Mk1 golf Warm 1.8 16v PL starting problems but bump start is easy

I am having trouble starting the engine after it is warm. It’s starts nicely from cold, however when it is warm the engine will turn over but not start.
If someone give me a push it bump starts very easily.
I just tried a new battery but this has not helped.
Does anyone know what the problem can be?


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DO this quick test when it is acting up.
https://www.volkswagenownersclub.com/threads/brianos-quick-grounds-test.134637/?post_id=765374#post-765374

If it works replace your grounds Battery to frame and frame to engine.

If you want to improve your starter solenoid current flow.

https://www.cabby-info.com/files/ignition/InstallingHot-startRelay.pdf

I checked the earths and it all seems to be good.
The starter motor is working normally, the car just won't spark/fire into life.

Pello316 said

I checked the earths and it all seems to be good.
The starter motor is working normally, the car just won't spark/fire into life.

Checking and knowing are the last things and the first things you should check.

Do my Quick test it is easy and may just work.

Bump start and working would suggest that you have a iffy connection or fueling issue.

Ok so I went for a drive to warm it up, started perfectly when cold. Tried to start the engine right away when I got home and again didn't start. I measured 13.08 volts between the battery and chassis with and with the jumper cables. Does anyone have any other idea please?

The normal voltage on a car that is running, should be 13.5 to 14V.

The purpose of the Quick Ground test is that your adding a new good ground path for the Engine and frame.

Once the jumpers are in place, does the car start fine?
Yes, then replace your battery to frame and frame to engine grounds.

No, then further information is needed.  As  a 1.8 16v was dropped in to your ride? there where wiring mods?

What fuel type is your ride?  Carbed, CIS, Digi?  

Does the starter engage, and spin the engine when hot, but the car won't start and engage. Or does the starter fail to spin?

Is it automatic? or Manual Transmission.

Tried tonight with the jumpers in place, no luck.
The starter motor is working fine but and turning over the engine but just does not start.
There are no additional mods, I have the original ceramic fuse box and the correct wiring loom for the pl engine.
I use normal unleaded fuel and the pl has the cis-e
It's a manual.
🤞

I had a similar issue with my 1983 GTi Cabrio - it just was such a pig to start once warm. Turned out to be the lift pump in the fuel tank had failed.

I've had other cars where a poor hot start was caused by the ignition coil starting to fail.

the lift pump is making a noise so i assume its ok, i have also replaced the one way valve on the main fuel pump hoping to make a difference but no luck either. if anyone can help i would appreciate it.

All the lift pumps that I have installed on my cabbies were quiet.  When they went bad, they either started to make noise, or the Main pump did. usually after 20 minutes of so of driving.

When I changed my one cabby to a single pump from a dual, the in-tank pump was noisy, but hearing it hum was a good thing.  I just turned the Radio up a bit.

Have you done fuel pressure tests when cold verses warm?
I know I had a digifant 90, that when the Fuel Pressure Regulator went bad there were warm start issues?
The residual pressure tests nailed it.
 

It could easily be a problem with the coil windings. The wires snap and when they are warm they expand and move apart sufficiently to produce an open circuit. When they cool they contract, touch again and all works fine. I would try checking to coil winding continuity, both primary and secondary with an ohmmeter, see if the resistance is markedly different when cold and hot. If it is it it's more than  likely the coil is shot.