Emulate injectors - how?

I know nothing of LPG conversions (but I do know something about
back-EMF/inductive kick). I guess I'm left wondering how someone doing
the conversion knew enough about putting in the resistors to fool the
computer but didn't know that the lack of inductive kick would create a
computer problem (i.e., didn't know enough to do a totally successful
real-world conversion).

But I guess that doesn't help you. I hope someone presents you with the
answer (which it would seem would be simple and off-the-shelf rather
than you having to re-invent the wheel so-to-speak).

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')


Peter wrote:

> Dodge Durango 99 5.9L, converted to run on LPG (single point). When running
> on LPG injectors are disconnected to prevent them from working (or rather
> the common positive lead is routed thru resistor so that voltage drop on
> injectors is insufficient for them to operate), and naturally PCM complains
> about open injector circuits. Alldata is pretty vague about P0201-P0208
> codes, and only says "if induction kick is not detected PCM will set the
> code". Apparently it checks not just for correct resistance but also for the
> 'inductive kick'.
>
> Anybody knows how to properly emulate injectors on this engine?
>
> Peter

Peter wrote:

>>just buy an emulator! i know AEB make them for 4, 6 and 8 cylinder
>>vehicles. wireing it in takes under an hour too

That's what I'm talkin' 'bout when I posted "I hope someone presents you
with the answer (which it would seem would be simple and off-the-shelf
rather than you having to re-invent the wheel so-to-speak)".

> Fairly pricey. A good 4-cyl emulator with coils instead of resistors will
> cost about 70$ (equivalent of). Do you know where in EU I can mail-order
> them for less?

By the time you got thru buying parts and taking the time to wire up and
debug your "one-of-a-kind" design, you'd wish you had chosen the simple
off-the-shelf solution. Of course, nothing wrong with trying to find a
better price.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

In message >, TBone
> writes
>
>
>"Peter" > wrote in message
...
>> >> Why don't you just disconnect the fuel pump and let the injectors
>operate
>> >> normally.
>> >
>> > I'm not sure that'd be wise. Many injector designs depend on fuel flow
>to
>> > cool the solenoid windings (i.e., to prevent them overheating and
>> > cooking).
>>
>> I'm not sure it's a good idea, too. Fuel pumps are designed to work
>> continuously, and disconnecting it could be yet another reason for CEL to
>> come on.
>
>
>While it is possible that the fuel injectors may overheat, the CEL will not
>be set by the fuel pump being disconnected.
>
There may be a fuel pressure sensor which would be triggered IIRC late
Volvo's have one. Incidentally my fuel pump does not run continuously.
There is a pressure switch on the rail which controls it. If you listen
you can hear the pump start up then after a few seconds switch off when
first switching on the ignition. I run my LR 4.0 litre V8 with injectors
running and pump off and have done so for 50k+ miles. Switch back to
petrol and absolutely no problem. We did this on the advice of a
technical consultant in this field who advised us that these injectors
do not rely on petrol for any form of cooling or lubrication. However I
don't recall whether he was actually referring to "all" injectors.
--
hugh
Reply to address is valid at the time of posting

On Thu, 2 Jun 2005, Bill Putney wrote:

> By the time you got thru buying parts and taking the time to wire up and
> debug your "one-of-a-kind" design, you'd wish you had chosen the simple
> off-the-shelf solution.

That there is an Engineering Truth. Bill, did I ever tell you about the
turn signals on the UM Solar Car of '99?

On Thu, 2 Jun 2005, hugh wrote:

> Incidentally my fuel pump does not run continuously. There is a
> pressure switch on the rail which controls it.

You're sure you're not seeing a fuel pressure regulator?

> If you listen you can hear the pump start up then after a few seconds
> switch off when first switching on the ignition.

That's how most all electric pumps are set up -- most systems don't toggle
the pump with any kind of a pressure switch, though. The momentary pump
run upon switching the ignition on is just the prime pulse. Usually just a
plain old temp/time pump duration lookup in the ECM, or even just a
fixed-time momentary run.

DS

On or around Thu, 02 Jun 2005 20:06:19 GMT, "TBone" >
enlightened us thusly:

>
>
>"Peter" > wrote in message
...
>> >> Why don't you just disconnect the fuel pump and let the injectors
>operate
>> >> normally.
>> >
>> > I'm not sure that'd be wise. Many injector designs depend on fuel flow
>to
>> > cool the solenoid windings (i.e., to prevent them overheating and
>> > cooking).
>>
>> I'm not sure it's a good idea, too. Fuel pumps are designed to work
>> continuously, and disconnecting it could be yet another reason for CEL to
>> come on.
>
>
>While it is possible that the fuel injectors may overheat, the CEL will not
>be set by the fuel pump being disconnected.

I've heard warnings against firing electronic injectors with no fuel, as
well.

you need an injector emulator. I don't know where you get one, but there
are such things as many of the more modern cars need 'em.

'course, if the computer is putting a warning light on, you could just
remove the bulb...

--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
Beyond the horizon of the place we lived when we were young / In a world
of magnets and miracles / Our thoughts strayed constantly and without
boundary / The ringing of the Division bell had begun. Pink Floyd (1994)

On or around Thu, 2 Jun 2005 23:49:10 +0100, hugh ]>
enlightened us thusly:

>There may be a fuel pressure sensor which would be triggered IIRC late
>Volvo's have one. Incidentally my fuel pump does not run continuously.
>There is a pressure switch on the rail which controls it. If you listen
>you can hear the pump start up then after a few seconds switch off when
>first switching on the ignition.

however, my 3.5 hotwire which may not be the same system runs the pump
initially when you switch on as you describe, and then stops, but AIUI this
is because it detects no ignition activity, but when you turn the engine the
pump starts again and appears to run continuously thereafter.

>I run my LR 4.0 litre V8 with injectors
>running and pump off and have done so for 50k+ miles. Switch back to
>petrol and absolutely no problem. We did this on the advice of a
>technical consultant in this field who advised us that these injectors
>do not rely on petrol for any form of cooling or lubrication. However I
>don't recall whether he was actually referring to "all" injectors.

On mine, again, I have 2 relays which interrupt the injector supply to each
bank; these have a wiring loom with 4 sockets and 4 plugs; you unplug the
injector plug from the injector and plug it into the socket instead, then
plug the other end of the wiring onto the injector. They have a delay on
switch-off which allows the LPG to get through from the mixer.

--
Austin Shackles. www.ddol-las.fsnet.co.uk my opinions are just that
Confidence: Before important work meetings, boost your confidence by
reading a few pages from "The Tibetan Book of the Dead"
from the Little Book of Complete B***ocks by Alistair Beaton.

In uk.rec.cars.fuel.lpg Austin Shackles > wrote:

> you need an injector emulator. I don't know where you get one, but there
> are such things as many of the more modern cars need 'em.

They are just electric solenoids... Perhaps a bunch of similar current draw
relays switching nothing in particular?

--
Athol
<http://cust.idl.com.au/athol> Linux Registered User # 254000
The state of infrastructure in New South Wales is a disgrace.
I'm a Libran Engineer. I don't argue, I discuss.

Daniel J. Stern wrote:
> On Thu, 2 Jun 2005, Bill Putney wrote:
>
>
>>By the time you got thru buying parts and taking the time to wire up and
>>debug your "one-of-a-kind" design, you'd wish you had chosen the simple
>>off-the-shelf solution.
>
>
> That there is an Engineering Truth. Bill, did I ever tell you about the
> turn signals on the UM Solar Car of '99?

I don't recall ever hearing it. Lay it on me!

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
adddress with the letter 'x')

hugh wrote:

> In message >, TBone
> > writes
>
>>
>>
>> "Peter" > wrote in message
>> ...
>>
>>> >> Why don't you just disconnect the fuel pump and let the injectors
>>
>> operate
>>
>>> >> normally.
>>> >
>>> > I'm not sure that'd be wise. Many injector designs depend on fuel flow
>>
>> to
>>
>>> > cool the solenoid windings (i.e., to prevent them overheating and
>>> > cooking).
>>>
>>> I'm not sure it's a good idea, too. Fuel pumps are designed to work
>>> continuously, and disconnecting it could be yet another reason for
>>> CEL to
>>> come on.
>>
>>
>>
>> While it is possible that the fuel injectors may overheat, the CEL
>> will not
>> be set by the fuel pump being disconnected.
>>
> There may be a fuel pressure sensor which would be triggered IIRC late
> Volvo's have one. Incidentally my fuel pump does not run continuously.
> There is a pressure switch on the rail which controls it. If you listen
> you can hear the pump start up then after a few seconds switch off when
> first switching on the ignition.

Depends on the vehicle in question. Most fuel pumps run continuously and
pressure regulation is done by releasing fuel from the rail back to the
fuel tank. Some late model vehicles simply moved this regulation fuction
back to the fuel pump itself, but it still runs continuously. I dont'
know about your specific vehicle, but on the ones I'm familiar with, the
only reason that the fuel pump shuts off a few seconds after turning on
the key is because the auto shut-down system isn't detecting ignition
pulses and kills the fuel pump. As soon as you start cranking the
engine, the fuel pump comes back on and (on these vehicles) STAYS on.