When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
5.0L (1979-1995) MustangTechnical discussions on 5.0 Liter Mustangs within. This does not include the 5.0 from the 2011 Mustang GT. That information is in the 2005-1011 section.
I checked the intertia switch and it is working properly. Not starting at all now. I tested for power at the fuel pump relay orange/black wire 12v key off. With the key on the pink and black wire had like .06 I jump the two and the pump runs. I also tried to ground the fuel pump terminal on the test port by the fire wall on the drivers side but got nothing. Anybody have any ideas?
There types of electrical issues can drive us normal people nuts lol.
Wish I could give a good explanation, but I'm just not that smart. From what I remember the PIP sensor tells the injectors when to fire. Why the fuel pump primes when turned doesn't make sense to me but hopefully someone will chime here and give better advice.
I'm assuming you went thru and checked all wiring and harness for loose/bad connections.
I usually don't plug another forum but my regular check list thread no longer exists so try this one.....
302army guy from this page has a video where he is doing test and his fuel pump turn on when he turns the dist also but he has another video. I have looked at the harness but havent tore it open yet was hoping to aviod that.
Still having a issue. What makes the fuel pump prime? I wont prime I will let the key one for a few minutes then without doing anything it will prime then next time it wont. Anyone have any ideas?
Last edited by 1988MUSKRAT; 10-20-2017 at 12:42 PM.
The ECU Uses The PIP Sensor Pulse To Trigger The Fuel Pump Relay
The distributer armature has a part attached to it with metal vanes (tabs) on it.The pip sensor has a magnet attached to it.When the distributer shaft is rotating,these vanes pass by this magnet and this tells the ecu the engine is cranking or running.
The ecu provides the ground that energizes the fuel pump relay.This ground is turned on or off to control the relay,which powers the fuel pump.This ground is located at pin 22 on the ecu.When the key is first turned on,the ecu turns this ground on for 2-5 seconds,then off,then back on again once it sees the pip sensor pulse.The 2-5 second ON period primes the fuel lines/rails,then the pump shuts off,then the pump comes back on again once the ecu sees engine rotation.
So,this explains why youre hearing the fuel pump run everytime you rotate the distributer left-right-left.Youre causing the pip sensor magnet to pass by the vanes and its signaling engine rotation to the ecu.
The following link should help you diagnose the issue.
The diagram details the startup procedure for the fuel pump.
Youve got me stumped on how the fuel pump can prime when turning the distributer if the tfi harness is disconnected?? Its supposed to prime when turning the distributer,but I dont see how its possible without the harness being connected?? There would be no communication between the pip and ecu,without the harness.If a no start condition is present,remove the spout plug from the tfi harness then try starting the car.If the car starts after spout removal,thats a verification of a defective pip sensor.
The following test will tell you whether its fuel or spark related:
Remove the small,black breather tube from the throttle body (runs to the passenger valve cover) spray starting fluid or carb cleaner into the throttle body port,reinstall the tube then attempt a startup.
If it starts & runs for a few seconds then dies,its a No Fuel issue.
If it doesnt start at all,its a No Spark issue.
If the fuel pump trouble shooting link didnt pinpoint your issue,the following link details EFI No Start trouble shooting.
BTW- the silver box youre referring to,attached to the starter solenoid,is the circuit breaker for the power windows and locks.It has nothing to do with your issue,but it is however attached to the same solenoid post as all of your fusible links and the positive battery cable.The diagram shows which links go to what.If the nut is loose,it could cause an intermittent power loss to those wires (example: the eec relay has one of these fusible links inline with it) Make sure the back side of the solenoid and the fender apron have clean metal to metal contact because the solenoid is case grounded.If this area is dirty or corroded or the solenoid mounting screws are loose,the solenoid will have a weak ground.
Another poster listed grounds you had asked about,but one of the grounds was not mentioned.The eec ground.This is the 10ga wire that connects to the neg battery post and runs to the fender apron.It then forks off and terminates at a black,tubular connector.This connector plugs into a mating connector.Make sure this ground is tight and corrosion free,especially where those two connectors plug together.If this ground is loose or disconnected,the fuel pump will run when the key is turned to the start position,but it'll stop running as soon as the key is released to the run position.This ground is the one that completes the ground loop,so its super important.Its the computer power ground.It feeds pin 40,60 & 46.The diagram below shows the eec ground route for pins 40,60 & 46.
BTW- pins 40,60 & 46 are connected to each other on the ecu circuit board,so a loose or corroded eec ground will affect all 3 of those pins.
I think its wiring relate now. The pump wouldnt prime I checked the ground cables and then the wires at the soleniod and when I touched one of the smaller wires it primed. And the car started. And has been starting. Now im waiting for the pump to not prime again to see if it indeed it is this wire.
11-04-2016, 01:46 PM
