22 replies to this topic

[kommander]

Will a faulty coolant temperature sensor result in starting problems?

 

My diagnostic reader has identified it as an error, and the temperature reads 59°C (the default value in limp home mode is 60°C).

 

The fuel pump primes and the relay has been tested with the ACR. The car also fires up using starting fuel or petrol poured into the intake.

 

 

 

[FlyingScot]

Shouldn't have difficulty starting. Will run rich however.

FS

[spiguy]

So the car fires up with fuel put in the throttle body? I take it that it then stops once that is consumed? if so then that strongly suggests fuel delivery problem. Blocked filter maybe? Or blocked pickup in the tank?  Is there any fuel at all spraying out the injector?  is it an SPi or MPi?

[kommander]

Yes it stops after the starting fluid/petrol is consumed. l can see fuel dripping from the injector, haven't confirmed a healthy spray.

 

It's an SPi...l'll be putting a test gauge to measure the fuel pressure.

 

Thanks

[hungdynasty]

Will a faulty coolant temperature sensor result in starting problems?

 

My diagnostic reader has identified it as an error, and the temperature reads 59°C (the default value in limp home mode is 60°C).

 

The fuel pump primes and the relay has been tested with the ACR. The car also fires up using starting fuel or petrol poured into the intake.

 

 

 

Yes It will, and that was my case actually.

 

It started with the coolant temperature gauge reading low while driving, just a little over the blue mark. When engine was cold, it wouldn't start until I kept trying for 7 or 8 times, took a few minutes, it would start. There was no problem to start when engine was hot. I though that could be fail thermostat so I changed it but problem remained. Diagnostic showed coolant sensor failure and the coolant temp was 59'C even engine was hot. I ended up changing the coolant temperature sensor and everything back to normal. 

[spiguy]

I would be very surprised if a failed coolant sensor alone would stop the car from starting at all. Hard to argue with that if it was your experience first hand, but the difference between cold start and an assumed value in the case of a failed sensor should not be the difference between a spraying injector and a dripping injector. if the injector is merely dripping then I think there is something wrong either with the delivery (ie blockage), the drive to the injector (wiring, ECU output etc) or the injector itself.

 

hungdynasty - in your case you said the car would eventually start - that makes more sense. In the case of the OP, it will only run with fuel added externally, and then cuts completely once that supply dries up. I don't think that is comparable to your situation where the car would eventually start and run, albeit probably badly as the fuelling would be very lean until the engine temp started to approach the assumed value (or at least warm up a bit).

Edited by spiguy, 09 November 2015 - 01:16 PM.

[hungdynasty]

I would be very surprised if a failed coolant sensor alone would stop the car from starting at all. Hard to argue with that if it was your experience first hand, but the difference between cold start and an assumed value in the case of a failed sensor should not be the difference between a spraying injector and a dripping injector. if the injector is merely dripping then I think there is something wrong either with the delivery (ie blockage), the drive to the injector (wiring, ECU output etc) or the injector itself.

 

hungdynasty - in your case you said the car would eventually start - that makes more sense. In the case of the OP, it will only run with fuel added externally, and then cuts completely once that supply dries up. I don't think that is comparable to your situation where the car would eventually start and run, albeit probably badly as the fuelling would be very lean until the engine temp started to approach the assumed value (or at least warm up a bit).

My observation was like fuel was not pumped during fail starts, not sure it was the injectors shut by ECU or fuel pump not pumping. It would eventually started but it was like al,al,al,al,,,,,,,allllllllll>>> start, definitely not a smooth start, and this was when engine was sitting overnight. I would get a pretty normal start when engine was hot.

 

Before I changed the sensor, idle speed kept above 1000rpm even engine was hot.After changing idle back to 850-900.

[Alpenflitzer]

Two guesses:  1. Fuel filter plugged     2. Injector plugged by fuel with dirt from filter/tank  and 3. Fuelpipe squeezed ? (which is very, very seldom)

 

When was fuel filter changed last time? It is recommended every 60.ooo km. 

 

Take off the fuelpipe before it reaches the injector and check fuel flow = fuel flows = injector dirty    fuel does not flow = filter plugged or tank.

[kommander]

Gonna install a pressure gauge on the fuel line to confirm.

 

I am assuming l will have to put 12v directly on the fuel pump to keep it running?

Edited by kommander, 10 November 2015 - 04:40 PM.

[tmsmini]

It should prime and hold pressure for a few minutes.

[peter-b]

I actually had similar problem, stuck injector. Couple of taps on top and away it went.

[kommander]

Ok guys, I wasn't able to install the pressure gauge, because of the factory hoses (thought there were hose clamps).

 

However, I put a 12v directly on the fuel pump, and a 9v to pulse the injector. There was a very healthy spray.

 

So I guess that rules out fuel delivery.

 

The following were done:

 

1. Check wiring from ECU plug to injector........healthy...there's a small change in the voltage at the injector       plug when I crank..both Vdc and Vac

2. Reset inertia switch......no start

3. Unplug inertia switch and jumper plug.....no start

4. Swap 2 other ECUs...no start

5. Diagnostic scan on all 3 ECUs reports the same CTS fault

6. Healthy 12v at fuel pump plug

 

I am awaiting delivery of the new CTS.

 

Any other suggestions?

Edited by kommander, 12 November 2015 - 04:16 PM.

[FlyingScot]

Fuel pump is driven from the ECU via the MFU (multi function unit or relay pack).
Can't remember which model you have Kommander but does it have an immobiliser (i.e. Is the pump being inhibited)?
Flaky crank sensor will also cut fuel pump feed.

FS

[kommander]

Relay pack has been ruled out, Diagnostic does pump relay test (also swapped another relay unit)

 

There's no immobilizer.

 

Crank position sensor not reported as fault on diagnostic scan.

 

Hoping it's not the crank position sensor...my parts have already been shipped!

 

Any other suggestions FS?

[kommander]

Received CTS today.

 

Unplugged the old one and plugged in the new one.

 

No start

 

Diagnostic scan still reads coolant temperature sensor circuit!

 

Wiring checks out healthy from ECU connector to sensor plug.

 

It's getting frustrating now!