1987 Ford Bronco HELP

B-Co Kid

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1987 Fullsize Bronco

351W 5.8L 4 BBl Holley

Gibson Headers

True Duals

Ok here goes (takes a deep breath in)

I have a 87 Full size, 5.8L 351W HO 4bbl Holley (stock). Rebuilt engine, tranny, and rear end. I guess the first problem that i have is,

there is not a whole lot of info and/or discussion on my particular truck. With that said, my rear antilock brake light has been on

for a while. The front brakes locked up once and was smoking. When i finally got the truck home, i bled the brakes. All of the brakes calipers bled

fine, except the rear passenger. It had to be pumped a few times, and finally fluid shot out. So im sure dirt or grime was lodged in there. Needless

to say, the front brakes havent locked up again. When braking, the truck doesnt stop like it is suppose to.

So, i finally did a check on the ABS system and it returned a code#7 Shorted isolation valve or defective ABS module. I saw on

another discussion board that there is no way to repair this problem. The ABS hydraulic unit has to be replaced. When i checked the procedure

for replacing the ABS module in my Haynes manual, it gave the procedure but then it also said that after it has been replaced, it will not work

effectively until it is taken into a shop that can correctly set it up. I think that is only for the all wheel ABS, but im pretty sure my vehicle

only has rear wheel ABS. If i replace the ABS unit, do i have to take it into a repair shop as well so they can set it, or will it be good to go upon

installation, since its on rear wheel ABS?? Next,

Whenever i make a turn, left or right, while moving..the rpms drop substantially (to about 300-500 rpms). And when i come to a hard stop, the same thing happens. I was told that it is probably my fuel pump, but just about everything is pretty much new on my engine. Is this an inherent problem with mechanical fuel pumps if this

is the problem? If its not the problem, what else could it be? carburetor is new or newish (remanufactured). fuel filter is new. fuel pump..new. wires and plugs..new

fuel lines..new.

 

miesk5

96 Bronco 5.0
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yo, for the RABS; from Chilton On-Line via most local Public Libraries (need you Card's Bar Code Number to enter site via you Library)

Rear anti-lock brake system testing-except 1993-96 Bronco models

CODE 7 Troubleshooting; inclides connector Pin-Outs

http://content.chiltonsonline.com/content/images/8492/images/84929116.pdf

http://content.chiltonsonline.com/content/images/8492/images/84929117.pdf

--

Next is to Pull EEC Codes for the other issue;

a Self Test by BroncoJoe19 @ http://broncozone.com/topic/14269-code-reader/page__pid__74587__mode__threaded

do the KOEO = Key On Engine Off portion first

& Remember to have engine @ Normal Operating Temperature before doing the KEY ON ENGINE RUNNING (KOER) portion

 

B-Co Kid

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yo, for the RABS; from Chilton On-Line via most local Public Libraries (need you Card's Bar Code Number to enter site via you Library)

Rear anti-lock brake system testing-except 1993-96 Bronco models

CODE 7 Troubleshooting; inclides connector Pin-Outs

http://content.chiltonsonline.com/content/images/8492/images/84929116.pdf

http://content.chiltonsonline.com/content/images/8492/images/84929117.pdf

--

Next is to Pull EEC Codes for the other issue;

a Self Test by BroncoJoe19 @ http://broncozone.com/topic/14269-code-reader/page__pid__74587__mode__threaded

do the KOEO = Key On Engine Off portion first

& Remember to have engine @ Normal Operating Temperature before doing the KEY ON ENGINE RUNNING (KOER) portion
Thats another problem i seem to have..i dont think my particular set up came with an EEC. And if it has one, i cant find it in

the area where it is suppose to be. I think i read somewhere, that the 87 B-co that came with the 4 bbl holley didnt have an EEC.

True or False?

 

miesk5

96 Bronco 5.0
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Thats another problem i seem to have..i dont think my particular set up came with an EEC. And if it has one, i cant find it in

the area where it is suppose to be. I think i read somewhere, that the 87 B-co that came with the 4 bbl holley didnt have an EEC.

True or False?
yo

Yep, I forogt that have the carb..

I know earlier yrs had the EEC3 w/MCU

Microprocessor Control Unit (MCU) Overview; "...The Microprocessor Control Unit (MCU) system was used on most 1981–83 carburetor equipped vehicles, and 1984 and newer V8 engines with feedback carburetors. The MCU system uses a large six sided connector, identical to the one used with EEC-IV systems. The MCU system does NOT use the small single wire connector, like the EEC-IV system. This system has limited ability to diagnose a malfunction within itself. Through the use of trouble codes, the system will indicate where to test. When an analog voltmeter or special tester is connected to the diagnostic link connector and the system is triggered, the self-test simulates a variety of engine operating conditions and evaluates all the responses received from the various MCU components, so any abnormal operating conditions can be detected.Diagnosis of a driveability problem requires attention to detail and following the diagnostic procedures in the correct order. Resist the temptation to begin extensive testing before completing the preliminary diagnostic steps. The preliminary or visual inspection must be completed in detail before diagnosis begins. In many cases this will shorten diagnostic time and often cure the problem without electronic testing.." READ MORE for Reading Codes & Diagnostic Trouble Codes (DTC's) Motorcraft & Carter use Solenoid to bleed air into idle & main metering ckts. Holley uses; remote solenoid with similar idle control; uses vacuum diaphram & valve for main metering control

Source: by Ford via arrc.epnet.com @ http://arrc.epnet.com/autoapp/7921vil/7921CH04_OBD_I_POWERTRAIN_DIAGNOSTIC_TRO.htm

try this;

EEC III Test by Tomco

http://www.tomco-inc.com/Tech_Tips/ttt3.pdf

As Steve83 once said, get the Red Haynes Manual

The red one is a VERY old edition, perfect for '80-86 trucks. It includes many older diagrams not found in later editions. For '87-96 trucks, a red cover that goes to '96, or an EARLY blue cover (as shown) would be much better because they contain much more info about EFIs, including superior wiring diagrams.



Unfortunately, the LATEST blue-cover edition has deleted much of this info, and isn't worth having.

 

B-Co Kid

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Oct 14, 2010
Messages
229
yo

Yep, I forogt that have the carb..

I know earlier yrs had the EEC3 w/MCU

Microprocessor Control Unit (MCU) Overview; "...The Microprocessor Control Unit (MCU) system was used on most 1981–83 carburetor equipped vehicles, and 1984 and newer V8 engines with feedback carburetors. The MCU system uses a large six sided connector, identical to the one used with EEC-IV systems. The MCU system does NOT use the small single wire connector, like the EEC-IV system. This system has limited ability to diagnose a malfunction within itself. Through the use of trouble codes, the system will indicate where to test. When an analog voltmeter or special tester is connected to the diagnostic link connector and the system is triggered, the self-test simulates a variety of engine operating conditions and evaluates all the responses received from the various MCU components, so any abnormal operating conditions can be detected.Diagnosis of a driveability problem requires attention to detail and following the diagnostic procedures in the correct order. Resist the temptation to begin extensive testing before completing the preliminary diagnostic steps. The preliminary or visual inspection must be completed in detail before diagnosis begins. In many cases this will shorten diagnostic time and often cure the problem without electronic testing.." READ MORE for Reading Codes & Diagnostic Trouble Codes (DTC's) Motorcraft & Carter use Solenoid to bleed air into idle & main metering ckts. Holley uses; remote solenoid with similar idle control; uses vacuum diaphram & valve for main metering control

Source: by Ford via arrc.epnet.com @ http://arrc.epnet.com/autoapp/7921vil/7921CH04_OBD_I_POWERTRAIN_DIAGNOSTIC_TRO.htm

try this;

EEC III Test by Tomco

http://www.tomco-inc.com/Tech_Tips/ttt3.pdf

As Steve83 once said, get the Red Haynes Manual

The red one is a VERY old edition, perfect for '80-86 trucks. It includes many older diagrams not found in later editions. For '87-96 trucks, a red cover that goes to '96, or an EARLY blue cover (as shown) would be much better because they contain much more info about EFIs, including superior wiring diagrams.



Unfortunately, the LATEST blue-cover edition has deleted much of this info, and isn't worth having.
So i dont have an EEC , but there is an MCU? or i dont have either one?

If i do have the MCU, where would i find it? How do i do a self test with the MCU?

I checked out that test by tomco-inc and i dont think my B-Co has a THERMACTOR AIR BYPASS (TAB) SOLENOID

or a THERMACTOR AIR DIVERTER (TAD) SOLENOID. Doesnt seem like that test would work for me.

My Blue Haynes manual is old, i got it when i first got my B-Co back in 2000. Its 11 years old so im assuming thats the old blue Haynes manual.

It covers everything for EFI models and carbureted models, but on the subject of doing self-test diagnostics, it only covers EFI models and using

an EEC. So since EEC testing is out of the question...what would be some reasons the rpms drop when turning or hard breaking? and as far as the

rear ABS, i will do the other diagnostic checks, but if the diagnostic check informs me that hydraulic ABS module has to be replaced, can i just replace it and be good back to normal or will i have to take it to a shop to have it set properly?

on a side note, the ABS diagnostic wire (orange/black) with the connector on the end, that i used to get the code #7, is it supposed to be connected back to something, because it was just hanging down and not connected to anything?? and also, where is the ABS MODULE HARNESS CONNECTOR located so that i can do the PINPOINT CODE 7 TEST?

 
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69bronc347

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i believe 86 was the split year, which had both carburation and fuel injection, but when they switched to the 87 body style all engines were fuel injected, so someone has converted back to carburation, so you are in a whole different ball game, as for the brake issue you can install a rabs unit your self, there is a bleeder on the unit to bleed it when installed, the idle drop issue i believe is caused by load from the powersteering pump, since there is no idle control motor to adjust idle, your idle is fixed by a adjustment screw on the carb, which will drop rpms when turning which would be a normal concern

 

Seabronc

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I don't know anything about anti lock brakes so no help there. However, 87 was actually the last year for a carbed 351W in the Bronco. If like 69Bronc347 says it is caused by the power steering pump load, you may have a problem with it. Do you have tires 33 x 12.5 or larger? If so you may want to consider doing a Saginaw Pump conversion. How does it idle in gear with the brakes on?(I am assuming that you have an automatic trany). If it seems like it is close to stalling, you may want to bump the hot idle up just slightly. That is done on a Holley carb by a screw that is just behind the throttle linkage. That takes a little trial and may take a couple of tries, just turn the screw a 1/4 turn in and see how it does. You don't want to do too much or it will be idling too fast in gear. About 500 to 700 RPM would normally give a comfortable stopped in gear idle. That will translate to about 1100 in Park or Neutral for an auto trany. If you have a manual trany then the idle, clutch in, be around 450 to 500 RPM.

Another factor to consider here is tha age of that carb, it may have some issues.

Good luck,

:)>-

 
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miesk5

96 Bronco 5.0
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yo,

RABS Self Test Diagnostic Connector Location; "...It comes out of a large loom under the dash, coming through the firewall, near the parking brake. On mine there are 2 similar connectors in that area, the correct one has only 1 black & orange (BK/O) wire running to it, & was hidden on top of the loom"

BK/O wire connects to pin #12 RABS Module



===

RABS Component Location



=============

For the MCU or EEC III; I haven't seen your year with all the orig equipt in years due to typical parts removal w/Out replacement and backyard work-arounds, so you'll need to look around the engine compartment and use the following as a guide;

For the TAD/TAB & Self Test Connector Location pic in 84-86;

Self Test Connector is RED (Steve titled it as the "EEC TEST Connector"

TAD/TAB is on the "right side" (passenger) near the AC/Ventilation Systems Vacuum Tank (black plastic ball type)

Source: by Steve83 (Steve, That dirty old truck) at SuperMotors.net



........

Self Test - & Connector Location Info in an 86; "...My Test Connectors and Battery are on the "right side" (passenger) behind a black EGR Vacuum Reservoir, my BKO is an 86 but as long as the Code Reader and Test Connector Plugs are the same it should be fine..."

Source: by JKossarides ("The Bronco", Jean)

 

B-Co Kid

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Seabronc is correct, 87 was the last year for carb'd 351W, and im quite sure everything was original on my B-Co

when i got it. As far as the power steering pump, i replaced it about a week ago with a remanufactured cardone (yeah yeah i know)

so that could possibly be the problem, nevertheless, it is newish. The carb is also a remanufactured Holley, so its newish.

The tires i have on there are 31x12.5x15. It is an automatic 3 speed, i think thats the C6. When it is in gear, with the brakes

applied, it idles fine. Its only when i brake hard or when making a turn while moving, that the rpms drop. And if my power steering pump

is the source of my problem when turning, what about when braking? I guess for now, i'll try idling up a little and see if that helps.

Update*

So i did the Pinpoint Code 7 test. After all was said and done, apparently i have a short in circuit 599 (PK/LGrn) between the module

and the RABS valve. It instructs me to repair the short and then proceed. Does this mean i have a bad ABS Module? When i tested the

resistence on the ABS Hydraulic unit, it was greater than 3 ohms, which is normal. So its not the hydraulic unit.

When i tested resistence at pin 13 on the abs module there was no reading (0.L) which is infinity or something right?

Im not very good with multi-meter stuff, but i think that means an open circuit or something. At normal, it should read greater than 10 ohms.

Me thinks me have a bad module. or could it be a short somewhere else? How much can a module run? are they even available anymore is probably a better question. Is it worth trying to correct this problem or can i do something to compensate? Another question i have is about the black and orange(BK/O)RABS Self Test Diagnostic Connector, is it suppose to be connected back to something, because mine was not connected to anything..

 
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Seabronc

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Seabronc is correct, 87 was the last year for carb'd 351W, and im quite sure everything was original on my B-Co

when i got it. As far as the power steering pump, i replaced it about a week ago with a remanufactured cardone (yeah yeah i know)

so that could possibly be the problem, nevertheless, it is newish. The carb is also a remanufactured Holley, so its newish.

The tires i have on there are 31x12.5x15. It is an automatic 3 speed, i think thats the C6. When it is in gear, with the brakes

applied, it idles fine. Its only when i brake hard or when making a turn while moving, that the rpms drop. And if my power steering pump

is the source of my problem when turning, what about when braking? I guess for now, i'll try idling up a little and see if that helps.

Update*

So i did the Pinpoint Code 7 test. After all was said and done, apparently i have a short in circuit 599 (PK/LGrn) between the module

and the RABS valve. It instructs me to repair the short and then proceed. Does this mean i have a bad ABS Module? When i tested the

resistence on the ABS Hydraulic unit, it was greater than 3 ohms, which is normal. So its not the hydraulic unit.

When i tested resistence at pin 13 on the abs module there was no reading (0.L) which is infinity or something right?

Im not very good with multi-meter stuff, but i think that means an open circuit or something. At normal, it should read greater than 10 ohms.

Me thinks me have a bad module. or could it be a short somewhere else? How much can a module run? are they even available anymore is probably a better question. Is it worth trying to correct this problem or can i do something to compensate? Another question i have is about the black and orange(BK/O)RABS Self Test Diagnostic Connector, is it suppose to be connected back to something, because mine was not connected to anything..
Just thinking about your tendency to stall on a turn or hard breaking. Since that is a reman carb, you might want to check to see if the fuel bowls are filling to the proper level. There is a sight plug in the side of each bowl. They when you remove the plug the fuel should be just at the bottom of the hole. If not you can do the float adjustment. If fuel runs out of it it is over filling and you will also need to do the float adjustment. Too little fuel may starve the engine when turning. And Too much may cause it to lug because of fuel dumping into the carb.

Good luck,

:)>-

 

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