Wiring for oil pump

THIS IS ALL ON MEMORY SO GET YOURSELF A WIRING DIAGRAM FOR THAT TRUCK!!!
If you have one you should install an inline fuel pressure gauge to verify that you are indeed not getting fuel pressure first. Assuming you have no fuel pressure, it could be one of a few things.
check all of you fuses
if ok, check fuel pump relay for activation during engine cranking. I believe in that vintage Ford, the oil pressure switch is responsible for activating the relay. So with a test light backprobe the activation wire at the relay. if you get activation power at the relay, and no relay activation, then yes it is the relay, but if you get nothing, then it will be the oil pressure switch. If you get activation to relay and still no pump activation then you might have a break in the wiring OR the fuel pump has short brushes.

I know thats alot to take in but hey thats what a diy forum is for right? Good luck!!!

If everything is functioning, it should be okay. The fuel pump relay derives it's ground connection for the relay coil through the switch- you should have 2 of them- 1 for the fuel pump and 1 for the gauge or dash warning light.

if one was cut off, it is likely that the cut wire has been spliced to the one wire that is connected. Sometimes the temporary priming initiated by the ECU at startup was connected there.

Check the fuel pump wiring under the car. If the connectors are exposed to the elements they could be corroded or dirty causing intermittent problems. It could also be the ignition switch. One other thought. Some gm cars have the oil pressure switch tied in t the fuel pump, so the fuel pump shuts off in case of loss of oil pressure. Sometimes the oil pressure switch will cause problems with the fuel pump not working. You could check this out by using a jumper wire in the oil pressure switch connector to bypass the switch to see if there is any change in the fuel pump problem.

sounds like the fuel pump is not staying on or the ingtion switch doesn't make in the run position ( happens alot to vehicals take have lots of keys hang on the switch) The sparp going away is easy to check with a test light theres a connector on the distrubutor that has a heavy red wire plugged in that goes to the B+ terminal it should be hot with the key in the run position. if it's dead fix the connection at the ingtion switch ( it's on top of the steering collum and all but one wire will be hot with the key on, that one comes hot in start) if it's good the fuel pump is next it has a fuse on the passenger side firewall next to the fuel pump relay. Fuse bad or relay bad or dirty it'll act this way. The start wire entergizes the pump in crank position. then the oil pressure switch takes over and keeps the pump on. theres 3 wires on the oil pressure switch the center wire works the light the left one is fuel pump fuse power and the right one is the fuel pump. the oil switch can go bad and the connection can go bad the wire can fall off or get broken. the wire to the fuel pump may not get all the way to the pump.. You can add power to any wire on the swich with out hurting anything. all of the wires will be hot with it plugged in and running. unplugged two wires are hot with the key on ones the light ( oil Pressure light) the other is the key on power for the pump with oil pressure the switch closes and the pump comes on and it'll be powered right off the starter as it's cranking. If the switch is leaking oil its likly failed too.

The fuel pump relay won't energize if the ignition is bad, or the fuel safety cut out is bad. Don't know what Dodge uses. Ford has an inertial switch in trunk. Many cars use the alternator. Some use extra wires to the oil pressure sender. Try looking at the wiring diagram on relay side, and jumper the outputs where relay plugs into, bypassing the relay completely. The pump should hum and you should get pressure. If not, make sure the tank isn't buiding up vacuum, and make sure the power and gound are good at the pump.

Your fuel pump relay is triggered by your oil pressure switch,try jumping across to bypass your fuel pump relay if truck runs then figure out why relay is not being triggered.

Check the injector for 12v on one wire. if good check the other wire for a ground witth the key on. The ground wire pulses from the ECM If you dont have 12v from one wire to the other but you have 12v from one wire to battery ground then be sure the ground wire is good to the computer. If you don't have 12 v at any time check for open hot wire or bad fuse. ADD 12v to the hot wire at the injector. DO NOT add to the wrong wire or you will fry the computer

The first thing you should do is to locate the oil pressure switch/sending unit.

It's a single wire terminal with plastic connect sensor from the engine block.


This switch serves two functions.

1) provide oil pressure reading

2) disable the fuel pump relay in event of oil pressure loss.

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When this switch is failing to provide the correct pressure to the ECU. The wiring harness can overheat and eventually create a short.

ECM1 fuse blow is because the harness is grounding/shorting.

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DO NOT drive the truck until you change the oil pressure switch.

After you change the switch,you should spend sometime to inspect the wiring between the fuel pump relay,ECU and fuel pump.


Please post up day on the comment window/page.

I will follow up on it later.


Good luck.

there is a fuel pressure regulator on the back of your injectors, change it, its a 13 dollar part, after you do that, buy a fuel pressure guage, hook up the pressure guage, turn the key to on possition, prime the like a couple times like you would do with a new pump, check the pressure it should be any where from 58 LBS to 62 lbs of pressure in the like, if its any lower the 58, you need to change your pump, with out 58 lbs of pressure the injectors dont get the correct pressure in each purge, hence the crank with no start.. you seem to know enought about pressure n stuff like that so u should get it

It is a well Known problem within the 2.7 L family ...
Here is the deal Go to the dealer get a Mopar oil sending unit.
once under the vehicle look to behind oil pan about center ways and take pigtail (wire) off sensor then remove unit .
once removed if alot of sludge is there clean area very good then install new unit and inspect wire if it connection even looks bad cut wire and add new wire (MAKE SURE TO USE HEAT SHRINK TAPE OR LIQIUD ELECTRICAL TAPE TO SEAL WIRE COMPLETELY. >>>>NOT JUST ELECTRIC TAPE<<<<)
Ok now thats done plug wire back into unit .
Note: 2.7 L engines also have sludge problems and need to have engine flush and oil pan dropped clean oil pump screen and pan then start useing synthetic oil you should be able to go about 10,000 miles useing synthetic and you will have to only change filter 2 or 3 times . this should solve issue and help extend life of motor. SB