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CAR CORNER
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But still no rise in Fuel rail pressure !!!

3/27/2018

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It's all about the pressure
 
Recently we had 2 separate calls both ford Transit vehicles that had been recovered in non start.
 
Both garages are very capable in their diagnostic procedures. And went through the usual tests for the fault codes that had been retrieved for fuel pressure.
They tested the leak back flow from the injectors first then performed a scope trace on the fuel pressure sensor. This indicated no rise in rail pressure.
 
Both garages then decided to test the fuel volume valve for the correct signal. And both proved to be present and looking correct. A current trace was taken and this also was as expected. So they took the decision
to replace the volume valve but this did not solve the issue.
 
Then they decided to call us at the Helpline for help.
 
We suggested the low pressure fuel circuit be tested first. The filter housing failed the vacuum check and was contaminated with what looked like water. So they replaced the housing and filter as Ford  said this was a common issue.
 
Then with a Pico WPS500 pressure transducer the suction on the inlet to the pump was tested. And this proved up as 500mb vacuum was present on cranking the engine. This is what we expected so the lift pump was functioning correctly.
 
 
But still no rise in Fuel rail pressure.!
 
So the only thing left was the high pressure pump had failed. But in a very short time without any warning on a low mileage vehicle. And 2  vehicles with exactly the same symptoms  at the same time same geographical area... Very suspicious. And both garages did not want to risk new pumps  without a defined answer why. 
 
So we decided to ask for a very simple test on the fuel. Even as the garages had decided the smell of the fuel was like Diesel...
 
We asked if they could test the specific Gravity of the fuel they had in the vehicle. After ordering a hydrometer with a range for Diesel fuel  with a range of 0.70 to 1.0 the fuel was tested.
 
The correct range we wanted was 0.82 to 0.88 for Diesel @16 deg C
 
The reading we got was 0.78 not far off but it proved to be Kerosene. And this was proof the pump had failed due to incorrect  fuel present.
 
A simple and inexpensive piece of equipment available online could save hours in diagnostic time. 
 
 
And a sample was tested with A Delphi Diesel fuel test tool proved conclusively by an independent consultant and the result  proved this fluid was not diesel fuel...
 
After a replacement pump and all the system cleaned thoroughly new fuel filter fitted. Both vehicles started instantly. 
 
Another success  to a difficult diagnosis. Proving yet again with the right tools and armed with good information all these problems can be solved.
 

 

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LIN a poor mans version of CAN.

3/27/2018

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Tales for this month....
​
Recently we have had calls from Garages with charging problems on various brands.
 
Case Study 1.   A Ford  Focus Tdci 2016 came in with a charging problem, and after some preliminary checks the garage decided the Alternator was faulty and a  genuine replacement was fitted.
 
Codes cleared and retested, but the Charge system still showing a fault and not charging.
 
This system Is a LIN controlled Alternator, Single wire control. As the garage has no experience with this system the help line was called for help.
 
After a little research it is showing the Circuit for the LIN has 3 items present  the Alternator, PCM and the Active grill. So time for the Picoscope to come out.
 
As LIN is a single wire 12 volt based network and we know what the signal should look like, we sent the garage a waveform for their reference, And  the signal they had was not as expected. Below is a good LIN signal taken from file.
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​A normal LIN signal ranges between 10 volts and 2 volts  (Ranging between  80% to 20% of a 12 volt signal).
 
As the alternator was already replaced we applied our attention on the other components on the LIN network. On closer inspection the connection at the Grill shutter motor we found severe corrosion and water ingress. On disconnection the LIN Signal returned as expected at the alternator and the charge rate was back to normal. This was not the first time we have seen this problem on a Ford Focus.
On some vehicles this LIN circuit will also include the the IBS (Intelligent battery sensor) to monitor the battery state for stop start systems and alternator feed back.
 
And as manufactures are using LIN as a cheaper alternative network solution we will be seeing more of these problems, considering it only has a single wire to communicate. So any fault on this circuit will cause total failure. 
We typically have calls on the help line every week relating to LIN problems, many relating to Window systems, this is a popular use for LIN and the controllers are exposed to water ingress with in the door modules on various brands and models.
 
Yet again we come back to the same conclusions that a scope as an essential tool for modern diagnostics, even for something a simple as a charging fault.
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What Do We Need To Service Your Vehicle...

3/27/2018

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There are a few things you'll need to have with you on the day,
​to make sure your Car Service goes smoothly:
Alloy wheel keys or locking nuts
As part of your Car Service, our technicians will need to remove your wheels to inspect the condition of your steering and suspension systems. Please bring your locking nuts with you, so that our team can carry out your Service without delay.
An empty boot
Our technicians will inspect the condition and tread depth of your spare tyre, which is usually located under the boot of the car. Please empty your boot of luggage and other heavy items before you arrive at the Autocentre.
Your service book
We'll need to check when you last had certain items replaced, such as spark plugs, brake fluid and cabin filters. This information is stored in your service book - please bring it with you so that we have everything we need to properly assess your car on the day.
Once your Car Service is complete, you'll receive a stamp in your service book.
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    AUTO TECH 1

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