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DENSO Starter

Does Denso Make An Starter With Oil Seal

 

 

Yes, Denso, as a top-tier automotive parts manufacturer, produces a wide range of starter models. Many starters are indeed designed with an oil seal. Its primary function is to prevent engine oil from leaking into the starter's electrical components, thereby protecting critical internal parts such as bearings and the solenoid.

For example, the starting motor of the electric installation 428000 1830 is equipped with a sealing ring inside.

DENSO Starter sealing ring inside
DENSO Starter sealing ring inside
DENSO Starter sealing ring inside

 

 

 

 

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E-star Auto Co., Ltd. As a professional Denso starter supplier and trusted provider of wholesale Denso starter solutions in China, we offer a comprehensive range of Denso starter motor China that align with strict OEM specifications, ensuring seamless fit and long-lasting performance.

When talking about Denso starters, there are plenty of other reputable brands and models worth researching and learning about.

Our catalog features cross-reference original Denso OEM part numbers, including 128000-2240, 028000-5730, 228000-0630,438000-4441, 428000-1210 and 28100-0L052. Our E-Star aftermarket replacement starters for Denso deliver power outputs ranging from 0.6KW to 9.0KW, fitting applications for all mainstream vehicle brands.

These replacement starters are engineered to fit Toyota models (Corolla, Yaris, RAV4), Honda engines (GX390, GX270), Mitsubishi & Isuzu commercial vehicles, and a wide range of industrial machinery. Fully verified against OEM mounting dimensions and electrical specifications, they offer direct bolt-on replacement with zero modifications required. Below are compatibility breakdowns for several genuine Denso OEM reference numbers.

 

Denso: 128000-2240,128000-9400,971280-9224,Honda 31200-ZH9-003,DB5B7, DB5BC HONDA Engine GX270K1-9.0H.P

honda starter

 

DENSO: 028000-5730 DSN2144 JOHN DEERE AM79743 TY6715

Application:JOHN DEERE 4300 Yanmar 3TNE84

Yanmar starter

 

DENSO:DSN2106,228000-0630,,228000-4992,228000-6640,228000-6670,

Komatsu: 6008134110, 6008134130, 6008135110, 6733816510, 6733826510

Application: S6D102 QSB6.7 PC200-6

komatsu starter

 

DENSO:4380004441

CAT:4882807

Application:CAT Engine C7.1 CAT 336D2GC

cat starter motor

 

Denso: 4280001210, 4280001211, 4280001220, 4280001221

Cummins: 2895341, 3102762

Application:MACK CH Series CASE 9150 Cummins ISX15

Cummins starter motor

 

DENSO:DSN1371,281005-4450,428000-2633,428080-2633,TG4280002631,TG4280002632

Toyota :281000L050, 281000L051, 281000L05184, 281000L052, 2810067020, 2810067060

WAI:33287N

Application:TOYOTA 2KD-FTV/1KD-FTV

Toyota starter motor

 

Our wholesale Denso starters match or exceed OEM quality standards, featuring precision-machined gears, high-grade copper coils, and factory-tested components that deliver reliable cold starts in extreme temperatures. Unlike generic replacements, these units maintain Denso’s signature durability—capable of over 200,000 km of service life under normal use—while supporting bulk orders for distributors and repair shops.

As a dedicated Denso starter motor China partner, we also provide full technical support, including compatibility charts, installation guides, and batch testing reports, helping you source with confidence.

 

how does a denso starter relay work

Let's break down how a Denso starter relay works. Denso is a major OEM supplier for Toyota, Honda, Ford, and many other manufacturers, so their design is very representative of how most modern starter relays function.At the beginning of most Denso starter designs, the starter motor itself does not come with a relay, for example: denso 428000 5120，428000 5120，denso 128000 4291.

Denso 428000 5120
01

The starter relay is an electric switch that matches heavy-duty starters. Its job is to safely control the small current from the ignition switch to supply the large current required for the electromagnetic switch of the starter motor, better protecting the ignition switch. For example: Denso 428000 5120，428000 5120, Denso 128000 4291, Denso starter motor itself does not have a relay, but relays are also added to the vehicle electrical system.

02

The Core Components of a Denso Starter Relay

A typical Denso starter relay (which is often integrated into the starter motor assembly as a starter solenoid) has four key parts:

1.Housing: The metal or plastic case.

2.Coil (Electromagnet): Two sets of wire windings inside the relay (the Pull-In Coil and the Hold-In Coil - explained later).

3.Plunger: A movable iron core that slides inside the coil.

4.Contact Disc (or Contacts): A large, heavy-duty copper disc attached to the plunger.

The Two-Stage Process of Operation

Here is a step-by-step breakdown of what happens when you turn your key to the "start" position.

Denso 428000 5120
Denso 128000 4291
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Stage 1: The Ignition Key is Turned to "Start"

1.Low-Current Signal: You turn the key. A small electrical signal is sent from the ignition switch to the "S" (Start) terminal on the starter relay.

2.Electromagnet Energized: This small current flows through both the Pull-In coil and the Hold-In coil, creating a powerful magnetic field.

3.Plunger Pulled In: The magnetic field pulls the iron plunger inward, sliding it towards the rear of the relay.

4.Two Actions Happen Simultaneously:

Action A (Mechanical): The plunger is connected to a lever that pushes the starter motor's pinion gear forward. This meshes the pinion gear with the teeth on the engine's flywheel (ring gear).

Action B (Electrical): The other end of the plunger pushes the large copper contact disc against two massive main terminals.

04

Stage 2: The High-Current Circuit is Completed.

5.Main Circuit Closure: The two main terminals are:

"B" Terminal (Battery): Connected directly to the positive terminal of the car's battery via a thick, heavy-gauge cable.

"M" Terminal (Motor): Connected directly to the starter motor's field coils.

6.High Current Flow: When the contact disc bridges the gap between these two terminals, it completes the high-current circuit. A massive amount of current (often 200-400 amps or more1000A) can now flow from the battery, through the relay, and directly to the starter motor.

7.Motor Cranks: With this power, the starter motor spins violently. Because the pinion gear is already engaged with the flywheel (from Step 4A), it cranks the engine over.

Denso 128000 4291

 

how to bench test a denso starter

Detection of simple starter motor:

Few individuals have professional starter testing equipment for wholesalers, so how can starter be tested without professional testing equipment.

Bench Testing (Starter Removed from the Car)

This is the definitive test to confirm if the starter motor itself is good. It simulates what happens when you turn the key.

What You Need:

A fully charged car battery (or a known-good jumper pack).

Two sets of jumper cables (or one set and a spare heavy-gauge wire).

Safety glasses.

Steps:

 

1.Secure the Starter: Place the starter firmly in a vise or on a stable, non-flammable surface. Ensure it cannot spin away. The starter will torque heavily when it engages.

2.Identify the Terminals:

Large Terminal ("B" or "BAT"): Where the thick battery cable connects.

Small Terminal ("S"): Where the thin wire from the ignition switch connects.

Ground the Starter: Clip the BLACK (negative) jumper cable to the negative (-) terminal of the battery. Clip the other end to the metal body or mounting ear of the starter. This grounds the starter.

Test the Solenoid (The "Click" and Gear):

Take the RED (positive) jumper cable.

Touch the red clip to the small "S" terminal.

What to watch for: You should hear a loud "CLUNK" as the solenoid engages and the pinion gear (the small gear) should jump forward.

Result: If you get the "clunk" and the gear moves, the solenoid is working. If nothing happens, the solenoid is faulty.

5.Test the Motor (The "Spin"):

Keep the red clip on the small "S" terminal to keep the solenoid engaged.

Now, carefully touch the red clamp itself to the large main terminal ("B") on the starter.

⚠️ WARNING: This will create significant sparks. This is normal but be prepared.

What to watch for: The starter motor should spin powerfully, smoothly, and loudly.

Result: If the motor spins powerfully, the motor itself is good. If it's sluggish, makes strange noises, or doesn't spin at all, the motor is faulty.

DENSO 228000-7670
By following this logical sequence, you can simply and effectively detect what's wrong with a starter motor. Always prioritize safety, especially when dealing with a powerful battery and creating sparks.
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how to ell a genuine denso starter
 

I have gathered some key strategies to help you distinguish a genuine Denso starter, focusing on packaging details, part inspection, and purchasing channels. However, the available information lacks starter-specific details like the exact location of serial numbers or images of genuine vs. fake starters.

01/

How to Spot a Genuine Denso Starter

The table below summarizes the main points to check based on general principles for identifying authentic auto parts and Denso products.

Checkpoint: What to Look For in a Genuine Denso Starter Red Flags (Potential Counterfeits)

Packaging: High-quality, sturdy cardboard with sharp, clear printing and correct logos. Holographic stickers or QR codes for verification. Flimsy box, blurry text, spelling errors, missing security features.

Part Quality: Precise machining with clean, smooth finishes; no rough edges or burrs. Denso branding is engraved or stamped, not just printed. Rough edges, uneven surfaces, cheap-feeling materials, poor welding.

Markings & Labels: Clear, legible part numbers and branding. Labels use specific fonts and include accurate technical details. Smudged or easily removable printing. Incorrect or missing part numbers, generic labels.

Fit & Weight: Identical to the original part in size, shape, and connectors; feels substantial. Slight variations in size or shape; feels lighter due to inferior materials.

02/

Purchase Advice and Next Steps

To ensure you get an authentic part, where and how you buy is just as important as physical inspection.

Buy from Authorized Sellers: The safest way to avoid counterfeits is to purchase from authorized Denso distributors or reputable Toyota OEM parts dealers. Be cautious with online marketplaces or sellers offering deals that seem too good to be true.

Verify Using Official Channels: Check the Denso website for official part catalogs and lists of authorized dealers. If a part has a QR code or hologram, use Denso's official verification system to scan it.

Inspect Upon Arrival: Carefully examine the packaging and the part itself before installation. If anything seems off, contact the seller immediately.

I hope this guide helps you feel more confident in identifying a genuine Denso starter. If you can provide the specific model of your vehicle or the starter, I may be able to find more detailed technical information for you.

 

how to rebuild a denso starter

 

 

Rebuilding a Denso starter is a very rewarding DIY job that can save you a significant amount of money. Denso starters, Widely used, are generally well-designed and serviceable.

 

Precautions

7.3 denso starter

Disconnect the Battery

Always disconnect the negative battery terminal before starting. The starter is connected directly to the positive battery terminal, and a short circuit can cause severe sparks, fire, or injury.

01

Work on a Clean Surface

Keep your workbench clean and organized. Small parts and springs are easily lost.

02

Professional Help

If you are not comfortable with mechanical and electrical work, seek a professional. You can also contact us and we will help you solve all your problems.

03

Specific Model Matters

While the core principles are the same, there are variations between Denso starter models (e.g., gear-reduction vs. direct-drive). We will take the 7.3 denso starter as an example.

04

 

Step : Disassembly & Inspection

Lay the starter on a clean workbench. Take pictures with your phone at each step to help with reassembly.

 

A. Separate the Solenoid from the Motor

1.Remove the two or three long through-bolts that hold the entire starter together. They run from the solenoid end to the motor end cap.

2.You can now gently separate the three main components:

The solenoid

The main motor body (with field coils and armature)

The end cap (with brushes)

DENSO 228000-7670

 

B.Inspect and Clean the denso Solenoid

 

 

1.The solenoid has a small plunger with a contact disc on the end and two large copper terminals (B+ and M) inside.

2.Inspect the Contacts: The high current flows through the contact disc. Look for severe pitting, burning, or melting. If the contacts are worn down, the solenoid kit should include a new contact plate and sometimes the terminals themselves.

If heavily pitted, they must be replaced.

3.Inspect the Plunger: Ensure it moves freely in its bore. Lightly lubricate it with a tiny amount of electrical contact grease if the kit provides it.

 

C.Inspect the Brushes and End Cap

1.The denso brush holder is attached to or part of the end cap.

2.Inspect the Brushes: Brushes are carbon blocks that press against the armature's commutator. They wear down over time.

Measure their length. If they are less than 1/4 of their original length or the wear limit specified in a service manual, they must be replaced.

A rebuild kit will include new brushes, often pre-installed on a new brush holder for easy replacement.

3.Check Spring Tension: The springs that push the brushes against the commutator should be strong and not corroded.

DENSO 228000-0251

D.Inspect the Armature and Field Coils

DENSO 228000-7670

 

1.Clean the Commutator: The copper bars on the end of the armature shaft are the commutator. Clean it with electrical contact cleaner and a rag. If it has minor scratches or burn marks, you can lightly polish it with very fine sandpaper (400+ grit). Do not use emery cloth.

2.Inspect for Damage: Look for signs of overheating (blueing), severe burning, or bars that are lifted or loose. If damaged, the armature must be replaced.

3.Check for Shorts to Ground: You can use a multimeter (ohms setting) to check for continuity between the commutator bars and the armature's steel shaft. There should be infinite resistance (no continuity). If there is continuity, the armature is shorted and must be replaced.

4.Inspect the Field Coils: These are the copper windings you see inside the starter motor housing. Visually check for cracked, burned, or damaged insulation. Also check for continuity between the field coil brushes and the housing. There should be no continuity.

 

E. Inspect the Drive Assembly (Bendix Gear)

1.This is the small gear on the end of the armature shaft that engages the engine's flywheel.

2.Check the Gear: Look for chipped, worn, or rounded-off teeth. Replace if damaged.

3.Check the One-Way Clutch: Hold the gear and try to turn the shaft in both directions. It should turn freely in one direction and lock completely in the other. If it slips in the "lock" direction, the entire drive assembly must be replaced.

4.Lubricate: Apply a very small amount of high-temperature grease to the shaft splines. Do not get grease on the clutch mechanism.

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Step 3: Reassembly

Reassembly is essentially the reverse of disassembly, but with new parts and careful attention.

1.Install New Components: Install all the new parts from your rebuild kit (brushes, solenoid contacts, seals, etc.).

2.Brushes: If you have a new brush holder, it's simple to swap. If you're replacing individual brushes, take your time to secure them properly and carefully slide the springs into place.

3.Armature Installation: Carefully slide the armature back into the motor housing.

4.End Cap/Brush Holder Installation: This is the trickiest part. You need to hold the brush springs back and seat each brush onto the commutator. A small pick or a straightened paperclip can help. Once all brushes are seated, the end cap should slide on smoothly.

5.Reattach the Solenoid: Before bolting the solenoid back to the motor, ensure the solenoid's plunger fork is correctly engaged with the drive assembly's shift lever. This is critical for the gear to extend properly.

6.Install Through-Bolts: Reinstall the long through-bolts and tighten them evenly.

 

Step 4: Bench Test (VERY IMPORTANT)

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Perform this test before installing the starter back in the vehicle.

1.Use Jumper Cables:

Connect the negative (black) cable from the negative terminal of a battery to the starter's metal case (a clean mounting lug is perfect).

Have the starter secured in a vise or on a stable, non-conductive surface. The starter will JUMP with a lot of force when engaged.

2.Test the Solenoid:

Briefly touch the positive (red) jumper cable from the positive battery terminal to the small "S" terminal on the solenoid.

You should hear a solid "CLUNK" as the drive gear shoots out and stays out. The motor should not spin yet.

3.Test Full Starter Operation:

Now, connect the positive (red) jumper cable to the large "B+" terminal on the solenoid (where the main battery cable goes).

Briefly touch the "S" terminal again.

You should hear the "CLUNK" and the motor should spin powerfully and smoothly. The gear should remain engaged until you remove the power from the "S" terminal.

If it passes this test, it's ready for installation!

Parts You'll Need

Denso Starter Rebuild Kit: This is the most important part. It typically includes new brushes, brush springs, solenoid contacts, seals, and gaskets.

Denso Solenoid Plunger Kit (if needed): If your solenoid is badly worn, you may need a full solenoid repair kit.

Drive Assembly (if needed): If the one-way clutch or gear is bad.

Electrical Contact Cleaner

High-Temp Grease

Multimeter

By following these steps carefully, you can successfully rebuild your Denso starter and restore it to like-new performance.If you encounter any problems during the reconstruction process, please feel free to contact us.

 

How to rebuild a denso starter solenoid

General Rebuild Procedure

The exact steps, fastener sizes, and internal configuration can vary between different Denso starter models.For example, for Denso starter motor 228000 5911,denso 228000 5911 replacing the switch is quite simple, with only 2 connecting screws.

For example, for 7.3 denso starter，denso high torque starter，denso gear reduction starter，7.3 denso starter，denso 7.3 starter， Replacing the switch is quite troublesome, as it requires disassembling the entire starter motor. You can directly disassemble the switch tail and replace the accessories.

1.Safety First: Always disconnect the negative terminal of the battery before beginning any work. This is critical because the starter is connected directly to the battery with a heavy, un-fused cable .

2.Remove the Starter: You will need to locate the starter on the engine (usually near the transmission bell housing), disconnect the electrical terminals, and unbolt it from the engine block .

3.Disassemble the Denso Solenoid: The solenoid is usually attached to the Denso starter motor body with two small screws or bolts. You may need to desolder or unclip a small wire connecting the solenoid's motor terminal to the starter's field coil.

4.Inspect and Clean:

Once open, you will see the large copper main contacts and the plunger. Inspect the contacts for pitting, burning, or excessive wear. These are often the primary cause of failure.

Inspect the plunger for smooth movement and the return spring for its tension.

5.Replace Parts: It's highly recommended to use a rebuild kit specific to your Denso starter model. These kits typically include new copper contacts, a contact disc, gaskets, and sometimes a new plunger and spring.

6.Reassemble and Test: Reassemble the solenoid and starter motor in the reverse order of disassembly. Before reinstalling it on the vehicle, you can perform a bench test by connecting it to a battery to ensure the plunger shoots out and retracts smoothly.

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How To Replace Denso Starter 128000-2750

Step 1: Safety First - Disconnect the Battery

Disconnect the negative battery cable. This is the most critical safety step. The starter is connected directly to the battery with a heavy, un-fused cable, and failing to disconnect power can cause a short circuit, severe sparks, or injury.

Step 2: Locate and Access the Starter Motor

The starter motor is typically located on the lower side of the engine, next to the transmission bell housing.

Step 3: Disconnect Electrical Connections

The starter will have several electrical connections:

A large, heavy-gauge cable that brings battery power.

A smaller wire or wires connected to the solenoid for the ignition switch signal.

Carefully note or take a picture of the wiring before disconnecting them. You may need to use a 13mm wrench or socket (sizes may vary) for these nuts and bolts.

Step 4: Remove the Starter Mounting Bolts

The starter is held in place by two or three mounting bolts.

These bolts can be long and may be tight. Use the correct socket (often 13mm or similar) and a breaker bar if necessary. The starter has some weight, so be prepared to support it as you remove the final bolt.

Step 5: Install the New Starter

Position the new or rebuilt Denso starter into place.

Hand-tighten the mounting bolts first, then torque them to the manufacturer's specification.

Reconnect all the electrical wires to the correct terminals, double-checking they match your notes or photo.

Step 6: Reconnect Battery and Test

Reconnect the negative battery cable.

Turn the ignition key. The engine should crank and start normally.

 

 

Our Factory

 

Shanghai E-star Auto Co., Ltd. is located in the bustling Minhang District of Shanghai. The production company covers an area of 24000 square meters and the construction area exceeds 23000 square meters. There are over 150 elite employees gathered here, including a technical team of over 20, who provide a continuous source of motivation for the company's research and manufacturing.

 

 

Company Honors

 

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FAQ

 

Q: How to tell a denso starter from clone

A: 1.Source: Did you buy it from a reputable, authorized seller?
2.Packaging: Is the box high-quality with sharp printing and correct labels?
3.Casting: Is the metal smooth, with sharp, legible logos and no rough edges?
3.Weight: Does it feel solid and heavy for its size?
4.Labels: Is there a permanent, stamped metal tag with the part number?
5.Terminals: Are the electrical connections clean and plated?

Q:How to tell a if a denso starter is genuine

A: 1.Check the Label:
Genuine: Has a permanently attached, stamped metal tag with a clear part number.
Fake: Uses a cheap, easily peeled-off paper or plastic sticker.
2.Feel the Surface:
Genuine: Casting is smooth; logos and lettering are sharp and precise.
Fake: Casting feels rough and sandy; lettering is often blurry.
3.Check the Weight:
Genuine: Feels surprisingly heavy due to quality materials like copper.
Fake: Noticeably lighter.
4.Do the Magnet Test:
Place a magnet on the main body of the solenoid (the cylindrical part).
Genuine: Magnet will not stick strongly (uses copper coils).
Fake: Magnet will stick firmly (uses steel or aluminum).

Q: How to test a denso starter

A: Simple Bench Test (Starter Removed from the Car)
This is the safest and most direct method to see if the starter itself works.
What you need: Jumper cables, a known-good car battery, and safety glasses.
1.Secure the Starter: Place the starter on a non-conductive surface (like a wood block) or secure it in a vise. Ensure it can't jump around.
2.Connect the Ground:
Attach the BLACK (-) jumper cable to the negative (-) terminal of the battery.
Connect the other end of the black cable to the starter's metal case. This grounds it.
3."Bump" the Power:
Attach the RED (+) jumper cable to the positive (+) terminal of the battery.
Briefly touch the other end of the red cable to the large main terminal on the solenoid (where the thick battery cable goes).
What to Look For:
Good Result: The starter motor should spin loudly and freely. This means the motor itself is good.
Bad Result: Nothing happens, or it spins very slowly. The starter is faulty.

Q: Should a denso starter be cleaned

A: Yes, but only if it's dirty or has been rebuilt. It's not routine maintenance.
1.When to clean: If you see oil, grease, or heavy dirt on the outside, or if you've just rebuilt the internal parts.
2.How to clean: Use an electronics cleaner spray or brake cleaner. It dries quickly and leaves no residue. Avoid water and harsh degreasers that can damage electrical parts.
3.Goal: Remove grime that could cause overheating or prevent the solenoid from moving freely. Don't force it to be spotless.

Q: Are there any special requirements for OEM purchases?

A: Yes, we require proof of trademark registration in order to print or emboss your trademark onto the product or packaging.

Q: Can you provide drawings and technical data?

A: Yes, our professional technical department will design and provide drawings and techical data.

Q: When can I get the price?

A: We will provide a quotation within 8 hours of receiving your inquiry for products without special requirements.

Q: Can I request to change the form of packaging and transportation?

A: Yes, We can change the form of the packaging and transportation according to your request, but you have to bear their own costs incurred during this period and the spreads.

Q: Can I request to advance the shipment?

A: It should be depends on whether there is sufficient inventory in our warehouse.

Q: How many different types of products your company manufactures?

A: We mainly produce various series of starter alternators, and currently have over 2000 products, making us a comprehensive product supplier.

Q: Do you provide sample ? Is it free?

A: If the sample is low value, we will provide the free sample with freight collect. But for some high value samples, we need to collect the sample charge.

Q: What's is your shipping service?

A: We can provide services for vessel booking, goods consolidation, customs declaration, shipping documents preparation and delivery bulk at the shipping port.

As one of the leading denso starter manufacturers and suppliers in China, we warmly welcome you to wholesale cheap denso starter from our factory. All custom made products are with high quality and competitive price.

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