EEC Relay Problem!!!
Thread Starter
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Senior User
Joined: Aug 2007
Posts: 371
Likes: 4
Hi,
Thanks FORD!
I just went out to the truck and did some tracing.
There are actually 3 yellow fuse linked wires that go to the starter relay.
There are also TWO yellow wires that go into the B+ supply on the EEC relay connector.
I took my Fluke and found which fuse link yellow went to each yellow relay wire.
One yellow wire has a bigger diamater fuse link than the other, the OHM reading on that wire from end to end (starter relay unhooked to EEC relay unhooked was 1.35 OHMS!
This seems high as the other yellow fuselink (smaller dia.) was only 0.2 OHMS!
I'm wondering now if I found the high resistance that, Not Enough Trucks, was trying to explain to me?
Opinions?
I'm going to look for a decent schematic that shows this wiring!
Thanks FORD!
I just went out to the truck and did some tracing.
There are actually 3 yellow fuse linked wires that go to the starter relay.
There are also TWO yellow wires that go into the B+ supply on the EEC relay connector.
I took my Fluke and found which fuse link yellow went to each yellow relay wire.
One yellow wire has a bigger diamater fuse link than the other, the OHM reading on that wire from end to end (starter relay unhooked to EEC relay unhooked was 1.35 OHMS!
This seems high as the other yellow fuselink (smaller dia.) was only 0.2 OHMS!
I'm wondering now if I found the high resistance that, Not Enough Trucks, was trying to explain to me?
Opinions?
I'm going to look for a decent schematic that shows this wiring!
Temporarily Deactivated
Joined: Aug 2003
Posts: 1,859
Likes: 2
If I understand this:
When you are measuring low voltage "out", check the voltage "in" and track it all of the way back to the solenoid, the source. In other words: check voltage while the circuit is under a load.
When you are measuring low voltage "out", check the voltage "in" and track it all of the way back to the solenoid, the source. In other words: check voltage while the circuit is under a load.
Fleet Mechanic
Joined: Mar 2014
Posts: 1,926
Likes: 116
From: Saskatchewan Canada
Well, I think you have found your problem. The yellow wires are designated circuit #37 in your diagram. One feeds the EEC power relay, the other the fuel pump relay.
You could do as FordF250HDXLT suggests and run a temporary power line to the input side of the relay, or possibly even run tests under load in around the area of that suspect fusible link.
You are likely moments away from solving this problem!
You could do as FordF250HDXLT suggests and run a temporary power line to the input side of the relay, or possibly even run tests under load in around the area of that suspect fusible link.
You are likely moments away from solving this problem!
Thread Starter
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Senior User
Joined: Aug 2007
Posts: 371
Likes: 4
Well, I think you have found your problem. The yellow wires are designated circuit #37 in your diagram. One feeds the EEC power relay, the other the fuel pump relay.
You could do as FordF250HDXLT suggests and run a temporary power line to the input side of the relay, or possibly even run tests under load in around the area of that suspect fusible link.
You are likely moments away from solving this problem!
You could do as FordF250HDXLT suggests and run a temporary power line to the input side of the relay, or possibly even run tests under load in around the area of that suspect fusible link.
You are likely moments away from solving this problem!
Thanks Ray!
Do you think the resistance (1.35 OHMs) is really high?
The problem that I see is IF I replace the fuselink and there is a short somewhere in that wire.
It will just blow again?
I guess I could peice the wire right in front of the fuselink and then see if the resistance drops?
If so then a new fuse link might work, if not then will probably need a new wire with fuselink.
Thanks for the help on this!
Yep I just looked up 14 Ga. wire resistance and they give 2.5 OHMs for 1000 FEET!
I guess I have a problem with 6 feet giving me 1.35! Ha!
Fleet Mechanic
Joined: Mar 2014
Posts: 1,926
Likes: 116
From: Saskatchewan Canada
When you do the math, you would be dropping over 5 volts across that 1.35 ohm resistance with 4A of current. Actual numbers will vary, but I'm sure the ECM pulls over 4A.
If you want to measure this, you need to do a voltage test at three points, all under load, so the key must be on. Check the voltage at the battery post of the starter solenoid. Then test the voltage after the fusible link. You can pierce the insulation of the yellow wire to do this. Finally test the voltage as applied to the input of the EEC relay. Again, the yellow wire and pierce the insulation. I expect you will read full battery voltage at the starter solenoid and you will read something equal to the 5 volts you were reading at the output of the EEC relay on the input. What you read at the splice for the fusible link will tell you if the problem is the fusible link and/or connection, or the yellow wire which runs along the rad cradle from the solenoid/fusible link to the EEC relay.
I'm still betting on the fusible link and/or connections.
If you want to measure this, you need to do a voltage test at three points, all under load, so the key must be on. Check the voltage at the battery post of the starter solenoid. Then test the voltage after the fusible link. You can pierce the insulation of the yellow wire to do this. Finally test the voltage as applied to the input of the EEC relay. Again, the yellow wire and pierce the insulation. I expect you will read full battery voltage at the starter solenoid and you will read something equal to the 5 volts you were reading at the output of the EEC relay on the input. What you read at the splice for the fusible link will tell you if the problem is the fusible link and/or connection, or the yellow wire which runs along the rad cradle from the solenoid/fusible link to the EEC relay.
I'm still betting on the fusible link and/or connections.
Thread Starter
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Senior User
Joined: Aug 2007
Posts: 371
Likes: 4
Hi,
Thanks!
My battery voltage is down but I hope to get it on a charger tomorrow if I can.
I work out of town and the truck is in the parking lot.
Not as nice to work on as at my house in the driveway in front of my little shop.'
I'm also hoping for a bad fuse link so I don't have to run another wire.
I might run a temp wire just to see if that puts me back in business.
I had a few problems at the same time it seems (truck has 300,000 miles!)
And this thing has been driving me crazy!
Thanks for the help, I do appreciate it!
Thanks!
My battery voltage is down but I hope to get it on a charger tomorrow if I can.
I work out of town and the truck is in the parking lot.
Not as nice to work on as at my house in the driveway in front of my little shop.'
I'm also hoping for a bad fuse link so I don't have to run another wire.
I might run a temp wire just to see if that puts me back in business.
I had a few problems at the same time it seems (truck has 300,000 miles!)
And this thing has been driving me crazy!
Thanks for the help, I do appreciate it!
Tuned
Joined: Apr 2007
Posts: 372
Likes: 15
From: Central Minnesota
Had the same problem mid 90s 250. Turned out to be the wire feeding voltage to the relay. After chasing everything for a couple of days, took the plug in connector to the relay apart. The + feed wire had only 1 strand of wire. This would pass voltage (read on a digital meter) but no current to power the relay. The clue came when I switched to an analog meter. These take a lot more current to work and the meter wouldn't register. Somewhere you've a corroded wire. This wire was corroded, not broken the others in the socket where flawless. Something in the factory soldering process? Who knows..................
Thread Starter
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Senior User
Joined: Aug 2007
Posts: 371
Likes: 4
Hi,
Yea, who knows is right!
I went back this afternoon after work and ran a resistance test again on the yellow wire infront of the fuse link and got 350 OHM's!!!
WTH? Tested just the fuse link and got 0.2?
Was hoping it would be the other way around.
Ran a straight B+ wire from starter relay to EEC relay.
Tried to start truck but would not start.
Then checked for voltage back probing EEC Relay and now have no power from ignition switch???
Got dark on me and quit for the day.
Will probably be a few days before I can get back to it but that's where I am?
Don't know why I lost ignition voltage?
This truck is driving me crazy of course, I fear I have some wire harness issues?
Yea, who knows is right!
I went back this afternoon after work and ran a resistance test again on the yellow wire infront of the fuse link and got 350 OHM's!!!
WTH? Tested just the fuse link and got 0.2?
Was hoping it would be the other way around.
Ran a straight B+ wire from starter relay to EEC relay.
Tried to start truck but would not start.
Then checked for voltage back probing EEC Relay and now have no power from ignition switch???
Got dark on me and quit for the day.
Will probably be a few days before I can get back to it but that's where I am?
Don't know why I lost ignition voltage?
This truck is driving me crazy of course, I fear I have some wire harness issues?
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Fleet Mechanic
Joined: Mar 2014
Posts: 1,926
Likes: 116
From: Saskatchewan Canada
That very well may be.
Had a glance back at your previous threads. Looks like endless tests and parts replacement and it is getting difficult to see exactly where you have been and what has been replaced. One of the hazards that comes with multiple threads.
I thought I saw somewhere that you had replaced the ignition switch. Given the poor quality of some replacement parts these days, it becomes quite possible that your new switch has failed.
Just a thought and I can agree that you may have harness troubles. May be worth the time to open up the firewall connector and make a simple visual check. Corrosion here could explain these multiple faults. Harnesses are quite reliable, but corrosion is the enemy. Visible corrosion usually means water. Any chance your truck got dunked in the past? Lots of older vehicles around that came out of floods and hurricanes.
Sounds like you have the correct tools and information on hand to troubleshoot. Pay attention to your power and ground distributions and you should come out with an answer.
Had a glance back at your previous threads. Looks like endless tests and parts replacement and it is getting difficult to see exactly where you have been and what has been replaced. One of the hazards that comes with multiple threads.
I thought I saw somewhere that you had replaced the ignition switch. Given the poor quality of some replacement parts these days, it becomes quite possible that your new switch has failed.
Just a thought and I can agree that you may have harness troubles. May be worth the time to open up the firewall connector and make a simple visual check. Corrosion here could explain these multiple faults. Harnesses are quite reliable, but corrosion is the enemy. Visible corrosion usually means water. Any chance your truck got dunked in the past? Lots of older vehicles around that came out of floods and hurricanes.
Sounds like you have the correct tools and information on hand to troubleshoot. Pay attention to your power and ground distributions and you should come out with an answer.
Thread Starter
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Senior User
Joined: Aug 2007
Posts: 371
Likes: 4
Hi,
Thanks Ray!
I did put in a new ignition switch but it was a MOTORCRAFT.
I try to go MC with everything I replace if possible.
This truck is driving me crazy and I wonder now if it would of drove a real FORD Mechanic crazy.....
Which I am not!
Things like the resistance reading on that fuse link yellow wire...
1.35 ohms one day and then 350 ohms the next???
This truck has been doing things like that since this started?
I had no idea it would get this bad starting out!
This has been a GREAT truck for 25 years but now...I don't know?
I'm wondering if any one makes a wiring harness for it?
I'll post back when I'm able to get back to it, working now and this holiday weekend too!
Thanks again!
Thanks Ray!
I did put in a new ignition switch but it was a MOTORCRAFT.
I try to go MC with everything I replace if possible.
This truck is driving me crazy and I wonder now if it would of drove a real FORD Mechanic crazy.....
Which I am not!
Things like the resistance reading on that fuse link yellow wire...
1.35 ohms one day and then 350 ohms the next???
This truck has been doing things like that since this started?
I had no idea it would get this bad starting out!
This has been a GREAT truck for 25 years but now...I don't know?
I'm wondering if any one makes a wiring harness for it?
I'll post back when I'm able to get back to it, working now and this holiday weekend too!
Thanks again!
New User
Joined: Aug 2021
Posts: 1
Likes: 0
I'm having this problem now.
Did you ever identify the cause of your EEC relay low (only 4.9V coming out) output voltage? I'm having this problem and i'm stuck. Thanks in advance.
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!
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!
Logistics Pro
Joined: Aug 2014
Posts: 3,570
Likes: 854
Well, he either fixed it or got rid of the truck 3-4 years ago.
Not sure why they were focused on the EEC socket relay.
Anyways, my first thought was bad ground or dirty battery posts on both positive and negative.
Then realized they only had 12.2V on the battery, that is low in my book. Should measure at least 12.5V.
So, first things first, charge the battery, and verify neg/pos terminals are clean shiny metal.
Not sure why they were focused on the EEC socket relay.
Anyways, my first thought was bad ground or dirty battery posts on both positive and negative.
Then realized they only had 12.2V on the battery, that is low in my book. Should measure at least 12.5V.
So, first things first, charge the battery, and verify neg/pos terminals are clean shiny metal.
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