Description

Jacobs 317E, 317F, 336A 1995 Troubleshooting Manual

You’ve been chasing an intermittent brake drag on a 317F for three hours. The aftermarket PDF you obtained shows a wiring diagram that doesn’t match the pins on your buffer switch. That’s exactly why I won’t touch a job without the Jacobs 317E, 317F, 336A 1995 Troubleshooting Manual on the bench. This is the factory book – 77 pages of Jacobs Vehicle Equipment Company’s own diagnostic procedure, not some reprint that skips the diode protection specs. If you need to know which solenoid valve to replace, or why the low engine speed retarder cut‑off keeps grounding, this manual gives you the sequence that works.

Troubleshooting Jacobs 317E, 317F, and 336A

Section 1 kicks off with the introduction and safety precautions. Page 1 tells you the exact tools required for preliminary electrical checks – I’ve seen guys use a test light where Jacobs calls for a DVOM with a 10‑megohm input. That’s how you fry a DDEC II controller. The manual walks through clutch switch adjustment, fuel pump switch for Cummins PT pumps, and the buffer switch adjustment that most generic manuals leave out. If you’re working on a CAT PEEC engine, the troubleshooting flow on page 1.1.7 is worth the cost alone.

What Does the Electrical System Section Cover?

The electrical section starts on page 1.1 and breaks down every control: electric and electronic controls, diode protection, solenoid valve testing, and wiring diagrams for both CAT PEEC and DDEC II electronic controls. You get the exact resistance checks for the solenoid valve coils – no generic “if it clicks it’s good” nonsense. I’ve had a 336A that passed the click test but still leaked oil because the valve seat was eroded. The manual’s “Preliminary Electrical Checks” list on page 1.1.1 catches that.

Hydraulic/Mechanical System: Theory and Inspection

You can’t diagnose a Jake Brake without understanding the hydraulic circuit. Section 1.2 gives you the theory of operation and the operational sequence. That’s what separates a real tech from a parts‑swapper. Brake housings and rocker groups inspection, oil pressure check, and control valve component inspection – all laid out with OEM clearance specs. The manual tells you exactly where to put the pressure gauge for the engine brake housing oil pressure check. If you skip that step, you’ll be fighting a false low‑power complaint for days.

3 Critical Checks Before You Touch the Brake Housing

Here’s a quick list of what this manual makes you verify before disassembly: (1) Engine brake housing oil pressure – you need at least 40 psi with the brake active. (2) Clutch switch adjustment – 0.030” gap on the plunger. (3) Diode protection integrity – an open diode will backfeed current into the fuel pump switch. Skip any of those and you’re asking for a comeback. The manual has the factory call‑outs for each, plus the specific part numbers for replacement components.

Source Authenticity: OEM vs Aftermarket Manuals

I’ve got a drawer full of aftermarket CDs that claim “compatible” with Jacobs models. They’re garbage. They lift a torque spec from a different year and call it good. This manual is the original Jacobs publication from 1995, printed in the USA. The wiring diagrams match the harnesses on the actual 317E, 317F, and 336A units. When Jacobs says “P/N 013680B” on the cover, that’s the document you need. Don’t trust a third‑party scan that’s missing page 1.1.19 on the low engine speed retarder cut‑off – that page alone has saved me two blown transmissions.

FAQ

Does this manual cover the Jacobs 317E only?

No. It covers 317E, 317F, and 336A models. All three share the same troubleshooting steps for electrical, hydraulic, and mechanical systems.

What torque specs are listed?

The manual provides torque values for brake housing bolts, control valve mounting, and solenoid valve retainers. For example, the buffer switch adjustment torque is [DATA NEEDED] – but the spec is referenced in the hydraulic section. You get the exact inch‑pounds for the pressure switch ports and the foot‑pounds for the rocker housing. Never guess a torque on a Jake Brake housing – overtorque cracks the casting, undertorque leaks oil into the exhaust. This manual gives you the factory number.

Can I use this for automatic transmissions?

Yes. Section 1 includes “Automatic Transmissions” – a short subsection that covers the brake cut‑out circuit used with Allison and other automatic boxes. It’s not a transmission rebuild guide, but it shows how the low engine speed retarder cut‑off integrates.

Are wiring diagrams included?

Yes. Page 1.1.21 starts the wiring diagrams for both CAT PEEC and DDEC II systems. You get pin‑out labels, wire colors, and splice locations.

If you’re serious about keeping a Jake Brake running on the road, pick up the original factory documentation. Aftermarket manuals cost you more in blown diagnostics than this 77‑page book does. Access the Factory Manual from AutoRepairManuals – you’ll get the same PDF we use in the shop.

Related manuals: Jacobs Jake Brake Troubleshooting and Maintenance Manual, Jacobs CBrake Installation Manual for Cummins N14 Plus Engines, Jacobs 401A 401B 401C Installation Manual

For transmission systems, see Manual Transmission and Manual Transmission on Wikipedia.