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350matt, Engineer
Category: Hyundai
Satisfied Customers: 21727
Experience:  Mechanical Engineer BEng Hons 22 years experience in car engine industry, 10 years in formula 1
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2.2l CRDi diesel 2012. It won't start. Sometimes it starts

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2.2l CRDi diesel 2012. It won't start. Sometimes it starts for about 4 or 5 seconds and dies. Low pressure fuel pump is fine, no ECU codes
JA: Have you ever replaced the fuel pump, or is this the original?
Customer: Original. I tested by cranking and checking fuel flow. Also I bridged the fuel pump relay and the diesel is coming steady and strong
JA: What is the model of your '12 Hyundai?
Customer: 2012, 2.2l CRDi diesel. D4HB engine. I am in South africa
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: Look, I maintained my BMW and Alfas for 42 years. Ner sent to garage but this car we bought for my daughter. Run for 15,000km without problems. I put an ELM327 in OBD2 connector and says no ECU codes. When I took off the fuel pump relay then it gave a primary circuit of fuel pump fault that was correct.
JA: Anything else you want the mechanic to know before I connect you?
Customer: also checked all the fuses.
Customer: replied 7 months ago.
OK, thank you


If you haven't already then its worth fitting a new fuel filter as if only slightly blocked this can lower fuel supply pressure and choke the main pump, the pump will be more sensitive to this when its cold as diesel thickens considerably with low temperatures.

if this is OK then also check the connections to the EGR valve, if either the vacuum pipe of electrical connection are damaged / corroded then the EGR can be on all time which certainly will hurt performance. Its also possible that its a fault with the EGR valve so its worth removing the valve and cleaning it out with brake cleaner, if it looks particularly clogged then replace it.

Also if its not injecting at all then check the connections to the crankshaft sensor, unplug it and check for corroded contacts and broken wiring, and consider fitting a new sensor - do the same for the cam position sensor

Customer: replied 7 months ago.
Hi Matt,
I have replaced the fuel filter and as I said the fuel flow is strong and when I disconnected now the fuel outlet hose there was still some pressure after a day being off. remember we are in South Africa, temperatures around 30 degrees Celsius. The fuel is very light and loose.I will do the other checks. Corrosion here in the highveld is about non-existent but I will check and use contact cleaner.The strange thing is that after a day "rest", like yesterday the engine started first thing normally but it run for only 5 seconds and then it won't re-start. It sometimes just hints to start but it does not.Will get back to you.RegardsAlberto

Hello Alberto

thanks for the extra information this sounds more like an electrical issue then,

as well as checking over the crank sensor ( which can suddenly fail) I'd also check the ECU power fuses and relay a cracked fuse will cause this for example, or a poor earth connection

Customer: replied 7 months ago.
Hi Matt,
I checked the connections of the cam sensor and crankshaft sensor. Both are immaculate clean. I put a bit of contact cleaner just in case. No change.To remove the crankshaft sensor appears quite a mission as one needs to remove the starter motor according to the detailed manual I have.The EGR also not easy to remove.Although I have lots of experience in BMW and Alfas I don't like to start swopping things in the dark. I would like to have a clear indication of where the fault is.I have run more tests through the OBD2 connector and no faults are found.I think I am at the point where it would be more practical to ask Hyundai to come and use their tools to checkRegardsAlberto

Hello Alberto

if you can get a Hyundai level scan tool plugged in then yes it will probably save a lot of time, as these should be a tool that can monitor things like engine rpm so you can see if the crank trigger is working etc

Customer: replied 7 months ago.
Hi Matt,
Engine rpm is fine. I used the ELM327 dongle and shows the rpm fine for the few seconds that run, but the ECU does not have any codes and it also looks at 39 PIDs but no fault.
Tomorrow morning the Hyundai guy will come (20 years experience) with the factory tools so we will see if he can detect anything in particular. Will let you know.


good luck


do you still need help?

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Customer: replied 7 months ago.
Hi, the problem is none of what you suggested it might be.I had a diagnostic people here that determined that there is no high pressure in the rail. (the loosen the high pressure fuel pipes and no fuel came through while cranking).I think it might be the fuel pressure regulator valve on the high pressure fuel pump or the rail pressure regulator. It could alos be the high pressure fuel pump itself.I have done the following test: Disconnected the fuel return pipe going to the fuel tank and bridged the fuel pump relay. Fuel flows out totally unrestricted like with the same strength as coming directly from the fuel filter. Is this normal?I don't know if without power the fuel pressure valves remain fully open or it means that one of the two is broken?Does the fuel go through the high pressure pump if the engine is not cranking?Also, the return pipes of the fuel pressure regulator and the rail fuel pressure pump come together so I don't know from which one of them the fuel comes through.


the lift pump should run through the high pressure pump and is returned to the tank with the high pressure pump being fed from this loop

as its running back to the tank unabated then it sounds like the 1st stage of the high pressure pump isn't functioning

whereabouts in the US are you and I'll try and locate a deisel pump specialist who can rebuild your current pump

which is a lot chepaer than replacement

Customer: replied 7 months ago.
Hi Matt,
I am in South Africa.
So, you think that the pump needs to be re-built, that is not just the pressure regulator valve?
Hyundai sells only the whole pump assembly, not the valve separately.
I thought in checking here with Bosch because there pump prices appear to be in the region of Rand 7,500.00 whyle Hyundai charges R 29,700.00 for a new one! (1 US Dollar = 13.5 Rand).
Otherwise I know where to go for a diesel specialist that can re-build the pump but I need to put the SUV on a tow truck. It is about 60km from here.


its possibly just the regulator but you could test this by restricting the return to tank so more of the flow is forced into the main pump

where the return line exits the pump it should be on a rubber line that you could crimp flat with some grips for a test

Customer: replied 7 months ago.
I thought of that. It is a quite hard plastic hose but I can put a grip. Will do that.Thank you
Customer: replied 7 months ago.
Hi Matt,
I did the following:
1. Put a grip on the high pressure pump return line and open the return to the tank (put a hose pipe to a container) and run the electric fuel pump by bridging the fuel pump relay socket. The fuel came again unabated, full flow.
2. Reconnected the return line to the tank but left the grip on the HP Pump return pipe and tried to start the engine. It did not fire.
3. Now I put the grip on the flexible hose to the tank after both return lines come together, (Fuel pressure regulator valve and rail pressure valve). I cranked the engine and nothing. Did not fire.
I guess this points to a faulty high pressure pump, ok?

Sorry to say that this does sound like the high pressure pump is faulty

often they can be rebuilt so it would be worth a call to your diesel specialist to see what they will charge you to strip the pump down and repair it

Customer: replied 6 months ago.
Hi Matt,
After all of this it was none of the possible causes you suggested.
It was a blow turbo that broke off and sealed the exhaust. That is why it sometimes started for a few seconds and the stopped because of back pressure and it would not re-start again until next day, where it did the same every time.
R 25,600.00 (1,513,00 British pounds) later the car is now running fine.

Hello Alberto

well thats a pretty unusual fault and not something I've heard of before

thanks for letting me know

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