Calling all diesel fighters!

[JonC]

I need some advice on my diesel fuel system. 
I’ve been having an ongoing problem with air in my injector system for a while, to the point that it’s doing my head in. 
It’s a vw td5 engine, with direct injection( I think). 
I have fitted a primer bulb in line, between the racor and the main filter. I’ve also fitted a NRV the right way around with a short length of clear hose so I can admire the bubbles. 
When I prime the system the bulb goes hard, there are no visible leaks and when I loosen the banjo on top of the filter there is a nice jet of fuel so I’m confident the filter housing is good.

After running for a while I turn the engine off and after above a minute  I get about 3-4 inches of air in the hose coming out of the filter housing.

Is this air being drawn in or is it a bubble from in the he system somewhere? 
I find it hard to believe that this much air could enter a system so fast without leaking fuel while running. 
Any ideas please? 

[Saintly Fish]

Must be a negative leak that sucks air in when the pump runs. But the static pressure when the pump is off is not enough to cause a seeable leak of fuel? 

[JonC]

The bubble in the pipe is maybe 10-15mlt, it appears in about a minute. There are no visible leaks, the engine isn’t hunting at high revs. 

[Andy135]

Agree with Neil. Air is being sucked in under negative pressure from somewhere. Start at the fuel line from the tank and work back from there, checking for cracks in the line and/or loose union connections. Do you actually need the primer bulb at all?

[GPSguru]

27 minutes ago, JonC said:

I need some advice on my diesel fuel system. 
I’ve been having an ongoing problem with air in my injector system for a while, to the point that it’s doing my head in. 
It’s a vw td5 engine, with direct injection( I think). 
I have fitted a primer bulb in line, between the racor and the main filter. I’ve also fitted a NRV the right way around with a short length of clear hose so I can admire the bubbles. 
When I prime the system the bulb goes hard, there are no visible leaks and when I loosen the banjo on top of the filter there is a nice jet of fuel so I’m confident the filter housing is good.

After running for a while I turn the engine off and after above a minute  I get about 3-4 inches of air in the hose coming out of the filter housing.

Is this air being drawn in or is it a bubble from in the he system somewhere? 
I find it hard to believe that this much air could enter a system so fast without leaking fuel while running. 
Any ideas please? 

 

Hmmm ............ I have finally fixed almost the same issue on the Jeep, which is a 2.8L VM 4 pot.

Does your Racor have a primer pump, and is the Racor-Parker  200 series filter housing ?

Even after changing all of the spill pipes, changing the Racor pump seals, and checking the whole system for leaks, the fault persisted. Finally, after speaking to Thomas Diesel (who are the UK main dealer for Racor) I ended up changing the whole filter head to the later 200 series. The tech guy at Thomas Diesel suspected the air leak was due to a faulty spindle seal on the Racor hand primer pump. These are not serviceable and are known to go 'hard' over time. There was no diesel leak as the jeep system works under vacuum as there is no pump in the fuel tank (i.e negative fuel pressure), so it sucked air through the spindle over time.

Changing the filter head has completely cured the issue, but not cheap at £200+, however, it was a bastid to change as Racor-Parker Uk did not have the NPTF (US taper thead) in stock and the projected delivery date was 20 - 30 weeks, but they did have the M14 metric head in stock, which meant that I had to re-route (and renew) the pipes. I fitted an M14 Banjo on the outlet and an M14 straight 10mm barb on the inlet, sealed with a dowty washer.

Edited December 1, 2021 by GPSguru

[JonC]

I’ve replaced the fuel lines, double clipped where possible. 
I have only added the primer bulb recently to try to force fuel through to the pump. I will remove it though . There is no inline electric lift pump on mine, though the workshop manual shows one. This seems to be common though. 
The air is coming out of the filter housing not from the supply. 

[JonC]

@GPSguru there is no air going into the primary filter from the supply line that comes out of my racor 

[JonC]

This is the primary filter in the engine bay 

[Andy135]

Poor or damaged seal between the filter head and cartridge then?

[JonC]

41 minutes ago, Andy135 said:

Poor or damaged seal between the filter head and cartridge then?

I don’t think so, when I pressurised the system then slackened the top bango fuel pissed out in a fine jet, as you would expect a pinhole to do so. 

[GPSguru]

56 minutes ago, JonC said:

This is the primary filter in the engine bay 

 

What is the secondary filter, because the air leak can be anywhere between the HP pump and the Tank.

[JonC]

It’s a racor of some type. 
I should have said that I have run from a drum of diesel into the primary and the bubbles still came back out into the clear tube, so I don’t suspect the secondary.  
the clear tube is currently the highest part of the fuel system so if figures that they will go there. 

[GPSguru]

17 minutes ago, JonC said:

It’s a racor of some type. 
I should have said that I have run from a drum of diesel into the primary and the bubbles still came back out into the clear tube, so I don’t suspect the secondary.  
the clear tube is currently the highest part of the fuel system so if figures that they will go there. 

 

You were replicating the tank with the drum ?

If that is the case, then the leak can still be anywhere between the injector HP pump and the primary filter, as you have eliminated any leak at the tank connectors and feed hose.

I am guessing the primary filter is a 30 micron and the secondary filter is either a 3 or 10 micron (most are 10 in the UK)

Post a pic of the secondary filter housing (known as the filter head)

Edited December 1, 2021 by GPSguru

[suzook12]

Jon, does the return line feed to the filter?

I have also had issues with that reinforced clear pipe before now, not sealing properly.

 

Is this causing cold start issues at all?

[JonC]

The clear pipe has only recently been added so I can admire the bubbles. 
From what I can see the diesel return goes from the pump into something at the bottom of the engine which I think is a cooler then back to the tank. 

[GPSguru]

9 hours ago, JonC said:

The clear pipe has only recently been added so I can admire the bubbles. 
From what I can see the diesel return goes from the pump into something at the bottom of the engine which I think is a cooler then back to the tank. 

The diesel return will comprise of the return from the injectors (spill pipes) and often a return from the HP pump. These then go into a manifold, which can be a box or pipe shaped, and then the return from there goes back to the tank.

If the primary filter is the highest point of the system, then that is why you see most air at that point.

Strange, but probably a very high percentage of air leaks in diesel systems are due to the filters !

Carefully inspect the pipe work from the HP pump back to the secondary filter and then back to the primary filter.

 

 

[JonC]

1 hour ago, GPSguru said:

The diesel return will comprise of the return from the injectors (spill pipes) and often a return from the HP pump. These then go into a manifold, which can be a box or pipe shaped, and then the return from there goes back to the tank.

If the primary filter is the highest point of the system, then that is why you see most air at that point.

Strange, but probably a very high percentage of air leaks in diesel systems are due to the filters !

Carefully inspect the pipe work from the HP pump back to the secondary filter and then back to the primary filter.

 

 

Thanks, I appreciate the input. 
The pipe from the filter to the hp pump has banjo fittings on each end, it is a rigid pipe with a flexible braided section in the middle. I will try to get a better look at it tomorrow but it certainly isn’t spraying out fuel. 

[Saintly Fish]

7 hours ago, JonC said:

Thanks, I appreciate the input. 
The pipe from the filter to the hp pump has banjo fittings on each end, it is a rigid pipe with a flexible braided section in the middle. I will try to get a better look at it tomorrow but it certainly isn’t spraying out fuel. 

If I'm correct (doubtful) and the flexi pipe bit is before the pump then it's not under pressure except for static pressure. It only has negative pressure ie sucking in not blowing out when pump runs. If the braided pipe has a small split then an air intake leak will not be visible as no fluid will come out, but the pump action can suck air in? 

[suzook12]

If banjo washers have been reused, you could replace those.

Is there a non return valve in the filter housing? Has it been checked?

[GPSguru]

22 hours ago, JonC said:

Thanks, I appreciate the input. 
The pipe from the filter to the hp pump has banjo fittings on each end, it is a rigid pipe with a flexible braided section in the middle. I will try to get a better look at it tomorrow but it certainly isn’t spraying out fuel. 

It will never spray fuel as the system works by Vacuum as you have no tank pump.

The area, which I would be looking at, is the primer pump and any pipework associated with it.

If you have a leak on the return, this is normal evident as a leak because it runs under positive pressure.

13 hours ago, suzook12 said:

If banjo washers have been reused, you could replace those.

If you can't get new washers, just heat up the old ones with a blow lamp to anneal them (make them soft again). I see you have Ali washers on the Banjo's, copper is preferred.

 

TBH, this type of fuel system air leak is often quite difficult to find as it is usually quite subtle, but also very annoying.

Edited December 4, 2021 by GPSguru

[JonC]

I’ve been down today, removed the clear hose and the plastic primer, they are just more trouble. If I can’t see the air then it can’t be there right?😀

I ran out of time but my next move is to remove a banjo and measure up the washers, so I can get all new ones and replace the filter in case the seal is damaged but I’m sure the problem existed well before my last service. 
 

I also need to measure up the banjo fittings so I can make a replacement line between the filter housing and hp pump. 

[GPSguru]

10 minutes ago, JonC said:

If I can’t see the air then it can’t be there right?😀

The air usually migrate to the highest point on the run, between the tank and the HP pump.

You only need to measure the Banjo bolt thread diameter to get new washers. They look like M14 (ish)

[JonC]

9 hours ago, GPSguru said:

The air usually migrate to the highest point on the run, between the tank and the HP pump.

You only need to measure the Banjo bolt thread diameter to get new washers. They look like M14 (ish)

There are plenty of party packs of washers available on Amazon etc, I’ll order a box, It’s the fittings to go on the hose ends that are more specific. 

[suzook12]

11 hours ago, GPSguru said:

If you can't get new washers, just heat up the old ones with a blow lamp to anneal them (make them soft again).

Now you are showing your age mate...... 🤣

[suzook12]

1 hour ago, JonC said:

There are plenty of party packs of washers available on Amazon etc, I’ll order a box, It’s the fittings to go on the hose ends that are more specific. 

Yup, not too many variations tho to be fair

If you want to be really posh, get Pirtek or HEL to make you some nice shiney braided hoses all round with compression fittings on to the banjos.....