[T3] 71 Squareback MT/FI - Intermittent Engine Stopping

[Jim Adney]

On 9 Jun 2020 at 16:00, Wisconsin Spryers wrote:

> Just recently, I've had two occasions recently while driving around town
> where the engine suddenly just stops. After coasting to the side of the
> road, I attempt to start the engine, but am unsuccessful. After waiting
> about 5 or 10 minutes I'm able to start the engine and drive on without
> issue. When taking my daily trips, except for this issue, I haven't noticed
> anything out of the ordinary.

Do you get the 2 relay clicks when you turn the key ON, even when it won't 
start. If so, that's a good sign that the FI is still working. If not, then we're 
looking for problems with the FI power relay.

Earlier, you sent me a photo of the fuel pump plugged in. I found a plug to 
compare and your plug looks to be plugged all the way in.

> When I was getting the car back on the road in 2018 (~1,300 miles ago after
> sitting under cover for about 18 years) I replaced all the fuel hoses, had
> the fuel tank "boiled out", installed a new fuel filter, and installed Jim
> Adney's 3-way primer switch along with his improved fuel overflow hose kit.

If you hear 2 clicks, try holding the primer switch in the momentary "prime" 
position while you try to start the engine. If it starts then, but dies soon after 
releasing the switch, then your fuel pump relay is going bad. I have good 
used OG replacements.

If you have a meter you can use to measure the fuel pump current, that 
might help. If the pump is drawing excessive current, that might cause the 
pump relay to overheat. I think normal current is 4 A or a little less. 8 A is 
definitely too much, and might mean that the pump is working against some 
extra load, like gas residue inside it. Some SeaFoam gas additive for a 
couple tanks might help dissolve that.

> Any hints on how to track down the cause would be appreciated.

If the FI seems good, I'd be wondering about the ignition coil or maybe the FI 
trigger points. This doesn't really sound like a FI problem, but it could be. Do 
you still have the black Bosch coil? If so, that's good. Other options are 
probably less reliable.

I have a little rig that you could borrow to watch for spark while driving. If the 
engine stops but you still have spark, the problem is probably fuel related. If 
there's no spark, then you need to look at the ignition system.

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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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