Fuel Pump not priming

Hi All,

I have had a few issues with my '89 Mk1 Golf Cabriolet - this is the latest one:

Fuel pump is not priming when ignition is on, I have checked the pump by giving it 12v and it definitely works, had multi-meter on it when ignition is on and it is not getting any power. So I changed the fuel pump relay, still nothing.

Any ideas? I haven't changed anything other than the relay and i have recently put a new starter motor on, but I do know it was priming after that.

Seen a few similar posts which mention ignition coil, so gonna check that tonight. But not sure what else to check.

Any help would be greatly appreciated.

Thanks

Is the lack of priming stopping it from starting up? A lot of aftermarket fuel pump relays don't prime, but doesn't seen to make much difference to starting.

Hi Darren, i had to change blown fuse #5, 15amp which is for fuel pump, have you checked it?

My genuine VW fuel pump relay does not prime and has never done so in the 20 years I've owned the car so it's completely normal.
I did try an aftermarket one from GSF which primes the fuel pump but managed to find a 2nd hand VW one which does not prime as I wanted a spare.
Never had a problem starting with out the pump priming as if the accumulator is doing it's job the fuel and pressure should already be in the system.
I have a 1988 Cabriolet.  
What number relay do you have fitted?
I think mine is a 62 but I will need to check.

LeeO said

Is the lack of priming stopping it from starting up? A lot of aftermarket fuel pump relays don't prime, but doesn't seen to make much difference to starting.

It isnt starting but it could be something else - just ruling things in/out at the min. I am going to unscrew a line on metering head to see if anything is coming through.

shaunyp said

Hi Darren, i had to change blown fuse #5, 15amp which is for fuel pump, have you checked it?

I am sure I have already checked it but will check again - would love it to just be a fuse! thanks!

mark1gls said

My genuine VW fuel pump relay does not prime and has never done so in the 20 years I've owned the car so it's completely normal.
I did try an aftermarket one from GSF which primes the fuel pump but managed to find a 2nd hand VW one which does not prime as I wanted a spare.
Never had a problem starting with out the pump priming as if the accumulator is doing it's job the fuel and pressure should already be in the system.
I have a 1988 Cabriolet.  
What number relay do you have fitted?
I think mine is a 62 but I will need to check.

I think it is a 62 but can confirm when I get in from work. Is there anything worth checking on the accumulator?

What actually is your problem as you have not said in your first post?

Car wont start?
Hot starting problems?
Cold starting problem?
Difficult to start?
Wont tick over/rev?
Etc…

The car should start from hot or cold with out the need to touch the accelerator pedal.  

I've never needed to touch my accumulator but I've read on here that if after the car has been running and if the accumulator bolt/screw is not to rusted you should be able to remove the screw/bolt at the back and if petrol leaks out the diaphragm inside is shot as that is what keeps the pressure in the fuel system.

I do not have your year vehicle, but here is my story; I have a 76 MK1 with a Zenith Carb. Stock for my car was a mechanical pump. They used this pump for two years, before going to CIS.  Very hard to find these pumps, and if found they have been sitting on the shelf for 30 + years. So I left my stock intentions behind, and went electric. With that said, I went through my fuel system thoroughly. I started with the sender which sits on the top of my tank. I replaced the sender and gasket (which leaked like a colander.) I cleaned the ground contacts, and replaced the fuel lines. The intake on your fuel sender could be gummed up, bent, or even short. This would prevent your pump from priming. installing a check valve where the fuel line go into the engine mat help hold fuel for a start, and allow pump to prime if still an issue.  Hope this is useful.

For further information on the proper relay:
http://www.cabby-info.com/Files/Relays.pdf

Visual inspection of the relays.
http://www.cabby-info.com/images/Electrical/CISFuelPumpRelays.png

All CIS and DIgi systems should "Prime" the pump on Ignition switch to the first Position.

The purpose of this is to prevent hot start vapor lock issues.  

If you have a Digi and have converted from  2 pumps to 1 it will still prime.

CIS engines seem to go through Fuel Pump Relays over here, so much so that folks carry a spare.

There is also a Rev limiter in-built in to the relay….