Help with solenoid--> starter

Hey all, thanks in advance for taking the time to read.
Very frustrating week/weekend here for me as I missed Wheelin' Walla Walla this year bc of this issue.
Car has been running great until about 3 weeks ago when I parked downtown and after lunch had a really sluggish crank. Got home and it sounded as if the rod in the starter was spinning fast but wasnt engaging the crank in the engine. I figured it was a power issue. I had a buddy come over and we changed the starter and the solenoid. Started right up. Last week same issue I thought maybe a battery issue so I kept it on a trickle as the battery was 6 years old.
Friday before the car show cruise went to get gas, had a sluggish crank again at home and then was dead at the pump after filling up. Over 2 hours at the pump I replaced battery with brand new one and changed the damn solenoid AGAIN. It sluggishly started and I got it home. Now dead. Fuel pump primes normally, all accessories work, battery tests perfectly and even the magnet switch in the solenoid is clearly flipping. You can literally hear and feel the switch in the solenoid when you turn the key ignition.
Maybe a grounding issue in the path between the solenoid and the starter? Starter casing touching something it shouldn't? There is just the one big wire from solenoid to starter ��
Anyone have this issue before? Any ideas?

Thank you all.

Check your battery terminals and all ground connections. Make sure the block grounding strap is in good shape and is solidly connected. You could run an extra ground from one of the starter mounting bolts to the frame.

Norm

I had a very similar issue with my 47 Merc that has a stroked 351W in it. Swapped starter and solinoid no help. Sluggish to no start when the engine was hot/warm. Started cold every time. What fixed it was switching from #4 to #1 Solinoid to Starter Cable and Both the positive and negative battery cables. Then adding an additional Bonding strap from frame to engine, doubling the capacity. (actualy halving the resistance). Then I wrapped the starter in heat shield. No issues since. Starts every time, hot or cold.

Thanks for the suggestions. I will try those this next weekend

When you say starter and solenoid I assume you have a separate solenoid mounted on the firewall or foot box correct. If so best thing to do is swap to a mini-starter w/ it's builtin solenoid and wire it like this.
Attachment 203854
The diagram is from an official Ford tech bulletin on how to upgrade an old Mustang to the newer style starter. They keep the firewall solenoid in position simply because people have often used the batt lug as a source for power for extra accessories. The solenoid now acts as a huge starter relay.
BTW this is a mini-starter
Attachment 203855
Hopefully someone will chime in w/ a part # or year and model Mustang to use when looking for the better starter.
Also before changing a long cable from trunk mounted battery to the solenoid, you might want to look into moving the battery to the RF of the engine compartment so you can have a <3ft long cable. See the Breeze mount.
https://breezeautomotive.com/shop/en...-1-4-roadster/

I have a 351W and running a Powermaster starter which is awesome. Not an area where I wanted to cheap out.

As mentioned, you have the "original" Ford starting system. They used a separate solenoid that was energized by the ignition/start and then powered the starter. Thus, the one wire connection to starter. That solenoid was known for issues but shouldn't on a new one. It basically is a large washer inside that once engaged will connect the two large lugs (one is BAT+ and the other is the starter) making contact to engage the starter. If everything is good, we used to tap the damn solenoid with a small hammer or block while turning key to start to "shock it" into working. Ah, the good ole days. Also as you mention, grounds are very important. One from engine to frame and frame to battery or even battery to block, but good ones. Also, some of those isolated solenoids were ground activated meaning you needed to have the base grounded as well.

If you have your starting circuit in good condition, even with the isolated solenoid, you can purchase an upgraded "stock" starter that will spin faster and better to help the sluggish stock model. Or, you can opt for what Craig mentioned and install a mini-style starter. Some wiring will be needed and if you go that route, ditch the entire issolated solenoid system, unless you need it for auxiliary items, but definitely the start circuit.

Now, all this being said, what kind of draw do you have on the starter cable when cranking? A clamp-over style ammeter works well to test and it shouldn't be pulling over 300A when cranking or you have issues somewhere. Also be aware of the snout length difference on starters.

Quote:

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Originally Posted by CraigS

When you say starter and solenoid I assume you have a separate solenoid mounted on the firewall or foot box correct. If so best thing to do is swap to a mini-starter w/ it's builtin solenoid and wire it like this.
Attachment 203854
The diagram is from an official Ford tech bulletin on how to upgrade an old Mustang to the newer style starter. They keep the firewall solenoid in position simply because people have often used the batt lug as a source for power for extra accessories. The solenoid now acts as a huge starter relay.
BTW this is a mini-starter
Attachment 203855
Hopefully someone will chime in w/ a part # or year and model Mustang to use when looking for the better starter.
Also before changing a long cable from trunk mounted battery to the solenoid, you might want to look into moving the battery to the RF of the engine compartment so you can have a <3ft long cable. See the Breeze mount.
https://breezeautomotive.com/shop/en...-1-4-roadster/

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I believe any Ford mini starter will work that was intended for a small block. I had a 14:1 c/r 349 small block in my drag car and used a mini starter for a F150 and never had any issues.

In my road race Mustang I mounted the battery in the passenger side rear floor. I used a remote solenoid in conjunction with the mini starter with the built in solenoid. I mounted the remote solenoid on a bracket on the roll cage as close to the battery as possible. I did it this way to keep the "hot" wire as short as possible. Without the remote solenoid the wire is "hot" all the time and had a run of about 8ft. With the remote solenoid that 8ft run was only "hot" when starting the engine. If things went "sideways" I didn't want an 8ft "hot" cable coming in contact with anything that would cause a dead ground.

Stang Racer that is a great use for an old school solenoid.

Make double sure your grounding system is correct, clean and tight. You should have a ground cable from the battery to the frame and the engine to the frame. The returning power trying to get back to the battery will use whatever it can find to make its way back to the battery. Such as clutch linkage, throttle cable, or random wires in the harness. Slow crank issues can usually be traced back to a bad ground if you know your starter and battery are good.

(bumping an oldish thread, I know)

+1 on double-checking the grounding.

I fought "doesn't want to start when warm" issue on an old F150 with the I-6 engine. I got it for cheap because of this issue.

Culprit ended up being the ground cable to the engine being disconnected, so the starter was pulling through a wimpy braided cable between engine and body.

I also up-sized the cables from factory (6-gauge?) to 2-gauge. No more starting issues.

I have a friend that went through the same problem. He was frying stater solenoids for no good reason. We replaced the starter with one for a 93 Mustang GT Solenoid built in. Eliminated the firewall one. No more issues.
Mike