How to: Lift Pump Fail Safe Fuel Circuit

[Fix_Until_Broke]

And it appears that I'm wrong again - I just had to run another errand and left the pump unplugged, started 2 more times just fine and noticed a bit of stumbling coming away from one stoplight and a couple miles later I tried killing it with my dash switch (I was close to home) and it died, but I couldn't re-start it by either bump or starter method - so I plugged it back in and after a bit of cranking, it re-started just fine.

Will this instantly leave you stranded if it fails? I guess I'm testing it failing electrically, not mechanically, so if the pump/motor locks up or something then maybe it could, but if it fails electrically, I don't think so. You might get stuck at the next place you shut it off though?

Just testing the operation here

 

[Left Coast Resident]

<SNIPITY,SNIP,SNIP>
Left Coast Resident - Excellent, well detailed procedure on how to do this, but, is it necessary?

Sounds to me like you just took a little while to run enough of the fuel out of the filter to the point that enough of a vacuum was created to make the engine behave like you had a clogged fuel filter.

I can assure you that before I modified and installed the lift pump, I set it on my workbench for a couple of weeks, and walked by it and stared at it periodically, considering all the VW design parameters, and wondering if anything needed tampering with. Then I put the Mity-Vac on the output barb and PULLED vacuum with it -- which it held for as long as I cared to leave the Mity-Vac connected. In other words, when the pump doesn't run, NOTHING gets through it.

 

[Fix_Until_Broke]

I'm suprised that my car ran as long as it did. I'll put my gauge on the pump again, but this time with the in tank lift pump disconnected and see what it does and how long it runs (it's a -30 in Hg/15 PSIG gauge). I have my thermostatic tee bypassed completely so all of it goes back to tank FWIW?.

 

[jackbombay]

So - am I just the oddball case where it works for me or has someone else had their PD lift pump fail on them in an ALH engine and it wouldn't run?

Mine ran fine with a bad PD pump for several thousand miles, I had one of the earlier modles, not sure of that makes a difference.

 

[dok]

:d :d :d

 

[Left Coast Resident]

Sometimes we refer to him as Baby Dok, though nothing's ever been pinned on him . . .

 

[alhutch]

T fitting @ McMaster-Carr

McMaster-Carr catalog page 139
Item number - 5372K613
Description - Durable Nylon Multi-Barbed Tube Fittings
Tube-to-Tube Connectors—Semi-Clear White
Size - 1/4"

Great post LCR!

 

[Tbirdtree]

Well, my lift pump has been in the car about a month with the LCR mod. Today after parking to run into the store, couldn't get the car started when I came back out. No fuel running through the clear line, disconnected the inlet line to the fuel filter turned key on, no fuel. Could still hear the pump running, so I decided to do a little parking lot investigation, and upon removal of the fuel pump, I had found the green fuel line had basicly disinegrated right before the connection that leads to the fuel filter. So to get home, I cut out the bypass section and connected the feed direct. Has anyone else had this happen? Is it possible I just had a fatiged/weak piece of fuel line? I have more of this, but I'm a little reluctant to use it now. Thoughts on why this may have happened? Was I the fluke?
Thanks,
Tom

 

[tothemax]

WOWWW This is not too good Tom.

Are you referring to th green Tubing – 2 feet of thin wall (3/8” OD, 1/4” ID, 1/16” thick) ‘firm’ Viton tubing, part #5119 K861 from McMaster Carr that was installed inside the fuel tank on the pump making the bypass?

I did mine a few weeks before yours and sourced the tubing from McMaster Carr as well. Maybe I should inspect mine except the removal and reinstall of the fuel pump is such a PITA !!

Anybody else having this problem?

Well, my lift pump has been in the car about a month with the LCR mod. Today after parking to run into the store, couldn't get the car started when I came back out. No fuel running through the clear line, disconnected the inlet line to the fuel filter turned key on, no fuel. Could still hear the pump running, so I decided to do a little parking lot investigation, and upon removal of the fuel pump, I had found the green fuel line had basicly disinegrated right before the connection that leads to the fuel filter. So to get home, I cut out the bypass section and connected the feed direct. Has anyone else had this happen? Is it possible I just had a fatiged/weak piece of fuel line? I have more of this, but I'm a little reluctant to use it now. Thoughts on why this may have happened? Was I the fluke?
Thanks,
Tom

 

[Tbirdtree]

Yes, the little chunk between the T and the outlet was all shredded like. I'm thinking that it must be a fluke because the rest of the tubing looked just fine. Mabey upon install, I used to much twisting/force to get it on and it fatigued it enough that the bit of tube couldn't handle the bit of pressure. Either way, I've decided to do it again tomorrow morning and hope for the best. At least it was an easy problem to diagnose, and with a few basic tools, my swiss army knife and very little light, I was able to get home just fine. If it happens again, I'll be sourcing some other tubing It's ironic that the mod to get you home when your pump fails, failed for me. Still a great mod though. Probably some sort of user error

 

[Tbirdtree]

Don't let me worry you Pierre. Unless some more folk chime in with tubing failure, I'd assume it's just my bad luck for the month. And if that's all the bad luck I get this month, I'll take it

 

[Left Coast Resident]

If you don't get the tubing / 'T' fitting lined up exactly (so that the vertical length will drop directly into the well) and there is side to side force on it (the 'T' fitting), it can happen. It happened to Baby DOK -- I opened up his pump and was careful to realign the lengths at the 'T' fitting (so that the tubing could drop straight down into the well opening). No problems since, and FWIW, no problems with mine.

A larger I.D. size Viton tubing so that it expands less to go over the 'T' fitting barb might help -- it can't be a lot larger though -- the problem is that the viton has to be thin wall to get into the well -- and also that the list of possible materials that will be compatible with HOT DIESEL is short.

On the other hand, if you think the diesel won't be too hot when it re-enters the tank (could be -- I don't know that anyone's ever measured it as it re-enters the tank), then there are probably more materials options.

 

[Tbirdtree]

Thanks for the tip, now that you mention it, it was probably a little unaligned. I'll make sure to have it propper tommorow. The part over the T was fine. It was more on the area going over the outlet. At least I wasn't the only one Thanks again for the input.

 

[DanG144]

Can anyone measure the max Outside Diameter of the fittings you are going over?

On a different pump (the POM "B" variant) I had to go to a larger tubing ID, and I went with a thicker wall, too. This gets pretty pricey. But I learned after a failure after 2 weeks use.

I also learned that you should NEVER use pliers or tools on this tubing. It is very tender and once you start a fault - a scratch or divot removed, and it gets under tension, it will grow to failure.

Dan

 

[MAXRPM]

Mine still working great with the LCR-mod, I installed it about 8-9 months ago, and it still pumping strong.

 

[jwlionking]

www.usplastics.com is a vendor I use for all plastic items I need.

 

[jsrmonster]

www.usplastics.com is a vendor I use for all plastic items I need.

Hey Jeremy, You got that sled ready to ride? I got another 97 AC 580 EFI that needs left side suspension straightened out. I've been working on all 5 sleds in my spare time - hehe. My boys are stoked to ride soon as they come home from college. I might go north this weekend, of course wife has different plans.

Biggest problem is my tranny is shot in my suburban (front band worn out) I'm rebuilding a spare tranny now ;-( I can pull my 2place, but forget about the pulling the enclosed trailer with slipping.

Jeff

 

[jwlionking]

Hey Jeff,

Yeah, got them all waxed and ready to roll! Just need snow. We better have a good winter this year. It's long overdue.

BTW, love the sig! Line 1 and 4 are so very true.

 

[shizzler]

No one's posted to this thread in a while but I thought I would bump it back up. Just did this mod on a new lift pump for my parents PD Jetta Wagon. Hopefully if it ever dies they'll be able to keep moving and get off the road before defaulting to a tow to the dealer for another raping.... As has happened twice with the original failing pump.

Couple thoughts from the process:

- Use some sort of lube to get the viton line onto the pump and sender connections. I couldn't get it on too far without any.
- Leave the float and sender piece unbolted from the pump when applying the viton line to the connections.
- Take your time with the otteker (sp?) clamps. They are a PIA.
- Also take your time slicing the original fuel line, I got antsy and pulled on mine before it was fully cut away, resulting in a violent release.

Other thought: The internal diameter of the 1/4 OD "T" is quite a bit smaller than any of the original orifices. Anyone think that this will adversely affect flow?

Otherwise, thanks LCR, hope this mod comes in handy some day. Well, actually, I guess I hope it doesn't.....

 

[Left Coast Resident]

. . .

<SNIP> Take your time with the otteker (sp?) clamps. They are a PIA.
Try nail pulling pliers (the cutting edge is at 90 degrees to your hand as you hold them) to cut into the Oetiker clamp. Piece of cake that way.

Other thought: The internal diameter of the 1/4 OD "T" is quite a bit smaller than any of the original orifices.
Next size up would probably be easier and better. My apologies.

 

[DanG144]

I should have one to try 5/16" tubing and wye on in a week or so.

I had one to try it on, but someone needed it.

 

[jsrmonster]

The "fail safe" lift pump mod is for rotary pump tdi's.

Good luck anyway with your PD.

 

[DanG144]

Jeff,
The tandem pump on a PD will pull fuel from the tank, if it has a path, and the lift pump fails.

The early PD's in Europe did not always have a lift pump.

With the grey and white pump that is all that is presently available, no pump (VE or PD) has a chance of pulling fuel through it.

So this mod is potentially beneficial to any TDI.

Dan

 

[jsrmonster]

Ok, if my PD pump dies, I'll just swap the feed and return lines and make sure it has over 1/4 tank.

Jeff

 

[DanG144]

You might need more like 3/4 to ensure the return line opening is covered with fuel, since it is open right at the top of the canister.

When operating in the tandem pump sucking/ no lift pump mode, like an ALH, then any air leak will suck air and not allow operation.

This seems to be why some PDs can run almost perfectly with no lift pump, and others poorly, and still others not at all.

A PD came into the shop last weekend with a non-operating lift pump. The car ran pretty good, but the fuel temps were pretty high pretty early.

Sure enough - the lift pump was dead. Since it was an original, it was able to suck fuel through the eductor line. This is not possible with the new grey and white pumps that have an external eductor line - unless you do this mod.

Dan

 

[jsrmonster]

My lift pumps came off a bora sport pd150 and return goes down 2" from bottom. Return lines must return to lower fuel level or else they aerate the fuel. Big problem in off road vehicles and boats. For Cummins use an AirDog or Fass, and no more problems with aerated fuel. (note 4motion fuel tank has dual fuel pickups, that is what the tee shown is for).
Jeff

return is 2" higher than pickup

 

[DanG144]

In the original pumps the return line goes to the bottom, but it had an opening in the line at the top of the canister.

If fuel level was very low in the canister (the eductor or check valve was not working - or extremely low fuel level) then the fuel would stay in the tube and exit near the bottom of the canister. If the eductor was able to maintain the canister full (normal operation) then the return fuel would bubble out at the top of the canister. This allowed the hot return fuel to overflow to the main tank, while the eductor pulled cooler fuel off the bottom of the tank to keep the canister full.

http://forums.tdiclub.com/showthread.php?t=225672

I have never seen the pump you mention. Is there a source for them in the US?

Dan

 

[DanG144]

Edit: I no longer recommend doing this mod. No hose I have tried has been tough enough (or if it was tough enough, it would kink). I have had about half a dozen failures OF THE MOD (on different cars) and NONE of the base pump.

My new grey top white bodied fuel lift pump came in today from BoraParts.com.

I modified it using larger tubing and components than LCR did originally.

I used 5/16" ID clear polyeurethane hose #1510 from www.ProCycle.us.​

I used 6 spring type hose clamps 14-0094 from the same source.
I used a 5/16 barbed check valve 47245K24 from www.mcmaster.com
I used a 5/16" barbed tee 5372K614 from the same source.

I cut the tee back, as did LCR.
As LCR did, I could see no way to make anything but large sweeping curves to avoid crimping the lines.
I mounted my tee directly on top of the pump.

I had earlier modified one using the 1/4" viton that LCR initially recommended, but the viton had failed on one person's pump, and I wanted to try a different material that was physically tougher. The 1/4" tubing is stretched to its limits to get over the pump's components.
The barb on the underside of the assembly top has a 9.25 mm bulge on it.
The barb on the top of the electric pump has a 9 mm maximum OD.

SnowCat has used this polyeurethane for his ALH clear fuel line for 3 years with no problem, and the vendor says it is good for fuel, WVO and BIO. So I thought I would give it a shot. It is also a lot cheaper than Viton.

This pump has a check valve in the return line, so the return line cannot be used as a fuel source, even with high fuel levels. You might also check yours out, Jeff (jsrmonster); I think I see the bulge of a check valve housing on your pump's return line as well. It was built into the top assembly.

Once modified this pump assembly should be even better than the originals. The original only had a tiny orifice to pull fuel through, and it had to overcome a spring loaded valve in order to pull fuel. This one will have much lower resistance to flow in the emergency, pump off, mode.

[/IMG]

[/IMG]

 

[Curious Chris]

Installed mine today. Test drive went well hard to quantify but no issues.

The modification went well and I used hose clamps on all the connections as I was a little leery of the 5psi pressure. I followed LCR directions otherwise. I tested the check valve by sucking on the out port and then blowing back.

I am doing the install in 3 stages: stage 1 pull the power cord from engine compartment to lift pump; stage 2 install lift pump doing all the wire modifications at the lift pump (power coming from X75), stage 3 I am going to do at DieselGrandads this weekend which is wiring in a relay with the on signal coming from the injection pump.

As I live in the frigid north, I know this mod will help my cold starts this coming winter. (I am also advancing my injection timing at DieselGrandads)

This is a great mod for ALH engines.

 

[rocketeer928]

I just ordered my parts today. It's too bad I didn't know about this modification when I was installing the lift pump a couple of weeks ago.