88 Bronco II Intermittent Low Pressure Fuel Pump

Asked by Dec 31, 2015 at 06:44 PM about the 1988 Ford Bronco II STD 4WD

Question type: Maintenance & Repair

My daughter's 88 Bronco 2 has been idling a bit
rough and sometimes low.  It wouldn't start the
other night while she was shopping.  Had it towed
home after driving to the mall and checking the
usual suspects.  I stopped checking stuff when I
didn't hear the in tank fuel pump prime.

I took another look the next day.  Listened again
for the whirl of the FP and heard only a click back
there.  Engine turned over, but wouldn't crank (just
a sputter).  I also found that the ground cable from
the battery had been damaged when one of her
belts broke a month or so ago.  It is getting spark.  
So, I haven't dug into the distributor yet.  I checked
the test port on the fuel rail and no fuel when I turn
it over.

I was convinced that it was the FP.  So, as I got
started working on it today, I sprayed some
starting fluid in the throttle body.  It started and ran  
until the SF burned off.

Now, I failed to follow the scientific method here
and injected 4 variables before I tried to start it
again.  1.  I pushed the button on the inertia switch.  
It didn't click or feel 'tripped'. (Not sure what it
should feel like if it's been tripped).  2.  I moved the
ground wire around a bit when reconnecting the
breather hose onto the throttle body.  3.  I moved
the vehicle a bit (short somewhere). 4.  I removed
the fuel pressure regulator vacuum line.

Immediately after that, I had my son turn the key
and I heard the whirl of the FP.  I removed the
vacuum line from the fuel pressure regulator and
had my son turn it over to check for fuel out of th
FPR.  It started right up and ran great.  It would bog
down a bit as I started to put the vac line back on
and stabilized as I would remove it again.  Revved
the engine a bit and put the VAC line on all of the
way and it seemed to adjust itself to run fine.

Of course, I'm glad it's running.  But, I'm worried
about sending her back to school with the
likelyhood that it will leave her stranded again.  I
am going to give it a mini-tune up tomorrow (plugs,
oil-fuel-air filters, pressure regulator, ground cable).

All that just to ask:  What might make the FP
operate intermittently?  Could it have been the
inertia switch, wiggling the ground cable, releasing
pressure on the regulator?

I'm looking forward reading some responses.

3 Answers

56,315

There are points in the fuel pump that get burnt and eventually the pump stops working but in the meantime it works some of the time. If if is not working and you bang on the gas tank and it starts working then install a new fuel pump before the car strands your daughter.

Thanks. I don't think the pumps an too expensive. So, as old as the vehicle is, I think will replace them both. Life's a journey, I guess. We'll see where it leads us.

Finished the mini-tune up today. Runs like a top now. I'm going to drive it for a few days to see if the issue arises again before send my daughter out in it. Im not going to replace the fuel pump unless it acts up again. After replacing the main ground cable and a few other damaged ground wires, I'm convinced that was the culprit. A couple of wires were hanging on by a few strands.

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