Ferrari Forums banner

BBi fuel pump problemconbt

5601 Views 27 Replies 0 Participants Last post by  James Selevan
The Boxer is on the lift, and

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 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?
1 - 20 of 28 Posts
The commutater needs a ground.

The commutater needs a ground....

I would suspect the pump is grounding thru an unidentified source allowing a complete circuit..
"The commutater needs a gr

"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

Isn't the pump mounted on isolator blocks?

The pump normaly grounds thru the 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

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 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.
See less See more
I think you have a short there

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 po

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 th

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.
See less See more
Coach: I think us Boxer owner

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 brai

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.
Jim S: There are steel tubes,

Jim S: There are steel tubes, and braided lines leaving the pump. This is the source of the "extra" ground. The more I think about it, the more I agree, that this may be academic.

I would like to start with the basics, and check the power supply first, but I need an in-line ammeter that is capable of up to 30A (my VOM only goes to 10A). Then, I would check the fuse connections, and relays. I believe the best way to check, all the above, is with the in-line ammeter.

Does someone have a source for must be the best!!!!!!!!!

The pumps, if working c

The pumps, if working correctly...should draw a constant 8-9amps. Anything more, IMO, would represent an internal problem.

In terms of the best DVM/DVOM, Fluke is the only choice. Likely, you'll need to purchase an additional shunt to read amperage over 30.

Hi David: I have an older Flu

Hi David: I have an older Fluke digital only goes to 300mA.

Also have a new Simpson analog meter, that goes to 10A..........sometimes, the needle is easier to understand.

Could you explain a shunt.......and how I would use it?

Henry and David - An easier wa

Henry and David - An easier way to check the current draw is to understand that 1) with a 16 ampere fuse (+/- a few percent), you are not drawing more than 16 amperes and 2) by temporarily installing an 8 ampere fuse, you can verify whether you are below 8 amperes (the fuse does not blow) or between 8 and 16 amperes (the fuse does blow).

That said, under normal use, if the fuse is not blowing, then the pump is likely working appropriately. A short across the pump's armature, or internal short to grown, will lead to hundreds of amps for a millisecond or so. A pump that seizes will quickly look like a short to ground and blow the fuse (no back EMF to create impedance to current flow).

Thus, it seems that the pump is working fine. If the injection system is starving for fuel, then you have either a bad pump, fuel distributor, etc.

I would not try to measure current drawn by the pump, as the amperes drawn will depend on load (instantaneous fuel consumption, pressure, etc.).

One observation - the leads connecting the positive voltage to the fuse block get EXTREMELY hot. This should be corrected. First, make sure someone has not removed the fuel pump fuse block (the separate middle fuse block) and inadvertently reinstalled it upside down. This will lead to the entire current load for both pumps flowing through one fuse only! The bus connecting the two fuses should be on top, not the bottom of the fuse block. Second, I would remove the tab connector from the top of the fuse block and solder/splice a splitter on the incoming red (positive) voltage line, connecting positive voltage to both tabs of the fuse block. The original design had a single tab providing current for both pumps. Finally, I would use a dremel and brass brush to carefully clean the tabs and fuse connector to reduce contact resistance.

If you have questions about the above, please ask and I will discuss with greater dealer.

Jim S.
See less See more
Oh, by the way, you asked abou

Oh, by the way, you asked about the shunt. Find your way to a Radio Shack or electronics store and purchase a 1 Ohm (approximately) 50 watt resistor. All these specifications are approximate (not critical). You must know what the resistance is, but you can measure this later.

Place the resistor in series with the fuse connector, such that all of the current flowing through the pump must flow through the resistor. Assume a 12-volt system, with 12 volts applied to the pump (which is not the case, but first approximation). By measuring the voltage across the resistor you can calculate current. Ohm's Law; Voltage = Current x Resistance. Measure the voltage across the resistance, divide by the resistance (for example, if 1 Ohm) and Presto- you have current in Amperes. The resistance of the pump is close to 1 Ohm, thus the shunt resistor will act as a voltage divider, and some of the 12 volts will be dropped across the resistor. But I am making this too complicated. Just put the resistor in series with the pump, measure the voltage across the resistor, and you will be able to calculate current flow. The pump will not be operating at the full 12 volts (some of the voltage is dropped across the resistor), but it will be close enought for government work. If you really want to know how to do this accurately, ask and I will organize my thoughts better, and give a precise explanation.

Jim S.
See less See more
>>I would use a dremel

>>I would use a dremel and brass brush to carefully clean the tabs and fuse connector to reduce contact resistance. <<

Fully agree this is a problem, not only on this particular circuit or Ferraris, but on many Italian cars. These blocks were going bad on new cars that were driven alot decades ago. IMO more contact surface area is the solution for excessive heat (resistance) across the circuit. I offered one solition to afford more contact surface area previously and there are plenty more.

Regards, JRV
Guys: Frankly, I just want to

Guys: Frankly, I just want to keep this simple, if I can.......I am not an engineer......nor, do I want to become one.

My plan is simple: The problem is in either the current flow to one, or both, the fuel pumps (elecrical), or the fuel output circuit, from the fuel pump (mechanical).......this would include the pump, FDs, warm-up regulator, etc.

My thought process needs to know WHAT exacly the problem is, before I understand how to solve it.

So, the first course of action would be getting the voltage readings at various stages, from the battery, to the fuel pump. I plan on using the wiring diagram to find the source of power to the fuel pump. I will then check the voltage (comparing to the battery voltage), to each connector, as it goes to the fuel pump..........the fuel pump being disconnected, at first. If any terminals are corroded, etc., then the voltage should I correct, in this assumption? This will rule out power source problems to the relay, and fuse, and to the fuel pump.

If the above are OK, then I can assume good power to the fuel pumps. Then I will have to check the mechanical side.........that being the pressures of the fuel pump, etc.
See less See more

yes this stuff can g


yes this stuff can get complicated in a hurry.

However it's not about becoming an electrical engineer, it's more about knowing the differences between real and imagined problems and rectifying actual existing the red hot one goes along thru a diagnostic process to eliminate anomolies that can act in concert to actually create problems. It is very common to find that "a problem" is in actuality several or many problems acting together simultaneously to create "the problem" such as "car won't start".

By systematically elimnating individual issues as one works thru a situation one finds in many cases that "the problem" is permanently resolved rather than temporarily solved.

Regards, JRV
See less See more
Well, I just recieved my new f

Well, I just recieved my new fuel pumps today. Resistance bench tests reveal: + to - is 1.6 Ohms; + to pump body is 1.6 Ohms; and, - to pump body is zero, or Jim S, and JRV are correct, regarding the left pump being OK (since the ground is coming also throught the body)........the right pump showed no connection between the - terminal and the body of the pump.

The fuse that gets hot actually goes to the right pump........still could be connections.

When I stated my course of action being, voltage checks at different levels, after more thought, I realize that these will all be the same. It is the "resistance" somewhere, that is causing the increase amperage.

Hence, I will follow each wire and connection from the source, starting with the battery, and check for resistance. Does this make sense?

Looking at the wiring diagram, the voltage source starts at the battery (+), with a separate wire going to a "Shunt for Ammeter". From here it goes, as a single wire, to the top left of the fuel pump fuses. Anyone know where the Shunt for Ammeter is? According to the wiring diagram, this is junction where most of the + wires come from.
See less See more
The shunt is under the floor b

The shunt is under the floor board on the pass side.

Regards, JRV
1 - 20 of 28 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.