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Air in diesel lines LT 2.4 non turbo
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MattyH View Drop Down
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    Posted: 30 Jan 13 at 14:15
Greetings all

LT35 with 2.4 non turbo diesel - I've got a problem with air getting into the fuel lines. Here's what's happening:

1. Engine starts and ticks over fine, no smoke when ticking over
2. It runs rough at higher revs, with a fair bit of light grey smoke
3. After I've revved it, I can see bubbles in the fuel line going into the fuel pump. These take about 30s to clear after I stop revving.
4. Slightly vaguer symptoms - seems to run better on full tank, engine sometime cuts out when braking coming down steep hills.
5. No fuel leaks apparent under the van.
6. Got standard looking, new fuel filter (with thermovalve) on engine, plastic inline type filter in NSF wheel arch.

So I guess this means air's getting into the system at high revs, from somewhere. Where's the best place to start looking for dodgy pipes/connections, given that there's no leaks of diesel out? Or is it something happening in the fuel tank?

Cheers
Matt
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volition82 View Drop Down
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Points: 972 		Post Options Post Options   Thanks (0) Thanks(0)   Quote volition82 Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jan 13 at 11:00
Air leaks in the fuel lines are a common problem.  I'd start at the diesel tank end with the fuel lines they will probably be perished.  Not sure if the tank pick up is the same on the diesels as the petrols but with mine (petrol) you have to drop the tank slightly to gain access to the start of the pipes.
 
The seal on the top of the tank could also be perished and i'd replace the filters for what they cost.  Unless you have changed them yourself recently.  You could have a dodgy seal on the filters or they could be a bit loose.
 
The running better on a full tank could indicate water and/or dirt in the tank.  If thats the case you'll have to drain and flush the tank.
 
All cheap to do but a bit of a pita, especially with the weather the way it is!


Edited by volition82 - 31 Jan 13 at 11:05
1989 LT35 - 2.4 Lpg/Petrol - Converted To Camper
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MattyH View Drop Down
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Points: 29 		Post Options Post Options   Thanks (0) Thanks(0)   Quote MattyH Quote  Post ReplyReply Direct Link To This Post Posted: 31 Jan 13 at 11:47
Cheers for that - all makes sense. Going to fit new filters to start with, then check condition of the fuel lines from tank to engine.
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Benjeboyheavey View Drop Down
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Points: 6 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Benjeboyheavey Quote  Post ReplyReply Direct Link To This Post Posted: 12 Feb 13 at 13:42
Have the same problem atm with my lt35 2.4 non turbo diesel ambulance and pretty sure is not fuel line changed fuel filter but made little or no improvement and no leaks. possible to be fuel pump????
BenjaminHeavey
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Benjeboyheavey View Drop Down
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Points: 6 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Benjeboyheavey Quote  Post ReplyReply Direct Link To This Post Posted: 12 Feb 13 at 13:43
Have the same problem atm with my lt35 2.4 non turbo diesel ambulance and pretty sure is not fuel line changed fuel filter but made little or no improvement and no leaks. possible to be fuel pump????
BenjaminHeavey
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MattyH View Drop Down
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Points: 29 		Post Options Post Options   Thanks (0) Thanks(0)   Quote MattyH Quote  Post ReplyReply Direct Link To This Post Posted: 12 Feb 13 at 14:32
I don't think there is a separate fuel pump - diesel is sucked through the filter system by the injector pump.

On mine, you can see air coming into the injector pump in the clear pipe between the fuel filter and the pump - so must be coming in somewhere else. I'm going to test by hooking up a supply direct to the fuel filter - see if it's coming in there or further back in the system.
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volition82 View Drop Down
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Points: 972 		Post Options Post Options   Thanks (0) Thanks(0)   Quote volition82 Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 13 at 09:57
Not sure about the diesels but my fuel pump is in the tank.  Well it was until it gave up and i've now got an aftermarket one outside the tank.
1989 LT35 - 2.4 Lpg/Petrol - Converted To Camper
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mat_the_cat View Drop Down
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Points: 1862 		Post Options Post Options   Thanks (0) Thanks(0)   Quote mat_the_cat Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 13 at 12:02
The diesel don't have a separate lift pump in the tank - it's drawn up by a pump within the injector pump. Bear in mind that an air leak in the return lines, or the IP itself can cause bubbles to be visible on the supply pipe as the return line is fed into a pipe connected to the filter.

A separate fuel supply is a good idea - I have an old lawnmower tank I use in such situations. But in your case all a gravity fed tank will do is prove there must be a fuel problem *somewhere*. If it draws up OK from a can in the footwell, then that suggests the problem is tank or front to back fuel line related; if not at least you've isolated it down to the IP or pipes under the engine cover.
Mid engined, 6 cylinder, turbocharged 2 seater - it can only be a VW LT!
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Benjeboyheavey View Drop Down
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Points: 6 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Benjeboyheavey Quote  Post ReplyReply Direct Link To This Post Posted: 14 Feb 13 at 20:06
Thanks for the info

Edited by Benjeboyheavey - 14 Feb 13 at 22:34
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Marco12 View Drop Down
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Hi MattyH, have you solve the problem? I can see air in 10 cm of the transparent pipe before starting the van in the morning. I don't know if this is normal or evidence that air is entering into the system or that diesel is going back to the tank when not running.
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woodyrich1965 View Drop Down
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had the same on mine it was the little plastic tee piece on top of the filter
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Marco12 View Drop Down
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Thanks, Woodyrich. for the answer. I have changed the part already but the problem persists. What is strange is that the air started to come after I changed the "water tramp" filter, on the left side outside the van. I can not see any problem there or in the line coming out from that filter. Maybe it's just a coincidence and the air gets the system somewhere in the line between the tank and the pump.

Apart from the starting problems in the morning, are there any other potential problems I may experience if I run the van for 1000km with air in the diesel?
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futureweb View Drop Down
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Did you manage to resolve this I am having the same problem I have a 1984 lt35 2.4d I am not sure if its a problem with the solenoid on the injection pump there seems to be very little suction on the fuel pipe it will run if I gravity feed a tank straight into the injection pump and have managed to get it to run off the fuel tank twice after stripping and reconnecting the wire that goes to what I am guessing is a solenoid but since then no joy.

I could use a fuel and wiring diagram and some idea on how to reconnect the odometer if any one has some diagrams, manuals or anything to help the mechanically stupid :)

Any help would be greatly appreciated thanks in advance
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Marco12 View Drop Down
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Hi. Yes, I solved it. At the beginning, as I couldn´t realize were the air intake was, I solved the problem by installing a small electric pump. Some time later, I realized that the there was a leak at the main shat of the diesel pump. I replaced the diesel pump main shaft o'ring. Not a difficult task, as the job can be done without removing the pump.
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Monster LT View Drop Down
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Originally posted by Marco12 Marco12 wrote:

Hi. Yes, I solved it. At the beginning, as I couldn´t realize were the air intake was, I solved the problem by installing a small electric pump. Some time later, I realized that the there was a leak at the main shat of the diesel pump. I replaced the diesel pump main shaft o'ring. Not a difficult task, as the job can be done without removing the pump.

Hi Marco. Interested in whether your still running it with the "small electric pump". Trying to understand if this was a chicken or egg? Someone I know had air bubbles going up the clear tubing to the pump. He changed most or all pipes from the tank to the filter for new clear tube and installed a non return valve and electric pump. Problem solved until a leak on the pump appeared pissing out diesel all over the pump belt. Now it needs the pump shaft seal replaced. So could it be that over time the seal gets weak and adding the electric pump blows it out? And new seal holds strong even with the electric pumps added pressure? Could the original leak have been masked by the effectiveness of the electric pump and a new problem or one waiting to happen been created by it? Or did the electric pump exacerbate and unmask the original problem - being the seal?
Also interested to know the procedure for replacing the seal with pump in situ. Is it in the VE pump manuals? Someone else was asking this a few posts ago too.
Thanks.


Edited by Monster LT - 01 Jun 18 at 00:45
LT45-TD-ACL-intercooler-4x4-1993
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Marco12 View Drop Down
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Points: 39 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Marco12 Quote  Post ReplyReply Direct Link To This Post Posted: 01 Jun 18 at 18:13
Hi. After repairing the oring, I disconected the electric pump. In my opinion, what happend is that the seal simply continues degrading over time, sooner or later the leak will increase. The electric pump may not have anything to do with this, it´s a very small pressure what is introduced to the system. I took the lt to the repair shop. Anyone experienced with bosch ve pumps can do the job. Simply tell them that there is no need to demount the pump to do it!

I don´t remember where, but there is a thread at lt-forum with this issue.
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futureweb View Drop Down
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Should there be much suction on coming from the inlet fuel pipe? it seems very week
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