Electrical Gremlins

[rusty ol ranger]

After rereading your post again...

I dont remember seeing this but you are getting full voltage to the fuel pump on the frame (hi pressure) right?

Theres only 6 things that get fuel to these things...the lift pump, hi preaaure pump, filter, FPR, rail, and injectors.

Try jumping the inertia switch? Doubt thatll help but itll take 5 seconds to do.

Corrosion on the relay plug?

Longshot but a plugged/kinked line?

 

[adsm08]

What is the function of pin 22 on the fuel pump relay? If it is part of the coil side it is probably the ground side and you see low voltage koer because the voltage is dropping across the magnetic coil.

 

[aball4620]

Converting a 2.9 to carburation is very expensive and tricky thing to do.(No 2.8 parts dont really work) Trust me i checked into it when i fought mine for a year before finally figuring it out.

Im stumped at this point though.

Ill summon the big guns..

@RonD @adsm08 @PetroleumJunkie412 @fastpakr

yeah I don’t think the expense and effort of converting and still having a 2.9 when it is all said and done is a worthwhile endeavor....

Still searching for a new or I guess remanufactured eec that isn’t cardone without much luck. That might be the only option at this point. They do Pop up in the local junkyards from time to time but it seems the $50 junkyard find vs $110 remanufactued is a no brainer. Seems like that is the next step here.

 

[rusty ol ranger]

yeah I don’t think the expense and effort of converting and still having a 2.9 when it is all said and done is a worthwhile endeavor....

Still searching for a new or I guess remanufactured eec that isn’t cardone without much luck. That might be the only option at this point. They do Pop up in the local junkyards from time to time but it seems the $50 junkyard find vs $110 remanufactued is a no brainer. Seems like that is the next step here.

I would go for the cardone. Should have a warrenty. Buy it from one of the big parts stores i doubt youll have an issue if it takes a shit.

 

[aball4620]

What is the function of pin 22 on the fuel pump relay? If it is part of the coil side it is probably the ground side and you see low voltage koer because the voltage is dropping across the magnetic coil.

So that is a normal reading then? I’m going off of http://www.auto-diagnostics.info/ford_eec_iv and the Haynes diagram. And yes it is the coil side. That diagram also has the “VIP test connector” branched off between the relay and the computer, but I’m not seeing where that is or what it is for.

 

[aball4620]

After rereading your post again...

I dont remember seeing this but you are getting full voltage to the fuel pump on the frame (hi pressure) right?

Theres only 6 things that get fuel to these things...the lift pump, hi preaaure pump, filter, FPR, rail, and injectors.

Try jumping the inertia switch? Doubt thatll help but itll take 5 seconds to do.

Corrosion on the relay plug?

Longshot but a plugged/kinked line?

Missed this first reply, I’ve checked power to so many things I forget if I’ve done the high pressure pump but will do it again. I must have as I hardwired it at one point but I’ll get it done again this weekend. I’ll also grab fresh compression readings. The inertia switch was removed and wire nutted by the PO. I still have the switch in the box ‘o parts that came with it. The three relay harnesses were all rotted when I got the truck, so when this started I soldered in new ends for all three - eec, fuel pump, and wot. I still think there could be a rotten wire somewhere deep in the harness, but it’s not at the ends.

I did have a slightly kinked feed poly line between the tank selector and the reservoir. I replaced that in a long shot but don’t see any others. But now that you bring it up I haven’t removed the rubber surround on the lines that attach to the fpr and rail. They were moved off to the side during the head install and that polyurethane does seem to stiffen up. Maybe there’s a kink in the feed line? I have a roll of poly fuel injection line from a different project, perhaps just replacing everything is the way to go.

 

[aball4620]

Going through the grounds couldn’t hurt either. Might try to find the 5-6 point splice this weekend as well.
The fuel system on this ting has been possessed since I got it. I replaced the high pressure pump shortly after. Then a year or two later going around a curve it sputtered and shut down. Checked the rail and there was no pressure. Had it towed home. Couple days later hopped in and fired right up.

 

[RonD]

Yes, the Carb thing is attractive when talking about it but not very practical when doing it, lol
Also need a HEI distributor conversion, as current TFI setup needs EFI computer

Pin 22 is the Ground for Fuel Pump relay's coil, computer grounds and ungrounds pin 22 to control FP relay

The VIP/OBD1 connector has a slot that is a tap for the pin 22 wire, seen here: https://www.therangerstation.com/tech_library/OBD_I.shtml

The Fuel Pump Slot is labelled in 2nd drawing

Key on, that slot should show battery voltage
Its important to test battery voltage key off, and then key on, FIRST, so you have a base line for TODAY'S testing
Key off voltage needs to be 12.3v to 12.8volts
Key on voltage should stay at 12.3v or higher, lower means battery is close to "end of life", EOL

Key on that OBD slot should show Battery Volts when measured to ground
Relays only use 1/2 an amp, .5amp, so won't be a big voltage drop unless connections are corroded

The voltage comes from EEC/PCM relay, EEC relay's coil is grounded full time, when you turn on the key the ignition switch sends the EEC relay's coil Battery Voltage, so it closes
EEC relay fuse then powers EEC(computer), fuel injectors, IAC Valve, most solenoids, and FP relay's coil

Battery Positive--------ignition switch-----------EEC Relay--------FP Relay-----------OBD slot-----------pin 22(EEC)

Not sure why you would see a voltage drop under 5volts with key on at pin 22

You can put a Ground Jumper in the FP slot on the OBD connector, this takes the EEC out of that loop, and FP Relay will power on the fuel pump full time when key is ON
This is good for testing, engine doesn't need to be running to test pressure or tank selector switches, and doesn't hurt anything to drive around this way, its what the Computer is suppose to be doing, grounding FP relay full time when engine is running

If Battery voltage is dropping at the FP slot then issue is at the 12volt end, corroded wires on EEC or FP relays
You can test voltage at easy to get to fuel injector wire, as these all share the same 12v as the FP relays coil with key ON
Either injector wire should show Battery Voltage with key on


Engine running voltage is alternator voltage not Battery voltage, so its different in that it will be above 14v just after start up and then 13.5-13.8v after a few minutes of engine running, assuming alternator and voltage regulator are working
You can switch volt meter to AC Volts, and test battery engine running, should show, under .5vAC
While its rare a failing alternator can leak AC volts which will cause odd issue with vehicle electronics

 

[adsm08]

Battery Positive--------ignition switch-----------EEC Relay--------FP Relay-----------OBD slot-----------pin 22(EEC)

Not sure why you would see a voltage drop under 5volts with key on at pin 22

Come on Ron, you are smarter than this statement. Pin22 is the ground, how many volts should you have on a ground?


My understanding was that the pin 22 voltage didn't drop until the engine is running. That means the relay is engaged and all the voltage drops across the magnetic coil.

Voltage should stay close to VBATT KOER because the relay isn't grounded and so the biggest load in the circuit is the open after the relay, so almost nothing drops across the relay.

 

[Dirtman]

@RonD And @adsm08 Fight Fight Fight.

 

[RonD]

LOL

Yes, its a Ground and you could test for that for 2 second with key ON, if you put meter on battery positive and pin 22 or OBD slot, it would show battery voltage for those 2 seconds
But before, during and after that 2 seconds it will show battery voltage(if circuit is working), and while engine is running, alternator voltage, if meter is grounded

It depends on how you place your meter, if you are testing for voltage then meter is grounded and other probe will show + voltage when voltage is on the wire being tested
If you are testing for ground then you put meter on positive voltage and touch other probe to potential grounds, when you see voltage on meter its a good ground

So you could test OBD fuel pump slot that way as well, engine running, meter on battery positive and other probe on the slot, should show alternator voltage because pin 22 wire is a ground and also a voltage wire

 

[adsm08]

LOL

Yes, its a Ground and you could test for that for 2 second with key ON, if you put meter on battery positive and pin 22 or OBD slot, it would show battery voltage for those 2 seconds
But before, during and after that 2 seconds it will show battery voltage(if circuit is working), and while engine is running, alternator voltage, if meter is grounded

You are wrong. If we were talking about amps you would be correct, but we are talking about volts.

Amperage is constant throughout the circuit. Voltage drops across the loads.

The relay coil is the load in this circuit. Assuming he had not other loads, or any excess resistance (not true, he clearly has upward of one ohm of resistance between the relay and the chassis ground) the voltage reading at the ground side of the relay, with the circuit active, would be half a volt or less. The voltage drops across the loads.

Electrical parlance has a specific term for a circuit that does have voltage on the ground side. A short.

 

[adsm08]

Ok, I got out the boy's electronics kit and build a demonstrator circuit.

Basic ~4.5 circuit, meter's showing VBATT

Open circuit voltage after the load

I lost a little more than I would normally have if I'd had a motor or an incandesant bulb, but this is a 2-way LED (turn it around and it lights up a different color).

Voltage after the load, with the circuit on

All voltage drops across the load.

 

[RonD]

Not sure how to respond, not what I see in voltage circuits I test, but I see what you are saying in your test

So I will stand corrected, but just came back from my 1994 after testing OBD slot and it still shows the 14v with engine running and meter grounded

 

[adsm08]

Not sure how to respond, not what I see in voltage circuits I test, but I see what you are saying in your test

So I will stand corrected, but just came back from my 1994 after testing OBD slot and it still shows the 14v with engine running and meter grounded

That is indeed unusual, as the voltage should have dropped across the relay.

Later today I'm going to test that on one of mine, which are using wiring from that era.