Priming pulse on CIS

Scott R · Scott R's Garage

This might be crazy, but to help compliment the sometimes pesky fuel accumulator why not add a priming pulse to the pump? When I had my EFI installed it primed the pump when the key was turned on.

Any of the electrical engineers know of a timed replay that I could add to the fuel pump circuit in the engine compartment? It would be simple to fake the sensor plate lifting by jumping the relay into the wire behind the relay cover.

cmonref · 10-17-2007, 03:48 PM

You want to fuel pump to come on during a "hot start" when you engage the starter to supplement the accumulator, all since the airflow sensor plate has not lifted yet? That is how the fuel pump already works, thru the two-stage fuel pump relay. The relay begins in the "start" stage, then when you release the key after the engine starts and the airflow sensor has lifted, the relay switches to the "run" mode.

Or do you want to switch the fuel pump on before engaging the starter to "prime" the fuel system and bring the pressure up? Sounds like you need a momentary on switch mounted near the ignition key.

Scott R · Scott R's Garage

Quote:

Originally Posted by Brian K. Haggard

You want to fuel pump to come on during a "hot start" when you engage the starter to supplement the accumulator, all since the airflow sensor plate has not lifted yet? That is how the fuel pump already works, thru the two-stage fuel pump relay. The relay begins in the "start" stage, then when you release the key after the engine starts and the airflow sensor has lifted, the relay switches to the "run" mode.

Or do you want to switch the fuel pump on before engaging the starter to "prime" the fuel system and bring the pressure up? Sounds like you need a momentary on switch mounted near the ignition key.

Yes, before the key is set to "start." In EFI when you turn to the second ACC position on the key you get a prime pulse for a few seconds.

It looks like I can build a timed relay board with a 555ic chip and a few dollars worth of parts. It's really a nice modern feature on newer cars, and I think it's what lead to the disappearance of accumulators in cars.