Hi Guys,

I picked up a 99 F150 with a bad engine, and decided to do my first engine replacement. It's out of a 99 expedition, but I kept my intake manifold and switched over all my sensors from the F150 engine. It was a great learning experience, but now that everything's back together I can't get the starter to kick with enough power to spin the bendix. Here's what I've done:

New starter
New battery
New battery cables (going straight to the starter posts)
New solenoid (fender mounted)
New ground straps - I replaced the old ones with big beefy sections of battery cable crimped into large connectors.

I have had the parts store re-test the starter many times, it always kicks and spins on the bench. Power draw is acceptable also. Battery has been trickle charged and re-tested (load tested), it's still good. All connections have been cleaned with steel wool or a wire brush and checked.

When I jump the solenoid terminals (positive to signal post) I the problem is still the same - small click from the starter but it won't spin. I have the starter mounted out of the truck (basically bungeed to the passenger front tire) so that I can watch it as I trouble shoot.

Any other ideas for what my problem could be?? Is there a starter relay for these trucks? The parts store told me that the fender solenoid is the relay.

Thanks in advance!

 

You have so many changes that the normal routine is out for diagnostics.
Basically you have to do voltage drop testing from the starter back toward the battery to uncover a bad connection. Test the ground cables as well.
At the starter you cannot have more than about 1 volt drop from a fully charged battery and preferably less over the whole path that includes the grounds.
.
The second question is how much drag is there on the starter by the engine?
The reason to ask is the flywheel and converter assembly.
Is there an issue there with proper parts fit and compatibility between the different engines?
If the converter is not set into the front pump, serious damage will occur to the transmission.
Better rotate the motor first by hand and assess the drag then do the voltage drop testing just in case there is a problem and the trans is not yet damaged..
Good luck.

 

Thanks for the reply - I have checked that the motor spins freely, it's easy to do with a 19mm socket and wrench. I had to spin it this way to get the flywheel to torque converter bolts all lined up and get the nuts on. It still spins easily, so I'm guessing I'm ok on the converter?

My research has told me that the expy and f150 motors are identical, even down to the flywheels and intake manifolds. The sensors all look the same but I switched them simply because I knew my old ones worked and wasn't sure about the donor motor.

However, this problem doesn't have to do with the motor from what I can tell because I am having the problem even when the starter is not bolted to the bell housing. I have tried it bolted up and hanging free and it acts the same, so I currently have it hanging free so that I can see what the bendix is doing as I test.

I will throw the voltmeter on it tonight and see what I get at various points.

 

After checking voltages, everything looks good. Voltage over battery was 12.63 so that was my starting point. Voltage over the starter terminals was 12.63, so no loss through the battery cables. Checked from positive post to various grounds (fender wall, intake manifold, truck frame) and all were 12.63.

I realized that there is a wire that I haven't replaced going from the pos. post to the fender solenoid. In the middle of the wire is a plastic housing and inside the housing is two smaller wires. I wonder if these smaller wires got burnt up? Is it some kind of in-line fuse? Also at the other end of this wire is a boot where it connects to the fender solenoid/relay and the smaller starter signal wire is connected to this boot. Would it be ok to just take a length of standard battery cable and run from positive post to fender solenoid? Does anybody have a wiring diagram that shows what happens in this boot or at the solenoid?

Thanks!

 

You have to test voltage drop under load.
Open circuit test does not do it.
Do first test at the starter to see how far down it goes.
Good luck.

 

You said you changed the motor. Did you get all of the ground cables hooked back up?
You should have a ground from the fire wall to the motor. There is also a ground wire from the starter to the frame. You have the starter hanging, Do you have a heavy ground from the motor to the starter. The ground wire from the frame won't do.

 

You have created the problem with all the new wiring you've done.
.
You have got to know that a starter motor is a certain type called an induction repulsion motor. This motor has no self limiting RPM like a normal motor.
.
If left go to run any extended length of time, the rpm goes so high the armature can fly apart from high rpm and overheating.
.
In starter service under the load of turning the engine, a limit is placed on it's rpm by the engine load.
This type motor draws very high currents and is the reason for the large cable sizes it needs, to produce enough torque for the application.
.
Put the starter back on the motor where it belongs, then get the correct cables in place.
Voltage drops are measured under current draw of the motor under it's normal load.
With such high currents you can't have more than a couple tenths of an Ohm total circuit resistance overall or the voltage drops so far the starter cannot turn the load.
You can't measure circuit resistance with normal meter because they will even see your test lead resistance and will mislead you.
The actual voltage drop across each connection under load is the only good way to find the problem.
Bottom line is your the bigger problem than the starter issue is.
Good luck.

 

I agree with the ground theory.......... check for a good ground from the battery to the motor ... not the truck frame that has rubber mounts. AS mentioned, check voltages while you are engaging starter... Starter needs a good ground when hanging on the fender.

 

Alright so this weekend I reminded myself of circuits class and took a bunch of voltages under load. No surprise there's a big drop:battery positive to starter positive 2.95. I will spare you the other 6 voltage differences I took unless someone is interested or thinks it's pertinent. I suppose I will mention battery positive to relay positive was .02, but there's not much current going that way anyways-it just powers the cab and starter signal wire.
Anyways, I replaced the starter to positive battery cable yet again, it actually clicks faster now but essentially no change.

I moved on to grounds again. Cleaned my ground strap connectors from top of intake manifold to fender wall, no change. I then replaced it with a 2ga cable and still nothing different. I scratch everything until it's shiny before screwing the cables back in. Starter went back into the truck even though that makes no difference, no change. So in an effort to find this possibly bad ground I took my pair of heavy duty and great condition jumper cables and used them to ground all over the place: neg. Battery post to block, intake manifold to truck body. Keep in mind I already have 2ga grounds from battery negative to fender, from fender to engine (intake manifold),and from starter negative to frame. After "scratching" the jumper cable grounds onto everything, no change.

I'm at a loss still. Jumping the solenoid, using my battery chargers jump start feature, and jumping the solenoid with the cab power and alternator cable removed all yield a null result. I thought that for sure would do it since the only wires involved then are battery to relay to starter and all the grounds. My only two other thoughts are the ground strap from the frame to the fender (even though I have previously simulated this ground being enhanced via my jumper cable trick) and the starter signal wire itself. It activates the starter to click but could the signal wire itself be lacking in power transmission capabilities? I doubt it because jumping the starter terminals does diddly squat to improve starter power too.
I'm thinking about ordering the ford factory positive cable bundle tomorrow for $160,which is insane but I've got nowhere else to turn. Again I have repeatedly brought back the new starter and battery to be tested, they're supposedly good.

Any last ditch efforts I could try? I have tried isolating the battery and starter essentially when I removed the cab power and alternator power and jumped the relay, so I don't see how else to get this effer working enough juice so that it kicks&spins!

 

"Voltage drop testing" isn't what people ordinarily think. It not only has to be done under load, but it's done across a single cable, wire, or connection in parallel with the connection, and is measured as a positive voltage.

If you place your voltmeter across the battery terminals and measure the voltage drop during cranking, this is a useful test but it isn't the kind of thing we're looking for.

If you are performing a voltage drop test correctly and are measuring 2 or 3 volts than that cable is definitely bad and should be replaced. Replace all of them, for that matter.

Should never see more than maybe 0.20 (two tenths) of a single volt across any one single cable or connection under load.

 

I understand-that's why the value I gave was from battery positive (battery post) to starter positive. This is then the voltage drop over the main battery (positive) cable which goes straight to starter positive.
I have since replaced that cable with another one and it's a little better sounding (starter clicks faster), though I didn't have a helper around to help me get the new vintage drop.
With a brand new cable I can't help but think my power loss is rooted elsewhere though.

 

Sounds like a start now that you see that large a drop.
Good luck.

 

Gee whiz, was your truck employed at a salt mine or something?? 3 volts is way off the chart. Replace ALL the battery cables, and ground straps/cables, from block to frame, and firewall to block, etc. This is an easy, inexpensive investment towards reliable year round cold and hot starts on any vehicle.

Grind down to clean bright shiny metal, free of any paint or corrosion. Coat connecting surfaces with NO-OX or grease. Tighten securely.

 

But what is the voltage drop with the new cable installed?


And I didn't see any voltage drop reading for the negative side of the starting system. (Put the red DVM lead on the starter housing and the black lead of the DVM on the negative battery POST (not on the clamp) and read the voltage drop while cranking. What does it read?)

 

See if this helps