How to: Lift Pump Fail Safe Fuel Circuit

When I asked him via PM DanG144 recommended the hose linked below in 5/16" and that is what I used.

http://www.dudadiesel.com/viton.php?affiliate_pro_tracking_id=17:18

is there any canadian vendors that sell these kinds of high quality tubing and such

Looked into this and decided against

Just to give my 2p worth on this issue, my lift pump failed recently. (Golf TDI 2002 PD engine) It started getting very noisy so I had a little warning, and the original pump was the 1J0 919 050 B. I actually removed the fuse to stop the awful noise and the car ran perfectly, as far as I could tell, but a mechanic told me it's not good for the engine to have to suck the fuel out of the tank so I did replace the pump.

Having read about the no-bypass issue, I tried to get a 2nd hand 'B suffix' pump, but without success, so I got a 2nd hand 'non-B suffix' pump and intended to follow these instructions and carry out the mod.

However, when the 'new' pump arrived, I found I could easily suck air through the outlet connector (via a plastic tube!) so wondered if perhaps the engine could also suck fuel out. I installed it, tested it under normal operation, and then pulled the fuse to see if the car would still run. It ran about a mile and a half then cut out.

But then it occured to me that the suction might work if the pump were fully submerged in fuel. (I had deliberately run the tank down to 1/4 full to make changing the pump easier.) I filled the tank, pulled the fuse again, and voilà! - the car runs fine!

So, of course the ideal would be that when the pump fails the car doesn't also fail, although it would definitely be better to get some notification that the pump has failed (engine hesitating, etc.) otherwise you could run with no lifter pump for long enough to cause other problems without realising it.

From that point of view the older, 'B suffix' pump was not ideal as the car would APPEAR to run perfectly without it. And a modified 'non-B suffix' pump could also give no warning of its failure.

Since with an unmodified non-B suffix pump it seems that any possible breakdown can be 'fixed' temporarily by simply filling the fuel tank up, I decided that I prefer the balance of reliability versus 'fault notification' that I have with a non-modified pump.

Now the absolute ideal might be to have a manually operated bypass with perhaps an extra connector fitted to the top plate of the pump, which has a tube fitted below, terminated with a strainer, which sits at or near the bottom of the tank. A 'T' piece arrangement in the tubing above the pump, plus a simple manual valve on the tube going to the additional fuel pick-up tube, would mean that if the lifter pump ever failed, one would have notification that the pump needs to be changed, and yet the car could be got going again in the meantime by simply opening that manual valve.

For me, part of the point of getting a bit of warning that a part will need to be changed is that I can then read up on how to change it, source a cheap 2nd hand part, and do the job myself on a day when I'm not working. A 'sudden death' of a vehicle for whatever reason means towing it to a garage and swallowing the cost of new parts and labour.

I'm really grateful to the original poster for the detailed explanation of this modification but if I were going to make a mod I think I would prefer to make it on the top of the pump as I described, with a manual valve. (Partly, I have to admit, that's because I don't really understand how the pump works and I feel more comfortable bypassing it entirely.)

But I have decided to live with the new pump unmodified. I think the chances of a pump failure causing me a real problem are slim. Firstly, it is likely the pump will become noisy before failing, so I can make sure to run with a full tank until I can get it replaced. Secondly, I generally carry a 5 litre can of diesel anyway so it may well be I can get out of trouble by pouring that in the tank to raise the level. Worst case scenario is I have to call the breakdown services and get them to tow me to a filling station. That would be annoying but would not cost me anything. (Or do those breakdown guys carry lots of spare fuel anyway?)

I've procrastinated doing this bypass mod to my pump. Regardless, I have a fuel pressure gauge installed at the fuel filter. It provides immediate indication of the failed pump, or in my case a few times over the years, an electrical issue with a sticky relay. I glance at that gauge any time my car doesn't start or if I feel a hiccup on the road. I also have an LED to indicate that voltage is applied to the pump, an indication that N109 and my relay are working properly.

its a nice write up by AL

I used to do this mod, and recommend it.

However my experience has led me to no longer suggest doing this.

The hoses available to me were too delicate. They would not last. I tried several different types.

All of the Viton hoses are physically weak. They routinely break after some physical defect or tear grows and rips. Quite often it was caused by hose clamps, or perhaps even the barbs on the connections.

It would be a different story if better hoses were available.

We created new failure modes doing the mods. The idea of the mod is very good. The execution, however, can reduce reliability.

So what about the originally recommended hose? I can understand the issue with the Viton stuff.

I used 5/16" ID clear polyeurethane hose #1510 from www.ProCycle.us. (mentioned in post #58)


I have the mod done with this tubing and so far no issues and it has been a few years!

ALL of the hoses (at least 3 different types and sources) have shown issues.

If the hose was tough enough to last, it would kink when it heated in the tank, even if it was unkinked on installation.

The Polyeurethane hose was only good for a few years of service. It will not last - it gets brittle and weak.

The viton would eventually tear.

The viton and rubber with fabric sleeve in between would kink - often after it got hot in the tank.

If you could get the corrugated hard hoses that were originally used - of the right length, it may work and last.

The idea is elegant, the execution is problematic.

I regret that I ever modified any of my (and especially my friends) pumps.

DanG144 said:

ALL of the hoses (at least 3 different types and sources) have shown issues.

If the hose was tough enough to last, it would kink when it heated in the tank, even if it was unkinked on installation.

The Polyeurethane hose was only good for a few years of service. It will not last - it gets brittle and weak.

The viton would eventually tear.

The viton and rubber with fabric sleeve in between would kink - often after it got hot in the tank.

If you could get the corrugated hard hoses that were originally used - of the right length, it may work and last.

The idea is elegant, the execution is problematic.

I regret that I ever modified any of my (and especially my friends) pumps.

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Wow this is definitely cause for concern

red16vdub said:

Wow this is definitely cause for concern

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Well, it's not the end of the world.

And it IS just my experience...

But it was very disappointing.

On the other hand I have had no problems with the polyeurethane hose set up. (I hope this comment does not trigger a remote failure!) It would be very interesting to get a survey of those who performed this mod and find out what the rate of failure has been.

any way to use steel fuel line for the failsafe circuit ?

I was wondering the same thing myself. Use threaded connectors. Might be a real challenge given the space constraints.

If anyone can do it, you can, Jimmy.

The fittings built into the pump, the canister lid and the jet pump are all barbed fittings - 8mm if memory serves.

Changing them all over, in the space available, as kiwibru mentions, would be very difficult.

There should be a previously modified pump (two in fact) at the GTG in January at my place. I would welcome input from anyone.

The only hose I can find that looks suitable is only available in 1 foot lengths or longer from McMaster Carr. It is a corrugated teflon hose that must have shaped ends, so it does not appear to be suitable in those lengths. http://www.mcmaster.com/#standard-plastic-and-rubber-tubing/=zi70x1 (it also comes in clear).

TheTDWagonGuy that sells the electric motor pumps for replacement has some source for hoses, given what comes in his kit. I have not approached him about this, but it seems the only present lead I have.

DanG144 said:

If anyone can do it, you can, Jimmy.

The fittings built into the pump, the canister lid and the jet pump are all barbed fittings - 8mm if memory serves.

Changing them all over, in the space available, as kiwibru mentions, would be very difficult.

There should be a previously modified pump (two in fact) at the GTG in January at my place. I would welcome input from anyone.

The only hose I can find that looks suitable is only available in 1 foot lengths or longer from McMaster Carr. It is a corrugated teflon hose that must have shaped ends, so it does not appear to be suitable in those lengths. http://www.mcmaster.com/#standard-plastic-and-rubber-tubing/=zi70x1 (it also comes in clear).

TheTDWagonGuy that sells the electric motor pumps for replacement has some source for hoses, given what comes in his kit. I have not approached him about this, but it seems the only present lead I have.

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hey Dan, how about using some rescued tank to engine bay plastic line from an mkiv junker ?... that line appears to be in and out same material so it may tolerate long term fuel submersion ... it's also fairly easy to work over fittings with a little heat assistance ... maybe try it out at the next gtg ?

That sounds good, Jimmy.

Did the LCD upgrade on the lift pump about 7 years ago in my alh and mine still going strong now and it is intact,,, methanol in bio does not respect even OEM fuel lines in our cars so rupture may be due to methanol??? ,,,could this be the culprit on hoses in the pump and it is creating havoc??? I have never used Bio in my alh only D2 and now HPR Diesel,,why mine still intact and now I see some lift pump hoses ripped???

If you end up needing new IN TANK fuel hose, look on this page, then scroll down a fair bit. You can find the corrugated hoses (my favorite) or you can get the solid elastomer (rubber looking) hoses.

I have personally seen hoses turn to mush when put into fuel tanks - just fuel rated hose will not work.

http://apeusa.com/html/kits.html