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Topic: High pressure fuel pump not priming (16v K-Jet) (Read 1358 times) previous topic - next topic

High pressure fuel pump not priming (16v K-Jet)

Hello all.

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.

Re: High pressure fuel pump not priming (16v K-Jet)

Reply #1 –
cant remember what happened  with mine, but i ended up changing both pumps, ignoition module and distrubuter.. cut out for no reason, similar issue i guess.

Re: High pressure fuel pump not priming (16v K-Jet)

Reply #2 –
As I was reading through your list I was going to say, stick a direct feed on the back of the pump but I saw you are getting to that.
I suspect the fuel is dead, can't answer your quesion about the relay, does it require some resistance or feedback that it's not getting from the pump?

Point to note, the first time I replaced my pump I bought an aftermarket one. After a couple months it failed. The issue was not with the pump mecahics, but the electic poles. When I wiggled the plug it worked while I had a hold on it. So I guess a bad solder joint inside the pump or something.

This left me stranded at work, I got a life home. I got a replacement under warranty and got it sent to my work, so fitted it in the car park over my lunch time.

This one only ran for a while, and when tested found it wasn't putting out quite enough pressure.

In short, if you have to replace the pump get a quality OE Bosch one.

Re: High pressure fuel pump not priming (16v K-Jet)

Reply #3 –
Quote from: Eddypeck on
As I was reading through your list I was going to say, stick a direct feed on the back of the pump but I saw you are getting to that.
I suspect the fuel is dead, can't answer your quesion about the relay, does it require some resistance or feedback that it's not getting from the pump?

Point to note, the first time I replaced my pump I bought an aftermarket one. After a couple months it failed. The issue was not with the pump mecahics, but the electic poles. When I wiggled the plug it worked while I had a hold on it. So I guess a bad solder joint inside the pump or something.

This left me stranded at work, I got a life home. I got a replacement under warranty and got it sent to my work, so fitted it in the car park over my lunch time.

This one only ran for a while, and when tested found it wasn't putting out quite enough pressure.

In short, if you have to replace the pump get a quality OE Bosch one.

Thanks Ed for this still haven’t had a chance to put a feed onto the pump yet but it f is it knackered and definitely look at getting an OEM pump.


Re: High pressure fuel pump not priming (16v K-Jet)

Reply #4 –
So the plot thickens

I manage to test the pump today with a feed straight from the battery and the pump constantly until I disconnected the feed I tried this a couple of time more just to be sure and the pump ran every tine.

So I reconnect the plug on the pump but before I tested it normally i boosted the battery for a couple of hours just incase it had dropped with all the testing I had done.

so with a fully charged battery and everything back as it should be I turned on the ignition and I could hear the pump running so I started the car and it fire up but only ran for about a minute then cut out. I tried to start it again but it wouldn’t fire just like before and the pump didn’t sound great then went quite again.

So what do we think is it a knackered pump or could it be a bad connection between the ECU and fuse box ??

Note in my previous test I only tested the voltage on the system I haven’t checked what current was being drawn.

Re: High pressure fuel pump not priming (16v K-Jet)

Reply #5 –
Just a thought when you tested the pump there would be no load When its pumping fuel there would be back pressure.
scs

Re: High pressure fuel pump not priming (16v K-Jet)

Reply #6 –
Yea good point 👍🏻

I’m going to go for it and change the pump and see if that sort it out.

I’ll keep you posted 🤞🏻🤞🏻