pushes the piston down and so on.
Your 2.9 fired when you gave it a fuel source, so ignition is functional.
Now, onto the injectors. The eec relay supplies all 6 injectors with 12 volts when the key is on. The PCM supplies the ground to turn the injectors on at the right time based on signals from the ignition system. (Thats why they are so closely linked together. (No ignition, no fuel)
You have ignition so The problem is in the injection system.
Your 2.9 is bank fired, which means the pcm fires them in groups of 3. This is why there are 3 wires at the grey plug for the injectors. 1 supplies 12v to all injectors and 2 wires that go to the pcm That will be grounded by the pcm when it is time to fire the injectors. Your noid light didnt flash, so either the 12v isn’t at the injector plugs or the ground from the pcm (pulsing ground) isn’t getting to the injector plugs. Or the pcm isn't supplying the ground to fire the injectors.
Start by testing for 12v at the injector connectors. (All 6 injectors should have 1 of their wires being the same color.
That one should have 12 v.
Let us know what you find and we can go from there

 

[Motech]

The connector behind them is a 3-prong/wire: Dark Green, Red, Tan/Red. I get 12v at KOEO on the red wire. It looks like "Tan/Red" goes back to the computer. (#59). I don't see any reference to the green wire.

Green also goes back to PCM. It's listed as light green w/ white stripe, and PCM fires 3 injectors simultaneously.

On a ground controlled switch/solenoid/injector/actuator (they are all switches), power flows in and out, so until the "out" circuit is grounded to turn it on, it will have 12 volts present.

Therefore, when all your connectors are plugged in, you should have KOEO voltage at all three injector circuits.

• Red = voltage in
• Lt Grn w/ wht = voltage out (of three injectors)
• Tan w/ red = voltage out (of three injectors)

Hope that helps.

 

[Jbrownjr]

Big success tonight. She starts and idles!

After confirming 12v at the black wire (for each of 6 injectors) I was suspecting the computer. I figured we'd test for continuity between the green wire to ECU and the Tan/red to ECU. After confirming the pin numbers I went into the passenger side kick-panel area...

(Computer removed. )

Over the past few months of troubleshooting, at one point I was testing continuity to the ECU...and late one night intended to plug it back in - but never did. (Sigh...)
I feel like I've taken a night-school class in auto mechanics, tackling electrical components like I never have before. You guys are great, patient, knowledgeable instructors!

Thank you!!!
(Sorry for the wild goose chase around the back 40)
That said, now we KNOW the wiring is good to the injectors and a bunch of other switches/solenoids/connectors - or it wouldn't run!

Next challenge deserves a new thread...'Please join us next time for "1986 B2 2.9L acceleration hesitation"'
She idles pretty well, but upon acceleration, it chokes. (Fuel/air mixture?)...

 

[goodO1boydws]

Big success tonight. She starts and idles!

After confirming 12v at the black wire (for each of 6 injectors) I was suspecting the computer. I figured we'd test for continuity between the green wire to ECU and the Tan/red to ECU. After confirming the pin numbers I went into the passenger side kick-panel area...

(Computer removed. )

Over the past few months of troubleshooting, at one point I was testing continuity to the ECU...and late one night intended to plug it back in - but never did. (Sigh...)
I feel like I've taken a night-school class in auto mechanics, tackling electrical components like I never have before. You guys are great, patient, knowledgeable instructors!

Thank you!!!
(Sorry for the wild goose chase around the back 40)
That said, now we KNOW the wiring is good to the injectors and a bunch of other switches/solenoids/connectors - or it wouldn't run!

Next challenge deserves a new thread...'Please join us next time for "1986 B2 2.9L acceleration hesitation"'
She idles pretty well, but upon acceleration, it chokes. (Fuel/air mixture?)...

Sounds like it might be the throttle position sensor.
(Or maybe stale gas or a partially clogged fuel filter now that gas is running through....what is it, 2 years? )
Is the problem limited to a certain rpm range, or does it bog down EVERY time you accellerate, no matter what rpm you're starting from?

 

[L\Bronco]

Big success tonight. She starts and idles!

After confirming 12v at the black wire (for each of 6 injectors) I was suspecting the computer. I figured we'd test for continuity between the green wire to ECU and the Tan/red to ECU. After confirming the pin numbers I went into the passenger side kick-panel area...

(Computer removed. )

Over the past few months of troubleshooting, at one point I was testing continuity to the ECU...and late one night intended to plug it back in - but never did. (Sigh...)
I feel like I've taken a night-school class in auto mechanics, tackling electrical components like I never have before. You guys are great, patient, knowledgeable instructors!

Thank you!!!
(Sorry for the wild goose chase around the back 40)
That said, now we KNOW the wiring is good to the injectors and a bunch of other switches/solenoids/connectors - or it wouldn't run!

Next challenge deserves a new thread...'Please join us next time for "1986 B2 2.9L acceleration hesitation"'
She idles pretty well, but upon acceleration, it chokes. (Fuel/air mixture?)...

Congratulations! That's how it goes sometimes.
I was neck deep in wiring H E L L in my 79 Bronco Resto mod and sometime between moving the PCM under the dash and shortening the main harness to make it prettier, I forgot 2 of the 9 major grounds and I went from running and driving to a flashing theft light.
I feel your pain.
Cheers

 

[Motech]

Next challenge deserves a new thread...'Please join us next time for "1986 B2 2.9L acceleration hesitation"'
She idles pretty well, but upon acceleration, it chokes. (Fuel/air mixture?)...

Maybe so, the new thread thing, but check your MAP sensor vacuum supply first. Those old hoses can get pretty squishy, crack up some and blah blah blah. If it squishes, leaks and even flakes off black powder when rolling in your fingers, all that can cause similar symptoms and more.

 

[Jbrownjr]

Maybe so, the new thread thing, but check your MAP sensor vacuum supply first. Those old hoses can get pretty squishy, crack up some and blah blah blah. If it squishes, leaks and even flakes off black powder when rolling in your fingers, all that can cause similar symptoms and more.

We replaced the MAP and vacuum lines last year some time. Seems healthy.
All ideas welcome!

 

[L\Bronco]

If you hold the throttle steady while its bogging will it recover? Or keep dying?

 

[Jbrownjr]

If you hold the throttle steady while its bogging will it recover? Or keep dying?

It won't die. It'll recover...mostly.
It idles pretty well too, but did die a few times when left alone for a few minutes.

 

[chrlsful]

reports on progress (lack there of) ?
Let's hear how dat thing runs in da cold...
8^ )

 

[Jbrownjr]

Sorry for the slow response.
Success!
(30 second video wouldn't upload, so here's a link)

Tried to get the front end aligned, but the steering box was failing. Finished replacing that just last week.
Aesthetics at this point. Replaced the front seats from a donor. Putting all the trim back after replacing the headliner a few months back.

 

[Motech]

Success!
(30 second video

That's 30 seconds of an idling engine.
What was your fix?