Electrical problem on start (with engine temp?)

[Sergey]

The temp and brake lights will come on in crank position regardless if it starts or not.

Hmmm....

EDIT: The red overheat and water in fuel lights are supposed to come on in the crank position. It's only a lamp check.

I did not know that there is a lamp check in 85 F250.
To summarize, here is how dashboard lights work on this truck for the last 25 years I know it

1. red Brake light comes on only when parking break is engaged, regardless of key On or key in Start
2. red Glow plugs light comes on when glow plugs are on, controlled by timer
3. red Water in Fuel light never ever came on, even when there was water in separator
4. red Engine Temp light never came on regardless of key On or key in Start, till this problem

And I thought it should be that way, since it all worked very reliably for decades.
It appears now that my truck wiring has a problem for a long time and I never knew ?

Thank you for providing schematics.

 

[Big Bart]

Some food for thought.

1) I would first just check the starting system from the soleniod to the starter. Take the wiring harness and safety switches out of the picture.
a) Get a multimeter and check the voltage at the battery terminals. (Confirm you have 12.2-12.6 volts.) Keep in mind you have two batteries but one good batttery will not always be able to overcome a second bad battery.
b) Get a remote starter switch. (Auto parts store if you do not have one, or make one.) Hook one side to 12v positive of the battery and the other to the starter soleniod starter post. (Small post that sticks off the solenoid that the truck energizes with 12v positive when you turn your ignition switch to to start.) Ford has two posts, one energizes the soleniod to make the contacts connect inside (You want this one.), and one receives 12v positive when the soleniod energizes and makes contact. (For the distributor on gassers.)
c) Push the button and you should hear or feel the soleniod click. The starter should also turn over, if not you have an issue with the soleniod, the starter cable, the ground cable to the block, corrosion, or a bad starter but not necessarily the truck wiring harness. (You can leave your ignition switch off. It works either way in this test. This way the truck glow plugs do not vary the voltage and the truck will not start, just turn over.)
d) Watch the multimeter to see what the voltage is when you hit the starter switch. You should not go below 9 volts. A little drop but not turning over, likely the soleniod is not likely working. Big drop but no start, likely a bad starter. Your auto parts store can test the starterto verify its bad.
e) Now hook the multimeter or a test light to the wire from the wiring harness that energizes the soleniod. Check for 12v positive power in the ignition start position. (With clutch depressed and in nuetral.) If no power when the key is in the start position then you have/also have a wiring issue. (Broken wire, corrosion, bad connector, bad ignition switch, bad clutch safety switch, and not sure but if it has one a bad nuetral safety switch. (I have a automatic, so neutral safety, no clutch safety switch.))

Now you can figure out what you are chasing down to repair. The high amperage starter side or the wiring harness side of the soleniod.

Good luck!

 

[Sergey]

I would look at the 10 gauge wire that goes down to the starter itself (the lighter wire, or "trigger wire"). They can get corroded or fall off after so many years. This is the wire that activates the starter, not the relay on the fender. If the solenoid on the starter doesn't energize, the engine won't turn over.

I checked the voltage on the black "trigger" wire going from relay on the right fender to starter. When I turn key to start position, then on some occasions there is 12v on trigger wire, on other occasions not.

If there is 12 v on trigger wire (even sometimes) I thought it has to be starter problem then? I went under the truck to inspect starter. Starter appeared to be covered with black sticky tar due to rear main seal leak. I then used half of a bottle of degreaser to clean starter. Then, starter outside looks okay after degreasing, but electrical part of starter - I can only see part of it - appears to be corroded.

The starter on your photo looks nice, clean and easy to work with. Actual one installed on my truck I hardly can reach its electrical part to visually inspect.
Do I have to remove starter to gain access to its electrical contacts ?

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[Farmer Rock]

I checked the voltage on the black "trigger" wire going from relay on the right fender to starter. When I turn key to start position, then on some occasions there is 12v on trigger wire, on other occasions not.

If there is 12 v on trigger wire (even sometimes) I thought it has to be starter problem then? I went under the truck to inspect starter. Starter appeared to be covered with black sticky tar due to rear main seal leak. I then used half of a bottle of degreaser to clean starter. Then, starter outside looks okay after degreasing, but electrical part of starter - I can only see part of it - appears to be corroded.

The starter on your photo looks nice, clean and easy to work with. Actual one installed on my truck I hardly can reach its electrical part to visually inspect.
Do I have to remove starter to gain access to its electrical contacts ?

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When you turn the key to the "start" position , do you hear a click from the fender mount solenoid?
It's definitely easier to get to those connections with the starter out, but you should be able to access the connections on the solenoid with the starter in, just not the short cable that goes from the solenoid to starter motor. Sometimes those short cables come loose and cause a bad connection that you can't find until you pull the starter.



Rock

 

[ISPKI]

If you are getting intermittent 12v at the starter trigger wire, between the fender mounted solenoid and the starter, then I would then check the wire from your ignition switch to the fender solenoid. If that signal is constant when ignition is in "Start" but the output from the solenoid is not, then most likely the fender mounted solenoid is shorted internally. I dont recall if that is a solid state solenoid or a mechanical solenoid/relay, since it usually clicks I would guess that it is likely a relay which can overheat and partially fail over time.

 

[Big Bart]

Ditto with ISPKI,


You should always get power to the wire that energizes the solenoid on the fender wall when you turn the key to start. If not, it simply is not going to tell the solenoid to power the starter. So only when it gets power it’s going to start. (Providing the solenoid and starter are working.)


Let's break this down again.


1) You only get occasional power to the solenoid activation wire. (Wire from starter switch to solenoid.) You need to fix this, so you get power every time you turn the key to start. But let’s see if you have other issues compounding this fix.

2) You don't suggest when it does get power that the starter turns. So let us know this is working, put the wire back on and try starting the truck say 10 times. Let us know if it starts. But lets keep diagnosing to save time checking and posting.

3) Put a jumper wire from the battery positive to the start post on the solenoid to simulate what the truck does when you turn the start key. Let us know if the solenoid does click, and if it clicks does the starter turn the engine over? If not your solenoid or starter is bad or has wiring issues. A solenoid can click but due to burnt terminals inside still not work.

4) Then take a good/heavy duty battery jumper cable and attach to the positive battery post and to the solenoid post that has the wire going to the starter. (Power up the starter.) If the starter turns the motor over the starter and wire is working.


Then let us know your findings. This way you can find/figure out if the wiring to the solenoid is the issue, the solenoid is good or bad, and if the starter is good or bad. (Could very well be a combination of things (Wire to and the solenoid.), so keep that in mind.) Also probably would not hurt to change the solenoid as they are cheap.


To Farmer Rock's point, in your pic it looks like the battery cable going to the starter has some rust or corrosion. I would suggest you take the cables off both positive battery terminals, remove the battery cable going to the starter, and clean the connection, then put everything back together. It may be part of your issue. IE - Starter is good, but due to corrosion voltage drop, the starter will not turn.


Let us know and we can suggest some help from there.

 

[Sergey]

Thank you all, lots of good suggestion to test different points on my old truck. May take some time. Will let you know what I will find.
Thanks
Sergey

 

[Sergey]

Ditto with ISPKI,
Let's break this down again.

1) You only get occasional power to the solenoid activation wire. (Wire from starter switch to solenoid.) You need to fix this, so you get power every time you turn the key to start. But let’s see if you have other issues compounding this fix.

2) You don't suggest when it does get power that the starter turns. So let us know this is working, put the wire back on and try starting the truck say 10 times. Let us know if it starts. But lets keep diagnosing to save time checking and posting.

3) Put a jumper wire from the battery positive to the start post on the solenoid to simulate what the truck does when you turn the start key. Let us know if the solenoid does click, and if it clicks does the starter turn the engine over? If not your solenoid or starter is bad or has wiring issues. A solenoid can click but due to burnt terminals inside still not work.

4) Then take a good/heavy duty battery jumper cable and attach to the positive battery post and to the solenoid post that has the wire going to the starter. (Power up the starter.) If the starter turns the motor over the starter and wire is working.


Then let us know your findings.

Let us know and we can suggest some help from there.

With several bright sunny days here I made the suggested tests on my truck electrical system.
Here is the picture showing where tests 3 and 4 were made - using Bradd's test numbering.
In test 3 the relay terminals are shorted to simulate relay closure.
In test 4 the ignition key "start" is simulated.
Both tests are successful and result in starter running and engine cranking.
So starter motor is good, starter solenoid is good, and starter relay is good too, as well as heavy wiring appears to be good. All these are factory original to my knowledge.
Due to sparks involved in these tests I only repeated those two times. It may be possible that if I were to repeat these tests 10 times there will be a case found when such test will fail.

I plan to replace starter relay anyway and to clean contacts on terminals to it, then to tests 1 and 2.

Thank you everybody

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[Big Bart]

The sparks are always a little un-nerving!

Solenoids are cheap insurance!

Glad you figured out where the issue was coming from. With some more testing you will find out was is preventing power to the solenoid on occasion. Suggest start at the ignition switch (key is moving it far enough, switch is making good contact.) go to the neutral (Auto) or clutch safety (Stick) switch for a look and testing, then look to the wiring and connectors. You will find it.

Let us know what the issue was!

 

[Sergey]

Hello,

I seem to fix the issue. The problem was in corroded starter relay connections. Both the red angular boot and the relay grounding. Apparently this relay grounds through its base, which was rusted. So, when there was 12V from clutch interlock switch coming, starter relay clicked but had not enough current to close fully, thus no starter motor action.
Sanded all connectors, and replaced starter relay with new one. Now starts every time. Hope it will last for a long time.

 

[Big Bart]

Glad you figured it out and all is well!