No power at Fuel Pump Relay Signal Wire, Injectors Not Firing

YooperSteeze · Sep 1, 2014

As the title says, I'm not getting enough power to the fuel pump relay and the injectors aren't firing. With a multimeter probe in the red signal wire terminal and the other on good ground, I read 2.3 volts when I turn the key on. Followed both signal wires to the ECM, no nicks or breaks in the insulation or anything. Full power to the wire for the pump, if I jump it the pump runs, but the truck won't. Get pressure to the schrader on the rail when the relay is jumped so I'm assuming the injectors aren't firing. No noid light to test it but seems fair to assume. Basically I'm at a loss, I hate electrical issues like this. Any insight would be greatly appreciated. Also, tried a different ECM and no change.

huh? · Sep 2, 2014

try pulling the wiring connector off the ecm. check for continuity between the battery ground cable clamp(since the neg battery cable will have been disconnected, please, so no burny-outy ecm like me) and pin numbers 20, 40, and 60 on the connector. it may be that the ground(s) for the ecm became disconnected or severed.

iirc, when i was trying to get my truck going the fuel pump relay wouldn't activate till the key was inbetween the RUN and START position(the fuel pumps would activate for the normal 2 or so seconds if i slowly turned the key to START and as i slowly let the key back to run). i read something in these forums at that time about circuits "scavanging" a ground and i think thats what happened at that point of rotation of my ignition switch. maybe i missunderstood the posters meaning but after i finally found that pin numbers 20, 40, and 60 on my connector had no continuity to the battery ground i snipped all three and ran a thicker wire joining all to the neg cable clamp. first click of key to run after that had pumps priming. turn a little more forward and truck started right up.

so, yeah............ told myself i wouldn't do the two-finger blah, blah, blah, but i did. got some practice in on the run-ons, too. hah!

to digest the above:

the ecm controls engine functions such as fuel pump relay and injector pulses by providing a ground for those ciruits. if the ecm has no access to ground via pin numbers 20, 40, and/or 60(and pin 16 is listed as ign-gnd on my printout of "TRUCK COMPUTER PIN OUTS" from fordfuelinjection.com) then those systems will mal- or not function. [/blah]

p.s. if you knew above info already or if i seem to be over explaining, there was no intent to insult your or anyones intelligence. sometimes i start posting with no exit strategy

kimcrwbr1 · Sep 2, 2014

You should have battery power at the fuel pump relay full time key on or off. The computer provides ground to the coil to close the contacts

kimcrwbr1 · Sep 2, 2014

http://www.therangerstation.com/tech_library/EDiagrams/files/Diagram_Enginecontrols4_0_3_0_1of3.JPG
Pull the EEC relay and see if there is corrosion on the connector pins it could be why the injectors are not firing

Ranger302Boss · Sep 3, 2014

Looks like a bad pick up coil or crankshaft posición sensor. If the ECM dont know the engine is rotating, never give the order to fuel pump and inyectors.

Enviado desde mi XT1053 mediante Tapatalk

Ranger302Boss · Sep 3, 2014

Finaly works?

Send from my Moto X using Tapatalk

enjr44 · Sep 4, 2014

What made it work? :dunno:

exbass94 · Sep 5, 2014

Make sure the EEC relay is good. If the EEC relay is bad, the EEC won't turn on. If the EEC won't turn on, the fuel pump relay won't get grounded and won't turn on. You also need to make sure the fuel pump relay is good. If either one is bad, it will produce the same no-start symptoms.

I had this problem with my Explorer. It was a bitch to diagnose, but turned out to be a super cheap and easy fix.

YooperSteeze · Sep 6, 2014

Still not running. Checked the grounds on the ECM, all good. Not crank sensor, as it doesn't even kick the pump on to prime it. If it were crank sensor it would still run for a few seconds when the key is on, but wouldn't fire. ECM relay clicks, so I'm assuming its good. Even so, I'm only getting 2.5 volts to the fuel pump relay signal wire when I should be getting 12 with the key on. I'm stumped.

Spott · Sep 6, 2014

Just because the ECC relay clicks, doesn't mean it's good. The contacts inside could be fried. The output of that ECC relay is the 12v input to the coil of the fuel pump relay (the computer turns it on and off by switching the ground).

So, you should check the output of the ECC relay, and the input, and if the input is 12v and the output is not, then replace the ECC relay. If the input to the ECC relay is 2.5v, then you need to chase wires and find out why.

Earl43P · Sep 7, 2014

Turn the key to Run, does the Check Engine Light come on?

If not, the ECM relay isn't working.

exbass94 · Sep 8, 2014

Just swap the EEC relay with the A/C relay or ABS relay and see what happens (don't swap it with the fuel pump relay, because like I said before, if either the EEC relay OR the fuel pump relay is bad, you'll get the same no-start symptoms)

freedom5 · Sep 10, 2014

Have you checked the inertia cut off?

bigdan002001 · Sep 10, 2014

^^^He beat me to it....I had a simlar problem in my 86. I just unpluged the intertia switch wire from the bottom and used a paper clip to shove into both terminals which will complete the circuit until I could get home and replace the switch.

Dan

No power at Fuel Pump Relay Signal Wire, Injectors Not Firing

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