Air in the fuel system. All. Of. The. Time.

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RobBBoi

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13
Location
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Hello all. Where on the 10p d2 td5 fuel system can air get in but fuel not get out? I've got performance issues which I'm convinced is fuel related. Every time the ignition is turned on the pump complains and gurgles and you can hear air in the head/injectors. Its had a new pump (non gen), pump seal, FPR rebuild, new fuel filter housing, housing fittings (including micro filter and duck bill) and fuel filter aswell as injector seals. There are no fuel leaks. No rise in the oil level. Head gasket has been done. Car starts on the first revolution with no prime needed. It has been mapped and used to pull all the way to the limiter. It hits about 3250 revs and just stops moving. There is very little smoke compared to before the issue aswell. Apart from a cracked head where can I look now? I've got more injector seals, a new fpr housing and rebuild kit (again) coming. I'm going to pull the injectors this week and check for a cracked head but symptoms don't match.
 
most of the system is under 4 bar pressure from pump to head it would show a leak,low pressure pump fills filter so youd expect it to show a leak to ,injector washers are usual culprit but non gen pumps are usually not worth fitting, though i have seen the piping piped up wrong
 
So surely there would be signs of a leak or at least some misting somewhere if the pipework was an issue. The seals have been done twice, with genuine items and it hasn't made a difference. There is a hissing noise in the head when the ignition is on and the pump is running.......
 
That hissing sound in the engine bay with ignition on is normal, cheap pumps are most of them noisy... based on the symptom
RobBBoi said:
Car starts on the first revolution with no prime needed. It has been mapped and used to pull all the way to the limiter. It hits about 3250 revs and just stops moving.
Click to expand...
i'm not convinced at all that it's air in fuel but it can be fuel pressure issue so better do somehow to insert a gauge instead of the FT sensor in the FPR and see the pressure.

also is it manual or auto? and explain better what do you mean in the bolded part? how does it stop moving? the rpm stops there or it revs up and doesnt accelerate or how?
 
I am going to put the VDO pump back in tonight when I get home and try it.

I don't remember the hissing there previously, not to the extent it's there now for sure. I'll upload a vid shortly.

It's a manual. You can feel the car back off when it hits a certain rev range, the car still revs and accelerates but not like it should, and the smoke just stops.
 
That seems like overboost cut out to me... remove fuse F2 from engine bay fusebox and go for a ride like that and if still the same check the pipework attached to the wastegate modulator also if the wastegate is not sticking...if the symptom goes away with F2 removed replace the wastegate modulator ...btw, is the EGR still on? , did you check the ECU red plug for oil?
 
It's not boost cut. Will remove F2 now and try it though.

Pipework is fine. Nanocom sees 1.3 bar and holds no problem.

EGR has been blanked.

Red plug is clear, another new harness fitted 2 weeks ago to eliminate it



Don't know if the link will work as using my phone but that's the hissing.
 
That hissing is normal while the pump is running, mine and others are doing it as well, it's the sound of fuel through the FPR.... you should have said you have nanocom, if the boost is steady while the symptom occurs and no fault codes then IMO it's fuel pressure problem... did you check the strainer under the FPR in the head to not be clogged ?
 
Yeah, micron filter is clear. When the new housing comes I'm tempted not to put it back and just see.

Just went out with F2 removed and no different.

About to change to another pump but not convinced it's the issue.

The fuel pump is 2 stage? Low pressure for the filter and return then high pressure to the fpr/head. How does that work? All on one relay or fuse or seperate? I'm wondering if its living off the low pressure pump......
 
The pump has only one feed, it's described in the WSM:

"The two stage pump comprises a high and a low pressure stage. The low pressure stage draws fuel from the swirl
pot through the filter. The low pressure stage pumps fluid at a pressure of 0.75 bar (10.9 lbf.in2) and a flow of 30 litres/
hour (8 US Gallons/hour) to the fuel filter. A proportion of the fuel from the low pressure stage also passes, via a
restrictor, through a jet pump which keeps fuel circulating in the swirl pot. The high pressure stage draws the low
pressure fuel from the fuel filter and pressurises it to a pressure of 4.0 bar (58 lbf.in2). The pressurised fuel is then
passed from the pump to the injectors at a flow of 180 litres/hour (47.6 US Gallons/hour). A fuel pressure regulator is
located at the rear of the engine and ensures that the delivery pressure remains at 4.0 bar (58 lbf.in2) by controlling
the amount of fuel returning to the fuel tank."
 
So realistically if the pump is running it should provide fuel at 4 bar (unless the pump is failing) The regulator just restricts return flow to keep the pressure in the head.

I take it if the voltage is low at the pump it wouldn't be working to full capacity, any idea what the voltage should be?
 
Also, something that might be related, the prime sequence doesn't happen. Ignition on and pumping the pedal doesn't do anything.
 
A different pump fitted now (different none gen). Absolutely silent and the moaning/gurgling has gone.

Worse performance.

Wtf is going on.

I'll refit the VDO pump tomorrow and hope for a different outcome. Someone remind me what the definition of insanity is.........
 
There are cases when the pump is running and doesnt create HP only LP, it's quite common, though if the MIL doesnt flash after the throttle was depressed 5 times it is an ECU missbehaviour so maybe that's the problem.... changing pumps over is not the way to rule this out, measure the pressure in the FPR and if it's good change the ECU
 
Injectors are coded yes, I'll double check them tomorrow.

I'm going to have to find someone with the kit to measure the pressure.

I don't think the lack of performance coincides with the purge not working, but it could.

I found a good vid on youtube and it shows how to test the pump and relay etc and which pin to test in the ECU. When the ignition is on the pin shows 12.something volts. With the car running it shows 1.something volts, surely that isn't correct....
 
Update on this.

Fitted a new genuine VDO pump. The old cheap pump stopped the hissing in the head, it's now back. Checked injectors are coded, they are fine.

On the nursery run this morning it was puffing a bit of grey smoke just as boost was kicking in.

Going to check the injector clearances again and check the timing this afternoon.
 
Do you have solved the issue? I had also air in the fuel system, didn't get it out. Coincidence helped me: I was working on the pump and for one week everything was ok....then the issue comes back. I decide to temporarily tighten the fuel lines with cable ties and the issue was gone

upload_2019-8-12_10-58-57.png


I have to find a more professional solution :-D
 
No, still not fixed.

The new VDO pumped stopped the gurgling and air noise but the performance still isn't there. I've also been getting some grey smoke when boost builds then it goes clear.
 
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