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Old 07-04-2005, 02:01   #1 (permalink)
captainmuddy
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86 Bronco no voltage to fuel pump, a little help please

Ok, here goes: on my 86 Bronco (302 AOD) it decided to just up and stop on
me. I tried bypassing the fuel inertia switch, have replaced the fuel
relay switch, the fuel pump(first thing I did), the entire fuse panel, and
the computer. I've checked the ignition module and physically checked ALL
the wiring (I removed the front dash!) I've got 1.72v all across the ECC
relay. I'm supposed to have 12v at the hot wire and 12 at the igniton when
the key is on, but got the 1.72v I've checked all the ground wires I can
find, and all other systems work fine, just nothing at the fuel pump. Any
suggestions would be greatly appreciated. Allen captmuddy@yahoo.com

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Old 07-04-2005, 02:01   #2 (permalink)
Jim Warman
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Re: 86 Bronco no voltage to fuel pump, a little help please

I can't be sure that you are esting voltage drops properly but your testing
indicates a some kind of power supply concern. This could be either hot
side or ground side related. Brush up on voltage drop testing and repeat the
tests. While the explanation may be confusng, vlt drops are easy to perform
and do tell a story if read correctly.


"captainmuddy" <captmuddy@yahoo.com> wrote in message
news:8c662bcd4f5c56b1e3ba0805e6b00d49@localhost.talkaboutautos.com...
> Ok, here goes: on my 86 Bronco (302 AOD) it decided to just up and stop on
> me. I tried bypassing the fuel inertia switch, have replaced the fuel
> relay switch, the fuel pump(first thing I did), the entire fuse panel, and
> the computer. I've checked the ignition module and physically checked ALL
> the wiring (I removed the front dash!) I've got 1.72v all across the ECC
> relay. I'm supposed to have 12v at the hot wire and 12 at the igniton when
> the key is on, but got the 1.72v I've checked all the ground wires I can
> find, and all other systems work fine, just nothing at the fuel pump. Any
> suggestions would be greatly appreciated. Allen captmuddy@yahoo.com
>



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Old 07-04-2005, 10:02   #3 (permalink)
CJB
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Posts: n/a
Re: 86 Bronco no voltage to fuel pump, a little help please

I had an identical problem on my Father-in-Law's 86 Bronco. Turns out that
one of the negative for the fuel pump is fed straight from the negative
battery terminal. It was one of those smaller leads coming from the post
clamp. Anyway, it was simply a crimp connector that wasn't tight enough and
over time had lost continuity all together.

CJB

"captainmuddy" <captmuddy@yahoo.com> wrote in message
news:8c662bcd4f5c56b1e3ba0805e6b00d49@localhost.talkaboutautos.com...
> Ok, here goes: on my 86 Bronco (302 AOD) it decided to just up and stop on
> me. I tried bypassing the fuel inertia switch, have replaced the fuel
> relay switch, the fuel pump(first thing I did), the entire fuse panel, and
> the computer. I've checked the ignition module and physically checked ALL
> the wiring (I removed the front dash!) I've got 1.72v all across the ECC
> relay. I'm supposed to have 12v at the hot wire and 12 at the igniton when
> the key is on, but got the 1.72v I've checked all the ground wires I can
> find, and all other systems work fine, just nothing at the fuel pump. Any
> suggestions would be greatly appreciated. Allen captmuddy@yahoo.com
>



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Old 07-04-2005, 10:02   #4 (permalink)
Shoe Salesman
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Posts: n/a
Re: 86 Bronco no voltage to fuel pump, a little help please


"CJB" <colonyparkwagon@excite.nospam> wrote in message
news:Hycye.14747$mr4.3291@trnddc05...
>I had an identical problem on my Father-in-Law's 86 Bronco. Turns out that
>one of the negative for the fuel pump is fed straight from the negative
>battery terminal. It was one of those smaller leads coming from the post
>clamp. Anyway, it was simply a crimp connector that wasn't tight enough
>and over time had lost continuity all together.
>
> CJB
>


I think you are talking about the neg for the computer. Ford used to put
that little black wire right near the battery. It had a connector right
there too that would corrode because of battery acid. Definitely worth
checking for on this truck.

>> Ok, here goes: on my 86 Bronco (302 AOD) it decided to just up and stop
>> on
>> me. I tried bypassing the fuel inertia switch, have replaced the fuel
>> relay switch, the fuel pump(first thing I did), the entire fuse panel,
>> and
>> the computer. I've checked the ignition module and physically checked ALL
>> the wiring (I removed the front dash!) I've got 1.72v all across the ECC
>> relay. I'm supposed to have 12v at the hot wire and 12 at the igniton
>> when
>> the key is on, but got the 1.72v I've checked all the ground wires I can
>> find, and all other systems work fine, just nothing at the fuel pump. Any
>> suggestions would be greatly appreciated. Allen captmuddy@yahoo.com
>>

>
>



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Old 07-06-2005, 10:01   #5 (permalink)
CJB
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Posts: n/a
Re: 86 Bronco no voltage to fuel pump, a little help please

"Shoe Salesman" <someone@microsoft.com> wrote in message
news:uDdye.10902$aA5.8117@tornado.socal.rr.com...
>
> "CJB" <colonyparkwagon@excite.nospam> wrote in message
> news:Hycye.14747$mr4.3291@trnddc05...
>>I had an identical problem on my Father-in-Law's 86 Bronco. Turns out
>>that one of the negative for the fuel pump is fed straight from the
>>negative battery terminal. It was one of those smaller leads coming from
>>the post clamp. Anyway, it was simply a crimp connector that wasn't tight
>>enough and over time had lost continuity all together.
>>
>> CJB
>>

>
> I think you are talking about the neg for the computer. Ford used to put
> that little black wire right near the battery. It had a connector right
> there too that would corrode because of battery acid. Definitely worth
> checking for on this truck.
>


Frankly, I found it doing a wiggle test, so I wasn't sure what exactly was
fed by that neg. I know the fuel pump relay, and therefore the fuel pump,
wouldn't energize when the connector was open, which was much of the time.

It's interesting that before I found the problem, a garage told my
father-in-law that he needed a new computer for that truck. I guess they
couldn't get any output from the computer, and therefore diagnosed the
computer as dead.

One more thing I should mention too. I had an 88 Crown Vic that would have
used a similar relay to feed the power to the fuel pump. I went so far as
to replace the fuel pump (like an idiot) and found that the new pump
wouldn't work either. Turns out the relay harness itself had an
intermittent connection.

CJB


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Old 07-06-2005, 18:01   #6 (permalink)
Rob
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Posts: n/a
Re: 86 Bronco no voltage to fuel pump, a little help please

CJB wrote:
> "Shoe Salesman" <someone@microsoft.com> wrote in message
> news:uDdye.10902$aA5.8117@tornado.socal.rr.com...
>
>>"CJB" <colonyparkwagon@excite.nospam> wrote in message
>>news:Hycye.14747$mr4.3291@trnddc05...
>>
>>>I had an identical problem on my Father-in-Law's 86 Bronco. Turns out
>>>that one of the negative for the fuel pump is fed straight from the
>>>negative battery terminal. It was one of those smaller leads coming from
>>>the post clamp. Anyway, it was simply a crimp connector that wasn't tight
>>>enough and over time had lost continuity all together.
>>>
>>>CJB
>>>

>>
>>I think you are talking about the neg for the computer. Ford used to put
>>that little black wire right near the battery. It had a connector right
>>there too that would corrode because of battery acid. Definitely worth
>>checking for on this truck.
>>

>
>
> Frankly, I found it doing a wiggle test, so I wasn't sure what exactly was
> fed by that neg. I know the fuel pump relay, and therefore the fuel pump,
> wouldn't energize when the connector was open, which was much of the time.
>
> It's interesting that before I found the problem, a garage told my
> father-in-law that he needed a new computer for that truck. I guess they
> couldn't get any output from the computer, and therefore diagnosed the
> computer as dead.
>
> One more thing I should mention too. I had an 88 Crown Vic that would have
> used a similar relay to feed the power to the fuel pump. I went so far as
> to replace the fuel pump (like an idiot) and found that the new pump
> wouldn't work either. Turns out the relay harness itself had an
> intermittent connection.
>
> CJB
>
>

that ground.... it grounds the negative side of the main ecm relay coil
... no ground no ecm
bought a truck years ago .. didnt run paid small sum of money ... fixed
ground and presto
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Old 07-07-2005, 07:01   #7 (permalink)
Tom Adkins
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Posts: n/a
Re: 86 Bronco no voltage to fuel pump, a little help please

Rob wrote:
> CJB wrote:
>
>> "Shoe Salesman" <someone@microsoft.com> wrote in message
>> news:uDdye.10902$aA5.8117@tornado.socal.rr.com...
>>
>>> "CJB" <colonyparkwagon@excite.nospam> wrote in message
>>> news:Hycye.14747$mr4.3291@trnddc05...
>>>
>>>> I had an identical problem on my Father-in-Law's 86 Bronco. Turns
>>>> out that one of the negative for the fuel pump is fed straight from
>>>> the negative battery terminal. It was one of those smaller leads
>>>> coming from the post clamp. Anyway, it was simply a crimp connector
>>>> that wasn't tight enough and over time had lost continuity all
>>>> together.
>>>>
>>>> CJB
>>>>
>>>
>>> I think you are talking about the neg for the computer. Ford used to
>>> put that little black wire right near the battery. It had a connector
>>> right there too that would corrode because of battery acid.
>>> Definitely worth checking for on this truck.
>>>

>>
>>
>> Frankly, I found it doing a wiggle test, so I wasn't sure what exactly
>> was fed by that neg. I know the fuel pump relay, and therefore the
>> fuel pump, wouldn't energize when the connector was open, which was
>> much of the time.
>>
>> It's interesting that before I found the problem, a garage told my
>> father-in-law that he needed a new computer for that truck. I guess
>> they couldn't get any output from the computer, and therefore
>> diagnosed the computer as dead.
>>
>> One more thing I should mention too. I had an 88 Crown Vic that would
>> have used a similar relay to feed the power to the fuel pump. I went
>> so far as to replace the fuel pump (like an idiot) and found that the
>> new pump wouldn't work either. Turns out the relay harness itself had
>> an intermittent connection.
>>
>> CJB
>>

> that ground.... it grounds the negative side of the main ecm relay coil
> .. no ground no ecm
> bought a truck years ago .. didnt run paid small sum of money ... fixed
> ground and presto


It's funny, sort of. Most folks will keep the B+ side (the wiring and connectors you
see) spotless, but don't understand the B- (body ground) side of things. The entire
body\frame\engine of the vehicle is the return path to the source (battery). Years ago
an old timer explained it to me simply. The whole car is one big cable going back to
the battery. If the path is blocked or open, you got problems. I've never forgotten that.
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