Matched Engine Sets — Each glow plug verified against specific LDW, KD, and F-series engine serial prefixes before dispatch.
Technical Specifications
| Parameter |
Value |
| Part Number |
ED0021000890S |
| Product Type |
Glow Plug |
| Cross-Reference |
ED0021000890-S, 0250200908, H1655, H1 655, 21000890, ED21000890-S, 13 721 655, 11.721.655 (reference only) |
| Machine Fitment |
Lombardini LDW 502–5100 series; Kohler KD170–KD600 series; Deutz F2L/F3L/F4L 413–519 series |
| Voltage |
12.5 V |
| Thread Size |
M12×1.25 |
| Overall Length |
72 mm |
| Fitting Depth |
24.5 mm |
| Cone Pitch |
63 |
| Spanner Size |
12 mm |
| Terminal Type |
M5 |
| Condition |
New Aftermarket |
| Warranty |
3–12 months against manufacturing defects |
| Standard |
ISO 9001 |
Application Suitability
| Engine System |
Related Components |
| Cold-start ignition (indirect injection) |
Injection nozzles, pre-combustion chamber inserts |
| ECU-controlled glow circuit |
Glow plug relay, timer module, wiring harness connectors |
| Cylinder head sealing interface |
Cylinder head gasket, valve stem seals, injector return lines |
| Engine overhaul refresh |
Piston rings, main and rod bearings, full gasket set |
Why the Same Part Number Ships in Multiple Variants
Correct cold-start performance depends on matching the glow plug thermal curve to the exact engine serial variant.
In the field, I have seen rebuild shops source glow plugs by engine family alone, only to find that a Lombardini LDW 505 built in one year range demands a different fitting depth than the same model designation produced later. The same applies across Kohler KD and Deutz F-series platforms where indirect injection chamber geometry shifted between production runs. A Glow Plug engine rebuild replacement that threads in perfectly may still sit too deep or protrude too far into the pre-combustion chamber, causing incomplete ignition or carbon wash-down on cylinder walls [NEED_CITE: diesel engine cold-start system diagnostic procedures for indirect injection platforms]. The failure does not appear immediately — it surfaces as hard starting on cool mornings, white smoke at idle, or unexplained fuel dilution in lubricating oil weeks after the rebuild.

System Role Within Indirect Injection Diesel Architecture
This Glow Plug serves the pre-combustion chamber ignition circuit found in Lombardini, Kohler, and Deutz indirect injection designs. Unlike direct injection engines that rely solely on compression heat, these platforms require each cylinder to receive a precisely timed thermal charge before the starter engages. The plug's heating element must reach target temperature within the dwell window the ECU or timer module allows, then sustain that temperature through the first several combustion cycles. When one plug in a multi-cylinder set degrades faster than the others, the affected cylinder fires late or misfires entirely, placing uneven load on the crankshaft and accelerating main bearing wear.
Serial Variant Verification and Rebuild History Considerations
An engine that has been through a prior overhaul may have had its cylinder head replaced with a casting from a different production batch, altering the effective fitting depth the glow plug must satisfy [NEED_CITE: cylinder head interchange and dimensional variance in small-bore indirect injection diesel engines]. Before confirming an order, I check whether the engine serial prefix falls within the range associated with the original head casting or a known service replacement. For Deutz F2L and F3L 413 through 519 series engines, the combustion chamber insert geometry changed across production years, meaning the cone pitch and protrusion requirement can differ even when the thread size remains M12×1.25. This is why I always ask for the engine serial number rather than relying on the machine model alone.
Reading the Specification Sheet Against Real Operating Conditions
The 12.5 V rating aligns with the glow circuit voltage profile that the timer or ECU expects — a plug rated for a different voltage will either heat too slowly, extending cranking time and flooding cylinders with unburned fuel, or draw excessive current and trigger premature relay failure. The 72 mm overall length combined with 24.5 mm fitting depth determines how far the heating element extends into the pre-combustion chamber, which directly controls whether the fuel spray ignites at the intended point. The M5 terminal type must match the existing harness connector; a mismatched terminal forces an adapter crimp that introduces voltage drop and inconsistent heat-up time across cylinders. The 63-degree cone pitch seats against the chamber insert at a specific angle, and deviation here causes hot gas leakage past the plug body during combustion, eroding the cylinder head bore over time.

The Hidden Cost of Specification Mismatch
When a glow plug fits the thread but carries the wrong fitting depth or voltage rating, the engine starts and runs — masking the problem through the initial post-rebuild test. Weeks later, the affected cylinder develops carbon buildup on the injector tip from incomplete combustion, the oil analysis shows rising fuel dilution, and the customer attributes the symptom to a faulty injector rather than tracing it back to the cold-start system [NEED_CITE: root cause analysis methodology for repeat cold-start failure in rebuilt diesel engines]. The engine comes back to the workshop, the cylinder head is removed again, and the rebuild cost doubles because the gasket set, head bolts, and valve stem seals must all be replaced a second time. This is the scenario that taught me to verify every dimensional parameter against the specific engine serial before confirming fitment.
Why Source This Component Through Our Engine System Desk
Our own production lines and qualified sourced supply operate under one warranty and one quality standard, so a glow plug ordered alongside a full overhaul gasket set carries the same inspection discipline. We stock across eight categories, meaning the cold-start components, piston sets, bearing shells, and seal kits for a complete LDW or KD engine rebuild ship in a single consignment. Minimum order is one piece — a single emergency replacement or a matched set for a full multi-cylinder refresh. Cross-reference verification covers superseded numbers and alternate references so that an obsolete Lombardini or Kohler reference still resolves to the correct current specification. Our technical team confirms voltage, fitting depth, and cone pitch against your engine serial before dispatch.
Documentation & Verification
- Commercial invoice listing each glow plug with engine serial cross-reference confirmation
- Compatibility sheet marking all OEM numbers as reference only for customs and receiving
- Quality inspection record including resistance measurement and heat-up time test per unit
- Warranty terms covering manufacturing defects under normal indirect injection engine operation
- Packing photographs showing terminal protection and thread condition before crate closure
- HS code and customs documentation aligned with engine auxiliary component classification
Installation & Rebuild Sequence
- Verify cylinder head bore condition and clean carbon deposits from pre-combustion chamber insert before inserting new plug
- Apply anti-seize compound to M12×1.25 thread only — keep heating element and cone face clean
- Torque to manufacturer specification using 12 mm spanner, avoiding over-tightening that distorts the ceramic insulator
- Confirm M5 terminal connection is tight and free of corrosion before reattaching glow circuit wiring harness
- Test each plug circuit individually for resistance and current draw before assembling remaining cylinder head components
- After initial start-up, log cold-start behavior across several morning cycles to confirm even ignition across all cylinders
Request a Fitment Confirmation
Provide your engine model, serial number prefix, and any prior overhaul history so we can verify the correct fitting depth and voltage specification for your specific build. If the engine nameplate is unreadable, a photograph of the existing glow plug alongside a ruler is often enough to confirm the overall length and thread pitch. For multi-cylinder engines, let us know whether you need a full matched set or a single replacement, and we will confirm availability and system compatibility before you commit.
Frequently Asked Questions
Q: What other components should be replaced alongside glow plugs during an engine overhaul?
A: During a full rebuild, we recommend refreshing the injection nozzles, pre-combustion chamber inserts if accessible, the glow plug relay or timer module, and all cylinder head gaskets as a matched set. Reusing old injector nozzles with new glow plugs can leave combustion quality uneven, undermining the cold-start improvement the new plugs were meant to deliver.
Q: How do I confirm the correct voltage and fitting depth for my engine serial variant?
A: Share your engine serial number or a photograph of the existing plug with its markings visible. We cross-reference the serial prefix against Lombardini, Kohler, and Deutz production records to confirm whether your engine uses the standard 24.5 mm fitting depth or a variant associated with a service replacement cylinder head.
Q: Why did the previous glow plug fail prematurely after a rebuild?
A: Premature failure often traces to a specification mismatch rather than a defective plug — incorrect voltage rating causes the relay to cycle improperly, while wrong fitting depth leaves the heating element outside the optimal ignition zone. Wiring harness corrosion and loose M5 terminal connections also create voltage drop that starves the plug of its required 12.5 V supply.
Q: Are glow plugs sold individually or must I order a full set?
A: We supply from one piece upward, so you can order a single replacement or a matched set for all cylinders. For engines entering a planned overhaul, replacing every plug at once ensures uniform thermal response and avoids returning to the cylinder head weeks later for a single lagging cylinder.