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High Pressure Fuel Pump won't run -tried a lot already. HELP!


eternalphoenix64

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So, like the title says, the fuel pump won't run. I'm starting to get desperate. This is the secondary, high pressure pump located on the frame.

Was working initially. Did a massive tune up (New TFI, cap, rotor, plugs, wires, coil) and suddenly the fuel pump wouldn't hum when I turn the key to the on position.

Replace pump and it still won't run. Decided to replace the relay and it STILL won't run.

Follow diagnostic process here: http://easyautodiagnostics.com/ford/4.9L-5.0L-5.8L/fuel-pump-relay-tests-1

Passes all of the tests except test 4. So I can get the fuel pump to run with a jumper wire, but it's not being activated by the computer. Diagnostic test to determine whether the problem is with the distributor or the computer says to check for spark off the coil. I have spark so I replace the computer.

THE FUEL PUMP STILL WON'T RUN!!!!!

HELP!!!!!

Thanks in advance.
 


mplummer08

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Did the 87 have the fuel safety shut off under the dash on the passenger side?

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Is the inertia switch tripped or defective? It's on the passenger floor up kinda under the dash. Little reset button on top. If it's not tripped or doesn't reset and work, try unplugging the wires and jump them.


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RonD

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It was a fairly common problem.

Originally there was a low pressure(lift) pump in the tank for Carb model engines.
When Ford started using fuel injection they needed to boost up the pressure, but still had a Sh*t load of the Lift pumps, so what to do............

They left the Lift pump as is and added a high pressure pump in the frame rail :)
But how to power it?
"Lets just SPLICE into the tank's fuel pump wire"
And they did, and the splice fails, gets corroded
Find it, follow high pressure pump wire to the splice, and re-splice it
 

eternalphoenix64

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But how to power it?
"Lets just SPLICE into the tank's fuel pump wire"
And they did, and the splice fails, gets corroded
Find it, follow high pressure pump wire to the splice, and re-splice it
I could believe that if it weren't for the fact that I can get the fuel pump to run by using a jumper at the relay.





I didn't get the original notification that there had been replies on this thread because it went to my spam folder. I have this posted in another Ranger forum, so allow me to share what I have done from that one and see if anyone here has any other ideas. (other post is linked at bottom in case I forgot anything here)

1 - forgot to mention that the previous owner had bypassed the inertia switch. I can confirm continuity, so I'm not looking at that as a possibility anymore.

2 - Tested relay connector, it checks out. I have one pin going to ground when the key is turned on, one pin that is a constant +12V, and 2 more pins that are +12V when I turn the key on.

3 - Confirmed that when I bypass the relay with a jumper, I get 40PSI on the fuel rail, so the pump is not only working, but it works correctly.

4 - Checked all the fusible links I could find (3 or 4 of them) in the area and found that all of them have continuity.

5 - Found and fixed a bad ground on EEC relay connector. That now clicks when I turn the key on, but the fuel pump relay still won't.

6 - Tested fuel pump relay connector again, and those are still good.

7 - Tried testing relay, and can neither confirm nor deny if the relay is good, as I cannot get it to click by applying +12V and Ground to the coil. Tried replacing the relay just to be 100% certain, and the fuel pump still won't run.

I have ordered a new relay connector for both fuel pump relay and EEC relay (EEC relay connector is cracked and a couple of the wires will slip out). My plan is to rebuild those, but if that doesn't work, I have no clue where to go with this and I appreciate any suggestions that anyone has.



http://www.ranger-forums.com/2-9l-3-0l-v6-tech-32/1987-ranger-2-9-secondary-fuel-pump-wont-run-150284/#post2117237
 

lil_Blue_Ford

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That is a weird problem. If jumping the relay plug makes the pump run, it sounds like a faulty relay, but it's hard to believe that you got two bad relays. Possible, but not overly likely. I'll try to give it some more thought


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eternalphoenix64

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As an engineer, I understand the basic principle of HOW a relay works. What I haven't been able to figure out is why THIS ONE won't work. If I have all the power at the correct pins, and the ground at the correct pin, why won't the coil energize? Must be bad relay. Go get a brand new relay, plug it in, coil still won't energize.

But here's something helpful finally - see attached images. Using the graphic, I was able to figure out which pins are the coil, and energize it. It works. The problem is in the wiring of the truck. Or, more likely, the layout of the relays (two from two different auto parts stores) that I've been getting. As you can see, the wires for the truck are not in the correct locations to match up with the wiring of the relay. For all intents and purposes, we can assume this is an NO (normally open) relay. I DID find out that the previous relay had a sticking contact anyways, so that was another contributing factor there. Sadly, I trashed the original relay, so lord only knows what happened to it.

Image details -
#1 - pin layout for the relay
#2 - pin layout as they go into connector, in same orientation as picture 3
#3 - orientation with connector, with pins marked, and wires labeled.

As you can see, I have a ground going to pin 3, 2 switched +12V going to pins 1 and 2, and a constant +12V going to pin 4, and nothing going to pin 5.

Obviously I have 2 options. I am getting a new connector, already on its way from Rock Auto. I have 2 options for wiring it in now. I can either wire it in and match what already exists and try to find the CORRECT relay, since I've apparently gotten two now that are the same but wrong for the existing wiring. OR.... I can wire it up to match the relays I've gotten.

My question for you all, based on your apparent experience with these trucks..... which one will be the best course of action?
 

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RonD

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yes, not a "standard" automotive Relay

Ford relay and socket

If you want to use that relay and socket then you will need to repin/rewire it

1 and 2 are 12v from EEC relay(ignition 12v) and Computer Ground, coil activation, no polarity

3 and 4 are the Load, 12v from fusible link(constant 12v) and wire to inertia switch, no polarity, passes 12v when relay is closed

5 has no connection


If you had the relay plugged in while testing the voltage then 1 and 2 should both read 12v ignition, because there is just a coil of wire inside the relay, so 12v in would be 12v out
With replay pulled out of socket only 1 or 2 would read 12v, making that wire the one from the EEC relay
Computer ground is harder to test for since it is ONLY A GROUND for 2 seconds.
Hook up meter or test light to battery +
Then hook other wire to the wire you want to test
Turn on the key
You should see 12v for 2 seconds
When you do that is the wire from computer and the one that goes to the coil in the relay
 
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eternalphoenix64

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Well.... I fixed the wiring. I got 4 different relays that all behaved the same, so I decided it would be best to just changed the truck wiring to avoid further difficulties in the future. Unfortunately, the ground for the fuel pump relay is now ALWAYS a ground, so I'm assuming that means I've done something to eff up the computer. I doubt it was the rewiring. I simply cut that off one wire at a time and used my relay with the diagram as well as my Haynes manual to wire up my new relay connector correctly.

I'll try to update once I get a new computer. I just wish I hadn't sent the one back that I'd already gotten.....
 

RonD

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The computers Ground wire to the FP relay has a splice to the VIP/OBD connector in the engine bay, so you can test or by-pass computer Ground as needed, that wire could be bare somewhere and grounded to body.

As said there is no Ground wire to the FP relay, only the computers temp ground to turn relay on or off
Relay has:
12v from fusible link
Wire to inertia switch

12v from EEC relay
and
Computer pin 22/VIP connector controlled Ground

But if you have fixed ground fuel pump will only run with Key on, EEC/PCM relay closed
 

eternalphoenix64

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So, things seem to be really effed up in the wiring right now. Not sure if it was something I did or not. But I've decided to get a new wiring harness off the EEC out to all of it's miscellaneous connectors.

What specs make a difference in what vehicle I can pull a wiring harness from? I know that it has to be a 1987 Ranger OR Bronco II. Beyond that, is it specific to transmission or whether or not it is 4WD?

Thanks.
 
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If you have dual tanks, im told the ground likes to corrode off the tank selector valve
 

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If you have dual tanks, im told the ground likes to corrode off the tank selector valve
If you have dual tanks, there's no ground on the tank selector valve.

The selector valve is a floating-voltage system.

If you select the front tank, one input wire is connected to +12V, and the other input wire to ground. If you select the rear tank, the voltage and ground are reversed. This wouldn't work if one terminal were hard wired to ground, because you would flip the switch and then it would connect the +12V line directly to ground, in a dead short. Bang, blown fuse, no fuel pump power.

Therefore, there cannot be an electrical ground on the tank selector valve. Never was, never will be.
 
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My bad then. I was just talking to someone yesterday who told me that happened to his 89 F150
 

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Had the same problem with my '88 2.9. I did the same jumper from the relay to the pump to prove the pump worked. I finally found that the O2 sensor is tied into the fuel delivery system, changed it and bingo, problem solved. Now dealing with a slight idle surge...
 

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