New Caterham ... "He no start"

[pickles]

OK Sleuths

 

Not getting much response from the official channels so let's try our trusted USA7s forum 😊

 

Have completed the build of my 620R, unfortunately it will not start or fire.

 

I turn the key and dis-engage the immobilizer. I hear the fuel pump prime and there is fuel at the rail

The dash display indicates that the gearbox is in neutral. And the red ignition light is illuminated.

The battery is good and the engine turns over.

I am not getting a spark at the plugs and am thinking due to the dry plug and lack of gas smell, that the injectors are not firing.

I have checked all fuses and relays … all good.

I took a look at the Crank Position sensor … ah ha! I thought its resistance should measure 450 Ohms … it is reading ‘Open Line’. Got a new one and that did same on the same thing on bench. Hmmm …. Then realized that the resistance, like voltage measurements would only be visible as a metal object passed through the magnetic field. So this now checks out.

Would love to get something out the ECU/OBD port but as Caterham aficionados know the ECO does not talk OBD2 … so may be out of luck here.

 

So Guys and Gals! What ya got that is going to get this old man on the road!

 

Pickles
 

[wdb]

There is a neutral safety switch -- is there a clutch safety switch as well? My modern cars will not start unless the clutch pedal is depressed.

 

 

[Vovchandr]

No spark or fuel certainly means something is telling ECU not to proceed with start as conditions aren't met. A few main culprits are cam signal, crank signal or safety shut offs. 

 

Hard to troubleshoot a motor that never ran as we don't have a solid base to start with. Could be one issue, could be several daisy chained together. 

[CBuff]

Inertia switch ?  When I change the oil I unplug it to cycle the engine without starting. Sometimes when I reconnect it doesn’t quite jump into action without some fiddling. Once it’s working it’s fine. 
 

Mine is mounted next to brake reservoir. On firewall. 

Edited September 5, 2025 by CBuff

[IamScotticus]

Add more blinker fluid.

Sorry 

[KnifeySpoony]

I also vote inertia switch. 

[MV8]

Inertia switches traditionally control the pump only. Not the injectors or ignition.

 

I'd look for battery voltage (with a light bulb or dvm) at the coils and injectors DURING cranking.

Edited September 5, 2025 by MV8

[pickles]

2 hours ago, MV8 said:

Inertia switches traditionally control the pump only. Not the injectors or ignition.

 

I'd look for battery voltage (with a light bulb or dvm) at the coils and injectors DURING cranking.

That is correct the inertia switch controls the fuel pump, and this does prime, if I disconnect the inertia switch the pump does not run. Thus I eliminated the inertia switch as an issue.

Edited September 5, 2025 by pickles

[slowdude]

Crank position sensor should have resistance. I just went through this on my car this afternoon and replaced my CPS.

CPOS on the Rover K series;

OLD: 1.36 k ohm

New: 1.41 k ohm

 

Given that the sensor is at minimum 15 years old, I just replaced it and will hopefully clear my ECU misfire.

 

I'm in the group of Crank / Cam sensor not reading to tell ECU to trigger. If you have pulled plugs and can smell gas, you know injectors are working. 

 

PLugs not getting spark would be due to Crank / Cam sensor.

[pickles]

Problem finally resolved.

 

Thanks to Bruce at Beachman Racing and Lee Bristow at Caterham for sticking through this. The underlying issue was a problem with the pinning for the Crank Position Sensor between ECU and the Engine loom. Pins on the ECU (11 & 12) are the black and white wire from the CPS, I had continuity on each wire, but the wires were crossed, the connection between the ECU and engine harness had been incorrectly pined. Chose the easy option and swapped pins at the CPS. Car started right up.

 

I wanted to get the biggest glass of hard liquor I could find but sadly in CT, after 6PM the package stores are closed. So a hazy IPA for me!

 

Vroom!  Vroom!

 

Now just have to put everything back together  There is not a lot of space in the 620 engine bay. It's amazing how much I moved around and disconnected to get access to the wiring loom. If it were easy, we would not do it!

 

Cheers

Pickles

[CBuff]

[jmaz]

I'll be starting the build of my 310 in a couple of months once it shows up in its crates, and one take-away I've gotten from reading build blogs and threads is that it's wrong to assume that the factory did even basic stuff correctly in terms of connecting up the electricals.  That sure makes it tough to diagnose problems since my first assumption would be that I screwed up something during the assembly.   I'm curious if these issues such as incorrect pin wiring, connectors not connected, etc. are typical or if they're just more apparent because they get mentioned when folks run into problems. 

[pickles]

Hi Jmaz

 

So pretty much everyone runs into issues for a variety of reasons, our fault as a builder, Caterham’s fault for making a mistake, a mistake out of the blue … But a couple of things stick in my mind …

 

I have now had 2 Caterham’s, and at times I have run into issues for all sorts of reasons… just 2 examples (But there are many!)

 

Bleeding my brakes … I put the wheels on my 360, lowered to the ground as my bleed tube was too short to reach with it on stands … I pumped those brakes and topped up that reservoir, I must have put thru 4 quarts of fluid through that system before I suddenly realized there was 2 bleed nipples, each side of the caliper … I was only bleeding one!! … I was frustrated when I could not get enough brake pressure, but the elation of what a fool I was, wiped the memory of that frustration!

 

My ‘no start condition’ on the 620 … Every time I went through my garage … empty the trash! … get the lawn motor! … etc. I would look at my green anchor and feel depressed … but now I am elated … am I at the winning line? Nah! But am closer 😊

 

At the end of the day Caterham are a small production manufacturer of some of the most exciting cars to drive (my wife just whispered over my shoulder … it is not a car it is your coffin 😊)

 

There is a great support network out there so do not worry … welcome it and embrace it … you will interact with the best people on both sides of the aisle.

(Opps, when I said the aisle, I do not mean the political aisle ... I really meant the 3000 miles from the UK to the US!) 

 

In short you did the right thing!

 

Happy building

Pickles

Edited November 26, 2025 by pickles

[jmaz]

Thanks!   Wise words that I'll keep in mind.  The challenges are a big part (probably the main part) of why I want to do this, and I'm looking forward to the process.

[pickles]

3 hours ago, jmaz said:

Thanks!   Wise words that I'll keep in mind.  The challenges are a big part (probably the main part) of why I want to do this, and I'm looking forward to the process.

I always describe the build as akin to Lego ... this car has been in production so long they have ironed out 'most' of the kinks. Bruce at Beachman Racing thinks I may hold the record for the quickest build, but then again, my wife on more than one occasion came down to the garage at 5 or 6 AM to find me asleep under the car  Wrench in one hand ... Beer in the other! Trust me you will have a blast!

[TN_Scooter]

After reading 4 or 5 blogs on building a 7, I was concerned about a few things myself. First was missing parts, second was things not working properly (gas gauge, lights) and third was car not starting due to whatever.  I got my kit towards the end of March this year and went through the inventory. I didn't get the half-roof and was missing the top grommet in the steering tube.  I let the dealer know and got the missing parts delivered in due time. As I was assembling the car, I found I was missing a bolt which I was able to get at Lowes. I followed the build manual and suggestions from the blogs. The car came together and by mid April I was taking my first spin around the block! I was concerned that the gas gauge might be off but it appears accurate. It does jump around a bit when going around a corner but I aim for the gas station when it reads about 1/4 tank. Others have had problems with the speedometer not reading accurately but mine was spot on at 30 and 40 MPH per the speed zone cameras that tell you how fast you're going near construction areas. It took a little bit to get it registered but by the end of July, I was legal in Tennessee. I've put over 2800 miles since then and am having a blast with the car. You are going to enjoy the project and remember that you have lots of experts on this site willing to jump in and help if you do run into issues.