New engine - but is it getting fuel?

[sgauvry]

To those of you that have been providing advice and following the build of my 1985.5 F150 5.0, I'm almost there with regard to having a working engine.  Remaining to be done is to drill a hole in my exhaust for a new O2 sensor that I want to move further downstream to ensure I'm getting exhaust from both headers, and weld in a bung.  And, I am waiting for one more air filter to arrive to complete my intake system.  That should be it, barring any major issues.  

Speaking of issues - I was expecting a few with regard to the electrical system but nothing that a tweak here and there would not cure.  Today, an issue popped up.

I cranked the engine to see what kind of fuel pressure I'm getting.  I can hear the rail HP pump engage for a split second, as it is supposed to.  I do not believe my in-tank sending unit is supplying fuel. The fuel gauge remains unchanged when cranking the engine.  

The first thing I'll check is to see that the tank unit is getting power.  If not, I'll have to do some checking to see where there's a break in the circuit.  

This is a single tank operation, so there's no tank selector that I'm aware of.  I'll also attempt to check relays to ensure they are working as they should. This is where I need to advice.  How do I go about checking relays to ensure they are opening and closing?  

Off to the dentist for now but will resume work on my truck when I return.  I'll take any advice you have to offer with regard to the fuel system.

Thanks!!

Steve

[Gary Lewis]

Steve - Page 103 (http://www.garysgaragemahal.com/electric-fuel-pump-control.html) shows the circuit. And you only have one relay. You can check for power out of it on the pink/black wire, which goes back to the in-tank pump as well as the in-line pump.

[sgauvry]

Thanks, Gary!  Saw that earlier, but I appreciate the feedback.  I'll let you know how make out. Probably
get to it tomorrow.

[vjsimone]

Are you still using your 4 wire heated O2 sensor ?

[sgauvry]

I know that until the sensor reaches about 650F it doesn't even start to generate voltage to send signal to the PCM. That causes the engine to run rich on short trips which is mostly what I do with that truck. A heated O2 is better for the engine overall to help it burn clean, improve fuel economy a bit, and to keep the O2 sensor healthy longer.  I suppose that should decide it for me.  

I'm moving the O2 sensor further downstream so as to be certain both exhaust are incorporated.  Waiting for a bung to arrive so I can do that.  I won't forget to ground it with a ground strap.  

Presently, I'm trying to figure why my in-tank fuel pump has 0 volts coming to it.  Once the sun comes up, I'm going to follow that pink/black H wire back to the external pump.  I know the external pump has power, so the problem is occurring between the two.  Shouldn't be too hard to figure.

Sure do love that "Electrical & Vacuum Troubleshooting Manual" you provided to me.  It opens a lot of doors to figuring stuff out.  Otherwise it's nothing but guesswork.  

[sgauvry]

Gary -

When I turn the ignition on I can briefly hear the HP fuel pump briefly engage.  That seems to be working as it should.  But the in-tank fuel pump has no voltage going to it.  I checked this several times with my voltmeter with the positive voltmeter prong connected to the pink/black H wire terminal on the fuel pump connector, and the black voltmeter prong grounded to the frame.

There's a connector downstream from the HP fuel pump in the rail; I believe it's C120. That connector has leads that go both to the tranny safety switch and to the in-tank fuel pump.  I disconnected C120 and checked the voltage at the pink/black H wire terminal.  I measured 4 volts.

How many volts are supposed to go the the in-tank fuel pump?

[Gary Lewis]

Steve - I'm confused.  The EVTM shows connector C120 as having the fuel pump wires in it, but not the start wire going to the neutral safety switch.  And it shows C121 as having the start wires going to the neutral safety switch but not the fuel pump wires.  So, are you sure that the connector you found has both fuel pump (pk/bk) and start wires (r/lb) in it?

But, moving on to the testing, the complicating factor here is the computer.  At the bottom of Page 106 there's a description of when the computer (ECA) is to pull in the fuel pump relay.  But, it doesn't really say that it will pull in the relay when the key is in Run.  And I don't think it does pull in the relay until the engine is spinning.  So I think what is happening is that the ECA is powering both pumps briefly when you turn the key on just to bring up pressure in the system, and then waiting until you crank the engine by turning the key to Start.

If you pull the little red/light blue wire off the starter solenoid/relay you should be able to turn the key to Start w/o spinning the engine.  And while the key is in Start you should have power to both pumps.  If not you need to see if the relay is being pulled in, but let's try this first.

[85lebaront2]

Steve, in tank pump on yours should get battery voltage when the relay is closed unless for some reason everything on the 1985.5 EFI system is completely different from the 1986-89 EFI pumps.

My AllData shows a 1000 ohm resistance wire on the feed to the in-tank pump, which was eliminated in 1986. If you are only seeing 4 volts, the one question becomes, is this with the pump connected? If so, then one of two possibilities, bad connection, or pump is stuck from sitting. If Ford used the same pump in 1986-89 then try bypassing the resistance wire and see if will run then.

[sgauvry]

Gary Lewis wrote

If you pull the little red/light blue wire off the starter solenoid/relay you should be able to turn the key to Start w/o spinning the engine.  And while the key is in Start you should have power to both pumps.  If not you need to see if the relay is being pulled in, but let's try this first.

IHi Gary - Thanks for getting back to me.

I did as you suggested.  Connecting to the pink/bl h wire at the in-tank fuel pump with the red/blue wire disconnected at the starter solenoid and with the key in Start position I got 0 volts.  

[sgauvry]

85lebaront2 wrote

If so, then one of two possibilities, bad connection, or pump is stuck from sitting. If Ford used the same pump in 1986-89 then try bypassing the resistance wire and see if will run then.

Interesting information.  My fuel gauge is reading as full, but I know there;s only about 3/4 of a tank.  It is possible the pump is stuck from sitting.  

I do not know how to bypass the resistance wire.  I'll look in my manual to see which wire that is, but how do I bypass it.  

[Gary Lewis]

Bill - I'm quite sure that AllData is wrong.  See below - it is a 1.000 ohm resistor and only used in the Bronco - according the a 1986 EVTM I acquired from a friend of mine.  

Steve - It is now time to check the fuel pump relay to see if it is getting power.  The easy thing to do is to put your hand on it and turn the key to Start - if your arms are long enough or if you have a helper.  If not, put your meter on the red wire of the relay and it should have 12v.  Put your meter on the t/lg wire and it should have 12v until you turn the key to Start and then it should go to about 1 volt.

[NotEnoughTrucks]

Steve, did your truck originally have dual tanks? I think I understand you are only running single tank now.

If so, is the correct tank selected? If you don't have a tank select switch, there is a jumper plug that is supposed to replace the switch.

If your inline pump is running and from the sounds of your description, it is running correctly, the in tank pump receives the voltage from exactly the same point on C120.

Bill, that resistor wire has a note in the diagram in the EVTM that says Bronco only. No idea why this is. (Gary beat me to it!)

I think your fuel pump relay is controlled correctly. With the engine not running, it will pick for a second, then release to shut off the fuel pumps. There is a handy point on the EECIV test connector for the fuel pump. Essentially, it is the ground side of the relay, same as the output from the computer. The fuel pump relay receives power from the EEC power relay when the key is on, the computer completes the circuit to ground. Grounding the test point allows you to troubleshoot the fuel pump wiring without the engine running.

[sgauvry]

Gary Lewis wrote

If not, put your meter on the red wire of the relay and it should have 12v.  Put your meter on the t/lg wire and it should have 12v until you turn the key to Start and then it should go to about 1 volt.

Gary - In the first test measuring volts on the red wire, I had 12 v.

On the second test with my meter on the tan/gr d wire, I had 26 volts and when trying to start it dropped to 0 volts.  

[Gary Lewis]

Disregard the 26v as that has to have been an EMF spike.  So the computer is closing the relay.  Now test the p/bk wire out of the relay.  It should go to 12v in Start.

If it does and the pumps don't run check the inertia switch just above the passenger's feet.  It may be tripped.

[Gary Lewis]

That's a good tip, Ray:

I think your fuel pump relay is controlled correctly. With the engine not running, it will pick for a second, then release to shut off the fuel pumps. There is a handy point on the EECIV test connector for the fuel pump. Essentially, it is the ground side of the relay, same as the output from the computer. The fuel pump relay receives power from the EEC power relay when the key is on, the computer completes the circuit to ground. Grounding the test point allows you to troubleshoot the fuel pump wiring without the engine running.

[sgauvry]

Gary Lewis wrote

Now test the p/bk wire out of the relay.  It should go to 12v in Start.

If it does and the pumps don't run check the inertia switch just above the passenger's feet.  It may be tripped.

The pink/black H wire tested OUT of the relay went to 12v.  The HP pump continues to engage as I can hear it, but the in-tank fuel pump makes no sound and is not putting forth any fuel. It still measure at 0 volts with red/blue start wire detached/attached from the solenoid.

Not sure how to engage the inertia switch. I jiggled the trigger at the top of it and depressed it a few times.  Never felt it engage, but my oil light now comes on.  It wasn't coming on before.  

[Gary Lewis]

The inertia switch is before the high pressure, in-line pump.  So if you are getting that pump to come on then you have power back that far.  And, as has been said, since both pumps run off the same circuit then you have a wiring issue between the high pressure and the in-tank pump.

[85lebaront2]

Yes, 1986 says Bronco only, 1985 shows it and looks just like the 1985 EVTM pages you shared.

[sgauvry]

Thanks Ray.  Not certain about dual tanks.  I bought it with only one in 2009. I have not seen a tank selector switch on it either.  

I know when I've plugged my diagnostic tester into the test plug I can hear the pumps working.  Maybe I'll do that just to see what happens.  

[NotEnoughTrucks]

Try as I might, I could not find an accurate reference to the connector for the tank switch, but it exists in all trucks.

On the dual tank trucks, there is a switch in with the heater controls, on single tank trucks, the switch is omitted, but the connector still exists near the heater control. There is a description of the 6 pin plug in the top corner of p.104 in the EVTM, but no references to connector number.

The plug that replaces the switch has two jumpers on it. There are two rows of 3 pins. The middle position will be jumpered to either the front or rear tank wiring. If the plug is missing, your in tank pump will not run and the fuel gauge will read empty. This is also a handy place to check for voltage to your in tank pump although it would not rule out a problem between the plug and the tank itself.

I also have had trouble with the fuel tank connectors. The connector body locking ears typically break off, resulting in an intermittent connection to the in tank pump and gauge sender. I sourced a replacement from Napa, but they are getting a little harder to find these days.