Principle of operation and purpose of heating

The preheating system, well known to French motorists for its heavy fuel oil fleet of vehicles, is used to start your diesel vehicle. If the device seems simple and doesn't deserve a separate article, it's still interesting to dig a little deeper into the subject to update some of the intricacies. As always, if you have any questions (in principle or concerning a problem with your car) or suggestions, do not hesitate to do it at the bottom of the page, you will get an answer quickly!

Why only diesel?

Preheating is only useful for diesel engines. Because, unlike a gasoline engine, a diesel engine works by self-ignition, that is, the fuel burns itself without a spark. But to achieve this result (fuel combustion), the air entering the cylinder must be compressed until it ignites the fuel. However, the chamber must be at a minimum temperature for the compressed air to come in with enough heat, so the glow plug acts to heat the air in the cylinder to a minimum (so a simple resistance turns red, which is the same as in a toaster or electric heater). In a gasoline engine, it is the spark that ignites the fuel / air mixture, so we don't care if the air in the cylinder is at its minimum temperature.

The other differences between gasoline and diesel engines are here.

Preheating: the difference between direct and indirect injection

If the principle of operation of these two types of engines is somewhat the same, the position of the spark plugs changes. With indirect injection, the spark plug will be located next to the injector in the combustion chamber. With direct injection, the spark plug is fed directly into the cylinder.

Note that indirect injection requires the glow plugs to fire much more often when it is cold because the compression ratio is lower. Being lower, it compresses air less, and then its temperature will rise less. This is why indirect injection diesel will be more difficult to run in very cold weather.

This is what direct injection gives in real life (Mercedes engine)

Thus, this provision applies to older diesel engines, all modern ones with direct injection.

More information about direct and indirect injection here.

Just for the beginning?

If the main role is to improve and promote startups, it should be noted that this also plays an “ecological” role. Indeed, you should know that a cold engine pollutes more than a hot one. Some particles do not burn well, which leads to the formation of soot and "parasitic" particles (in some way unburned). In direct injection engines, the glow plugs continue to burn even when the engine is just started to increase the temperature in the combustion chambers, which then allows combustion to be optimized and therefore reduced pollution.

Preheating problems?

In the event of a failure of the preheating system, you will have several possible symptoms. You may have strong vibrations at the first rpm of the engine, some cylinders that are too cold will not ignite, so there is an imbalance created by the engine that does not ignite all of these cylinders (then the HS spark plugs will need to be replaced). You can also have a significant amount of smoke when the engine is cold, indicating that the combustion is too cold and that it has not burned out.

Here are the latest reviews of opinions posted on the site's test sheets:

Citroen C3 II (2009-2016)

1.4 HDI, 70-speed manual transmission / C3 II, January 2009 / steel wheels / 180 km / sec. : replaced only the malfunction of the BSM (under warranty)

Citroen Saxo (1996-2003)

1.5 D 58 h 80 000 km, 2000, 13p, exclusive : Candles preheating, rocker arm adjustment

Mercedes E-class (2002-2008)

320 CDI 204 hp bva, 320мкм, 2003 г., avangarde : sensors, srs malfunction, seat belt retention system malfunction, box preheating, battery consumption even when stopped.

Nissan Qashqai 2 (2014-2021)

1.5 dCi, 110 hp, BVM6, 116000 km / s, 12/2014, 16-inch rims, Tekna finish : candles preheating and the exhaust gas analysis sensor is blocked.

Toyota Rav4 (2006-2012)

2.2 D4D 136 hp 300000 YEAR 2010 OCTOBER : CANDLES preheating Replaced 295000 km ONE REAR BEARING RIGHT SIDE OTHER BRAKES FOR NORMAL MAINTENANCE TIRE BATTERY

Seat Ibiza (2008-2017)

1.6 TDI 105 HP 158000 km with 2010 SC 15-inch rims : seeing preheatingDPF valve nozzles

Citroën C6 (2005-2012)

2.7 HDI V6 205 inches : 120000km replaced two egr valves twice as many chassis triangles in front of sensors three abs four spark plugs preheating at the generator, all the plastic sheaths on the electrical lines break, of very low quality for a car supposedly at the range, and now the on-board computer is broken. I have driven a Citroen for 75 years and this will be my last, I also have a 33 year old - an old Honda prelude which I am sure of more and much less problems despite the horribly directional wheels and since Citroen has abandoned the 6-cylinder engine.

Audi A4 (2001-2007)

2.0 TDI 170 hp BRD, BVM 6, 320,000 2007км, XNUMX, Sline : Fuel pump relay /preheating HS due to water in the compartment in which they are housed. FAP EGR / Intake duct dirty, cleaned after a little disassembly.

Volvo C30 (2006-2012)

1.6 d 110 can : The problem of a blocked fap from 120000 60 transferring a car to a degraded mode (+ -XNUMXh I would say) it is necessary to add an egr valve, an additive reservoir, a spark plug preheating and relay preheating because everything folds into a loop ... only about 3-4000. After 180000 10 km and 2000 years, the windshields broke off (factory malfunction depending on the specialization), which led to the penetration of the battery into the central computer, which is obviously not protected !!!? ? , exchanged for XNUMX euros only for Volvo, generator.

Renault Scenic 2 2003-2009

1.5 dCi 105 hp 250000 XNUMX : replacing the window regulator module 20 ?? it takes 15 to 20 minutes

Peugeot 3008 2 (2016)

1.6 Hybrid2, 225 hp, 2021 GT facelift, 7,4 kW charger option and compatible Green'up cable : During the first filling, blockage at the level of the filler neck. It is impossible to return the slightest drop. Again at the car dealership, RAS, and the same at the supermarket. Mishandling the gun on my part ??? Some front brake pad noise during parking maneuvers. Always in the parking lot, cornering noise in dry conditions (tire noise?. These two points need to be checked because there is an RAS on the road.

Alfa Romeo 156 (1997-2005)

1.9 JTD 126 hp Manual 6, 235000km, 2004 : 2 months after the purchase, there was a big problem with the gearbox, which cost me 950¤. After 7 months, the gears are not switched again. The car smells of dirt +++ (not suitable for the next inspection). Throttle Bores, HS Steering and Suspension Balls, Spark Plugs preheating UG, constant unidentified whistle when driving. I'm an alfist, but this will remain my worst car

Renault Scenic 3 2009-2016

1.6 dCi 130 hp 2014 bose edition sunroof 217 km : Rear right door lock (under warranty) Turbocharger return hose (100 km) Replacing front and locking shock absorbers (000 150 km) Replacing battery (000 160 km) Replacing spark plugs preheating (180 km) air conditioner leak (000 km)

Toyota Rav4 (2001-2006)

2.0 D-4D 115 hp Manual transmission, 300 km, 000 g. : Problem with recirculation, does not start hot. When the cold start gets harder and harder. I replaced the egr valve, 2 solenoid valves, 20 km / s turbocharger and I replaced preheatingYou have a solution to this problem. Please give me a solution.

To be rio (2011-2016)

1.4 CRDI 90 ch Rio Premium 2012, 60000km : Parasitic noises in the plastic from the first days Creak of the driver's door after 6 months. Interior rearview mirror, which adjusts in a few days. Rear door seals, melted in the sun. Limited sound insulation (false). preheating (spark plugs, relays, calculator) completely out of order at 55000 km, estimated 1600 ?? + brake caliper for UAH 500

Volkswagen Arteon (2017)

2.0 TDI 190 hp BVA, 52000 km / s, : Excessive wear on front inner tires, geometry must be retained after tire change. Yellow engine warning light comes on ... Access to suitcase, spark plug preheating Replacing HS with 4 and Bing 345 ¤ more Garage reminder for Arteon that dumps the fuel pump from the tank needs to be replaced on this model (hence my fuel failure when I still had 60 km / sec to do it myself) if you exceed a quarter Your tank dashboard display is no longer real. For a model that should be better, I am very disappointed ... And if you sell it in 2 years, you will lose 57% welcome to Volkswagen ... Goodbye Volkswagen😠

Audi A1 (2010-2018)

1.6 TDI 90 bhp 2011 : candle preheating 240 km, meeting at Audi only after 000 days (ASAP) to find out what the orange light is and if I can ride with it, buy a small 7th electronic diagnostic car, online guide to replace spark plug 70 hours for training, 2 euros a pair of candles and a key, and that's ok. Thanks Scala.

Mercedes B-class (2005-2012)

180 CDI 110 ch Manual gearbox, 240000km, Year 2006, Sport package : Candles preheating

BMW Series 5 (2003-2010)

525d 197 ch E61 Pack M 525XD 2008 242000 km Automatic : CCC module (comfort, screen turns red) Shock absorbers (front and rear) All front aluminum arms and tie rods, high clearance Rear tie rod locked - not adjustable Steering links, wear Lower ball joints, high clearance Drilled aluminum Air I hose / C -> Inlet Turbo broken (turbine clogged) Diesel particulate filter Intercooler, leaking Diesel particulate filter differential pressure sensor 5 Spark plugs preheating (out of 6) Sunroof blocked (open ...) High pressure hose Air conditioning A / C compressor clutch Bluetooth module not working Wiring Rear door almost cut off


Diversity module (aerial amplifier in the tailgate) Motor Boot lid Battery 1 Drilled rear air spring


The electronic modules in the spare wheel are rusted. Front left and right hub bearing. Broken left universal joint on the side of the wheel. Hydraulic engine support. Elastic crankshaft pulley. Water pump + additional belt tensioner. car probably

Mercedes C-Class (2007-2013)

220 CDI 170 ch manual transmission, 130000km, 2009, 16 ″, classic BE, : -Replacement of the water pump-replacement of nozzles-malfunction of ELV-EZS-leaks and replacement of the hose-replacement of the calorstat-malfunction of the rear lights. - flexible back train - candles preheating- oil leak

All comments and reactions

Dernier comment posted:

Author (Date: 2021 10:08:13)

hi everyone I have a 2007 Alfa Romeo gt. My big problem. First start in the morning, starting at a quarter turn. I drive without problems. The second cold start will not start. © the machine laughs.

I practically changed all the spark plug sensors and the preheating unit are new, the suitcase does not malfunction and still does not work

Il I. 1 reaction (s) to this comment:

• Administrator SITE ADMINISTRATOR (2021-10-08 20:18:11): Possibly an element in the fuel pump.

  A relay that gets moody during the day, an occasional Common Rail sensor, a clogged tank, etc.

  In principle, there is something to look for.

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