Hi,
Been working on a crank,no start problem(s)!

Fixed the no spark problem but have now hit a wall with a voltage drop on my EEC relay!

I have 12.2V going in from the battery but only 4.9V coming out.

I have 11.8V going into the switch side and a good ground.

By the testing procedures this would indicate a BAD relay but....

I have now tried all together THREE NEW relays and have installed a new Borg Warner connector!

I am admittedly lost on this?

I cannot figure how I can have the right voltage going in and half coming out?????

Oh yea, when I supply B+ voltage to the red out supply wire with my PP3, the truck starts and runs!!!

Any ideas on this is appreciated!

 

The problem may be your relay socket, particularly a corroded connection on the battery side contact.

 

Hi,
Thanks, as I said....

I installed a NEW Borg Warner connector!

This test to be a BAD relay, but I've tried 3 new ones?????

I just ordered a "Bosch Type" relay and will hook that up straight to the wiring!

See what that does????

 

Sorry, missed that.

Still, check what happens to the battery voltage going in to your relay when the relay is energized. Bet it drops from 12 to something much more equal to what you are measuring on the output. Cause will still be something high resistance in the supply line from the battery. I believe this would be the yellow wire and it is fed by a fusible link at the starter relay.

 

Hi,
No, I am checking the supply from the fusible link and it is 12.2V!

I know and understand the confussion as this makes no sense!

!2.2V going in and 4.9V coming out???

When I put B+ to the red wire (supply OUT) the truck starts!

I know WHAT the problem is but NOT why it is happening????

Thanks!

 

Well, I'll try again.

You know the vehicle runs when you put the battery voltage directly to the relay OUTPUT. This means you do NOT have a short circuit between the relay and the ECM and the circuit is intact.

You know you have full 12 volts applied to the INPUT relay and I am going to assumes that the relay is not energized. You also know the voltage at the relay OUTPUT only reaches about 5 volts when the relay is energized. ( Ignition on). This indicates that when the load of the ECM is connected to the switched relay circuit, there is sufficient resistance between the relay and the battery to drop the voltage. Please note the voltage drops only when the load is connected by the relay contacts. That is how resistance works in a series circuit. Ohm's law stuff here.. We know the resistance is not in the relay contacts or the relay socket. 3 new relays would be sufficient here. We also can assume the battery voltage at the battery terminals is not dropping thanks to your test with running battery voltage to the relay output, presumably from the same vehicle battery. So, there must be resistance between the INPUT of the relay and the positive battery terminal.

But where?

I happen to know that there is a single yellow wire of a fairly heavy gauge running from the ECM relay to the battery positive post of the starter solenoid through a fusible link near the solenoid. This portion of the circuit contains unwanted resistance. This will likely be a corroded spot in the wire, or more likely a corroded connection at the fusible link, possibly even a damaged fusible link.

Sorry to over explain, but I wanted to make sure we are understanding the same thing here.

 

...................................

 

Not too long ago someone referenced a YouTube video from an experienced mechanic where he had perhaps a similar (same?) issue that really dogged him. Ultimately he sorta gave up and just ran a new length of wire in place of the suspect circuit.

I don't have more details than that - the post above seems to suggest a similar diagnosis.

 

89' F-150 - What engine do you have ?

 

What happens when you put a jumper in your relay socket, between the Yellow Terminal & Red Terminal ?

 

Another check you can do is power up one of your relays, and measure the resistance on the switch side of your relay.

 

FYI -

https://www.f150forum.com/f10/eec-relay-problem-398247/

 

That one certainly led him down the garden path!

Not his first kick at it here either.

https://www.ford-trucks.com/forums/1...d-voltage.html

I'll stand by my conclusions about the fusible link and starter relay end connections. FWIW, that yellow wire runs across the rad cradle from the solenoid on the passenger side to the relay on the driver side fender well.

 

Hi,
Thanks "Not Enough Trucks" I work out of town and my truck is broke down in the parking lot and that is where I have to work on it and this has been a VERY aggravating issue!

Thanks again for the help and explaining the "theory" of the voltage drop.

Admittedly, I thought if I got B+ voltage from the starter relay fuse link (yellow) wire that that could be no problem?

I see now what you are sayin about "load" when the relay comes on from the ignition wire.

ScannerDanner is the guy with the 88 F-150 4.9L (just like mine but mines an 89)

However he didn't have but about 5.0V coming from the yellow fuse link wire to begin with. (I believe!)

I am now charging my battery as it is finally down, but will go look (again) and see if I can find the yellow fuse link wire, to look for damage.

VJsimone, I have replaced my ignition switch as it did have some "burn/discolor" on a couple of terminals?

Does not mean the wiring is good but I think I will chase the yellow fuselink relay first.

The starter does work with a charged battery!

Thanks for the help!!!

Once again sorry fellas have been all over the Internet on multiple Forums trying to get a handle on this!!!

 

Just rule it out temporarily to test it.Run a fused wire directly off the battery and feed it a 100% known,clean battery voltage.Within a few mins,you could have all your issues resolved.Then,you could either replace the original fusible link or simply insert a fusible link in your new circuit,run directly from the battery.No rule says you can't run a new line.