I have a 1987 F-150 4.9L automatic that seems to have some wiring problems. This is going to be a long post to describe the problem and what I have done so far.

Truck had a starter that dragged or cranked slowly and sometimes not at all. The truck would start when it cranked. When starter would not crank sometimes a jump would work, other times it wouldn't. Sometimes after sitting it would start.

Replaced starter and all was well for a short while then slow or no crank began again sometimes.

Found wires on starter realy were getting very hot sometimes; hot enough to soften or mellt the insulation around the smaller wire connector on the battery side of the relay. Terminal on relay broke one day so the relay was replaced. Truck started ok after relay replacement.

Truck was running and died and then would not re-start. Found no spark condition. Followed testing procedures for coil and ICM on troubleshootmyvehicle.com and traced to malfunctioning TFI ICM. Replaced TFI with new one that tested good but still no spark.

I then suspected the PIP sensor and since the cap and rotor were in bad shape and loaded new distributor at O'Reilly's was $85 I went ahead and put in a new distributor. I replaced the plugs and wires at the same time as I didn't know the age of the ones in it. (I've had the truck less than a year.)

Still no spark. Was instructed to pull SPOUT and check and still no spark.

At this point the only thing not new was the coil so I threw one on this morning and charged the battery. Then things changed and got weird.

When I tried to start it the starter cranked slowly like it was straining to turn the engine. I turned the key off and checked under the hood. I didn't see anything out of place so I crossed the relay and engaged the starter. The starter cranked normally at regular speed.

I then turned the key to run but did not engage the starter. I went back to the engine and crossed the relay to start and the starter labored to turn the engine again and I noticed that the wires on the battery side of the relay were warm.

Now I'm completely stumped as it must be a wiring problem and that's as far as I've gone.

I'm hoping that some of the experts here take the time to read this epistle and will help a poor bastrd like me out.

 

I don't think you have a wiring problem.

Where is your advance set at?

Another thought, anytime I hear O'Reilly's, $85, and new distributor in the same sentence, I think offshore junk. Put a quality pickup, cap and rotor into your old distributor and reinstall it.

 

The first thing I would do (If I were you), would be to take a wire brush to the starter/block ground and clean till it's nice and shiny and clean the positive AND negative battery post(s) till clean and shiny.
Wire brush/clean the frame where the negative cable is bolted to the frame as well as that metal connector on the negative battery cable too.
Wire brush/clean the firewall where the ground strap bolts to it as well as the terminal and the firewall to block ground points.
Clean the ground point on the fender near the negative battery post as well as the terminal too.

If you've got the funds, investing in a new quality set of positive and negative cables wouldn't be a bad idea as well.

To me, it sounds like a "major" resistive grounding problem.....hence the "hot wires/relay" you spoke of.

Remember, the 4.9's use the starter bolt as the primary ground from the battery.

Watching to see how this pans out......


Bob

 

My thought here is replace the battery cable from the positive battery post to the relay, and also the cable from the other side of the relay to the starter. I believe both should be 4 gauge. Something is causing the hard turning situation.

Is your battery in good condition? Do you have all the cables on the relay in the correct place? The only thing on the one side should be the cable going down to the starter.

 

Pay attention!

This tells me that the starter can crank the engine normally. No wiring problem here. The problem occurs when he turns the ignition on. Too much advance can make the engine hard to crank, but there is another clue here. There is spark and fuel if this condition occurs. Probably fixed it with the coil.

If the starter is trying to turn against too much advance, current draw will increase and the cables will get warm.


Just a wild guess here, but battery cables and cleaning grounds ain't going to do it this time.

 

Thank you all for your helpful replies.

Thank you especially NotEnoughTrucks2014. I believe that you have hit the nail on the head with respect to the slow/resistant cranking. Since this only began after I installed the new coil. This makes the most sense to me. I did a sloppy, quick job of dropping in the new distro. I'm going to remove it and set #1 to TDC and drop it the correct way tomorrow.

I'm also going to check the PCM and fuel pump relays tomorrow. I haven't done that yet.

All of the batt cables are of the correct gauge but I'll remove all of them and polish the connections.

I'll report back tomorrow after I get my list completed and hopefully have a running truck again.

 

All good advice already said...I had a battery that was shorting out internally that caused some intermittent issues with my truck. One day it was good another I had slow starts and warmer than normal batt cables when I poked around looking for the problem. Battery went in and out of high resistance when I checked it with a meter while I struck it with a screw driver on the side. I replaced the battery and problem solved. Probably not your issue but ya never know...

 

Thanks for the added information and suggestion 1Fastboy.

I probably should have added that the truck has a new Interstate battery on it and my charger is one of the electronic jobs that would have likely indicated a bad bad battery when it was attempting to charge it. Again though, all information gained and shared is good information.

I'll be back with the results of my additional testing later.

 

Thank you, thank you, thankyou NotEnoughTruck2104!

You were right on the mark. Today I turned the engine to #1 TDC and set the dizzy appropriately. Truck fired right up.

I don't believe that the new dizzy was needed but it was already installed and can't be returned so it's in to stay.

I believe now that my original problem was a failed TFI ICM and coil.

I'll add to this that the timing mark on this 1987 F-150 was no more that a little 1/16" notch on the inner (closest to the block) edge of the harmonic balancer. What a lame timing mark for Ford to use. It was barely discernible. The way that I confirmed that the tiny nick in the balancer was actually the timing mark was to set the engine to #1 TDC.

Thanks for all of the help and suggestions from everyone.

Merry Christmas!