Fuel pump

[lambjames85]

Hello all. I am new here I purchased a 94 Ford explorer this past spring and since having some issues. I currently have an issue of not starting. Sounds as the fuel pump is not turning on. Do not hear the winding sound when i turn the key to the on position. Fuel pump has been replaced about 2 months ago, fuel filter, fuel cutoff switch, computer, checked all fuses/solenoids. Starter turns the engine over with ease everything else sounds great except missing the winding sound and no fuel. Any suggestions before i tear into electrical I would appreciate.

 

[IZwack]

Check fuel pressure first at the fuel rail.

 

[tk1251k]

Check in the power box under the hood for the 30 amp eec fuse.

 

[arco777]

Agreed with tk1251k, check the EEC fuse and the relay for the EEC as well. If the computer isn't getting power then it won't activate the fuel pump.

If it is not as obvious as a bad fuse or relay, grab a multimeter or test light and start tracing where power is and isn't.

One way to notice that the EEC isn't getting power, is that not only will the fuel pump not prime, but also there will be no spark at the spark plugs while cranking.

 

[unclemeat]

I am having a similar problem with my 91. I have replaced the fuel pump and relay and that did not solve the problem. I pulled the computer Saturday and am replacing it and the ECM relay.

The computer had a oil film on it. I am assuming that it is oil from the capacitors in the computer (a common problem). I will see if it works this weekend.

 

[tk1251k]

I have read about the capacitors three of them I believe leaking and causing problems. I believe the 91 is under the hood right. Keep us informed. I will check on that asap. thanks

 

[arco777]

PCM is behind passenger kick panel.

 

[lambjames85]

my pcm looks brand new but changed it anyways. found a way to get it started however not the safest. bypased relay by pulling wires out of Distribution box. but hook it back up normally does not work so still working with electrical trying to find out what exactly is the problem.

 

[lambjames85]

found a bunch of wires coming from the steering column that had been partly stripped were someone started to install a remote starter/security system. not to check all the rest of the wires and make sure everything has good conections

 

[lambjames85]

Quick question and overlook on my part. Trying to collect more information. Put key in turn on (not start) there should be a check engine light correct? on a 1994 Ford Explorer on the left side of the steering wheel? If not that means computer not getting power correct?

 

[arco777]

Quick question and overlook on my part. Trying to collect more information. Put key in turn on (not start) there should be a check engine light correct? on a 1994 Ford Explorer on the left side of the steering wheel? If not that means computer not getting power correct?

Correct, that or the CEL is burned out.

 

[lambjames85]

sorry still learning CEL? so can i get a new computer and plug and play or chase wires?

 

[arco777]

CEL = check engine light.

Doubt you need a new computer. Chasing wires would be the thing to do in my opinion. Make sure the EEC relay and fuse (separate from fuel pump relay and fuse) are good and that there is power to both. With key on the relay should click to life and the fuse should be flowing 12v through it. If not, trace backwards to find out what isn't active and why.

 

[lambjames85]

That is what I am going to start today.

 

[AutoDoctor]

not trying to treadjack but... im looking into a guys 92 thats got a new pump and relay installed the relays even clciks when the key is turned but no pump action. I checked the power at the pump /body harness plug above the rear axel. I was reading like 7.62 volts and the battery is over 12volts. I also checked and even bypassed the intera switch. so what would give a 7 volt power to the pump? all i can guess is a crappy wire or ground. and im wondering if i should just run a new set of power wires from the fuel relay to the pump. any ideas or comments?

 

[MrShorty]

so what would give a 7 volt power to the pump?

The computer. I'm not sure how to explain it (in part because I'm not knowledgeable about solid state electronics), but the fuel pump circuit is tied into the PCM at the fuel pump monitor pin. Something about the internal circuitry of the fuel pump monitor circuit (inside the PCM) causes a 6-8 V "ghost" voltage when there is not other voltage source applied to the fuel pump circuit.

Basically what the 7 V ghost voltage is telling you is that there is a break somewhere in the fuel pump circuit. Keep working your way towards the battery until you get to a point in the fuel pump circuit where there is 12 V. The problem in the circuit will be between the last point with 12 V and the first point with 7 V.

 

[AutoDoctor]

so from pump id check to the int. switch, fp relay, then do i go power source or signal? ok after a sec to think about it the power level the relay is putting out is the same it is getting in... not from the signal(pcm). the pcm signal is just telling the relay to open or close the relay..... so the output voltage from the relay is the same as what is supplyed. its a 92 4.0 unit if i didnt already post it. and the wiring i have for the relay is red, lt blu-org, blk-yel,dk grn-yel(x2). the blk-yel goes to fuse #1 in dist box, 1 of the dk grn-yel wires is from #8 FPM @eec the other is to the inertia sw, the lt blu-org runs to the self test output (sto) conn and it is hooked to the fp#22 wire from the eec, the red wire is ran to a point where other items hook up like eec relay and map. and if im doing it right the red and lt blu-org wires are the coil wires(signal input and ground) the dk grn-yel is the common (power in) and the blk-yel is the normaly open (power out). so if thats right the red is switched power input aka signal, lt blu-org is 12-, blk-yel is power out to fuse #1, dk grn-yel is 12+ power in aka power source. so the red wire voltage is what the relay power out is... in my case the red is around 7 volts?

 

[MrShorty]

blk-yel is power out to fuse #1, dk grn-yel is 12+ power in aka power source.

From your description of the wiring diagram, I'd say these two are backwards. blk-yel looks like it should be power in (hot at all times) and dk grn-yel is power out to the pump.

so the red wire voltage is what the relay power out is... in my case the red is around 7 volts?

This doesn't seem right. That red wire is the power wire to the entire engine management system (including the fuel pump relay coil), and should have 12 V whenever the key is on. If there is only 7 V, that suggests something is wrong with the EEC power circuit. At this point, I would suggest determining if the problem is isolated to a point between the EEC relay and the fuel pump relay, or is it common to the entire EEC power circuit. Does this red wire have 12 V at the EEC relay?

 

[AutoDoctor]

all the listings above were based off a wireing diagram i was looking at. I was trying to make out what was what. and if my thinking is right the relay is only gonna put out what the power in(not the signal from eec) is all the signal from the eec does is tell the relay ok turn on or off right?

 

[MrShorty]

all the signal from the eec does is tell the relay ok turn on or off right?

This is correct, but it is unclear to me which pin at the PCM you are designating as the signal from the EEC. The EEC tells the fuel pump relay to close at what your diagram is saying is the lt blu-org wire going to pin 22. The computer applies ground at this point to allow current through the coil side of the relay, which (if all is working correctly) closes the fuel pump relay.