Lengthening initial on-time of fuel pump

[Circlotron]

My VP runs on LPG and it seems like the gas lockoff solenoid is controlled by the same relay that powers the fuel pump (not totally sure – the wiring inside the car looks like WW111). When you turn the ignition on the pump runs for a moment then switches off because the engine is not running. Same deal with the gas solenoid of course but I would like it to run for maybe 5 seconds before turning off. This would hopefully make it easier to start. What it does currently on gas, especially if it has been sitting for more than a couple of hours, is fire up immediately, run for half a second then stall. Then you have to crank it for about 5 full seconds to get going again.

What would I have to change in the bin to set this timeout value?

[VL400]

AFAIK its not something that can be configured on the 808, its handled by another chip on board and you cannot change its operation. The VR auto PCM was the first that the fuel pump can be controlled/configured by software.

[VK_3800]

The fuel pump relay already has a basic override in the oil pressure switch, why not add another with a momentary push button? Just hold it down for however long you like to prime, no need to bother when it hasn't been sitting

[Holden202T]

if your running $12P tune could you use a flex table to power the relay, and then also use the fuel pump one (so it will work when the engine is cranking and running)

VL400 might be able to tell us if theres a felx table selectable axis that will be like an ecm on time or something like that ? if so can use that for the axis of the flex table to make it drive a relay for that time maybe ?

[Circlotron]

Yeah, I might just try the push-button approach.
I did actually try a setup that switched a relay on whenever it was on gas, and the contacts made a path from the purple cranking wire of the ign switch to the lockoff solenoid, but then I found that the the circuit that powered the relay coil went off with the engine not running as per the existing problem...

[VL400]

12P does not have an uptime counter it has an engine runtime counter only, couldnt use a flex output for this but would have been pretty neat as it could be mapped to coolant temp too.

A push button sounds like the easy option!

[festy]

You could rig up a simple timer relay using a 555 IC to hold the fuel pump on for an additional few seconds after the ECU has initiated priming.
Something like this circuit should do the trick?
Have it powered off the ignition, and triggered by the ECU's fuel pump relay wire.
Put the timer's relay in parallel to the existing pump relay so initially both would be closed, then when the ECU stops priming the timer's relay stays engaged for a pre-set time before dropping out. The time is adjustable with the pot in that circuit.
Once you started cranking, both relays would re-engage but the timer's relay would open again after a few seconds leaving the fuel pump managed by the ECU.
There's heaps of cheap 555 timer kits on ebay that would make it pretty simple to implement.

[Circlotron]

I eventually did a push button thing. Still didn't fix starting problem. I think it might be too low vacuum when cranking. Has a gas research carb and an ordinary Impco Model E converter and I read that it should have a supa sensitive converter calibrated to the carb. The idle mixture hose normally would have a brass jet in it but is has none and even like that and with the idle mixture screw fully in it still idles slightly lean so maybe it's a converter issue.
---------------------------------
P.S. I got the above all typed out and ready to submit and suddenly the computer went spak and the screen went all blocky (got new vid card recently) and the mouse wouldn't operate the submit button or anything else for that matter. Had to push reset button and when it all started up again the text was still there!!! Howzat!!