Needing some help. Working on my son's first truck 1984 F250 6.9. The engine is slow to crank, we've replaced the starter with a gear reduction starter, two new batteries, new starting solenoid on fender, new positive battery cable. The negative cables have no corrosion and are not kinked or have been worn through. Any ideas on what to look for? I'm going to pull the ground cable ends off of the block get. chassis and clean those .

Thanks for the help
Chad

 

Here's the information you need.

https://www.ford-trucks.com/forums/1...w-starter.html

 

You have at least 3 positive cables on that truck. One going across the radiator from battery to battery, and one going from the batteries to the solenoid and then one from the solenoid to the starter.

I had a diesel like this where everything had been replaced, and it still cranked slow. After much experimentation, I found out the mounting surface where the starter mounted was corroded. You could see the burn marks in the new starter flange where it mounted. I had to take a drill and mount a sanding pad on a mandrel and put it in the drill, and go over that whole surface grinding down a bunch of white corrosion off the bellhousing area where the starter mounted. Cranked over fine after that.

 

Does your installation have the battery ground cable going all the way to one of the starter hold down bolts.
Also, I guess with dual batteries, you would have to connect the negative posts together with an extra cable. To avoid using the engine block as a grounding path for current.
If the battery ground cable takes a shorter path to the nearest engine block mounting point, you could use the same point to add a ground cable all the way to the starter mounting bolt.

Jim

 

The diesels had two heavy ground wires. Driver's side battery negative went from the battery to the front corner on the driver's side of the block. The pass side battery had another heavy ground cable going from the battery neg to the pass side front corner of the block.

 

Yes, that's the the ground cables are run. I did pull off the ground cables and the copper has severe oxidation. I'll let you all know the results when I replace the cables and verify no corrosion between the starter and bell housing.

 

Thanks for the information. It's all been very helpful. I've replaced the ground cables from the block to the batteries and I've ran additional ground cables from the block to the frame, block to the starter and block to the cab. It will spin over like a top, but the batteries run down fairly quickly, so I was going to pull start it. Should I leave the injector lines slightly cracked or just tighten them down and pull it all over the field until it fires?

 

Why were the lines open up?
Was the filter changed and if so fill it with fuel if you can.
I would leave them tight as you dont want to spray fuel all over the engine bay.
I know you are not to use starter fluid but a vary little shot would not hurt it and the motor firing will bring the fuel up faster than pulling it.
Dave ----

 

I had to replace the IP. Yes the filter was changed and I filled it with fuel and bled the Schrader valve.

 

Did you ever run through the voltage drop test suggested back in post #2?

You've said “the batteries run down fairly quickly” but is that based on the starter cranking speed? Or did you measure the battery voltage to be sure?

One possibility is a marginal connection somewhere in the starter circuit. This adds a bit of resistance which generates heat. The heat increases the resistance, starting a vicious cycle. Meanwhile, the starter slows down so the poor batteries get blamed.

That's why I keep pimping the voltage drop test. It’s a hybrid test that does two important things: It makes sure the batteries can deliver the massive flow of electrons required by the starter. And it makes sure the rest of the starter system can deliver that flow without undue restriction.

A starter system in good working order should be able to reliably get the crankshaft spinning at a healthy clip. No idea about endurance, but most starters require a cool down period after 30 seconds or so. Don’t burn up that poor starter trying to purge the fuel system. There’s no need to pull start the truck. The starter should be able to handle it. Figure out why it can’t and fix that.

The fuel system was designed to be purged within the time constraints of the starter duty cycle. If that isn’t happening, and the starter system is doing its job, the fuel system needs some love.

For best results with the voltage drop test, duplicate the fault conditions as much as possible. This will aggravate the fault and make it easier to pinpoint.

 

I did the volt drop test prior to replacing the ground cables. When I put a charger on it, it will spin the engine quickly. I've added a video showing it turning over. It's now spinning over much faster. Now I think my issue is just getting fuel to the injectors. But I could be wrong.

 

Have you run the test after replacing the cables? May sound crazy, but there's a very valid reason.

Let's say you have more than one fault, not a rare situation at all. The voltage drop test would have found the worst one first. This was the primary choke point, reducing current flow through the entire circuit. After fixing Fault A, previously unknown Fault B joins the chat and starts acting up because current flow returns closer to normal everywhere. Wasn't noticeable because it was overshadowed by Fault A.

 

If you use starter fluid disable the glow plugs. There should be no reason to use ether on a diesel. Also if your battery quickly runs down after charging it fully I question the condition of the battery.

 

For help with changing out an IP I recommend you start a thread over on the IDI forum.

https://www.ford-trucks.com/forums/forum117/

You'll find more help with that aspect.
Have you tested your glow plugs and what kind of GP system do you have?

there are many things that could be causing hard starting so start a new post over on

https://www.ford-trucks.com/forums/forum117/

 

I am guessing you have not owned or done a fuel injection pump or fuel filter change on a diesel?
You better have some really good batteries as you will need to crank the sh** out of the motor to get fuel to the injectors.
I had a 1986 GM 6.2 from new for 16 years, 230k miles when I sold it so I know what it takes to get fuel to the injectors and get it to run.

He found cables that were a problem but now sounds like the batteries might be a little weak on his rig but once it is running should start easy if the glow plugs are working.
Dave ----