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Case Study: Ford Fiesta non-start

By autotech-nath on September 26, 2022

Case Study: Ford Fiesta non-start. Vehicle:Ford Fiesta EcoBoost 1.0 2016 engine code M1JHMileage: 66,714No initial fault codes or check engine light displayed on dashboard – By Des Davies AAE MIMI, Top Gear Motor Services.

The customer drove the vehicle into a car park, selected reverse gear to manoeuvre into a car park space and the vehicle had stalled and refused to start again. Two other garages had tried to start the vehicle, without success. The last garage stated there was a spark and fuel being delivered to the engine, that the compressions were good, and they did not know why the car would not start or run so the car was towed into my garage.

My initial thoughts were to ignore the previous diagnostic advice from the other garages and do my own checks to confirm why the engine would not start, because if it has a spark that is also timed correctly, fuel delivered to the combustion chamber and a good compression pressure then it should technically run!

The first test, after getting as much information from the customer as I could, was to check for an engine light being displayed on the dashboard when cranking and then to interrogate the system using my scanner inserted into the EOBD port. There were no fault codes as the previous garage had cleared them, not particularly helpful. I checked the live data on the scan tool, but this did not present much information and I did not want to crank the vehicle longer than necessary.

I connected the battery support unit as the previous garage technicians had been cranking, checking and testing without one and the battery output was low. I am currently using the BSU from Traction Charger, which I find to be an excellent product.

Where to start!

This system needs a spark and, at the correct time, fuel and air delivered to the cylinders, plus good compressions in all cylinders.

I like to start where I have the easiest access to a system or component, so I began by checking for a spark at the coil-on- plug system to reconfirm if we have a good strong spark using my spark tester. This quick and easy test showed that we had a good, strong spark. I then decided to check the fuel injection system to see if the fuel was being delivered to the cylinders correctly. I could

check the fuel pressure using a fuel pressure tester but a
quick, non-intrusive diagnostic check I like to perform on any vehicle is using my 4-gas exhaust gas analyser. Inserted into the exhaust tailpipe I can see if the fuel is being delivered into the cylinders and can check for any anomalies. I love using my exhaust gas analyser as it provides me with a lot of information on the actual burning of the air/fuel mixture inside the engine combustion chamber. See Figure 1 below for the results:

Figure 1: 4-gas exhaust gas analyser results, cranking.

I expected at least to see the HC readings go high indicating raw fuel not being burnt in the cylinders if the fuel was being delivered to the combustion chambers. Normally, these readings peak to well above my exhaust gas analyser maximum readings if there is an abundance of fuel in the combustion chambers.

The previous garage stated that there was fuel being delivered to the cylinders, well this wasn’t showing here! So, no fuel is being delivered or being combusted inside this engine?

What is my next plan of attack then? Well, I have a spark but no sign of fuel getting to the cylinders, I could hear the fuel pump being primed when I switched the ignition key on… I could check the fuel pressures or injectors to see if the injectors are being commanded to spray the fuel into the manifold/ cylinders. Hey presto! The check engine light decided to come on and shine a nice bright light for me. So, let’s check for fault codes again now, see Figure 2.

Figure 2: Fault codes later presented themselves.

Code P0342: Camshaft Position Sensor A Circuit Low

The PCM (Powertrain Control Module) sets code P0342 when it detects that the camshaft position sensor circuit on engine bank 1 is sending a reading that’s erratic or otherwise outside of the manufacturer’s settings. The PCM then illuminates the Check Engine light to alert the driver to the problem.

The PCM needs this information to provide proper strategies for ignition timing and fuel delivery. When the input is low or otherwise incorrect, the PCM will not have enough information to provide the proper timing for these functions. This sounds familiar to me, what do you think?

Figure 3: Camshaft sensors circuit diagram.

Code P0368: Camshaft Position Sensor B Circuit High

The PCM uses the “B” Camshaft Position Sensor to tell it when the Crankshaft Sensor signal is correct, when a given Crankshaft Position Sensor signal is timed to Cylinder no 1 for timing, and it is also used for fuel injector synchronization/start of injection.

It was now time to work smarter and not harder, I needed to check the engine management system diagram using technical data to check these two camshaft sensors and circuits for their correct operation. Let’s get my trusted 4-channel PicoScope out…

The camshaft sensor output wires for sensor 1 is the white/ green wire and sensor 2 is the yellow/blue wire, see Figure 3, and in Figure 4 you can see the results using the PicoScope. No output signal was being generated from both the sensors, the live feeds and ground were good – could both sensors have malfunctioned? It’s not impossible (I’ve been there before) but highly doubtful.

Figure 4: PicoScope results.

Time for more tests

Rethinking my strategies, I decided to do a quick non-intrusive test to check the relative compressions on this engine using an amp’s clamp, see Figure 5, and to confirm if the camshaft is rotating for the cam sensor to produce an output to the ECM. Without this signal, the injectors are not going to spray fuel into the inlet manifold/cylinders.

Figure 5.

Where were my humps? Well, there we have it then, no compressions. How did the previous garage have good engine compressions? I’m not here to judge others, we all make mistakes and sometimes make poor judgements. I have learnt the hard way not to rely on customer information and other workshops’ interpretations of symptoms and their testing methods.

I do all my tests from scratch in a logical manner, it may take longer but it is more accurate; taking steps, rethinking, and then backing up if I am uncertain about my test result.

Use other testing methods and equipment to recheck your work, if the results taken are not what you expect them to be. Yes, I know! Hooking your leads up to an oscilloscope or disconnecting and dismantling systems or components to get access can be time-consuming and difficult, but they give you a more accurate result and confidence is everything! Don’t guess-test it, it will cost you dearly in the end.

I could visually see that the engine crank shaft pulley was turning on cranking the engine, but I believed the camshafts were not rotating, giving the cam sensors no output signals to the ECM. To confirm this, the front engine covers need to be removed to inspect and investigate the drive from the crankshaft to the camshaft to see why these components are not functioning correctly.

On removing the oil cap, I could not see the camshaft at the front of the engine rotating. This EcoBoost engine has a timing belt in oil and the teeth of the belt had stripped and all the remnants were now in the sump, pump, and oil supply system.

What I tend to find is that customers do not put the correct grade of oil in these engines, and they also do not service these vehicles at the correct intervals that the vehicle manufacturer recommends, which is detrimental to this engine and its components.

In addition, if the vehicle system has been over-fuelling for a while, it will contaminate the engine oil and the results are damage to the timing belt causing catastrophic internal damage. Game over for this engine as Ford now recommends a new engine as the bits of belt have gone into the oil pump and oil galleries with the potential of blocking the oil supply to the critical components.

Diagnosing systems and components in a logical manner using the correct data, tools, and equipment and with your knowledge of these systems and components will help you to fix the vehicles quickly and safely.

Test don’t guess! Knowledge is power!



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