View Full Version : EFI Starter Solenoid Options (?!)

09/18/10, 08:23 PM
I just read a “new one” that I have not heard before.

I needed to get a new starter solenoid as I am getting to the last stages of my Painless wiring harness install and finishing up my off-the-frame work on the Chariot. When I pulled the new solenoid out of the box, a little note falls out saying “Do not use this starter solenoid with engine control computer. This solenoid does not use suppression diodes. Use of this solenoid on vehicles with engine control computers WILL result in permanent damage to the computer/processor.”

Seeing as to how I am running EFI with an A9L, and I just spent some time doing fancy wiring and all, I am of a cautious frame of mind just now, and thought I better see what everyone thinks about this new fact.

While I am on the subject, is there a better solenoid to use with the new mini-starters, EFI, and a G4 alternator set-up? That "I" terminal is mighty lonely sitting there without any wire on it now.

09/18/10, 08:31 PM
Here is what I used...

1984 Tempo W/2.3L (Canadian) the starter solenoid has the diode and both
the "S" and "T" posts l like the Bronco
Napa P/N ST404
Napa price $14.64

Here is the BDW brand part number... sold at Advance or Autozone-Starter Solenoid #S5049

09/18/10, 08:43 PM
Being cautious is a perfectly valid response right about now. I'd say.
Lots of guys using the standard old Bronco (non diode type) relays without any trouble, SO FAR, but personally, I'm not going to take the chance and have planned all along to use one out of a later Explorer or pickup. I think I just asked for a '98 Explorer part at the auto parts store.
Put one in an EFI conversion we just did. Really doesn't take any more thinking than just a tiny re-orientation of some wires.
However at least some of them do not ground through the body, so be awary of that. If you get one of those, you'll simply have to run a dedicated ground wire from it's post to the body. It looks like your basic "I" post on a standard relay/solenoid, but is for grounding.
You'll know if you need it, if you hook up only the Green w/red (or Violet if Centech) "START" wire and nothing happens.

Not worth experimenting I'd say. Just get a diode suppressed one and be rest easy.


09/18/10, 08:44 PM
Oh, and the reason I didn't try to find one like Greg was mentioning (good to have that part number, thanks) was because the EFI ignition didn't require an "I" wire anymore.


09/18/10, 09:26 PM
I'm not running EFI yet but plan to soon & I dont run a solenoid w/ my gear reduction starter as it has it's own solenoid on it. Is mounting one on the fender even required w/ the mini starter for proper EFI operation?

09/18/10, 09:45 PM
Good info. I have been thinking for some time now that the solenoid seems redundant on a min-starter setup since the solenoid is just being used as a relay. Is there any reason why you couldn't just use a relay to activate the mini-starter wire? The B+ could go to a stand alone terminal and all battery needs and the starter power cable could go there. That would clean up the inner fender mightily.

09/18/10, 10:40 PM
I cleaned mine off entirely and it works flawlessly. Extended the old trigger wire from the old solenoid and ran it down to the starter solenoid and ran the large batt cable directly down from the battery to the starter. The solenoid on the mini starter has no requirement for a relay. Makes wiring a snap and really cleans off the inner fender.

09/18/10, 11:37 PM
The thing that goes on the fender near the battery is a relay; the small cylinder attached to the starter motor is a solenoid. (

I converted my '83 from carb to EFI, and I've used both types of relay. Currently, I have a suppressed one installed. (

Note that the lower small terminal is NOT a ground on that particular relay. I don't think I've ever seen a new-style relay with an external ground, but the older style; yes. (

09/20/10, 12:10 PM
Came across one of the new style with ground stud in a buddy's collection. Don't know the original application though. In his stack, it could literally be from anything starting with a '92 F250 PowerStroke, several years of Super Duty pickups (also all PowerStrokes), a '92/'96 Bronco, or an Explorer/Mountaineer.
He's had that many applications in his driveway or his side yard just over the last three or four years!


09/20/10, 12:23 PM
...Is mounting one on the fender even required w/ the mini starter for proper EFI operation?

As you found out with your current application, no, it's not "required", theoretically. But many Bronco owners have found it necessary just for the correct functioning of their new starters. Not sure yet why some have trouble with the starters running-on for a moment, while others don't, but it's more common than we'd like.
Maybe it's more a result of different starter/solenoid designs, rather than something in the electrical system of the Bronco? Dunno, but enough have had the issue fixed by using the original Ford fender-mounted relay to keep it in mind if you ever have a run-on issue.

In theory, you should not have to use any separate relay at all, since, as has been said, the solenoid mounted directly to the starter takes on that function. It doesn't hurt anything to use the original relay, but if it's not needed, leave it off.
But hey, you do whatever works.

So basically, if yours works directly, you're good to go. If you experience a little run-on after changing over to a stock Ford PMGR (permanent magnet, gear reduction) or aftermarket mini-type starter, then wire it through the original relay as a sort of "isolator" from unwanted signals.


09/20/10, 12:27 PM
Oh, and just so nobody thinks us Bronco owners are crazy/loco experimental wiring trolls, if I'm not mistaken even Ford originally wired their solenoid-equipped PMGR starters through the original fender-mounted relay at first. Then, after a few years of doing it that way, they now wire directly to the starter.
If someone can verify that, and knows why, that'd be great.


09/20/10, 12:46 PM
Came across one of the new style with ground stud in a buddy's collection. Don't know the original application though. In his stack, it could literally be from anything starting with a '92 F250 PowerStroke...Are you sure it's a ground stud? As my pics show, there were several with a small lower stud, but many were an "S" terminal (like the one I use). If it's an S, don't put a ground wire on it... :o But the later diesels use a similar relay for glow plugs, and that one might have a ground stud.

The solenoid pulls a LOT more current than the relay, which is why Ford used the relay. Even those that don't use the big fender-mount relay still have a Bosch/ISO relay in the fuse block.

The relay doesn't prevent run-on in the stock Ford configuration (shown in that diagram above); that's caused by the Bendix sticking on the shaft, which jams the lever & holds the solenoid's contacts engaged. But if you wire the relay to bypass the starter solenoid's contacts, it WILL prevent run-on.

09/20/10, 01:28 PM
I had thought it might be one of the glow-plug relays, because he's replaced a few of those over the years. I'm pretty sure that I've seen reference to the ground circuit, but I can't say just where.
In this particular case though, it's definitely working that way. I tried it initially without one, just bolted to the fender. When it didn't function at all (no clicky), I grounded the second small terminal (neither one has any kind of identification marks) and it worked perfectly.
Now you've got me thinking and I'll go test the new one I bought. Just to see what's up. If the ground is an unusual attribute, then that may point more towards the PowerStroke glow plug relay.


09/20/10, 01:34 PM
Oh, and yeah, totally forgot about the box-mounted starter relay. Most vehicles I've fiddled with have some sort of a regular-type starter relay in the main panel, now that I think about it.
Thanks for pointing that out.

So a solenoid may draw more power than our switches would like after all. But because the starter is usually used for such a short amount of time, problems with switch life don't always crop up. If so though, it might still help the switch last longer to use a relay. But GM didn't use relays (to my knowledge anyway) all those years in the old days (pre-'80's or so?) either. So either their ignition switches were more robust than ours, or the solenoid just doesn't draw enough to be too worried about and everyone runs relays just to clean up the back of the switch maybe.

In either event, I like relays for both of those reasons. So use them wherever I can.
And since we (as 4-wheelers) tend to use our starter motors more often and longer than most, maybe it's a good idea no matter what.
Any thoughts on that?


09/20/10, 01:45 PM
8.7 million NEWER ignition switches had problems, even WITH a relay! ;) I wouldn't push those old ones... (

09/20/10, 01:52 PM
Hmm, those look to be on the old system though. So probably more of a literally defective switch, than just simply an overloaded system?
That was back when they were still using the old fender mounted relay, at least in the trucks affected, so would have gone bad no matter what

Still, I'm with you about not pushing our old switches. Keep 'em as happy and healthy as you can, for as long as you can. Otherwise, just like any other electrical component, they know exactly when you're the farthest away from help, and will pick that moment to drop dead.
Good enough reason for me to use a relay.


09/21/10, 12:43 PM
I just checked the replacement relay I have (SS598T) from the later model truck Steve, and it's wired normally. That is, it's grounded through the base and has an "I" terminal.
Neither terminal is marked of course, but the instructions(!) included in the box clearly listed it as such.
So I'm guessing that the relay we're currently using is indeed from the PowerStroke glowplug application. I'll check that later when I pop on down to my local crack dealer, uh, I mean auto parts supplier.

To avoid any potential confusion in the future, I'm going to replace the existing one with the new one. That way, if I'm not around when someone makes a quick trail-repair, they won't be tempted to re-install the ground wire to an "I" post.
Might have a certain entertainment value, but it won't be pretty.

Just remembered where I'd seen the listings with ground studs too. A link here to a relay supplier had pages and pages of relays. Many of which looked just like the typical Ford fender-mounted starter relay. A few of them were listed as having a ground stud and not being grounded through the base. Unfortunately though, they were not clearly listed by application as to what they were for. They sometimes said "Ford", but not a year or model.
If I can find the link again, I'll post it up for future reference.