I finally got my 1988 F350 motorhome running again. I replaced the original starter with a newer style PMGR unit and changed the wiring at/from the fender mounted solenoid as must be done to get the new starter to crank properly. So in this case the batt+ cable goes to the solenoid just as before but now the starter cable also goes to the very same terminal. The second large terminal now only provides juice to energize the solenoid of the new PMGR starter. So in effect you end up with two solenoids, the original one now energizes the PMGR solenoid. Have faith, that is how it must be done in order to use the new starter.

So anyway, I replaced the original stock solenoid while I was at it which meant that all wires had to be removed and reinstalled of course. I stacked all the factory wires along with the batt cable and starter cable on one post of the new solenoid. As I said, the other post is used only to energize the new starter solenoid. So here's the deal. Now when I connect the pos batt cable to the battery I get a small arc indicating a current draw. This arc occurs whether the ignition is on or off. By process of elimination I found the wire which is causing the current draw and disconnected it from the stock solenoid. So now my arcing problem is solved, but I get no juice to the dash and no spark either. The engine will crank using a test switch/button but will not fire. By reinstalling the disconnected wire the engine starts and runs fine. Out of curiosity I disconnected the wire and using a jumper connected it to batt pos terminal. Same story, engine runs and starts fine. But here is the mind blower, with engine running I disconnected the jumper wire fully expecting the engine to stop. But it didn't. What the heck is going on here? When I tap the jumper to batt pos I hear a clicking sound like a relay switching but I have not been able to locate any relay. Aargh!

The wire in question is gray colored, has a fusible link built in, and appears to be 10 gauge.

Please help!

 

Sounds like you have probably looked into this already but here is a write-up on PMGR conversion:

How To Properly Wire Your PMGR Mini-Starter - Ford Bronco Forum

Think of the poor schmuck who comes along behind you and has to try to fix it next time.

 

Sounds normal to me.
The wire you disconnected feeds the Ignition switch, and to the alternator.
You called it gray but what you are looking at is a green fuse link. After the fuse link it turns to a black wire with a orange stripe or red stripe.
When you disconnect it with the engine running (bad move) you are running the engine off the alternator. Disconnecting this wire with the engine running could send the voltage on the wire to over 100 volts and blow out the EEC computer module and other items connected to this circuit.
It is also normal for it to have a small arc as it is providing power to pin #1 of the EEC computer module for its keep alive memory and also to the radio memory.

 

Thanks for the link for installing a PMGR starter. Lots of good info there.

BTY, I bought my two new PMGR starters from DB Electrical. I bought two because I also have a 1988 F450 flatbed with manual trans. Starters are brand new and a super deal at less than $50 each, no core required and free shipping included. Item #3225 for manual trans and 3226 for automatic trans. I have bought from DB before with good results.

 

Will check milliamp current of offending wire just to be sure it doesn't zap the battery when vehicle is not driven.

 

Ford says to disconnect the battery if the vehicle is to set for more than 2 weeks to keep from running the battery all the way down.

 

If you didn't add any wires (other than the new orientation for the new starter), then whatever is drawing power now was probably drawing power before the change. So likely that spark is not an indication that you'll be having a problem.
If the battery does start draining now though, then something changed. I don't think I've ever heard of a PMGR starter drawing power without actually closing the switch and cranking the starter, but I suppose it's possible.

You'll often see and hear a small spark when connecting wires back when the battery is still connected. Same as you'll see and hear that same arc when all those others are connected, and you're simply re-connecting the battery cable.
It still happens even on older, simpler vehicles. And yet it still catches me by surprise sometimes! I even give myself the old internal rolling-eyes look (when nobody else is around of course) whenever I get caught off-guard and startled by the snap sound.
You'd think by now I'd remember...

And while I don't know if Ford still does it in the brand new stuff, they continued to use the factory fender mounted relay/solenoid long after they went to the PMGR starters in the early '90's.
It made sense to keep it, because as a relay it takes the higher load of the starter-mounted solenoid off of the ignition switch. And as a power stud it still gives them a convenient spot to put all those other power leads!
I don't remember even looking under the hood of a current model truck. Do they still use the fender mounted relay? Or is it extinct now, after all these years?

And did you keep the old starter relay by any chance? If it was working before, I would keep it as a spare. Unless you bought a known good brand, like Motorcraft or some old NOS stuff, I would definitely start carrying a spare.
Of all the modern parts we throw at our Fords, that is likely the #1 most often failed new part. Some in as little as a week or less. Some as quickly as the second or third start attempt. If they were lucky enough to get one that worked at all that is!

Good luck with the new starter. I think it's a great upgrade for our older trucks.

Paul

 

Well today I attempted to drive the E350 motorhome home. It did not go well. The engine sounded just fine at an idle and would rev up smoothly so I put it into gear and headed out. It became immediately apparent that something was wrong as when attempting to cruise the engine stuttered and backfired and barely ran. I went about 3 miles that way and then my brake pedal went to the floor. I gave up and pulled the rig over on a wide shoulder of the country road I was on and then called a tow truck. Two hours later the MH was home but not running.

After a few more hours I started the engine and it sounded okay but would not rev as it should. Amazingly my brake pedal was now back up and seemed to work. Go figure. Maybe stuck calipers boiled the brake fluid?

Anyway, I ran it for a few minutes and then attempted to shut it down by removing the pos battery cable from the batt. My ignition switch used to work but does nothing now so removing the pos cable has shut the engine off in the past. To my amazement the engine continued to run with the batt pos cable removed. I had the drivers door open and the dome light was on and I happened to notice that with the battery cable connected it was brighter than when the cable was disconnected. I double checked voltage with the battery cable connected and it read 13.8V. With the battery cable disconnected I got 12.5V from the cable to ground which indicated a second voltage source was present in addition to the battery. The engine continued to run. So on a hunch I loosened the solenoid connection that all the power wires go to. Sure enough, when the connections were loosened the engine uttered a big fart like vacuum being released. It was really loud and seemed to have come from the air cleaner housing. Then the engine died supporting the theory of a second voltage source providing ignition.

In my initial post I mentioned the "gray" wire with the fusible link being the source of current drain which caused arcing when I attached the batt cable to batt pos. I looked more closely at the wire and it looks like the original color of the wire was either green or yellow and it then becomes black with an orange stripe after the link. The current being drawn is several amps and not in the much lower range of current draw for a clock or radio. This wire is currently attached to the solenoid post in addition to all the other power wires.

Please help! This is the craziest electrical problem I have ever seen.

Randy

 

Read post #3 above again. It still applies.

Smooth idle and when the engine stuttered and backfires under load most of the time it is bad spark plug wires or the spark plug wires are not on all the way.

Also sounds like it is time for a new master cylinder.

Now I would say you need to check for the stored codes but you may have already lost them by removing those wires. That KOEO codes may help some but not like the stored codes would have.

The engine running with the battery disconnected will run for a short time but the voltage will slowly drop and it will soon die. As noted above this is a bad idea as the voltage can spike to over 100 volts when the battery is disconnected with the engine running. The battery is a filter for the charging and voltage reference for the alternator.

 

Here is what that wire does.



For the 60amp alternator:

And for the 70 & 100amp alternator:

/

 

Thanks for the info subford. This will help a lot.

Still confused about running with battery disconnected. Residual magnetism in the alternator field maybe? Far as I know alternators cannot generate a field current.

Randy

 

Alternators do not have any Residual Magnetism like the old generators did.
Perhaps you have a battery for the coach also and its parallel charge relay was pulled in all ready so you were running off the coach battery with the chassis battery disconnected.

 

The engine kept running because that 13.8v was coming from the alternator itself. Any other battery would likely still register only 12 to 12.6 volts unless it was just being charged. And even then it would only read that higher voltage for a few moments. Well, in theory anyway...
As long as you can't turn the key off, your alternator will continue to put out enough power to run the whole vehicle (that's what it does normally) for as long as the engine is spinning.
You have to kill the ignition, kill the alternator (bad choice of words!), or kill the fuel supply to stop the engine that way.

But as said, don't do that! It's not good for modern alternators. Yes, we've all done it in the past, and it was a semi-legit test of whether the alternator was charging or not. But the better test of that is the volt-meter and don't pull cables while it's trying to keep the battery charged.
We probably just "get away with it" when we don't do harm to a modern alternator. In other words, when your alternator still charges, you got lucky.

And I have to ask, why you're running this with a faulty switch after all the work you've been through to get to this point? Get a working switch in there so you don't have to think about it.

Paul

 

New switch is on the way. I had to move the MH or else hence the haywired switch. The whole adventure has been a nightmare. But at least it is home now where I can work on it much more easily. Only 33k original miles on it but sat for several years until now.

Randy

 

My 1987 has 5 wires on the alternator. It is a 65 amp Ford alternator. Two batteries under hood plus the RV chassis battery mid frame underneath. Need some basic E350 wiring schematics to start to decode this unit as if has obviously been hacked over the decades by previous owners. Amazed it still runs and charges...