Ampohm BZX 1019 from fuel pump - what is it?

[Lewin A.R.W. Edwards]

I'm repairing a fuel pump from a friend's 1971-vintage car, and I
encountered this component that I can't identify. It's a black plastic
cylindrical body with the part# (AMPOHM BZX 1019) silkscreened on it,
and two stranded wires (red and black) coming out of one end.
ampohm.co.uk has no information. It looks rather like some kind of
custom hybrid part.

The pump is basically an automatically-oscillating relay in which the
contact arm also flexes a diaphragm pump. When the coil is energized,
the solenoid pushes out, opening a set of contacts and de-energizing the
coil. Spring pressure returns the contact arm. There's also a kind of
pneumatic feedback system acting on the contact arm, that keeps the
circuit open if the pressure in the fuel line is above some threshold,
but that's not germane to the issue.

The pump wasn't working at all, due to crusty deposits on the contacts.

The unknown component measures as open-circuit on every scale I can
measure; even capacitance and inductance. I have seen mention of diodes
in the fuel pump (there are -ve and +ve ground versions of the car, and
the shop manuals say "connecting the wrong way will destroy the diode
inside the pump"), so I am _assuming_ this part is a snubber diode,
failure of which caused rapid arc-induced aging of the relay contacts.
For the time being I sanded off the oxides and put a 1N4001 diode
(meatiest thing in my junkbox) across the coil, and that has him running
at least. But I think the 1N4001 is very under-specified for the job,
and I'd like to have a better idea what this part originally was and
what I could use as a sub. One thing that puzzles me is that the black
wire from this weirdo part went to the ground side of the coil. If black
was supposed to indicate the diode anode, then it's wired in the reverse
orientation from what it's supposed to be.

Any insights appreciated.

 

[Chaos Master]

Data received from Lewin A.R.W. Edwards on port COM1:

I'm repairing a fuel pump from a friend's 1971-vintage car, and I
encountered this component that I can't identify. It's a black plastic
cylindrical body with the part# (AMPOHM BZX 1019) silkscreened on it,
and two stranded wires (red and black) coming out of one end.
ampohm.co.uk has no information. It looks rather like some kind of
custom hybrid part.

BZX1019 looks like a ZENER diode.

[]s
--
Chaos MasterŽ, posting from Brazil. REPLY TO GROUP!
"People told me I can't dress like a fairy.
I say, I'm in a rock band and I can do what the hell I want!"
-- Amy Lee

Note: this e-mail address goes to /dev/null.

 

[Lewin A.R.W. Edwards]

Chaos Master wrote:

Data received from Lewin A.R.W. Edwards on port COM1:
cylindrical body with the part# (AMPOHM BZX 1019) silkscreened on it,
and two stranded wires (red and black) coming out of one end.

BZX1019 looks like a ZENER diode.

Any idea what voltage?

 

[Chaos Master]

Data received from Lewin A.R.W. Edwards on port COM1:

Chaos Master wrote:

Data received from Lewin A.R.W. Edwards on port COM1:
cylindrical body with the part# (AMPOHM BZX 1019) silkscreened on it,
and two stranded wires (red and black) coming out of one end.

BZX1019 looks like a ZENER diode.

Any idea what voltage?

10V or 19V, I think.

[]s
--
Chaos MasterŽ, posting from Brazil. REPLY TO GROUP!
"People told me I can't dress like a fairy.
I say, I'm in a rock band and I can do what the hell I want!"
-- Amy Lee

Note: this e-mail address goes to /dev/null.

 

[nospam]

"Lewin A.R.W. Edwards" <larwe@larwe.com> wrote:

Chaos Master wrote:

Data received from Lewin A.R.W. Edwards on port COM1:
cylindrical body with the part# (AMPOHM BZX 1019) silkscreened on it,
and two stranded wires (red and black) coming out of one end.

BZX1019 looks like a ZENER diode.

Any idea what voltage?

There are some zener diode series the part numbers for which begin with
BZX. I don't think your part is particularly likely to be a zener diode
from the BZX part number.

AMPOHM seem to make a range of encapsulated parts for automotive
applications, mostly capacitors.

In this application I suspect a simple diode would do the job. A diode
wired to allow current to circulate through the coil when the contacts open
would prevent contact arcing. It would also delay the return of the
solenoid under spring pressure a little or reduce the frequency the pump
buzzes before it gets regulated. I suspect that is not a bad thing.

The peak current in the diode will be the same as the current in the coil
which you can measure or work out from measuring the coil resistance.

If slowing the collapse of current in the coil is a bad thing for some
reason then the part could be a resistor/capacitor snubber just to protect
the contacts, or perhaps a zener and normal diode in series.

If you are convinced the BZX 1019 part is dead try breaking it open to see
what is inside.

 

[Lewin A.R.W. Edwards]

Hi,

AMPOHM seem to make a range of encapsulated parts for automotive
applications, mostly capacitors.

Right, I browsed their www site, but they don't provide much specific
info.

In this application I suspect a simple diode would do the job. A diode

That was my _guess_ but I wanted opinions. I couldn't see why a zener
would be necessary here, since it's known that the kickback voltage
will be the opposite polarity from the battery pulse.

The peak current in the diode will be the same as the current in the coil
which you can measure or work out from measuring the coil resistance.

It's hard to measure I in-ckt, but the coil has a resistance of about
6 ohm, so I can take it from there if it's a simple Ohm's law
calculation. But I thought the kickback voltage could be considerably
more than the supply voltage - like, hundreds of volts. What regulates
the speed with which the magnetic field collapses?

If you are convinced the BZX 1019 part is dead try breaking it open to see
what is inside.

It's really REALLY tough material, but I'll try. Thanks!

 

[nospam]

larwe@larwe.com (Lewin A.R.W. Edwards) wrote:

Hi,

AMPOHM seem to make a range of encapsulated parts for automotive
applications, mostly capacitors.

Right, I browsed their www site, but they don't provide much specific
info.

In this application I suspect a simple diode would do the job. A diode

That was my _guess_ but I wanted opinions. I couldn't see why a zener
would be necessary here, since it's known that the kickback voltage
will be the opposite polarity from the battery pulse.

The peak current in the diode will be the same as the current in the coil
which you can measure or work out from measuring the coil resistance.

It's hard to measure I in-ckt, but the coil has a resistance of about
6 ohm, so I can take it from there if it's a simple Ohm's law
calculation.

For the current it is (assuming the coil is powered long enough to reach
maximum current). .

But I thought the kickback voltage could be considerably
more than the supply voltage - like, hundreds of volts. What regulates
the speed with which the magnetic field collapses?

The current in the coil wants to continue to flow, it will generate a high
voltage if you try to stop it. The diode allows the current to continue to
flow through the diode and coil in a circle. There is no 'kickback' because
you are not trying to stop the current.

The initial diode current will be the same as the coil current when the
contacts opened. The circulating current does work against the coil
resistance and diode voltage drop. The current decays as the energy stored
in the coil is turned into heat. The magnetic field reduces with the
current.

If you put a zener diode in series with the diode then the 'kickback' is
limited to the zener voltage and the circulating current has to work
against the zener voltage and will decay much more quickly.

The frequency the pump 'buzzes' at would be higher with a zener diode. That
would probably increase the pumping capacity maybe that is how it is
supposed to be?

If the BZX 1019 is a diode and zener in series then you would not measure
anything with a meter. You would need to apply more than the zener voltage
to get any current to flow. I would try to test if on a bench power supply,
with a low current limit wind up the voltage to see if and when current
starts to flow.

 

[Watson A.Name - \"Watt Su]

"Lewin A.R.W. Edwards" <larwe@larwe.com> wrote in message
news:dC61d.25711$Wv5.1114@newsread3.news.atl.earthlink.net...
[snip]

Any insights appreciated.

Since Ampohm seems to be a capacitor maker, wouldn't it seem prudent to
assume it's a capacitor? And that's usually what's put across these
kinds of things, for RFI and spark suppression. I would try to get
another one from a junk yard or some other source, and measure both to
see if the original is okay. If not, then replace it.

 

[Lewin A.R.W. Edwards]

Since Ampohm seems to be a capacitor maker, wouldn't it seem prudent to

I thought this initially, but if you look at their web site, they also
make "other automotive noise suppression devices". Also like I said,
the shop manual says there is a diode in the pump - and this is the
only possible thing that could be the diode.

I tried putting the unknown component across a 60Hz 15V p-p AC signal
and it didn't distort the waveform at all. So I doubt it is a cap.

kinds of things, for RFI and spark suppression. I would try to get
another one from a junk yard or some other source, and measure both to

This is a pump from a 1971 Midget, not commonly found in junk yards :/