Fuel pump running all the time

[stan346]

Hello, I have a 1994 Ford Ranger 4X4 with the 4.0L engine and standard
transmission... 285,000 miles and running great till yesterday.
Started missing and surging...blowing black smoke and dying.
This morning while messing with it, I noticed the fuel pump was
running all the time. Tried removing the vacuum line to the
fuel pressure regulator and it made no difference. Bad vacuum line
or regulator?
Also checked the plug wires, sparkplugs, reset the computer.
Oh it also will run just fine when I start it, for about a minute if I let it set for a few minutes...then the problem returns.
Thanks for any help!

 

[jhammel85]

Sounds like the Fuel Pressure Regulator.

Check the fuel pressure at the rail with a gauge. I would look up the spec for the 4.0 but my 2.9 is 40psi with the key on, engine off and about 35 or so with it running.

It sounds to me that it's no good. Mine did not show any signs other than run like total crap and blowing black smoke (too much gas). my fuel pressure was off the charts. It was over 100PSI according to the gauge.

If that checks out OK, Check the Fuel Pump Relay. When you put power to the Fuel Pump Relay, does it kick on? Maybe it's stuck on?

 

[stan346]

fuel pressure regulator?

I was thinking it might be the fuel pressure regulator.
Don't have a fuel pressure gauge..So I guess I'll spend the
$75.00 for a new one and see if that fixes the problem.
Out of curiosity, I reset the PCM and it ran fine for about
12 miles and then started throwing a Check engine light,
dying, and blowing black smoke when it would run.
Thanks for the response.

 

[stan346]

The fuel pump relay is working fine...I swapped it with another and if I unplug it
while the engine is missing and sputtering...the engine starts running fine again.
If I do key on but engine not running, I can hear fuel going through the regulator
and the return line to the gas tank.
Thanks!

 

[jhammel85]

I would try to reset the PCM again to see if you can recreate that again. If it does that again, its more along the lines of something electronic throwing a fit. There are numerous sensors that help regulate the Fuel to Air Ratio...Perhaps one is dying off.

 

[Bird]

Changed any parts before all this started?

 

[Hahnsb2]

I'm confused. Are you saying the fuel pump runs with the key off? If so the relay wire that the computer sinks to turn on the relay may have rubbed through the insulation somewhere and is grounding out.

 

[sbsrlewis]

Trace the wires for the pumps. I agree with HahnsBII because I had the same issue a few years back except mine was self induced n I replaced a lot of relays n even the pumps. Until I figured it out I was disconnecting the battery when I arrived at my distention. Mine ended up being a sheet metal screw I had put n the inner rt fender to hold the plastic splash liner out of the way. I ended up driving the screw into a wiring bundle n it was shorting out the pump. Some times u could turn it off n it not run but then come on later. Good luck.


Steve

 

[stan346]

The fuel pump runs all the time with the key on but engine not running.
Unless I reset the pcm and then it works correctly for about 12 miles.
I reset it again today and will drive a bit this evening and post the results.
Thanks for the help!

 

[stan346]

Also, no parts changed or screws changed, etc..
Thanks

 

[stan346]

Problem Solved!!
It was one or more sticking fuel injectors. I guess some bad gas gunked them up.
A hefty shot of Dollar General injector cleaner and in about 5 miles of running all
was normal again! Thanks for the help!