Longer Cranking Needed

[AlexD 2]

I'm in the process of re-commissioning an '88 1.6 GTi after about 7 years spent in a barn, it's running and has an MOT but I'm unearthing a few niggles. The latest runs as follows: It has been starting fine for a little while, idling a little high at ~1300rpm. Recently I noticed that it has been taking longer and longer to start, the starter turns and eventually it fires. It's worse when it has been off for ~30 mins after being warmed up. When it does start it is very rough for a few seconds before clearing and running fine. I'm now worried that soon it won't start at all, does this sound like something that pug's tend to do or shall I go through a more generic troubleshooting process.

[Anthony 1,003]

Excessive cranking over before it eventually starts is often a sign that pressure isn't being held in the fuel system and that the fuel pump is having to re-pressurise the system before there's sufficient fuel being injected for the engine to fire. Usually this is down to the one-way valve on the fuel pump failing and allowing the fuel to drain back into the tank when the car is left parked up for more than a few minutes.

[jamie_1992 66 1 Cars]

Could lack of compression be an issue here

[AlexD 2]

There has been some mucking about with the fuel pump, it had a new one which seemed to stop working very quickly so I got a second hand one. I'll check it out, is the valve separate to the pump? Compression is probably fine as it hoons about fine and doesn't seem to be losing oil.

[Jolly Green Monster 51 1 Cars]

should be easy to check.. turn the ignition on and off a couple of times and then crank it.. ie. up the fuel pressure before cranking

[luggy 13]

Excessive cranking can also sometimes be an early sign of the coil breaking down

[AlexD 2]

Coil? Hmm, there's something not right with the way the car runs, it feels like early stage HT problems, leads or coil perhaps. It's really rough on start up, and then clears reluctantly and just occasionally while under way it hesitates. Not consistently but every now and again. Though of course fuel delivery problems would probably feel similar too. Will do some investigating.

Edited February 7, 2014 by AlexD

[luggy 13]

Seeing that you've already replaced the fuel pump I'd go for

1. Replacement coil

2. Compression test

Then you'll have covered fuelling, sparks and mechanical.

Good luck

[Anthony 1,003]

should be easy to check.. turn the ignition on and off a couple of times and then crank it.. ie. up the fuel pressure before cranking

That won't work on an 8v as they often don't prime at all and usually will only do so a single time if they do. It would work on a GTi-6 conversion like yours though as helpfully they prime every time.

 

You could prove it reasonably easily by using a short bit of wire to energise the tachymetric (fuel pump) relay for 10-15 seconds or so to ensure that the fuel system is upto pressure before starting. If it then starts quickly as it should do then you've found the culprit.

[AlexD 2]

Slow progress on this due to lack of garage and child etc. I replaced the coil and it didn't cure the problem and I noticed it was running very rough so I fitted some new plug leads. Then it wouldn't start, I've finally figured out that I managed to knock a wire off the coil when fitting the lead. What a muppet. Anyway, it now starts and runs really rough, I suspect only on 3 cylinders.

 

The fuel pump is getting power (~9V on quite a flat battery) and it is pumping fuel when cranking, though I have no way of testing at how much pressure. Most of the time the rev counter stays put when I crank, until it starts but on at least one occasion it fluttered while cranking. I'm not sure which pins to bridge on the tachymetric relay, but figure that it is probably ok if the fuel pump is working?

 

I may have connected the leads up wrong, but I did carefully only do one at a time, and I have re-seated the leads a good few times to check.

 

The dizzy cap is my next thought but it seems ok visually. Not great, but ok. Other ideas gratefully received.