Mk2 16v 1988. Fuel pump not priming ignition

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.

 

It's possible that the fuel pump motor brushes are either worn down or sticking. You could connect a meter or a 12v bulb across the pump supply to measure the feed voltage and see if that remains constant when the pump stops working. This would tell you whether the problem is the supply or the pump.

I take it that the in-tank lift pump is working throughout this? Seems likey that it's a failing high pressure pump.

 

hi h8v

Thanks for this it’s much appreciated. The lift pump in the tank is running and I have checked the voltage at the plug for the hight pressure pump and I was getting 11.8v I watched a video on YouTube about the k-jetronic system and it said the pump runs efficiently with a supply voltage of 11.5v and above, so it’s looking like the high pressure pump is on its way out then.

 

My ‘84 K-jet has the same solenoid valve. If it’s operating correctly as the idle drops below approx 800rpm (due electrical load on the alternator) if it’s working you’ll here a click from it (which can even be heard from inside the car) and the revs will pick back up to 1000rpm. Cars with aircon have two of them.

 

Checked the lift pump put put and got a good 400cc in 10 seconds so that’s good. So I’m going to change the high pressure fuel pump.

I started to strip it down and ended up snapped the pipe connection at the pump end ‍♂️‍♂️

does anyone know or know where I can get the part number for a new fuel line( pump to accumulator) ?


TIA

 

I'd be willing to bet good money that it's the main pump - at some stage or another on the life of a Mk2 they will fail and it's worth changing them out - RJ will chime in but I think some of that piping may be NLA from VW and it may be a matter of sourcing a second-hand replacement or building up something yourself.

 

Yea I think so too. I’ve order a new pump and a set of fuel lines too so I’ll keep you posted when it’s done

 

My transfer/lifter pump failed recently. Car wouldn’t run and main pump was very noisy. When I got the lifter pump out of the tank I tested it on bench with 12v and it ran fine. Put it back in the car and did the volume test which it passed with flying colours, 450ml in 10 seconds. Thought it must have been a bad electrical connection at the lifter pump. Cleaned up the connections and all was well for about 100 miles then it did it again. Rough running, eventually cutting out, with noisy main pump. Got a new lifter pump from Heritage, installed it and been good as good ever since. My lifter pump failed with an intermittent fault so be thorough and your diagnosis and keep an open mind.

 

Hi Rustbuster

Thanks for this I’ll definitely Bear it mind.