Hot start issue - accessory relay II - priming

[madstudios]

I've noticed something interesting when I was updating relays on my car...
My car always prime fuel when I turn on the keys, with the engine cold or hot.
So I bought new accessory relays for my car, but after I've installed them, the pump stoped priming, and after that it was very difficult for a hot start...
First I thought it was bad fuel, (reliable gas stations in Brazil are hard to find).
But then I remembered that my pump always primed before the update. So when I put back the old relays...problem solved!Everything is back to normal.
I never thought that the accessory relays had something to do with priming fuel, and don't remeber to read anyone mentioning about them having some relation with hot start issues...
Any thoughts?

[David T]

If you are having hot start problems you most likely have a bad accumulator. The old RPM relay masks the problem because it runs the fuel pump (primes) the motor before you start the car raising the Rest Pressure. One test would be to use the newer relay (the one that doesn't run the fuel pump and prime the motor) and do the plug swap. If it starts right up that will confirm that you have a rest pressure problem.

[Chris 16409]

What kind of Aux relays did you buy? That's weird they would affect the fuel pump priming. Some RPM relays would always prime and others would only prime of the voltage was high enough or something like that. Dave M. can confirm that. If you buy his solid state relay, then the fuel pump will always prime.

[Bitsyncmaster]

When I had the OEM RPM relay, it would prime most of the time but if I had a battery charger on, it would not prime. My car also does not have the capacitor near the idle switch and it would re-prime if I touched the gas.

My solid state RPM relay will always prime. I don't think the prime does much for a hot start problem. The prime does seem to start your engine faster (instantly) on a cold engine.

[abiberacher]

Thanks buddy,

had the same problem here. After updating the electric system on the car, the fuel pump stopped priming as it used to do since.
I also tried to flip back all the old relays step by step to find where the problem was, but I didn't put both old Heavy Duty Accessory Relays back at the same time.

That does the trick, when installed both metal housing "Hella" relays again, the fuel pump started to prime again when turning the key to Pos.2

I can't explain why, 'cause it makes no sense, but it worked!