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Technical / High pressure fuel pump not priming (16v K-Jet)
I have a 91 plate Mk2 GTI 16v and last weekend it died on me like it ran out of fuel (It hadn’t thought).
When I got it home and had the time to look at it I noticed the high pressure fuel pump underneath wasn’t priming when I turned on the ignition. So, I had a look in hear to give my some help and ideas on what cause of the fault might be, so this is where I am at.
I first I went for the quick hits I checked the fuel pump fuse and that was ok, I removed relay 67 and fitted relay 18 in its place and the pump still wouldn’t run.
So i removed the fuel pump fuse again and with the ignition on I checked with my meter what voltage I was getting at the fuse terminals and for a couple of seconds my meter was reading 11.8v then would go to 0v. I checked again multiple times and it was the same. so this made me think that relay 67 was faulty, so I bought a new relay and fitted it and the pump still doesn’t run.
so I fitted relay 18 again and checked what voltage I was getting at the fuel pump fuse terminals and this time I was getting a constant 11.8v but the pump still wouldn’t run when I put the fuse back in.
so next I checked (with relay 18 still fitted) the voltage to both the lift pump and the hight pressure pump both had voltage to them
The hight pressure pump I had 11.8v at the plug
The lift pump had 9.8v at the plug (not sure why this was lower)
when I plugged the lift pump back in I could hear it running so I know this pump is working.
so next I tested both my new and old relays to make sure they worked (and to rule out if I bought a duff relay) and they both worked.
So what I can’t understand why both relays 67 are not staying energise when the ignition is on.
Also I’m guessing that if the high pressure fuel pump isn’t working with relay 18 fitted that the pump must be defective. I am going to test this next by taking a 12v feed from a spare battery I have and connecting it straight onto the pump this should hopefully let me know if the pump is knackered.
If you pump is knackered I still don’t understand why relay 67 isn’t staying energised 🤦🏼♂️
Sorry this is long winded and I hope all this make sense and TIA for any help.