|
My '79, 5 speed does run the fuel pump when the key is turned on. I don't think it's for 3 seconds but it is more than 1. During that time I don't hear the injectors so it is strictly building fuel pressure. If it has been a long time since last operational, I cycle the switch on-off several times.
On the '79, the fuel pressure regulator on the fuel distributor has a "push valve" on the return from the warm-up regulator to help maintain fuel pressure after shut-down and help prevent vapor lock. This was added some time around 1978 so your car may not have it. That would make the "prime" function of the relay a nice feature. The time delay is performed by a small electronic circuit in the relay itself, I think you would see it if you took the metal cover off.
The relay in my car is not original, I think it may have come from an Audi dealer, but the original did operate the same way.
If this hot-start problem is recent you may also want to see if your residual pressure drops too fast after shut-down and identify the cause. Even without the "push valve" I would expect some residual pressure.
Good luck
|