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12 contributions to RMS Auto-electrics/Diagnostics
Diesel High Pressure Fuel Pump Question.
In the workshop we have 3 different manufacturer vehicles with a diesel fuel problem. Two have been fuelled with Petrol. I am trying to find out information, however I having difficulty finding the answer. On the high pressure fuel pump at the engine, remove the tank return pipe and insert a pipe to a collection container. Turn on the ignition, the tank pump primes and stops when the pressure reaches about 4-5bar at the fuel supply port of the high pressure pump. Am I right in saying there should be no diesel going back to the tank from the high pressure pump until the engine is cranked? What is the expected resistance of the return valve solenoid / pressure regulator in the high pressure pump? Using Alldata and it is not mentioned on the 3 vehicles.
0 likes • 2d
Update. Vehicle 1, had a fuel filter gasket improperly fitted, so no fuel being delivered to high pressure pump. Vehicle 2, fuel cut off solenoid open so fuel going back to tank, nothing going to the injectors. Vehicle 3 is the Mercedes B180 in another post.
Mercedes Starts and Stopped after 2 sec, Wont Run
Mercedes B180 2016, Diesel, Renault engine. Back story, Customer put petrol in!!!!!. Drove car, then engine stopped. Called Fuel Dr, they cleaned lines and tank. Engine ran for a couple of weeks then Engine stopped again. Called Fuel Dr again, told all is good however customer told them to do it again. Car never ran. Came to the garage. 1/4 tank of diesel in the tank. Only fault codes were low fuel pressure related. Has a long cranking time, varies from 2-10sec. Did a Picoscope capture on fuel tank, 3 phase motor and all good. Did Picosope on injector using Amp clamp and all injectors are good. Did an injector leak off test. small amount of diesel going to the vials. Removed fuel intake line to fuel filter, primed tank pump to remove excess fuel. Changed fuel filter put 6ltrs of diesel in tank and primed the pump and filter. All good. Pressure at high pressure fuel pump on start is approx 500bar then goes to 250-300bar. Then engine stops. Pressure at high pressure fuel pump drops to 0bar in approx 1 min. Checked fuel at injectors and there is fuel and pressure. Changed high pressure fuel pump and timing belt (was due a change). Told ECU new high pressure fuel pump. Reset adaptive values. Still the same, starts and runs for 2 sec then stops with various cranking times Difference after new high pressure fuel pump and timing belt is there are no fault code present, alternator appears not to be giving out a charge. Sounds and feels like the engine is being told to stop after it start. Q. Could alternator no lin signal cause that? Other ideas beside new injectors? Going to do a injector amp and voltage check tomorrow.
0 likes • 12d
I have a set of them. Great for doing high pressure side.
0 likes • 2d
Update, High Pressure pump and injectors replaced. Can runs without faults for a couple of seconds more. Looked at the air side as we know the fuel side is good. Remove the turbo intake pipe from the air filter and air pipe to the Intercooler, engine now runs with a lot of smoke. Looked at the turbo and plenty of end float movement on the shaft. Got permission from the customer to replace turbo. Removed the subframe, DPF low pressure egr, many other items. Remove the turbo, the shaft for the inlet and exhaust where not connected. Turbo is FUBER. Waiting for reman turbo and parts to arrive for the rebuild.
Anyone come across this issue, Jag XE (X760) 2016
Real left light cluster and BCM issue. Turn on ignition, press brake, left brake light comes on for approx 1 sec then turns off, not to come on again unless you cycle the key. Other lights in the cluster are side, reverse, indicator, these all work. Side are LED, reverse & indicator & brake are normal bulbs. Normal operation from the right cluster, no issues. Unplugged left rear light cluster, checked resistance inside light cluster, no issues. Plugged light cluster back together. Checked voltages. Side are battery +, indicator is battery +, reverse is 1.9V, press brake pedal, brake light is 6.9v for 1 sec then 0.0v. Checked right light cluster for comparison. Side are battery +, indicator is battery +, reverse is 7.2V, press brake pedal, brake light is battery +. Went to the BCM, right brake light has battery + when brake pressed. Left brake light has 6.9v for 1 sec then 0.0v when brake pedal pressed. So no issues with the wiring, it appears the output signal from the BCM for left brake light and possible left reverse light is causing the issue. Anyone else had this problem?
Anyone come across this issue, Jag XE (X760) 2016
0 likes • Sep 1
tried resetting the Protection under the special functions. It did not work. Could it be the module?
0 likes • Sep 6
Problem solved. Bulbs changed for the 3rd time and it worked. Checked bulb resistance and a little higher by about 0.3Ohms. Dont know if the 2 brake bulbs in one cluster are in series parallel.
citroen c4 picasso c156d
hi everyone i have a citroen c4 picasso with a c156d, passed over to my workshop from another. we had a fault code for the right rear abs sensor which was a corroded wire which we have repaired and the ABS lights are gone. This is the 2 pin style on the motors and not the older 4 pin ones. Reg : AF67 YGV VIN: VF73ABHZTHJ882074 Fault code: C156D- permanent not clearning i have an xtool d8w only at our garage, when attempting to do electric activation or the parking brake nothing happens, when doing replacement of motor and caliper using the diag nothing happens. Vehicle no longer has parking brake.
0 likes • Sep 6
Sound like a correlation issue with the ABS module and EPB and parking brake switch. ie ABS module dose not know position of EPB when the EPB switch is used. As Steve said, try maintenance mode enter and exit procedures. Could also look BCM to see if the EPB switch is activated when pressed.
Bank holiday live session
https://www.skool.com/live/SDMWJ5GF4ND
0 likes • Aug 30
Great, What time is the session?
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Roger Boyle
1
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@roger-boyle-8330
A car and motorbike technician who wants to learn more on electrical diagnostics

Active 2d ago
Joined Aug 2, 2026
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