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Pelican Technical Article:

Replacing the Warm-up Regulator

Mike Holloway

Time:

30 minutes30 mins

Tab:

$100 to $400

Talent:

*

Tools:

5mm Allen, 12mm wrench, 14mm wrench

Applicable Models:

Mercedes-Benz 450SL (1975-80)

Parts Required:

Warm-up compensator

Hot Tip:

Good time to replace rubber lines

Performance Gain:

Improved cold starting

Complementary Modification:

Replace fuel injectors

The warm-up compensator is also known as the warm up regulator. If your acceleration is muted the warm up compensator may be broken or on its way to being kaput. The warm up regulator increases the fuel flow making the flow richer. The warm-up regulator applies opposing pressure on the injector pins of the fuel injector. When the engine is cold the warm up compensator reduces the pressure applied, which allows more fuel to flow to the injectors. As the warm up regulator heats up the pressure is increased. A warm up regulator failure occurs when there is a loss of pressure available from the warm-up compensator/regulator.

Before you do any work on your car it is important that you wear safety glasses, work gloves and dispose of all fluids in a safe manner. If you are draining coolant, keep in mind that it is poisonous and should be treated as such. Animals and small children have been known to die from ingesting coolant. If you have to jack up your car, make sure to use jack stands and chock your wheels as well as applying the parking brake. Protect your eyes, hands and body from fluids, dust and debris while working on your vehicle. If you're working with the electrical system, disconnect the battery before beginning. Always catch fluids in appropriate containers and properly dispose of any fluid waste. Recycle parts, packaging and fluids when possible. Never work on your vehicle if you feel the task is beyond your ability. Always use eye and hand protection.

Using a 12mm open-end wrench, loosen and remove the fuel line from the warm-up compensator.
Figure 1

Using a 12mm open-end wrench, loosen and remove the fuel line from the warm-up compensator.

Using a 14mm open-end wrench, loosen and remove the fuel line from the other side of the warm up regulator.
Figure 2

Using a 14mm open-end wrench, loosen and remove the fuel line from the other side of the warm up regulator.

Disconnect the electrical input jack by pressing the securing clip and pulling it out.
Figure 3

Disconnect the electrical input jack by pressing the securing clip and pulling it out.

Using a 5mm Allen wrench, loosen and remove the Allen screw that secures the front of the warm up compensator.
Figure 4

Using a 5mm Allen wrench, loosen and remove the Allen screw that secures the front of the warm up compensator.

Using a 5mm Allen wrench, loosen and remove the other Allen screw that secures the back of the warm up regulator.
Figure 5

Using a 5mm Allen wrench, loosen and remove the other Allen screw that secures the back of the warm up regulator.

Disconnect the fuel pulsation dampener.
Figure 6

Disconnect the fuel pulsation dampener. The device is designed to regulate the control pressure. The fuel pulsation dampener normally does not have to be replaced but the lines feeding the component may need to be replaced due to cracking.

Disconnect the rubber lines feeding into the warm-up regulator.
Figure 7

Disconnect the rubber lines feeding into the warm-up regulator.

Once removed, look inside the line for signs of deposits or corrosion.
Figure 8

Once removed, look inside the line for signs of deposits or corrosion. These lines need to be replaced.

Disconnect the vacuum check valve.
Figure 9

Disconnect the vacuum check valve.

The warm-up compensator/regulator is now ready to be replaced.
Figure 10

The warm-up compensator/regulator is now ready to be replaced. Replacement is the reverse of removal.

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Comments and Suggestions:
Mike Comments: i have a 1984 500SL when i first start it it won't accelerate the rpms will drop almost die out until its warmed up then its fine would this fix it?
August 15, 2017
  Followup from the Pelican Staff: Could be an issue with the fuel pump. I would perform a fuel delivery system test. Check fuel pressure, volume and quality.
- Nick at Pelican Parts
 
volleybob Comments: I have a 1975 Mercedes 450SL. I drive it regularly. Great running car. It started using much more gas than normal...smell of gas in the cab while running often. Went in for a fill up and drove off like normal...started missing..surging and dying. Made a few miles and then stopped. Thought it was bad gas, but no. Had it towed to a "foreign car repair shop". Told me it was the fuel pump and something in gas. Replaced pump, spark plugs, filter, and tested gas. Nothing in gas but same symptoms. The car will start but dies withing mins or runs longer and dies. suggestions???
April 13, 2017
  Followup from the Pelican Staff: Sounds like you have a stuck open fuel injector. Try monitoring system resting fuel pressure to see if it drops. If so, try to isolate the injector causing the drop.- Nick at Pelican Parts  
Nick Comments: Where can I buy a warm up regulator? I don't see any for sale here?
June 27, 2016
  Followup from the Pelican Staff: Give The Pelican Parts parts specialists a call at 1-888-280-7799. They can figure out what part or repair kit you need.
- Nick at Pelican Parts
 
Ret lineman Comments: My 380sl floods until it warms up! Could this be my problem
January 8, 2016
  Followup from the Pelican Staff: Possible. Or faulty temp sensor or high fuel pressure. - Nick at Pelican Parts  

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Page last updated: Mon 10/23/2017 02:44:40 AM