HELP! MY TRUCK WON’T START!

HELP! MY TRUCK WON’T START!

So there we were, hundreds of miles from home, pulling a trailer, with a truck that wouldn’t start. Geez...aren’t 12-valves supposed to be reliable!? As it turns out, it was no big deal, but a nonstarting truck can definitely give you that sinking feeling. We’ll explain.

One of the more common problems on virtually all ‘94-’98 Dodges, as well as some generators and tractors, revolves around the P7100 injection pump. While the pumps themselves are extremely reliable and hardly ever fail, the shutoff solenoid that is mounted to the pump fails often. Our ‘95 project truck dubbed the Green Monster already had its solenoid replaced somewhere down the line, but it still failed yet again (probably because it was a Chinesemade knockoff verson). The shutoff solenoid activates a governor lever that allows fuel to flow into the pump, which allows the engine to start, but also to stop, because cutting off the fuel is how virtually all diesels are stopped from running.

So our solenoid was bad, but fortunately we weren’t dead in the water. Thankfully, even

if your solenoid is weak, you can still almost always start the truck by turning the key on, walking around underneath the hood, and then manually moving the governor lever back towards the firewall of the truck. It’s a pain (and something that would be horrible in traffic) but at least that will get your truck going down the road again.

Still, we weren’t excited about the prospect of hopping out and opening the hood every time we needed to start the truck, so we contact our buddy Rex Gully who owns Allied Diesel in Windsor, California. Like us, Rex is another 12-valve aficionado, and owns a fleet of them, including a 10-second race truck. Gully recommended using one of the shutoff solenoids from Larryb’s Diesel Parts. Larry has been in the business for years, and has all sorts of electrical parts for worn out Cummins engines, including starters, relays, cables, and yes... shutoff solenoids.

With Rex manning the wrenches, we were walked through the fairly straightforward process of replacing the shutoff solenoid.

It’s a task your average shadetree mechanic can perform, as only basic hand tools are required and there’s only a couple steps where things can go wrong. After around a half hour of installation and adjustment, we were back on the road again, and now could truck happily down the road without worrying about the next time we turned off our Cummins engine.

Our buddy Rex Gully helped us out with the solenoid install so we could take some photos. To gain access to the shutoff, it’s a lot easier if you just take off the intake horn, so that was Gully’s first step.

Our new shutoff solenoid and brackets (in case anything was missing) came from Larryb, who has been in the diesel industry for decades. Larry makes all sorts of electrical parts for diesels, including a shutoff solenoid kit. There’s even a more advanced version, with a fusible link and 70-amp relay.

We could tell by the blue wiring cover that our factory shutoff solenoid had already been replaced at some point. Still, it was hit-and-miss on working, so it needed replaced.

There’s a small vertical lever down on the injection pump where the shutoff solenoid connects. This is the lever you have to turn back towards the truck (with the key on) if you get stranded.

When you’re removing the shutoff solenoid, keep in mind that there is a tiny keyway on the pump lever that you definitely shouldn’t lose!

Here’s the new Larryb solenoid compared to the old one. As you can see they’re virtually identical, except Larry’s hasn’t seen the ravages of time.

A couple bolts and a cotter pin were the only things that needed to be removed to take off the factory (or in our case previously replaced) shutoff solenoid.

There is some adjustment in order to get things right. When we tried to slide the end of the lever on, it came up a little too short.

After we had on (and off) working correctly it was time to reinstall the intake horn. Now with a new shutoff solenoid we were ready to hit the road, with the dreaded no-start firmly in our rearview.

In order to keep everything happy, the shutoff lever needs to be wide open to match when the lever is at full fuel. Luckily, the solenoid can easily be adjusted with just a couple wrenches and some patience.

In many cases of P-pump swaps (onto VE or VP44 trucks) you’ll be sold the pump, but maybe not the bracketry. For this reason new brackets are included in the Larryb setup, which we installed mostly because they were shiny!

With the key on, we gave the starter a bump, which is what triggers the solenoid. Here you can see the solenoid in the “up” position (which means fuel is on).