• Welcome Visitor! Please take a few seconds and Register for our forum. Even if you don't want to post, you can still 'Like' and react to posts.

1987 Bronco II extremely low voltage only at in-tank fuel pump connector


RobbieD

2.9l Mafia
Joined
Aug 6, 2007
Messages
3,985
Reaction score
3,606
Points
113
Location
Georgia
Vehicle Year
1984,1990,1994
Make / Model
Ford
Transmission
Manual
2WD / 4WD
2WD
My credo
Toonces drives a Ranger . . . . just not very well.
So, when the problem first started through now, neither pump will run?

Does the fuel pimp relay click when you turn on the key or jumper the test connector?

Do you have power at the inertia switch?
 


TastierCash

New Member
Joined
Feb 23, 2024
Messages
24
Reaction score
2
Points
3
Location
Mississippi
Vehicle Year
1987
Make / Model
Ford Bronco II
Transmission
Automatic
So, when the problem first started through now, neither pump will run?

Does the fuel pimp relay click when you turn on the key or jumper the test connector?

Do you have power at the inertia switch?
Neither pump will run, the fuel pump relay does click and complete the connection and the inertia switch reads 12v when I touch the multimeter leads to the wires.
 

RobbieD

2.9l Mafia
Joined
Aug 6, 2007
Messages
3,985
Reaction score
3,606
Points
113
Location
Georgia
Vehicle Year
1984,1990,1994
Make / Model
Ford
Transmission
Manual
2WD / 4WD
2WD
My credo
Toonces drives a Ranger . . . . just not very well.
OK, inertia switch has +12V going in AND out. Do confirm that both the Orange/Lt Blue (power in) and Black/Pink (power out) both have +12V.

Then, check the Black/Pink wire at connector C161. Again, you want to probe both sides, to confirm that power is going IN and then OUT of the connector. On the OUT side of the connector C161 there should be TWO Black/Pink wires crimped into the single terminal, one power wire to each of two fuel pumps.

If you found +12V coming out of C161, then you should also find it at each fuel pump's Black/Pink wire.

If you do reach the point, where you can confirm power at both fuel pump connectors, if the pumps still don't run then the fault will likely be an open circuit on the pumps' ground wire.
 

TastierCash

New Member
Joined
Feb 23, 2024
Messages
24
Reaction score
2
Points
3
Location
Mississippi
Vehicle Year
1987
Make / Model
Ford Bronco II
Transmission
Automatic
I have yet to check all of the wiring, however I do know that the inertia switch has power in and out and that what I believe to be c161 has power going in, I have yet to check going out of 161 or anything past it again. I do plan on doing at least a half teardown of the engine to check the pistons and the interior components of the engine soon, I haven't decided whether I am or not yet. I did have an issue where a bolt from the EGR valve snapped off halfway through removal but the other came out fine, however once I welded a nut to the end of the broken bolt and removed it I noticed that it looks like the threads got cross threaded at some point and I don't know what I should do about it. It looks like its only cross threaded about halfway through the threads on the intake but before and after the halfway point it looks fine. I also should have mentioned (if I haven't already) that I currently have the upper intake manifold removed from the engine. If you have any ideas please let me know. Thank you.
 

TastierCash

New Member
Joined
Feb 23, 2024
Messages
24
Reaction score
2
Points
3
Location
Mississippi
Vehicle Year
1987
Make / Model
Ford Bronco II
Transmission
Automatic
So I never got to checking the wiring, but the other day I installed new fuel injectors and afterwards the pump in the tank started working again and the truck fired right up. I really don't know why it started working again randomly but I've yet to check the frame mounted pump to see if it works. I've also now found a different issue, some vacuum lines seem to be disconnected from where they should be and I have no clue where they go.
 

SenorNoob

Well-Known Member
TRS Event Participant
Joined
Oct 24, 2012
Messages
2,488
Reaction score
632
Points
113
Location
Middle Tennessee
Vehicle Year
1988
Make / Model
Ford
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Manual
2WD / 4WD
4WD
Total Lift
1.5" Front + 4" Rear
Tire Size
245-70-R16
If it's still readable, there is a diagram on the core support of vacuum lines.
 

TastierCash

New Member
Joined
Feb 23, 2024
Messages
24
Reaction score
2
Points
3
Location
Mississippi
Vehicle Year
1987
Make / Model
Ford Bronco II
Transmission
Automatic
@SenorNoob
If your talking about the diagram next to the hood latch then it is still there, however I don’t really know how to read those diagrams and I don’t know if it would help much with a few of them. Specifically one that has a T joint has it go in a total of 3 directions.
 

SenorNoob

Well-Known Member
TRS Event Participant
Joined
Oct 24, 2012
Messages
2,488
Reaction score
632
Points
113
Location
Middle Tennessee
Vehicle Year
1988
Make / Model
Ford
Engine Type
4.0 V6
Engine Size
4.0
Transmission
Manual
2WD / 4WD
4WD
Total Lift
1.5" Front + 4" Rear
Tire Size
245-70-R16
I am. The lines on the diagram are only useful for where they end. One line is one hose with no breaks.
Can you post a picture of the sticker and the lines in question?
 

Uncle Gump

Token Old Guy
TRS Event Staff
TRS Forum Moderator
Supporting Member
VAGABOND
TRS Event Participant
TRS 25th Anniversary
Joined
Sep 17, 2018
Messages
14,068
Reaction score
13,637
Points
113
Location
Ottawa IL
Vehicle Year
2006/1986
Make / Model
Ranger/BroncoII
Engine Size
4.0L SOHC/2.9L
2WD / 4WD
4WD
My credo
Lead follow or get out of my way
So...

From my 86 EVTM... not alot there... I'd say they missed at least some of the "mark".

Should be a speed density fuel system so... you'll have a MAP sensor. The other engine port is EGR/EVAP duty.

20240412_104821.jpg
 

Uncle Gump

Token Old Guy
TRS Event Staff
TRS Forum Moderator
Supporting Member
VAGABOND
TRS Event Participant
TRS 25th Anniversary
Joined
Sep 17, 2018
Messages
14,068
Reaction score
13,637
Points
113
Location
Ottawa IL
Vehicle Year
2006/1986
Make / Model
Ranger/BroncoII
Engine Size
4.0L SOHC/2.9L
2WD / 4WD
4WD
My credo
Lead follow or get out of my way
There is also HVAC somewhere...

If your label is readable... post it.
 

Sponsored Ad


Sponsored Ad

Staff online

Members online

Member & Vendor Upgrades

For a small yearly donation, you can support this forum and receive a 'Supporting Member' banner, or become a 'Supporting Vendor' and promote your products here. Click the banner to find out how.

Latest posts

Truck of The Month


Mudtruggy
May Truck of The Month

Recently Featured

Want to see your truck here? Share your photos and details in the forum.

Follow TRS On Instagram

TRS Events

25th Anniversary Sponsors

Check Out The TRS Store


Sponsored Ad


Sponsored Ad

Sponsored Ad


Amazon Deals

Top