Fuel pump should come alive or not.
07-31-2018, 06:38 PM
#1
Rennlist Member
Thread Starter
Fuel pump should come alive or not.
Hi,
I realised something today: after my engine overhaul i think the fuelpump has different behaviour then before. I am chasing some gremlins so i thought this might be something.
Its a '79 manual euro kjet cis with one pump under the fueltank.
Before i always would turn the ignition to on, wait 2 seconds and then would switch to start the engine. When in on position on i would hear the fuelpump come to life. Sounded like turning and then stop, after that i would start the engine.
Now when i turn the key to on, i hear nothing. I wait for 2 seconds and then i start and it starts fine. Warm and cold. So there is no starting problem at this point. It does whine a bit like always.
Am i making this up? Or am i right and should it come alive when turning to on. And: is there a problem when it does not?
Thanks in advance!
I realised something today: after my engine overhaul i think the fuelpump has different behaviour then before. I am chasing some gremlins so i thought this might be something.
Its a '79 manual euro kjet cis with one pump under the fueltank.
Before i always would turn the ignition to on, wait 2 seconds and then would switch to start the engine. When in on position on i would hear the fuelpump come to life. Sounded like turning and then stop, after that i would start the engine.
Now when i turn the key to on, i hear nothing. I wait for 2 seconds and then i start and it starts fine. Warm and cold. So there is no starting problem at this point. It does whine a bit like always.
Am i making this up? Or am i right and should it come alive when turning to on. And: is there a problem when it does not?
Thanks in advance!
07-31-2018, 10:00 PM
#2
Chronic Tool Dropper
Lifetime Rennlist
Member
Lifetime Rennlist
Member
It’s a function of the fuel pump relay. The circuit inside detects an initial charging of a small capacitor when the relay is first energized, closes the relay until it’s charged. Spinning the engine causes tach pulses that partially discharge the capacitor. If it doesn’t happen often enough, the cap finishes charging and the relay opens. Your chance of having the pump run on key-on it no cranking depends on time since last run and the state of the ignition (position) when the engine stopped last.
08-01-2018, 08:27 AM
#4
Rennlist Member
Thread Starter
Thanks for the feedback. Could be Bobs explanation very wel, because i am driving the car more often, like weekly, so it could be it is not discharging.
@JP, thanks for your reply. But does a fried relay engage the fuelpump? I mean the car starts?
@JP, thanks for your reply. But does a fried relay engage the fuelpump? I mean the car starts?
08-01-2018, 09:30 AM
#5
Rennlist Member
No, the pump wouldnt run if relay is out. Just that a maybe is the timer part may have died , so yours is not priming. If it starts OK hot and cold, whats the problem ?
jp 83 Euro S AT 57k
jp 83 Euro S AT 57k
