Grease injector checks for SL-V auto-lube

A grease injector is the metering valve in a single-line automatic lubrication system. Each time the pump pressurises the supply line, every injector pushes one measured shot of grease to its own bearing or pin, then reloads when the line vents. If a point is running dry, the quickest checks are the indicator pin, the output setting and the weep hole. This guide uses the SKF Lincoln SL-V injector as the example, because it is one of the injectors we supply for trailer and truck spare parts and heavy equipment fleets.

What a grease injector does in an auto-lube system

SKF describes the SL-V series as metering devices for single-line, high-pressure centralized lubrication systems, for greases up to NLGI 2. Output can be adjusted from the outside, and an indicator pin lets you see the injector work (SKF SL-V product page).

Lincoln calls this layout a Centro-Matic system, a single-line parallel system: one supply line feeds every injector, and each injector acts on its own. According to Lincoln's SL-V brochure, that means the output of each point can be set separately and the system can be extended. If one point is blocked by a crushed line or a tight bearing, the rest of the system keeps working (Lincoln SL-V injector brochure, PDF).

That last point matters in the workshop. A blocked point does not stop the pump, so nobody notices until the pin or bush on that point starts to wear. The injector is where you find it.

How one lubrication cycle works

The SKF manual for SL-V injectors (form 404436) splits each cycle into four stages (SKF SL-V injector manual, PDF):

1. At rest, grease from the supply line reaches both sides of the measuring piston and fills the measuring chamber. The indicator stem is pulled in.
2. As line pressure rises, the slide valve moves, closes one passage and opens the path to the outlet. Pressure now acts only under the piston, which pushes the measured grease out to the lube point.
3. The piston stops when the indicator stem hits the adjusting screw. That stop is what sets the output. The injector holds this position until the supply line is vented.
4. When line pressure falls to the vent pressure, the slide valve returns, grease moves to the top of the piston again, and the injector is ready for the next cycle.

So an injector only works if the pump builds enough pressure and the line then vents properly. On the SL-V, the manual lists 1,850 psi (128 bar) minimum operating pressure, 6,000 psi (413 bar) maximum, 2,500 psi (172 bar) recommended, and a maximum vent (recharge) pressure of 1,000 psi (69 bar).

SL-V grease injector specifications

These figures come from the SKF manual and our SKF Lincoln 01-085771 SL-V injector part page.

The SKF manual also says SL-V injectors can be mounted in any position and used in circuits with SL-1, SL-11, SL-32 and SL-33 injectors. Lincoln's brochure says the SL-V is fully compatible with the SL-1, so worn SL-1 injectors can be swapped one by one without plumbing changes.

Five checks when a lube point runs dry

Work through these in order. The first two take a minute and need no tools beyond a grease gun or the pump's manual cycle.

1. Watch the indicator pin. Run a lube cycle and look through the clear cap. The stem should move as the injector fills and dispenses. If it never moves, the injector is not cycling: check line pressure and venting first, then the injector.
2. Check pump pressure and venting. If the pump does not reach the minimum operating pressure, the slide valve never moves and nothing is dispensed. If the line does not vent down to the recharge pressure, the injector cannot reload for the next cycle.
3. Check the output setting. On the SL-V, turning the adjusting screw clockwise until finger tight gives the minimum of 0.015 cu in. Each turn out adds 0.014 cu in, and about 5 turns gives the maximum of 0.080 cu in. On the SL-V XL, about 20.5 turns gives 0.305 cu in. Tighten the lock nut to 90 to 110 in-lbf (10 to 12 Nm) and refit the cap (SKF manual; see also Jasper Engineering's SL-V adjustment table). Someone may have wound a screw all the way in.
4. Look at the weep hole. SKF says the SL-V has a weep hole that shows worn or damaged internal seals, and a small amount of weeping can be normal. When the amount of grease grows every time the injector cycles, the weep has become a leak and the injector needs service.
5. Check the line from injector to lube point. A crushed line, a broken fitting or a seized bearing blocks that one point while the rest of the system carries on. Disconnect the line at the bearing and cycle the system to see whether grease arrives.

The SKF manual adds one installation note: in small systems, or where injectors sit close to a high-output pump, line pressure should not rise too fast, or output can be smaller or inconsistent. Lincoln recommends adding a length of high-pressure hose between pump and injectors to slow the pressure rise.

Repair or replace the injector

SKF lists separate service parts for SL-V and SL-V XL injectors, and SKF's product page says individual injectors can be removed easily for inspection or replacement. In practice, the choice comes down to time and how many points are affected:

• One injector weeping more each cycle: a seal or repair kit is an option if your workshop rebuilds injectors.
• An injector that does not cycle with good line pressure and venting: swap in a replacement injector and bench check the old one later.
• An older SL-1 bank that keeps failing: replace injectors with SL-V units as they wear, since the brochure says no plumbing changes are needed.

Parts we have quoted for Lincoln auto-lube systems include:

• SKF Lincoln 01-085771 SL-V grease injector (replacement injector for SL-V manifolds)
• SKF Lincoln 01-085781 SL-V XL grease injector (higher-output version)
• SKF Lincoln 81713A SL-1 injector and Lincoln 85770-5 SL-V five-port manifold. Search them by number on the parts index.
• Lincoln 01-272970 SL-V repair kit and Lincoln 250158 SL-1 injector repair kit, also on the parts index.
• Pumps, vent valves such as Lincoln 84980, guns and seal kits listed under the Lincoln parts brand page and lubricants and chemicals

Always match the number stamped on the injector or manifold before ordering. Our guide on finding the part number on an old trailer part explains where to look when the label is worn.

Why a dry point costs more than an injector

An injector that stops cycling does not raise an alarm on its own, because the rest of the system keeps working. The first sign is often wear on the pin, bush or bearing it was meant to feed. Watching the indicator pins during a service is a small job compared with replacing those parts. On trailers, manual grease points need the same attention, for example brake camshaft bushes, covered in our article on brake camshaft bush wear.

To get a quotation, send the injector or manifold part number, the number of points, and a photo of the manifold through our quotation page. We supply from Balikpapan to fleets and workshops across Indonesia.