New Caterham ... "He no start"

[jmaz]

Are there steps that might be taken early in the build process to verify that the engine harness has been assembled correctly by the supplier?   

 

Are there similar factory-/supplier-related weak points that warrant checking in the kits, rather than assuming things are going to be OK out of the box (crates)?  Volt meter connectivity tests comes to mind, but is that feasible and comprehensive enough?   

 

And is there a good set of wiring diagrams available?  I've seen the ones in the 2015 Build Manual, but they're not very clear - at least, after an initial look.

[BruceBe]

Generally, the juice is not worth the squeeze. From the perspective of time, use the car itself as the test harness. I you get a no-start, there are basic troubleshooting steps to identify whether it's air, spark, or fuel. The fuel pump does not run during cranking, but should prime at key-on (and immobilizer light off). The ECU is simply waiting to see a crank position sensor signal during cranking, and it starts firing coils and injectors. Once you identify whether its a spark or fuel, or both problem, then start working from the outside in, toward the ECU. Checking for a crank position signal is a very early test.

 

For crankshaft position, note that despite being an AC signal, polarity is very relevant - otherwise that MBE ECU will not initiate coil/injector operation. If the pins are flipped (black and white wires) at either the big chassis connector, or the ECU itself, no worky. The camshaft position sensor also utilizes black and white wires - we've seen them swapped with the crankshaft position sensor at the chassis connector.

 

Cheers,

-Bruce

 

[NSXguy]

18 hours ago, jmaz said:

Are there steps that might be taken early in the build process to verify that the engine harness has been assembled correctly by the supplier?   

 

Are there similar factory-/supplier-related weak points that warrant checking in the kits, rather than assuming things are going to be OK out of the box (crates)?  Volt meter connectivity tests comes to mind, but is that feasible and comprehensive enough?   

 

And is there a good set of wiring diagrams available?  I've seen the ones in the 2015 Build Manual, but they're not very clear - at least, after an initial look.

 

For someone with general mechanical but limited automotive aptitude referenceing a good wiring diagram is probably the better way to QC as a hedge against these types of electrical gremlins during the build. 

 

For others possessing solid automotive understanding and trouble shooting skills, You'd scope out the trigger signals and verify that patterns look good. Cranking with the timing light would also tell if you have trigger/sync issues to correct prior to first start( Sync/trigger issues are by far the biggest culprit leading to no start on modern or older project/build cars) . Typically on a modern standalone engine management(i realize that may not be the case here), the issue could be solved without even needing to depin and repin the Crank sensor. often times you can select a different sensor edge in the software from falling or rising triggering depending on how it is pinned as seen in the scope trace. 

 

In either scenario, when/after assembling a 7 and before initial start, "pre flight" checks should be done to confirm readiness:

-Check fuel pump primes with key on engine off (confirm check injector solenoid actuation as well, easier with aftermarket ecu)

-Check TPS sweep and actuation/calibration and adjust if necessary 

-check crank position functionality (scope, check timing with timing light; if on engine management, adjust arming thresholds)

-Check oil level and prime engine to build oil pressure before start (many ways to do this. easiest- removing spark plugs to lower load on starter)

 

 

Edited Tuesday at 04:14 PM by NSXguy

[BruceBe]

The majority of the time, the wiring in the car will be correct. For a modern Caterham, a gauge sweep, fuel pump prime, and immobilizer deactivation at key-on will tell you to start cranking. Putting aside any initial mechanical priming of the engine for oil pressure (plugs removed, coil and injector connectors disconnected for prime), several sub-10-second cranking cycles should result in some combustion or a start. If not, as mentioned earlier, we start working from the outside-in, starting with the simple and working to the complex. For example - are the grounds all connected? The Caterham schematics are primarily designed to help the supplier build the harness, not troubleshoot an electrical issue. As such, they are some of the harder schematics to use for this purpose - doable, but not intuitive. For a modern Caterham, If you are getting neither spark nor fuel during cranking, once grounds are checked, start focusing on the crankshaft position sensor - a clean, correct signal from it to the ECU is what gets the party started.

 

None of the above is done "during" the build. Powertrain is installed, and everything is wired-up and full of fluids. Oh, and the gearbox is in neural, right?

 

Cheers,

-Bruce

 

[jmaz]

Thanks, Bruce and NSXguy, for your responses.  I'm not currently trying to diagnose any issues but I expect to be starting a 310 Encore build next month.  

 

Jim