View Full Version : Extra Solenoid for Starting / Diode Needed for Extra Starter Relay?
I'm in the process of installing a relay to trigger the starter on my 6.5 and help take the load off the ignition contacts - the same process Robyn has outlined here in the past using a F0rd fender mounted starter solenoid.
I agree with the idea of heavier contacts to offload the ignition switch too, just curious - how much currrent draw can the OEM starter solenoid pull? Seems a foglamp style relay (Bosch 30-40A) could do the job, but I won't argue with experience.
More important is the diode question. Cautions are included in Solenoid literature that advise use of a diode across the coil to avoid spikes getting zapped into the on board electronics, ECMs, etc. Some the the foglamp harness have the diodes included.
Should we use them and if so, what would be the right size and where can they be found? Thanks.
I agree the Ford solenoid is major overkill. It is designed to carry the starter current; all you need to off load is the solenoid current. For that matter, replacing one starter solenoid with another may not be the most prudent course of action. The Bosch relay should be more than adequate for the task.
As for the diode, I'd definitely do it. twhen you interupt the current through any coil (relay coil, solenoid or ignition coil) the energy of the flowing current is transformed into voltage. You can fire a spark plug or fry a computer or burn the switch contacts.
So, why isn't there a diode across the starter solenoid? Might solve the original problem...
A common 1N4004 diode should do the trick.
So, why isn't there a diode across the starter solenoid? Might solve the original problem...
I must have missed it -what is the original problem with the START circuit?
I must have missed it -what is the original problem with the START circuit?
The problem with the GM design is that it draws a healthy amount of current through your starter/ignition switch. Converting to the Ford design takes that load off the starter circuit.
I see what the guys are trying to do here with the smaller Bosch relay. But, I have always gone with the full swap with the Ford solenoid. With mine, the only wire that runs to the starter is the heavy cable, and the only time it carries power is during the start cycle. With the setup using the smaller Bosch relay, you still have that heavy cable with full power all the time.
DmaxMaverick
06-18-2007, 13:49
The problem with the GM design is that it draws a healthy amount of current through your starter/ignition switch. Converting to the Ford design takes that load off the starter circuit.
I see what the guys are trying to do here with the smaller Bosch relay. But, I have always gone with the full swap with the Ford solenoid. With mine, the only wire that runs to the starter is the heavy cable, and the only time it carries power is during the start cycle. With the setup using the smaller Bosch relay, you still have that heavy cable with full power all the time.
Like was said earlier, using the Ford solenoid is just swapping one starter solenoid current for another. Granted, the Ford solenoid draws less current than the GM solenoid, but it's not that much less. And, you'll be energizing 2 starter solenoids simultaneously, so anytime you have a low battery issue (which is never at a convenient location), the extra solenoid may remove your cranking ability.
Using the smaller relay would have considerably less current demand than the Ford solenoid, and greatly reduce the load on the ign switch. The batt+ cable will always be where it is, and has not a single thing to do with ign switch loading. It is only the source of power for the starter field and ACC circuit, which always has to be where it is, no matter how you route the wires/cables. Add all the solenoids you want, but each additional is more load on the system as a whole.
The GM solenoid draws about 10amps, and the Ford draws about 2. I doubt that the 2 amps is going to make a difference in cranking.
My statement about the battery cable appears to have been misunderstood. Yes, the cable is always there, but with the Ford setup the cable is not energized unless the switch is in the "Start" position, and with the GM setup the cable is energized all the time. I am just not a fan of having a "hot" battery cable running down to the starter.
DmaxMaverick
06-18-2007, 18:46
The Ford solenoid is a lot more than 2 amps. More like 10. If you are testing one cold on the bench, the amps will be considerably lower, compared to on a vehicle under a cranking load, and heat and extended cranking times add to that. I have several, doing several different duties on several different vehicles. They are cheap and you can find them anywhere, which is the #1 (and probably only) reason I have them.
If you make that cable "cold", you'll also have to reroute the acc. power, which is also ran from the solenoid "hot" side. You will also have a timing issue between the 2 solenoids, because both will have to be energized, and contact made. Fuzzy, but I've seen solenoids burn up in series on a regular basis. I'm not sure what you mean about the always hot cable. They've been that way for decades, and the only problems I've seen are during cranking, in which case, the cable will be hot in any case. Poor maintenance or redesigned routing is an exception, but that's easily fixed. My opinion, but I think you are going to complicate things by trying to simpify them. More power to you, though.
Is this about the chronic IGN sw failures, with no WTS, no instruments, and no run from START?
The one I used is slightly smaller than the top of a soda can and has two ears to mount the thing with some 1/4 inch bolts or sheet metal screws.
It is only a relay and takes very little current to activate it.
The solenoid on the GM gear drive starters pull a buttload of amps to pull the gear train in and then drop off to a more modest load to hold the thing locked.
The issue is, as the igniton system gets time on it the switch loses its ability to pass enough amps and this causes the solenoid to pull in slower and weaker than is optimal. The result is the heavy contacts arc a lot and then carbon up. Now the current draw on the starter itself goes through the roof and it goes away :(
I spent a couple hours fooling with my Burb running this crap down.
The simple addition of the starter relay took all the load off the Ignition switch and then allowed for about half again the power available to the solenoid.
The difference in how a brand new starter worked was quite noticeable.
The solenoid draws about 20 amps to pull in and then drops off to about 10 give or take to hold it.
The fuel pump is also run with that same circuit during startup and it comes off first before the starter solenoid gets its power. :eek:
OOOOps
The little Ford relays are cheap and do a right smart job and wont hurt anything.
If anything the wierd amp draws and brown outs from the stock system will do far more harm than the addition of the relay.
Just what I found after smoking two good starters in a month.
Robyn
My Cummins had a World Class Rebuilt starter - I was suspicious of it's operational quirks, so I pulled it apart.
Shoulda been labeled Third-World Class Rebuilt - slightly copper-plated steel studs and the big contactor washer - all the rubber-ized insulation on the field coil ends had been abraded off by standing the case on the end with the exposed coil windings - the new motor-shaft bearings had little or no grease - etc.
Sure did look good from the outside, tho.
Anyway, the Lift Pump wire should not be on the S terminal on the starter solenoid - is a seperate terminal for that purpose, and that wire goes to the LP Relay, not the LP itself, so the current requirement is minimal.
If the later starters do not have the accessory terminal, still no big deal, as the LP relay coil current-draw is insignificant.
My question being - are you guys having trouble with the START contacts in the IGN switch?
The usual symptom of failure is, engine will crank but won't start - which is the several IGN and ACC contacts.
??????
HMMM
Question
Will this switch issue cause the dash volt meter to read low even though the charging system is in fine shape and has 14.6 at the batteries. (new top quality alternator installed yesterday)
My 95 dually I just bought has an issue that way, although the voltage at the rear lights is only 12.7
Not sure about this issue yet.
Everything else seems fine.
I need to check out the engine grounds and the battery cables real good before a tear into the switch.
Robyn
Could cause that symptom, but is usually the instrument cluster connector contacts - quite often, R&R'ing the instrument cluster will burnish the contacts, restoring electrical continuity to the gages.
Also the harness grounding on the passenger-side head and up under the dash.
And the main electrical bulkhead connector, lower driver's-side firewall, which supplies power and ground to the IGN system, lighting, START, and etc.
Main thing with the Ford style relay is that you are getting full battery voltage to the starter to pull in the plunger , not 9 volts or whatever comes from the ignition switch . Lots of people use that setup on drag cars to get around the heat soaking from headers . If you have issues cranking , this could help assuming all else is in order .
The design of the Ford starter is completely different from the GM starter. The Ford solenoid is designed to switch a couple hundred amps. The GM solenoid only draws 20 or so amps. Not optimal for the Ford solenoid. Maybe it wouldn't make any difference, but the Bosch relay is a better match for the application.
Using the Ford relay to switch power to the starter itself just adds another point of failure, IMHO.
The design of the Ford starter is completely different from the GM starter. The Ford solenoid is designed to switch a couple hundred amps. The GM solenoid only draws 20 or so amps. Not optimal for the Ford solenoid. Maybe it wouldn't make any difference, but the Bosch relay is a better match for the application.
Using the Ford relay to switch power to the starter itself just adds another point of failure, IMHO.
Perhaps, but so does using the Bosch relay. I have also had heat soak problems (as someone mentioned before) and those problems went away when I went to the Ford setup. I have some pics of what I did - maybe they can better explain the setup.
JeepSJ,
Your photo link says they are moved to the attic...
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions Inc. All rights reserved.