new bosch fuel pump not pumping on engine test stand with 3.2 carrera???

[marlinaness]

I thought I had a bad fuel pump, so I bought a new Bosch for a 3.2 carrera. Engine is on a test stand.

I originally did not get any fuel pressure when using a small gas tank that fed a hose hose feeding the fuel pumps. I can hear both fuel pumps running, but neither wants to pump anything out the pressure end of the pump. I tried them both 1) connected to the engine, 2) connected only with the filter, and then 3) connected with nothing on the pump outlet end. I verified fuel was in the pump.

I am connecting the two leads to the battery charger. Is there a secret? Do I need to ground the case also? I can't believe they are both bad.

Has anybody else experienced this?
recommendations?
thanks
Marlin

[boyt911sc]

Marlin,

Are you connecting the FP wire terminals correctly? Positive (red) @ + and ground (brown) @ - terminal. Is the FP running at all? Could you post some pictures? Is the FP made in Germany or somewhere else? Keep us posted.

Tony

[Joe Bob]

Red + to + on the battery, brown or black - to negative on the battery, if it doesn't spin....give it a whack. Still no spin, return it or give it the float test.

[marlinaness]

yes,
I connected straight + to + and neg to neg on the battery charger. I can hear both the Bosch OEM correct fuel pumps spinning. THey are both Bosch like shown on Pelican for the 85 Carrera. Even though it is spinning, nothing comes out. I tried filling both sides to make sure it was full of fuel and that didn't help. If it is spinning I just can't see how it wouldn't push fuel. It did get warm to the touch after a few seconds so somehow the fuel is just not priming or something (even though it is under gravity feed.)

I opened up another one I had that leaked and they are pretty straightforward with small rollers at the bottom that force the fuel. I have not tried a float test. What is a float test?

I was really surprised to discover that the fuel goes through all the armatures and electrical parts. I would not have guessed that.

thanks again for the recommendations
Marlin

[Joe Bob]

Float test is tossing it into the lake or other large body of water.....%^b

[marlinaness]

oh, I thought it might be submerging the whole thing in gasoline and then testing it since many of these are submersible in gas. That would help ensure no cavitation (if that is the problem). I have never heard of a fuel pump that spins but doesn't pump.
thanks
Marlin

[Joe Bob]

They do that when the vanes wear out. Usually it's a gradual reduction of pressure. Something internal may have broken.

You could try and open it up and see if anything is obvious. The high pressure FI pumps aren't all together user friendly...but can be pricey as you may well know.

Did you buy new or used?

[marlinaness]

the first one was used, but I was informed it was good from a reliable Pelicaner.
the second was new from Bosch.

So, I can surmise that my procedure for testing is ok and I just got unlucky? In other words gravity feed with a simple hose and it should should out the other end.

On the one I opened I saw smaller roller bearings that force the liquid to move out the exit port as they are moved in a circle. seems simple and can't see how it would go bad.

I think I will try one more "submersion" test to make sure it is well primed. I suppose if I can use gas, I can use water just as well for the test.


thanks
Marlin

[Porboynz]

Love to see a photo of your test setup. If the fuel pump inlet is gravity fed from your test fuel tank then I would suggest connecting an actual auto battery rather than a battery charger, that way you are sure you are getting the correct voltage and enough current.

[marlinaness]

I am travelling all week, but will take pictures when I get back. Pretty simple set up.

Since I wasn't having any luck so far, I decided to try a submersion test, so I put the entire pump in water and hooked to the batter charger. Still only a few bubbles and the same lud noise. I also did try a battery on the car, but it only clicked after the water test. Put it back in the water with the battery charger and noticed it was drawing about 10 amps, probably about right for a Bosch for this setup.

I ordered a new pump. Hopefully it will be here when I get back.
Marlin

[Quicksilver]

A battery charger is not a good power source for testing any component. To charge a battery you need a higher voltage then the battery and then you run the current through the battery backwards to charge it.

Unless you add a battery to your test rig to stabilize the voltage who knows what kind of power you are getting. It may be way over voltage and is almost certainly rectified AC instead of DC.

As mentioned before, the 3.2 pump is primed by gravity so pulling fuel up from the source is outside of its design parameters. Also the pump is cooled and lubricated by the fuel running through it. If you ran the pump for too long with nothing in it it could be damaged.

[marlinaness]

thanks for the insight
I started all the testing with a car battery on the test setup and the fuel was gravity fed, but it didn't work although I could hear it turning quite loudly, much more so than any other I have ever heard. All the tests involved gravity feeding the pump fuel with the final test with it submerged in water to make sure it would be cool and no cavitation. Only in the last few tests did I use the battery charger. I used the battery charger for additional testing after I removed the fuel pump.

I will probably dissect it to see what I can learn.

I will use only a battery on the new one.

thanks
Marlin

[ShakinJoe]

If these things were used at some point and not properly "pickeled" when put in storage, they will not work.

[Porboynz]

Submerging in water probably will not harm the pump but its really not necessary or to be encouraged. The cooling is done by the fuel inside the pump. Submersible fuel pumps designed to sit inside a fuel tank are very different in design and operation to Porsche Bosch fuel pumps. I use kerosene as a test liquid as its approx the same viscosity but safer to work with than petrol. No rust problems either and any remaining kero will mix OK with petrol. If the pump is really running you will feel it jump in your hand when it starts as the armature spins up. If someone has dismantled the top section where the rollers are and not reassembled it correctly then you will get low or no fuel pressure.

[marlinaness]

good insight. No movement when I hooked up power. Just the noise. So, I consider it junk right now.
thanks
Marlin

[Porboynz]

You do have to wonder what would make a noise if the armature is not spinning, most peculiar. Maybe its spinning but very slowly? (called cogging I think)