BBi fuel pump problemconbt

The Boxer is on the lift, and I started on some simple tests. The safety switch was disconnected, so that I can run the pumps with the ignition on.......car not started.

Ignition on........I can hear the pumps. I felt them with my hand and both where working. Voltage across the pump terminals was 10.8 V each.

Ignition off.......I disconnected the ground wire from each pump, where it attaches to the frame. Ohm reading across the pump terminals was 0.5 Ohms each.

Things now get interesting! I thought of checking the votage, at the positive terminal of each pump, with ignition on, and ground still disconnected.

I turned on the ignition, and was surprised to hear the left pump working.........with NO ground. Underneath, I felt each pump, and the left one was on!!!!!! I measured the voltage and got: Right = 11.63V; Left = 11.33V (and running).

I then touched the ground wire to ground, of the right pump, and, as expected, saw a few sparks, and the pump started working........disconnecting the ground wire, the pump stopped.

I tried this to the left pump, even though it was running. I noticed a little difference in the sound, with wire grounded. However, the pump was running all along.

Is there a short in the left pump?

The commutater needs a ground....

I would suspect the pump is grounding thru an unidentified source allowing a complete circuit..

"The commutater needs a ground...."

I agree. Therefore, the ground circuit, in the pump, must be finding a different way to a ground.........probably through the body of the pump, I would suspect. This, I feel, is not right..........suggesting an internal short.

Isn't the pump mounted on isolator blocks?

The pump normaly grounds thru the body...so any ground to the body acts in the same manner as the ground wire.

If you look around I suspect you will find a ground path of some type, mabybe even thru the metal braided fuel hose?

JRV: The pump is mounted to a steel bracket, that mounts on the frame, with cushions (rubber insulators) between.

I just tried another test:

Ignition on.......ground disconnected.......left pump running, as before. I then placed the + probe of my meter, to the + terminal of the pump. I recieved the 11V reading when I placed the - probe to the body of the pump, even the body of the accumulator, and filter.

On the right pump, not running with ground wire disconnected, the only place where I got a voltage reading, was when I placed the + probe on the + terminal of the pump, and the negative probe onto the chassis.......measuring battery voltage.

"The pump normaly grounds thru the body...so any ground to the body acts in the same manner as the ground wire." I do not agree, in this case, with the BBi. The pump has 2 separate terminals; one positive, and one negative. It is the negative terminal that goes to a chassis ground, completing the circuit. Remember, the pump body is insulated.

I think you have a short there. Have you tried switching the two relays in the fuse box? Doyou still get the same readings>

has anyone noticed how many posts there seem to be each time a Boxer has a problem. My old thread was over 60 posts...this one , continued from the general discussion section, sounds very promising. I think a new fuel pump will solve the problem...and then again, how about switching the fuel pumps themselves?

Coach: I plan on switching the relays, but I stripped 2 of the Phillips screws of the floor panel holding the relays.....need to get them out first.

My first concern was to get to the source.......namely, the fuel pumps.

I just checked the continuity, between the neg post, of the fuel pump, and that of the body of the fuel pump. The left pump shows continuity, but not the right pump.......hence I feel there is an internal contact (short), of the neg side, with the body of the pump.

It appears that the 12V+ feed is normal to both pumps.

When you had your problem, being one on the + feed side, did you get an erradic signal going to the fuel pump(s)? With all the things done, I don't recall if anyone tested the voltage right at the fuel pump itself.......did they?

Bad, or weak, fuses and relays will affect the + supply signal to the fuel pump. A bad fuel pump will affect the fuel output directly. However, both can show similar symptoms......since, the overall result would still be improper fuel delivery.

I am trying to do this in an understandable (to me) sequence.

Coach: I think us Boxer owners are a RARE breed.......we like to work on our own cars, more than owners of other models!!!!!!!! Maybe we are just old and stubborn?

I ordered 2 fuel pumps.....should get them this week. That will leave one as a spare.

Henry - do you have steel braided fuel lines leaving the pump? This may represent a path to ground.

I am not sure I understand your concern. Activation of the pumps is controlled by supply +voltage to the terminal (through the fuse and relay). Whether the pump is providing internal grounding may be academic if it is working. Perhaps it is the right pump that, by not providing the ground, is malfunctioning. If there were an electrical short within the pump, you would blow a fuse. On the surface, it appears that the pump is doing exactly what one would expect it to.

Jim S.