1982 1.6 GLi electrical nightmare - fused fuel relay and ignition problem

OK so here’s the story:

Out in the car the other night, suddenly popped, farts and cut out in the dark. We got rescued and towed the car back the following day.
PART 1

First diagnosis was that the fuel pump was not running with the key. This is the ceramic fuse box system that primes the pump before ignition on. So tried the following:

• Hooked the pump up to a battery via a fuse. Pump runs so it’s not that.
• Bridged the battery and output terminals of the fuel pump relay. Pump runs all the time, so the wiring from fusebox to pump is ok too.
• Set up a temporary piggy-backed relay to drive the fuel pump with the key turned on. This works, turn the key to on and you can hear the pump running.
• Try to run the car and there appears now to be no spark. Damn.

PART 2

So I’ve solved one problem (fuel pump priming) but I still have another. Logic tells me that I’m unlikely to have 2 problems starting at the same time, so they are probably related. The culprit points to the fuel pump relay.
This is the ‘hen’s teeth type with the fuse mounted on top. I managed to find a NOS one for about £100 a couple of years ago. This is on an extension socket that was added as a ‘dealer recall fix’ in the 80s; presumably because the solution before was even worse.
So thinking about the lack of spark, there appears to be a couple of possibilities:

• I think that this relay has a rev-limit function. Presumably some way this relay sends a signal to the ignition to kill the spark at high revs. If this signal was stuck ON by a relay failure then presumably I’d have no spark.
• Alternatively the ignition module/coil could have died.

So my questions are:
Do you think that I’m following the correct process?
What is the best process to try to trace the ignition problem?
Can anyone think of an alternative process that I might use instead of buying another hen’s teeth  321906059C relay to test if that’s the problem?

Fuel pump priming is a myth, some do it and some don't and it makes no difference to running.
I'd be looking at a failed hall sender in the distributor first

lhasadreams said

Fuel pump priming is a myth, some do it and some don't and it makes no difference to running.
I'd be looking at a failed hall sender in the distributor first

Thanks for the response Ade. You might be right about the importance of priming but it did work until recently, but certainly there was no pumping noise at all until I made the relay mod. Now I can hear the pump running. So let's presume the fuel side is sorted for the moment.

I just tried for a spark from the lead into the distributor so there's nothing doing at the ignition.

It could therefore be a hall sensor problem as you suggest. Is there any way to test it?

The fuel pump runs from the coil, so if your coil isn't reacting to your spark, then it is an ignition issue.

Check your grounds, do the quick grounds test.
https://www.volkswagenownersclub.com/threads/brianos-quick-grounds-test.134637/?post_id=765374#post-765374

Then reset your timing or set it statically and see if it has Jumped.

Test your ICM hall generator what feeds the coil and things.


Ignition switches have been know to go bad, if it starts with the starter and you release the switch it stimbles and dies it may be an ignition switch on the run side that is faulty.

Rev limiter relays use the ignition feed and a counter to open the relay to reduce fuel at the Bosch designed limit of RPM.  The Fuel pump relay is a switching relay, that is it turns on and off with the ignition, but as the engine is spinning, but the frequency of the pulses makes it appear that it is on continually, but it is counting….


 

Briano1234 said

The fuel pump runs from the coil, so if your coil isn't reacting to your spark, then it is an ignition issue.

Check your grounds, do the quick grounds test.
https://www.volkswagenownersclub.com/threads/brianos-quick-grounds-test.134637/?post_id=765374#post-765374

Then reset your timing or set it statically and see if it has Jumped.

Test your ICM hall generator what feeds the coil and things.

Thanks for the advice Briano. I think the earth wire is less than the best so a new one will be fitted (measued a few ohms resistance at certain points on the car). The car does have bad earth syndrome.

I have a man locally who is going to look at the hall sensor for me.

testing the hall sender:
https://www.vwvortex.com/threads/overnight-1985-cabriolet-wont-fire-and-starter-runs-even-with-ignition-off-and-key-out.5639375/#post-76701010