IDI Electrical Gremlins

[90Mistake]

My '90 IDI 250 has a new alternator, batteries, and I've tried 2 new voltage regulators, cleaned and verified grounds. I used to be able to start my truck with a quick jump while I was in the troubleshooting phase (initially it wouldn't charge so I though voltage regulators) but now it wont even crank.
Ill turn the ignition for the WTS light to go out and all the dashlights will just fade to black after a few seconds and Ill have no power whatsoever. Its like my glow plugs are drawing everything my batteries have to offer or my voltage regulator isn't letting any juice through.
Sometimes I'll turn my headlights on for some draw and my dash volt meter will come out of the red but I'll get one good crank from the starter before I'm dead again.

If this post makes me seem like I don't know anything about what I'm talking about, you're right! I've been reading through the forums and done the best I can with the little knowledge I have. Truck has been a trooper for the few thousand miles I've owned it and i've replaced so much, but I'm afraid being a parts replacer is the extent of my knowledge. Any help would be appreciated.

 

[franklin2]

The regulator doesn't do anything unless the engine is running. So forget about that for now.

1st thing to do is manually charge the batteries with a plug in battery charger. Make sure they are topped off, this will probably take all night if they are dead.

Then try to crank it. If it still dies out, you most likely have a connection problem at one of the batteries, or a corroded large cable. You could also have a bad ground or ground cable where it hooks to the battery or where it connects to the engine block on both sides.

With those large cables, a bad connection can pass enough juice to run the radio or a few lights, but when the large current draw from the glowplugs or the starter hits the bad cable or bad connection, it cannot pass all that current and everything dies out.

 

[Austin86250]

had the exact same issue it turned out be the positive battery cables
it was a hard one to diagnose as it had 12v to everything and strong power until I cranked it had me stumped for a while
buy the whole positive cable harness

 

[Big Bart]

My '90 IDI 250 has a new alternator, batteries, and I've tried 2 new voltage regulators, cleaned and verified grounds. I used to be able to start my truck with a quick jump while I was in the troubleshooting phase (initially it wouldn't charge so I though voltage regulators) but now it wont even crank.
Ill turn the ignition for the WTS light to go out and all the dashlights will just fade to black after a few seconds and Ill have no power whatsoever. Its like my glow plugs are drawing everything my batteries have to offer or my voltage regulator isn't letting any juice through.
Sometimes I'll turn my headlights on for some draw and my dash volt meter will come out of the red but I'll get one good crank from the starter before I'm dead again.

If this post makes me seem like I don't know anything about what I'm talking about, you're right! I've been reading through the forums and done the best I can with the little knowledge I have. Truck has been a trooper for the few thousand miles I've owned it and i've replaced so much, but I'm afraid being a parts replacer is the extent of my knowledge. Any help would be appreciated.

Charge the batteries and then test for 12.4-12.6v. If less I would have your new batteries tested where you bought them.

I would also clean the wires going to the starter solenoid on the fender well, that is where the truck cab pulls the +12 power from. (The side with 4 or more wires going to it.)

It sounds like bad batteries or voltage drop on the cab power due to a bad/corroded connection. FYI just because you bought new batteries does not mean one or both are not bad out of the box.

If your dash is going dim

1) Your batteries are likely at less than 9v. Not charged, lack capacity, or were bad out of the box. (Or you drained them all the way down too many times and killed them, but they are under warranty.)
2) You have a bad +12v connection from the fuse box to the starter solenoid or starter solenoid to the positive side of the battery. The batteries are good and hold 12v but the wiring to the cab has a voltage drop along the way. So turns on, as the wire heats up the bad connection the dash lights fade off due to voltage drop. Usually fixed by cleaning the connections on that circuit. Start with the connections on the starter solenoid.
3) A voltage drop from the fuse box to the dash.
4) A bad ignition switch. Common wear item on these old trucks. Located on the steering column by the brake pedal.

If your batteries test at say 12.4 volts but after running the glow plugs for 15 seconds and turn off now the batteries now read between 6-10 volts your batteries are bad or rated too low. The glow plugs can run your batteries to say 10v when on but the batteries shoukd bounce back to 11-12.6v when the glow plugs go off.

If after fixing the dash lights your truck still has starting issues check out this thread.

The PDF version at the bottom of the thread is easier to follow.

How to diagnose when your IDI starter will not turn the engine over

How to diagnose a Ford IDI pickup that will not turn over or turn over correctly. (Van’s are similar.) This tech article is to help those less familiar with how your starter system works. It will help you through a set of tests to help you figure out what to do when your truck will not turn...

www.oilburners.net

 

[90Mistake]

I was cleaning grounds and testing my solenoid with a screwdrover when all of a sudden my throttle linkage glowed orange and burnt up! Gonna check ground from block to cab first and get back

 

[IDIDIDIhoDhoDhoDO]

Throttle cable passes right over the glow plug solenoid. Is it possible the sheath on your throttle cable wore through back there and was shorting to a 12+ terminal at the GP solenoid?

 

[Big Bart]

I was cleaning grounds and testing my solenoid with a screwdrover when all of a sudden my throttle linkage glowed orange and burnt up! Gonna check ground from block to cab first and get back

So let’s talk this through.

When you jumped the solenoid did you turn on the key just prior? This fact will help us guide you.

When you jumped the solenoid with a screw driver the starter wanted to power up. It needs a lot of amperage. FYI that does not turn on the glow plugs or anything inside the truck but if you turned on the key prior it should have turned on the glow plugs for say 8-15 seconds and any options left on inside the truck. (Heater fan, radio, etc.)

Above in your opener you said all your grounds where cleaned and verified, so I assume they were good. If you had a good block ground the starter would not of used your throttle cable as a ground. To your point the cab may have been looking for a ground. I do not think the truck body would use enough amperage to make the throttle cable glow but perhaps if you had on lights, fan, and a stereo on high it would. By now guessing you have addressed the cab ground.

So double check your block ground is clean, grease free, and tight. The battery cables on these trucks are getting old, corroding, splitting, and thus are becoming less conducive. So check your cables for splits and corrosion if so replace them, rock auto sells them. Maybe yours are bad, many have had to replace them.

Send some pics for us to look at.

If the starter has a good +12 (positive) from the batteries and a good -12 (Negative) from the batteries via the block ground it would not use the throttle cable. (It’s looking for the path of least resistance.) If engaging just the starter (Not the glow plugs) with a screw driver on the solenoid is causing the throttle cable to glow it’s likely the following.

1) A bad ground cable to the block. (Corroded or cracked inside.)
2) A bad ground connection at the block. (Pull, clean, sand, and tighten.)
3) Your starter is fried and grounding out so much even the battery cable is overwhelmed. So it seeks additional grounding from the throttle cable. This means pulling the starter and having it tested.

IDIIDI has a good point, it might be related to your glow plug system. If you turned on your key, then went to the solenoid and used a screw driver to jump the starter. It might be the glow plug system is arcing onto your throttle cable. So nothing to do with the starter just happens to be at the same time as starting. Glow plugs go on when you turned the key on, stopped when the timer shut them off, or when you turn the key to off. To you it appeared as the starter did it, but it was just happening at the same time. So check to see if the throttle cable is touching a glow plug wire, the glow plug solenoid on top of the controller, or the controller. The controller/solenoid unit is supposed to have a plastic cover but they break or fall off so many are missing it.

But with the key off, if you use a screwdriver to test the starter solenoid, that does not turn on the glow plugs on a 7.3. It does not turn on anything in the cab. So if the key was off when the throttle cable got hot, it’s a ground issue to the block, a bad battery cable, or the starter is arcing out and is shot.

Let us know what you find.

 

[franklin2]

I was cleaning grounds and testing my solenoid with a screwdrover when all of a sudden my throttle linkage glowed orange and burnt up! Gonna check ground from block to cab first and get back

You are getting close. Like was said above,more than likely one or both of your large grounds to the engine block is bad. So when the starter demanded all that power when you shorted the solenoid, it found a smaller ground through the smaller ground wires to the cab, and then through your cable. When you check your smaller cab and other sheetmetal grounds again, don't be surprised if they have been a little toasty also.

Using the keyswitch, the voltage dropped out enough to drop the solenoid out and sort of protected everything. When you shorted the solenoid you forced the issue. Sometimes you have to do that to figure out the problem.