Jetronic fuelling problem 1983 golf gti

My 1983 Golf GTI wouldn’t start after I had left if or a month or so. I took the injectors out and found I had no fuel going to them when I operated the starter, although you could hear fuel running back into the tank.
 I found that the Viton O ring on the fuel pressure regulator has disintegrated. I cleaned off the bits of rubber  as best I could, changed the O ring for a new one and assembled. The result is that I no longer get fuel running back into the tank, but I still get no fuel spray from the injectors. Any suggestions as to what to look for next please?

Hi

As the pressure regulator rubber has failed, potentially all the rubbers in the fuel system could do with replacing, if they're the orginals on the car.

Depending on the amounts delivered at the injectors the easiest order of thing are:

1. Test the injector flows.
2. Remove a shim from the pressure regulator.
3. Check the WUR sockets clean.


TESTING INEJECTOR FLOW

To check the fuel system is working correctly, firstly without the engine running, use a 17 relay in slot 2, or remove the fuel relay and connect the WUR positive to battery positive, giving live feed to the pump & pumping fuel to the fuel distributor.

Either way disconnect the WUR so it's not heating and affecting fuel pressure for this test.

Steve Harper does it here on one of his videos:

Removing, cleaning and testing CIS injector flow on a vw Mk1 golf gti - YouTube

So with all injectors out & in jars or measuring containers, metering head shroud off, get the pump running.


FUEL PRESSURE TEST
Ideally having a fuel pressure testing kit to accurately test the correct fuel pressures, see this video here for a guide.

Mk1 VW Bosch CIS Fuel Pressure Test - YouTube

In absence of a fuel pressure kit, test by lifting the metering head plate by pinching the bolt with fingers, or using a stick magent. Anything above 2.5BAR and the stick magnet can't lift and it's very hard to lift pinching the bolt.

At 1 - 1.5 BAR it's easy to lift.

Lifting the plate, the plunger inside the fuel distributor should drop and allow fuel to travel through the plunger and out each fuel line.


TEST INJECTOR AMOUNTS
If it's easy to lift and fuel comes out of the injectors, get the stopwatch out, at the same time, start the stopwatch and lift the metering plate to full height then let go at 30 seconds, there should be between 68ml & 72ml in each container.


DIFFICULTY LIFTING PLATE
Can't lift it? the fuel pressure could be too high.

Get some microfibre towels to catch any fuel leaked.

Firstly, turn off the fuel pump, lift the plate with a pliers or grips and let of the pressure via fuel at the injectors.

CHECK THE WUR
There's 2 allens holding the WUR on, 2 banjo bolts to the 2 WUR fuel lines, loosen all of them, then remove and rest the WUR ontop of the rad.
Disconnect each fuel line an inspect, the wire mesh should be clearly visible, if not it could need a clean or a rebuild.

https://vwgolfmk1.org.uk/forum/index.php?page=topicview&id=new-technical-non%2Fryan-mk-1-setting-up-my#post_1680131

To 'clean' spraying in a some brake/carb cleaner and very gently poke a microfibre into absorb any debris. Pouring some thinners in to break up any fuel gunk on the mesh, but follow up with plenty of carb cleaner.


CHECK THE PRESSURE REGULATOR
Remove the pressure regulator valve again and remove any shims that are there, it maybe that the new rubber has increase pressure and not as many shims are needed.

Redo the 1st test for the injector measurements and see if the plate is easier to lift.


Ideally having a fuel pressure testing kit to accurately test the correct fuel pressures, see this video here for a guide.

Mk1 VW Bosch CIS Fuel Pressure Test - YouTube


TESTING THE SYSTEM BY RUNNING CAR
Put it all back together.
inectors back in, bit of rubber grease on the injector rubber seals
connect WUR plug
tighten WUR pipes, (leave WUR on top of rad for now)
tighten pressure regulator
connect fuel relay

minus:

- leave injector number 1 out.
- leave the metering head rubber shroud off.

Put a screw driver in the metering plate so the plate is manually lifted 1-2mm, that's 1000-1200RPM.

Then try and start the car and see if it starts.

You should get fuel out of injector 1 as you turn the car over, the car should start & run.

If it starts, turn it off, remove the screw driver and try again, see if there's fuel at injector 1.


 

I have the fuel pump wired on all the time. I have no fuel spraying out of the injectors. I'll check any filters on the WUR and see if any fuel comes out of the injectors

Have you checked the in tank fuel pump mate

There is no in tank pump on this golf model
I can get fuel spurting out of pipes when I slacken them off. I must have a blockage either in the WUR or part of the fuel distributor I think.  Are the any filters in the WUR or pipes leading to and from it?

golfy1 said

There is no in tank pump on this golf model
I can get fuel spurting out of pipes when I slacken them off. I must have a blockage either in the WUR or part of the fuel distributor I think.  Are the any filters in the WUR or pipes leading to and from it?

WUR - built in mesh filter

Ah, For 20 secs I got an image of a filter in the WUR which has now disappeared, but seemed to show filter built in. I will investigate thanks.
There is something wrong with this picture display system though

Ah got it, I'll have a look at that, thanks