Emulate injectors - how?

On 02/06/2005 21:23 Peter wrote:

>>over to the bank of "dummy" injectors. The fact that they don't have a
>>moving pintle might affect the waveform a bit, but I bet it wouldn't be
>>enough to trip the computer. It would add a lot of complexity since you
>>would have to put in 8 relays to switch over from the real injectors to
>>the dummies, intstead of a single relay to cut in the resistor on the
>>common side.
>
>
> Yep, 8 relays it is. I've considered it, but this would mean ungainly bundle
> of wires, relays and coils of unknown inductance (or injectors from
> junkyard). Are there relays that will switch 4/8 separate circuits?

You can get 4-pole double-throw relays, can't remember where I seen them
but I definitely came across them as I was going to use it as part of a
car-phone kit with the two front speakers (two wires in each being
switched hence the 4-pole required). Never seen an 8-pole, but it would
be pretty huge packaging wise - the 4PDT has 14 pins!

Paul.

In message >, Steve >
writes
>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.
You could be right, but it's done 50k+ miles on LPG with typically the
petrol pump used once a day just to prime the system to start on petrol
to avoid a lot of cranking to get the gas through if its stood for a
while. I actually put the switch back to gas before actually starting
the engine.
--
hugh
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