Diesel D5 Common Fuel Pump Issue

zakmuh · Post by **zakmuh** » 22 Dec 2021, 11:21

Hello

I'd appreciate if anyone could help with diesel issue I'm having in my 2007 XC90. At key position II, fuel gets to HP pump but when cranking flow stops and would not continue. I have to wait for like 5 mins and then turn on the ignition for fuel to flow.

Scanned for codes but no codes found. I have tried to prime the fuel system but fuel would not flow out of the HP pump, so bleeding common tail or connections at injectors had no point. Checked all the fuses and relays and all are intact.

To me it looks like ECU cutting the tank fuel pump supply as soon as cranking. Could this be due to a problem with the pump? This seems to be a very common on Volvo diesel models in the UK but couldn't find a fix

Thanks in advance

zakmuh · Post by **zakmuh** » 30 Dec 2021, 07:04

I'm just going through what we have checked so far and some other thoughts...

So far...:
Lifter pump (Low Pressure pump) in the tank is priming - so no need to check relays or wiring connections
Flow from lifter pump is steady and consistent up to HP pump - so fuel lines have no leaks
During priming, fuel would flow from HP to CR and also to fuel return lines - this is normal
When cranking fuel flows from CR and up to injectors but very low - no pressure
When cranking pressure sensor voltage remains at 0.51v - no pressure building up in CR
when cranking fuel returns line on HP pump side has same amount of fuel as to when priming - this is again normal and HP pump is not leaking
when cranking fuel returns lines connected to injectors having fuel coming through (not coming out of injectors) - this is normal

Basically fuel is coming to HP pump but no enough pressure there in order to inject into combustion chamber, hence no start. There are two things concern me:
1. When cranking fuel returns line on HP pump side has same amount of fuel as to when priming....I'd expect returning flow to reduce as SCV would allow half of the fuel to pistons to pressurise the outlet flow to CR?

2. Should I check if injectors are click to cranking? If the are not, then could ECU be cutting the signal cos all 5 of them cant be at fault

3. Immobiliser - leaving the widows and bonnet open and locking the car with key fob isn't triggering the alarm but red flashing light is on on the dashboard. Can I assume the immobiliser is not working? Could this me causing any starting issue?

I'd highly appreciate some advice to get it going again.

Thanks
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zakmuh · Post by **zakmuh** » 02 Jan 2022, 03:31

Morning all. Today's update

In this video I'm checking the SCV connected to the pump. SCV gets closed when ignition ON and very small amount of air getting to plunger side. Is this how SCV should work?

I'd highly appreciate if you could advise me on this

Thanks

zakmuh · Post by **zakmuh** » 12 Jan 2022, 09:23

SOLVED!

Car is now sorted. The issue I had was...I had not done the priming correctly, therefore there were lots of air in the fuel line. I did the key On and OFF cycle for over 20 times (as advised by Volvo) and then car started straight away.

If you remove any fuel system line (like a hose or a banjo bolt or high pressure pipe etc), it sucks air in then stops sending fuel to common rail. When you turn the key to ON (ignition on) and if you have air then you could hear fuel flowing in there inside the fuel filter housing under rear passenger seating location. So you have to prime until you hear nothing but whining noise. This is achieved by above method, ON and then OFF

Cheers