The Fuel Pump Problem, looking for complete solution

[mg93108]

Hi
One thing I've learned in reading LOTS of posts here in the 411/412 forum is that there's TONS of knowledge here. I'm hoping to tap into this knowledge and ask the "experts who really know this topic and have first hand knowledge" with it to respond to an issue that plagues, has plagued, or will plague all of us.

What do we do about dead fuel pumps?

Apparently it's a common problem to see fuel pumps fail. I understand that there are reasons why fuel pumps may not run while in the car, but this question is related to fuel pumps that have been bench tested and determined to be dead.

It seems like there are two reasonable solutions to end up with a running fuel pump that is reliable. Certainly this rare and difficult to find fuel pump is a challenge to deal with, not to mention potentially very expensive.

Solution 1: Keep it stock
I've heard people discuss a guy named Jim Adney who possibly rebuilds these. I finally found an email address for him on www.vwtype3.org. I did just email him. Certainly if he can rebuild these, and provide these quickly, and not too expensively, it seems to make sense just to utilize his services. Especially where he a fellow VW fan. If Jim reads this, or if someone can contact him and ask him to weigh in on this, that would be great.

Solution 2: Retrofit it with a modern fuel pump
The other suggestion out there that I've read about is related to retrofitting these old fuel pumps with one that is right off the shelf and commonly in stock. I've read about a few different models (and years) from an 80's vehicle. This is where things get a little fuzzy. I'm hoping to find a definitive answer on three things related to this retrofit.

1) What is the exact Make, Model, and Year(s) vehicle that uses this "replacement" fuel pump? I've heard a couple of different Ford products. But has anyone ever actually done this on there own car? And seen it work properly? Please don't respond with "Well, I heard that there was this guy..." or "It seems to me that what would work is..." Who has first hand knowledge on this? One of you guys must. I'm amazed at the wealth of experience here. If you could share this info, that would be awesome.

2) How is this to be plumbed? I'm hoping that someone can provide a clear drawing of the fuel lines, including tank, filter, pump, return lines, and gas heater line, etc. I've read about using a "Y" and not a "T" but it's really hard to follow the written description of this layout. A picture/drawing would be so super helpful to all of us! I for one, and I'm sure there are many others, will really appreciate this, now and in the future!

3) How should this be wired? I would expect that a different fuel pump could possibly be wired differently. I've also read discussions about bypassing relay(s) as to avoid their potential failure. A narrative discussion with a wiring diagram for this would be super helpful!!

I've read a bunch of these forums posts and there are mixed messages with differing solutions. My goal in writing these questions is to resolve this issue for others, and all of us included, to learn how to address this known issue.

As I mentioned above, please don't reply unless you have really done this successfully. I'm sorry to sound bossy but after reading tons incomplete and contradictory posts on this topic, I'm hoping that we can get a "Samba Service Bulletin" written for fuel pumps on these early fuel injected motors like the ones in the 411s.

THANKS BIG TIME!!!

[/u]

[raygreenwood]

The original pumps are excellent quality and suited well to the car. I have numerous of them including one NOS.

For me the usefulness of the stock pump ends there. Not putting any sleight against Jims work.....but unless you for some reason need the system to be 100% stock in every way for show sake.......there is no reason to keep using the stock pump in my book.

Out kn the road its:

1. Its hard to find one
2. Remans of any level can have reliability issues
3. They are prohibitively expensive
4.there are many excellent options

The risk for me on a long trip.....is that it goes out.and even though you have a spare on hand....that may be a spare of questionable longevity because its 40 years old and being kept in a bag oiled. This may force you to have to make connections out on the road in the middle of nowhere for a new pump type anyway.

There are certain risks i am not up to taking when its simpler not to. Its bad enough having to live with certain items like 45 year old transmissions.....cant help that....but i can help this.

If this were CIS injection. ...there are not to many even modern day pumps that i would trust at that pressure and flow rate....running long term. I would stay with a Bosch 044 even though its expensive and getting harder to find.

There are several modern pumps that more than fit the bill for D-jet. And there are plenting of options for screw in intake port fottings for everything from nipple for rubber line and clamp to modern nylon (which i will be going to and will be making a connector tutorial by Christmas).

All you need to do is make a bracket, change the run of one Y fitting and wplit the plug into two discrete connectors.
The cost is about $100 max.

I will post part #s later after work. Ray

[mg93108]

Thanks for your reply Ray. I agree that it makes sense to retrofit it. If you wouldn't mind explaining how to do that, that would be great. My son's 411 is currently DOA and he has no vehicle to drive. We'd appreciate whatever advice you could give us. He's a really good guy and he loves this car.

[kirk knighton]

Both of my fuel injected Type 4s have had their original pumps replaced with Vanagon pumps and they work fine, just fine. My 1971 411 is D-Jet and my 1974 412 is L-Jet. Both have the same pump.
When I replaced the one in my 412 it had a NOS Bosch stock pump in it about 3 years old. But it died, just like the one before it, which was a rebuild.
I, too, have a NOS Bosch spare in my garage, but who knows how good a 30 year old pump will be?

[raygreenwood]

I just got in off the road. In the am i will post a few part #s. The Airtex pumps the type 3 guys use will work fine and there are numerous Bosch turbine pumps that work very well from modern cars. Ray

[mg93108]

[KTPhil]

Search the Type 3 forum for this; I think you will find several threads with just what you are looking for.

[raygreenwood]

[KTPhil]

[mg93108]

[raygreenwood]

Vespa93103....was there a new question to go with your repost?

I have successfully used a wide range of pumps on type 3 and 4.....several of them not even because I researched what would fit...but simply because my pump was dead....and I had a pump at hand from another fuel injected car of similar engine size and same or higher fuel pressure. In reality...for basic operation....those two things 90% of the time are all you need to know.

In fact...the first odd pump I ever used on my 411 was from a Nissan 280ZX. I needed a pump...it bolted right up with minor changes and bracket work and a bridge connector to the D-jet pump plug.

Yes...you "can" get into issues of whether the pump pulls more or less amps etc....and you should...but in a pinch....anything that can pump 1 lpm unrestricted and produce 35-40 psi or less...will generally work.

As for your question about the "T" versus the "Y"....there should be no real question.
The factory D-jet system used a "Y" between the return line from the engine, the fuel tank return nipple and the return port on the pump ....on ALL type 3 and 4...every last one of them used a "Y".....there has never been a "T" from the factory. Many digifant cars use a "Y" in the same position for similar reasons.

It is part # 7 in the diagram...311-133-525.

In short...a "T" fitting creates turbulence when secondary flow (from the fuel return from the engine) intersects the main run of fuel flow from the pump. A "Y" prevents this...and can prevent turbulence from reducing flow . The direction the "Y" faces....to prevent this...is also important. Its directional.

This is not just an automotive VW issue. I deal with fluid pumps for liquids of a wide range of viscosity in my line of work...peristaltic, diaphragm and gear pumps. Having a "Y" instead of a "T"...many times is a make or break situation with fluid flow consistency.

Why is this important when its just return fuel? Because that return fuel is critical to keeping volume at the "dish" area where the fuel pump pick up is when the tank is low. The pump is constantly flowing fuel to the return and so is the engine. It needs to flow unimpeded and its even more important on type 3 because the there is a partially covered bowl at the pump inlet point.

I also believe from experience that the inlet flow from return is very helpful to keeping silt away from the pickup tube sock. I get rid of this problem/risk anyway by using an external strainer.


Its for the same reasons they manufacture, sell and specify plumbing "wyes"..instead of just making everything a "T"...and its not just convenience.....its for flow.

When going to a two port (L-jet style) pump without a return port do we need a "Y" or "T" at all.....and why?

When going to a two-port pump like an L-jet pump.....because most two port roller and turbine pumps both have reduced self priming abilities when compared to the D-jet style three port pump....it is sometimes very helpful to have the "Y" fitting to allow the return flow to help form a pool or accumulation of ready ready to allow the pump to draw from.

And when you install the "Y" fitting for a two port pump...it gets flipped from what you see in the diagram above.
WHY does it get flipped?...because now...this is not just a passive flow issue (meaning fuel getting pushed)...now the pump is directly drawing from the "Y" fitting. The whole purpose of the return line "Y" fitting on a two port pump system....is to allow the pump to draw ...essentially...from two ports on the tank in times of need. This drops any potential restriction by half.

This is where things get murky. When reading the myriad of threads and discussions where the "Y" fitting comes up....there are always a handful of people stating.... "thats crap...I have never run a "Y" or a "T" or I use a "T"...and have for 120 years on 10,000 engines at 1 million horsepower...never needed it" ...whatever...dont care. Don't have time to teach physics to everyone.

And yes....you can run without it...generally...and get away with it. Perhaps your two port pump is just low enough compared to tank height to never have a noticeable prime or draw issue...perhaps you have just been lucky and never hit the right stretch of road with a sweeper curve at just the right fuel tank level.

Personally...I dont believe in luck with engines and fuel systems...and I dont drive a piddly type 1 based engine that I can essentially (cost aside)...get serviceable parts for anywhere. As far too many have found out (and not just in VW's)....one gulp of air or one second of pump cavitation at high rpm and max advance....and a hole blown in a piston can ruin your day.

With twin port pumps in D-jet systems, the best way I have found is with an Extra "Y" feeding the fuel inlet just north of the filter. This essentially turns the fuel filter into a much more effective accumulator. I will post some diagrams asap. Ray

EDIT: So why does a roller cell three port D-jet pump self-prime easier than a an equivalent roller cell two port pump?

From what I have found through some testing.....its because of the return port. The return port is essentially the outflow from the relief valve. The relief valve is there to make the pump "self limiting". It keeps the output volume down somewhat....and that creates lower head pressure across the roller cells....which makes it easier to move fuel through the roller cells and allow more fuel into the roller cells...which equates to better actual suction at the inlet port.

In fact...the actual roller cell flow rate ability....of the D-jet style pump....is MUCH higher than the rating....but not in a reliable manner...because of the construction of the pups of that era.

If you want to see this....be sure you are wearing safety glasses and have a fire extinguisher...and a spare pump handy. Just cap off the return port and hook up the pump..essentially making it a two port pump. If you are just using the stock 28 psi regulator...you may be just fine....but the outlet flow from the return line will go up by about 50%.....and the pump will be loud and lose prime very easily.

And....if you are using a regulator from a more modern system that has pressure north of 36psi....the increased volume and lack of relief valve(now that you have effectively locked the pressure relief by capping it off) ....will cause the pump to spray fuel all over the place from every o-ring..effectively ruining the pump unless you havee a new seal set.......ask me how I know...

[mg93108]

Thank you Ray!! You're the man!!

[Lars S]

Great writeup Ray! (as usual)

Thanks!

Lars S
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold

[Methusela]

Does anyone have any info on the fuel pump arrangement on 1974 412s with the L-Jet system? I've seen the pumps on L-Jet Beetles and Buses, which have all been inline 2-port style . . . so that's what I was expecting to see when I crawled under my recently-acquired '74 412 for the first time last weekend.

But instead, on my L-Jet car, the fuel pump is a 3-port style, like a D-Jet Type IV or Type III. From the wiring it looks like it was grafted in at some point, which is never a good sign I know.

Knock on wood it works fine, and the car runs great. But for future reference, for when it inevitably fails, shouldn't it be an inline 2-port pump, like other L-Jet VWs? And if so, will any old L-Jet pump do -- one from a Beetle or a late Bus? (I ask because all the parts houses I checked list pumps for D-Jet Type IVs, and pumps for L-Jet Beetles and Buses, but no one seems to list anything for a 1.8 L-Jet 412 . . . shouldn't it be the same as the other L-Jet cars? None of the Type IV manuals I've found say much about the L-Jet models, so I kind of feel like I'm stabbing in the dark here.)

Any advice on this would be greatly appreciated. I've owned and driven a/c VWs all my life, but am new to the Type IV world and want to know exactly what I'm dealing with!
_________________
+++++++
lots of VWs, two Panhards, and a sun-baked Nissan truck

[raygreenwood]

[Methusela]

Thanks, Ray! Much appreciated!
_________________
+++++++
lots of VWs, two Panhards, and a sun-baked Nissan truck

[titan3c]

Question: My car, a 71 sedan has 127,000 miles on it, and has the original fuel pump, and seems to work just fine. I do notice that it starts easier with a full tank. When the tank is low it is slow in getting started. Should I expect this pump to fail, considering it age and usage? Bob

[Lars S]

127000 miles thats about when my pums used to start leaking at the big seal around the top...often after having been left dry for a while.

I dont think your starting issue has to do with the pump.
I always "prime" the system before a cold start by turning the ignition on and off 2-3 times making the pump run some seconds, building up the pressure before cranking and it starts wery quickĺy after that.

Lars S
_________________
Porsche 914 -72, Bahia Red daily driver
VW411 2-d -70, White, sold
VW412 4-d, -73, Gold Metallic, daily driver
Suzuki T500, -69, Candy Gold, sold
Suzuki K50, -77, Black, daily driver
BMW R69S -69, White, sold
Husqvarna 118cc, -47, Black, Sold

[titan3c]

I'm glad you said that. That's the way I start mine in cold weather or after it sits for a long time. I always thought my cold start valve wasn't working before I started doing that. I'll check my fuel pump to see if it's leaking where you mentioned. If it's leaking couldn't you smell gasoline? Bob

[raygreenwood]