Solenoid Question

[ByronRACE]

I've just finished converting my '74 International Grumman Kurbmaster Step Van RV with the heart of a 1st gen '92 Cummins Automatic truck and it's running and driving just great.

But, I have a few questions and would appreciate some help.

On the injection pump I see two solenoids. The top one is the FSS. What's the bottom one for? Do I need it or want it? I saw something about cold start advance...but am not sure what that is or why I would want it.

Why are there two solenoids for the grid heater? I assume this means there are two heating elements. Why two? I intend to do something simple like connect both of them to a relay with a push button on the dash so if it's very cold, I can push the button and heat the intake air. What are the hazards associated with doing this? How long can I keep the grid heater activated before it is damaged? How cold does it have to get before the truck won't start without it?

Is there any reason why I would want the fuel heater? Is there any reason why I can't just leave it there and leave it disconnected? I see there's a kit to eliminate it. I don't see why I would care if it's hanging there or not.

With the stock H1C turbo and a stock downpipe, and the stock intercooler, what should my boost gauge read at WOT at the top of 3rd?

Thanks a bunch!

Byron

[CumminsPower59]

I can answer most of your questions. The bottom solenoid you see is the KSB, or cold start advance. It can be helpful in colder weather to get things started. There are two versions that are common, the 89-91 (NON-IC), and the 91.5-93. The earlier one is already advanced and when 12 is applied, it retards timing to normal. The later ones are set at normal timing and when 12v is applied, it advances timing. The first is designed to have 12v applied all the time, but the later is not. It can burn out if 12v is on it for too long.

There are two grid heater elements in the intake, stacked one on top of the other, therefore two relays. Come folks go the push bottom route for the grids.

Fuel heater is personal opinion, if you have quality blended winter fuel, you may not need it. Over time they may leak around the main O-ring at the top or the connector on the side. The O-rings can be hard to find, but I used one off an old oil filter and it works great. There is a delete stud that you can buy so that it can run without a heater.

As for stock numbers, I'm not sure on that. Could be anywhere in the 15-20 psi range I'd guess.

[DMan1198]

The ksb can be used for a bump in horsepower due to extra timing allowing more of the fuels energy to be utilized. It isn't strictly needed, but it can be useful

If you were to turn the grids on for 15 seconds the intake horn would be hot enough you couldn't touch it

[CumminsPower59]

Like Dman said, you can use the KSB for a bump in power, you can hot wire it to a switch and put 12v directly to it. This only works with the 91.5-93 pumps. The older pumps you can just leave it unhooked.

[ByronRACE]

This 10,000lb RV is never going to be fast. Especially with the current 4.88 rear gearing. So, I'm going to leave the power-adder mods alone for now until I get this thing debugged and put some miles on it.

To clarify the intended purpose of this advance solenoid on my '92, what is better during cranking and cold-start? More advance or less? Should I hear this relay click when power is applied? I can hear the FSS, but I do not hear the KSB click when power is applied. It does draw current. If it helps during cranking, I can wire it to the start circuit can't I? CumminsPower59 says you can't leave power connected, so I'm assuming it wants more advance during cranking (which seems backwards, from what I know about gasoline engine management).

My grid heaters draw current and do get warm, but they get nowhere near as hot as what is described by Dman1198. I wired them both to power and had them for about 20 seconds or so and the intake horn was just body temp. I wonder if they are damaged. They both draw current.

I'm going to add a solenoid question now. I am turning on Overdrive today on my A518 non-locking transmission. As I understand it I just apply power to the solenoid and that gives me 3rd over. To make this automatic, it seems to me I can hook a hobbs switch up to the governor pressure port on the transmission and set it such that it applies power when the vehicle reaches the right speed. Does anyone happen to know what the expected pressure coming out of the transmission will be when I'm going 43ish MPH? The tire diameter is 32" and the rear end ratio is 4.88. I want to order the right hobbs switch.

[CumminsPower59]

Since yours is a 92, it'll help with cold start. You probably won't hear it click, and wiring into the start circuit won't do much good, these things usually fire with just a spin of the key, so it won't be energized for long...no where near long enough to do any good. Just put it on a switch, and when it's cold out, flip it on till the idle smooths out some. As for your grids, they are working just fine.

[ByronRACE]

Thank you.

So it's not for cranking so much as it is for warm up. And, as you said...if I just left it wired to key-on power all the time, it would burn out. I could put it on a timer along with the grid heaters. One push, grid heaters turn on for 10 seconds, and this solenoid stays on for 2 minutes. Any reason not to do that? It would not be difficult to do.