Hesitation under load

[Krafty]

542 fuel pump secondary circuit failure pcm to ground

 

[chris93]

Help me, does that mean I need a new fuel pump. I disconnected the negative battery terminal, reconnected and the tried to start again, she almost kicked over but nothing.

 

[chris93]

Would this contribute to the misfire and hesitation?

 

[Krafty]

the problem is in the circuit between the pcm, fuel pump relay and the fuel pump. now possible problems are shorts in the circuits, poor connections somewhere or... your inertia switch is partially activated.

the inertia switch on the driver side, up aginst the fire wall to the left of the brake pedal or behind the right kick pedal.Push the reset button on the top of the switch to compete the circuit.

 

[Krafty]

short answer is yes, bad ground = resistance in the circuit = low voltage = minimal operation of the pump

 

[Krafty]

if you can test the wire going to the fuel pump at the tank and you get 12 volts then the problem is either a connection in the tank or the pump itself

 

[chris93]

Pump is not kicking on when I turn the key

 

[Krafty]

did you try the tests I suggested? if we can find out how far the power goes before it shorts then we can rule out the different components.

 

[Krafty]

also try unplugging the connector at the fuel tank and reconnecting it in case it was the bad apple. might as well start with the easy stuff first.

 

[chris93]

Okay so I tapped on the relay and the fuel pump kicked on and she started but ran rough then stalled. I can't seem to get my hand up to the plug for the fuel pump, there is fuel at the rail too but doesn't seem to be under much pressure.

 

[chris93]

Inertia switch is fully depressed so I can't reset it

 

[Krafty]

do a wiggle test around the fuel pump relay and see if any particular wires make it work or not work. if you can't find it out that way, try getting a hold of a fuel pump relay from a scrap yard or a buddy with extra parts lieing around and see if it works any better.

 

[Shadow_D]

There is nothing wrong with using Seafoam, it does help and after use, your engine will run smoother. There have been some reports of issues that *MAY* occur with it's use...

Rather than trying to explain these issues, The link below talks about most all of them.

http://www.expeditionforum.com/showthread.php?t=7500&highlight=Seafoam

I still plan to use Seafoam in my Expedition.

 

[miesk5]

yo, Since this is a 93, correct?

Try swapping da HORN Relay w/Fuel Pump Relay

Press Horn button... if it gives ya the temper tantrums... ya got it!

Then try starting & running.

... if same, then plug Horn Relay into PCM relay, try again



Power Distribution Box Diagram in a 93

Source: by Troll Banned (Bronco Rob, BroncoRob) at SuperMotors.net

 

[budster 95]

Just a heads up. I have a 93 also, there was no plug on my fuel pump. (its the old style, hardwired in) Maybe this is why you cant feel the connector. Good luck

 

[budster 95]

TPS sensor failure will also cause popping thru the intake, and backfiring. The TPS is a variable resistor, ya really dont want any kind of liquid in it. Maybe some electrical contact cleaner would help, but i dont think they are a serviceable part. We still dont know if you have fuel pressure. Let us know how your coming along with this.

 

[chris93]

Very little to no pressure at the rail. She won't start at all now and the fuel pump doesn't kick on when you turn the key. I haven't been able to work on it since yesterday morning due to work, but will swap the relays and test for power to the pump. Ill keep you all posted. Thanks everybody for all the help so far.

 

[miesk5]

yo,

ok, EZiest thAng to do now in this weather is to make sure the Horn works.

Pull relay and swap into FP relay slot...

next would be to place it in PCMs slot...

Was a Wiring Diagram [osted yet?

If not, see this for a 95 (see #4) Source: by ... Guess Who? Yep!..my pal, Seabronc (Rosie, Fred W) at Ford Bronco Zone Forums

For da FUEL PUMP/Sender Connector; "...The larger surface-mounted connector (WPT454) was used until '93; in '94, it switched to the smaller round inline connector. (Pump side: WPT330/WPT335; Truck side: WPT111/WPT807/WPT81..."

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



For instructions on how to cut out a cargo area floor pan section for fuel pump/sender access, see this by my pal, Seabronc (Rosie, Fred W) at Ford Bronco Zone Forums; get a patch cover from local yard...

GL!

 

[budster 95]

I'm in the process of replacing my fuel pump also, get the right tool for the gas line connectors, before you attempt to remove them. This tool is also used for replacing the fuel filter, i would suggest you change that also. Have fun!

 

[chris93]

Yeah the diagram is posted thanks. If it is my pump (probably, its the original one) I sure hate to cut into my floor, but probably beats the heck out of dropping the tank, which lucky me is full...