Problems after tii fuel pump swap - UPDATE 2

[Ensign]

7 minutes ago, jgerock said:

Are you sure the expansion tank isn't where you have a leak?  That's where mine leaked from rust at a seam. 

I'm quite sure. I can watch fuel seep from the seam in the pump. Also, I did not have a leak with the new pump installed.

Edited November 8, 2018 by Ensign
typo

[Ensign]

12 hours ago, Einspritz said:

IIRC there is an O-Ring seal  there in the plastic head.

 

interesting...

I guess I have nothing to lose. I'll open it up and take a look.

[Ensign]

Bav Auto was nice enough to give me a new 5-series fuel pump. Unfortunately the results were the same as with the first pump. I would like to continue the trouble shooting, and get the engine to run properly with the new pump, but the snow is coming and I need to get the car into storage for the winter.

So, I am working on the OE pump to stop the leak and reinstall. EINSPRITZ remembered an o-ring seal in the pump, so I removed the end cover with the inlet port to take a look. (see photos below)

The o-ring sits in a tear-drop shape groove. I measured the existing ring as best I could and ordered 5-pair of o-rings in varying sizes, plus and minus of what I measured.  I got lucky today and knocked the cover on the floor and, to my surprise, a steel plate separated from the cover, exposing a second o-ring. (sometimes it pays to be clumsy)

The o-rings I used are 2mm x 34mm Buna-N 70 from the O-Ring Store, although a 33mm or 33.5 mm may actually be the correct size.

If I can stand the cold tomorrow, I’ll remove the 5-series pump and reinstall the OE pump.

 

 

 

 

 

 

[PaulTWinterton]

Well isn't that cool.  I wonder what other restoration options are possible on the old pumps.  I have one that is extra-noisy but functional.  It would be fun to rebuild it to "new" condition.  I wouldn't hesitate to use it if it was reliable.

 

And too bad about the 5series pumps.  What's that about?  A bad batch?

 

 

[stephers]

I have done the same to these pumps, replaced the o rings and after that, they work well, Porsche and Alfa use a very similar pump.     Make sure that steel plate is very flat and smooth. I use 400 then onto 600 wet and dry on a piece of plexiglass and sand it so it is perfectly flat and smooth.     These pumps are pretty robust.

 

Thanks, Rick

[Einspritz]

Rick;

 

Do you recall what size O-Ring you used?

[Einspritz]

To follow up on your original question, and one I have addressed elsewhere, is the fact that the OE wiring for the original fuel pump is insufficient for the amperage draw by some 12%. Add the fact that your wiring harness is probably original and the resistance goes up substantially. A slower running pump (either one) will produce less than the rated output.

 

If you can get the proper green / white wire, it should be 3mm or larger in order for the voltage drop to be de-minimus. If not, then 10Ga. will suffice. The ground wire is so short (at the trunk) as to not have any effect, but it is always wise to replace that too for good measure.

 

The differences in the pumps are that the OE pump produces Greater than (or no less than) 103 L/hr @ 5.0 Bar and the replacement produces 110 L/hr. @ 3.0 Bar. And yes, 3 Bar SHOULD be enough, at least for anything than WOT. The fuel pressure is limited at the back of the injection pump, so you might want to test the pressures to see if the valve is operating properly. A low pressure will affect the the idle as you have described.

 

The OE pump is also used on injected 6 cylinder cars of the era, so the output is more than sufficient.

 

HTH

[jimk]

1 hour ago, Einspritz said:

The differences in the pumps are that the OE pump produces Greater than (or no less than) 103 L/hr @ 5.0 Bar and the replacement produces 110 L/hr. @ 3.0 Bar. And yes, 3 Bar SHOULD be enough, at least for anything than WOT

I have reservation that the original pump is rated at 5 bar flowing 103 l/hr.

This early design pumping system from the tank pump operates at 2 bar at all times and the max engine consumption isn't over 60l/hr. The 3 bar pump is entirely capable of engine demands at the system operating pressure.

[Einspritz]

Page 3.

Mini-Katalog__EKP.pdf

[jimk]

Sure, but not the original oem pump selection, I would believe.  Bosch would have gone for a replacement pump that fits a number of cars.  The 2 bar system has been history for quite a while.

A point of reference: A pump rated at 110 l/hr @ 5 bar would pump more than 110 l/hr at 3 bar, but not a lot more because positive displacement pumps have a steep performance curve.  So using the conservative 5 bar flow, 110 l/hr, that would be good for 320 hp, a bit more than the Tii would put out.  60 l/hr is good for 175 hp and the air needed at 12:1 Air to Fuel ratio would need more than the Tii pumps at 7250+ rpm.

So the 3 bar pump should do it.  I use one to supply fuel to the S14 and have dynoed at more than 175 hp 

[Einspritz]

11 minutes ago, jimk said:

The 2 bar system has been history for quite a while.

 

The 2 Bar system is from the pressure limiting valve at the back of the injection pump head, not the fuel pump itself. While the modern EFI systems run, IIRC 50-60 psi, which is what the injector injects at, where the Kugelfischer pump takes that 2 Bar fuel pressure and increases it to ~450 psi. which is far superior for atomization and only bested by direct injection systems.

 

The OE pump is used on many cars and BMWs including the 6 cylinder cars and the 2002 Turbo. My back of the envelope calculations show that a Tii will use roughly 13.2 L/Hr, the 6 cylinder cars ~19.8 L/Hr. and the 2002 Turbo 20.4 L/Hr at 8 Lb. boost. So sure, the replacement pump should work, but sometimes, as in this case, does not.

 

From Page 2:

The pump always conveys more fuel than the maximum amount needed by the engine so that the necessary pressure can be maintained in the injection system under every operating condition. Excess fuel is returned at another point to the fuel tank.

 

In this instance where the OE pump works and the replacement does not, I would test the check valve at the back of the injection pump head to see if it is up to the test or is lazy. That would account for the 3 Bar pump not working well and the OE pump being able to overcome the lazy valve with higher capacity pressure and volume.

[Son of Marty]

Just like when you go to the doctor he takes your vital stat's at this point we need to see your k-fish stats IE  fuel pressure and volume. I think Einspritz is on to something with the pressure valve. 

[jimk]

28 minutes ago, Einspritz said:

Tii will use roughly 13.2 L/Hr,

I think it's more like 43 l/hr at 126hp output using 0.55 lb fuel /hp-hr burn rate.

[ray_]

21 minutes ago, jimk said:

I think it's more like 43 l/hr at 126hp output using 0.55 lb fuel /hp-hr burn rate.

 

That's pretty bad gas mileage.

 

[PaulTWinterton]

3 hours ago, Einspritz said:

I would test the check valve at the back of the injection pump head to see if it is up to the test or is lazy.

 

What test would you use to determine if the check valve is lazy or correct?