Rover SD1 Forum Snippet #19 - Debunking Cold Start Injector Mythology

Now, in the context of engine temperature, 35 deg C isn't all that hot, so in a very hot climate like California or Oz, the squirt time is very low, maybe less than a second or two at the most. Even in Blighty at average summer temperatures - it is still low. On a coldish day in Blighty, say above freezing, perhaps 2 - 3 seconds and even at freezingpoint, say 4 - 5 seconds.

But that isn't the whole story, because for the most part, the engine fires pretty much straight away when the Efi is working correctly and the driver stops cranking immediately so the CSI also stops squirting immediately. IT DOES NOT CONTINUE ON ITS OWN.

So what goes wrong to make owners think its a good idea to disconnect the CSI? Well, mostly its because the Efi system is misbehaving due to other reasons and the owner has to crank the engine several times to get it to start. Problem is, the CSI re-energises every time the engine performs a new cranking cycle and repeats its squirting at each cranking event until before very long, the engine really is flooded.

NOW IT WONT START AT ALL! So lets blame the CSI? After all, thats where the flooding is occurring, isn;t it? WRONG! The CSI generally does exactly as it is required to do, it is a robust item that rarely fails in normal service - the same thing applies to the thermotime switch.

Let's look at the situation objectively. If the standard Rover V8 Efi System is correctly set up and starts reliably with the CSI and thermotome switch connected correctly, then upon removal of the CSI, etc, starting will become a tad more difficult, and progressively so, the colder it gets.

That situation can, to some degree, be mitigated by pumping the accelerator to trigger the ECU acceleration and full load enrichment circuits to richen the starting mixture just enough for the engine to fire and, once its fired, cranking ceases, the enrichment circuits go back to sleep and the ECU tries to resume normal management of fuel mixture according to coolant temperature, air temperature, the state of the Extra air Valve and the Throttle Plate position. Nothing else!

What the ECU does not have, however is a residual of cold start fuel atoms swirling around inside the plenum chamber, adding extre richness to the mixture for a short while until it dissipates completely. During that short period the ECU can struggle to maintain combustion and the engine takes a while to pick up its rpm. Again, a situation that can be mitigated by dabbing the throttle pedal to enrichen the mixture and raise the rpm above the stalling point.

Conversely, reverting back to the situation when the CSI is correctly installed and working correctly, when the engine cranks and fires, it displays that characteristic surge of rpm resulting from the burst of atomised starting fuel injected directly into the plenum WITHOUT ANY NEED TO DAB THE THROTTLE and artificially raise the rpm. The CSI system manages that, all by itself.

Now of course, none of the above necessarily applies to modified Efi systems unless one is willing to evaluate individually, what non-standard changes might do to the engine starting process or performance. So, for example:- if one fitted a skewed or wrong ECU, or an adjustable ffuel pressure regulator or hot wire system or megasquirt or Jaguar injectors and air flow meter, expect some differences to occur.

To summarise, if a person has been forced to remove the CSI because the engine is flooding continuously when starting then either: a) the CSI system is faulty and should be tested accordingly or, b) the Efi system needs fettling. MOSTLY, IT'S THE LATTER and to deal with that issue read the essay on the Rover SD1 Efi System Health Check here:

Because one of the introductory observations (above) came from California where the Federal Efi system rules, some of these rationalisations might be affected by the shape of the of the plenum or by the design of the ECU, meeting, as it must, more stringent emission objectives, those elements being somewhat outside the scope of the better documented UK version of the system.

By and large, though, the truth of the matter is this: If the Rover SD1 V8 Efi fuel management system is set up correctly then starting performance under any temperature conditions will always be optimised when the Cold Start Injection System is installed. However, having said that, it is well known that the engine can be started in any (or at least, most) temperature conditions without a functioning CSI facility by "dabbing or pumping the throttle, cranking and resting, cranking again" until it it fires lumpily into life.

One would not, however, expect to see such similar advice in the Owner's Handbook under the heading "Starting the Engine in Cold Weather" without the manufacturer becoming the laughing stock of every journalist present at the vehicle launch ceremony! That sorta adds a tad of reality to the original purpose of the Cold Start System and completely debunks the ascertations of the erstwhile guru, methinks! I'm sure you'll agree? Or maybe not! Why not have your say? After all, as everybody knows:

Mythology Thrives on Misguided Opinions and the Teachings of Erstwhile Gurus!

For a full technical article on the Cold Start Injection System, read the PDF available here:

For more Rover SD1 Snippets, click here:

Rover SD1 Tech'l Articles:......................................................................................................Site Contents:

Click image to enlarge

Replace the Rover SD1 Heater Matrix

Modern versions of Rover SD1 Efi Cold Start Mythology says the system is not needed in temperate climates and can even be dispensed with in cold ones.

In a topical SD1 Club Forum thread, Mobydick wrote: Mark Adams (the erstwhile guru) told me the cold start injector (CSI) was not really necessary in this country so I disconnected it, blanked off the plenum opening and converted the fuel spur to support a fuel pressure gauge. Result? Even during a very cold snap I turn the engine with a couple of dabs on the throttle and away it goes.

Conversely, Walden in California, USA. replies: I have four Rover SD1's and none start properly without the CSI in place. I have dabbed the throttle, cranked and cranked, let it rest and cranked again. Eventually it may, or may not, start. Its a real pain. This is true even if the weather is warm but we do have some very cold winter mornings. Fixing the CSI or it's related electrical component (thermotime switch) always solved the problem.

So whats going on here? If the system really isn't needed then why was it designed into the original system. Surely the esteemed Spen King design team knew what they were doing, didn't they? Or perhaps it needed an latterday guru around to advise otherwise?

Thirty plus years later here is the gospel according to St. Alban, another pretentious guru seeking to debunk the mythology and straighten out bent opinions. It's a tough job but someone has to do it! Searching for truth!

Just to put things into contect - the operation of the CSI which is controlled by the thermotime switch is pretty much as follows. When its working correctly the thermotime switch mounted on the inlet manifold near to the thermostat senses coolant temperature there-abouts and determines for how long the CSI will squirt. The colder it is, the longer it squirts but only during the period of cranking.


The absolute maximum the CSI can squirt for is 12 seconds - at minus 20 deg C, even if cranking continues for longer than 12 seconds, the reason being - to avoid flooding - ( Hmmmmnnn - probably already flooded after 12 seconds methinks!!!!!). The minimum it will squirt for is Zero seconds even when cranking but the coolant temp has to be above 35 deg C. So between "brass monkeys" at minus 20 deg C

Stop Press

A Major Review of Rover SD1 V8 Electronic Ignition System

Description & Analysis Here:

Components & Testing Here

Ramon Alban


About Me

Flying Faces

Crazy Rubberband

Vintage Freeflight Articles

Model Flying Tips'n'Tricks

Rover SD1 Tech'l Articles

Rover SD1 Efi Comp'nents

Rover SD1 Tech Manuals

Rover SD1 Tips'n'Tricks

Photo & Media Gallery

Site Contents & Map

Contact Me

My Family


View My Stats

Problems with this site? Email Fatfingers Visit Sam35