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GTC Cologne - Hard to start when hot

Posted: Sat Jun 29, 2019 10:09 pm
by JPL1
Hi, I have been trying to use my GTC as much as possible recently (it has sat around too long doing no miles under previous ownership). However, why the engine is hot, it is really hard to restart, having to be cranked over for quite a while on a full throttle to get it to go. Then it runs quite rough for a while after with a bit of stutter. Fuel evaporation or fried wires? I've seen both offered on 6a discussions. My Cologne seems to have been retro-fitted with a Webber and a GKN filter.

GTC Cologne - Hard to start when hot

Posted: Sat Jun 29, 2019 10:19 pm
by scimjim
Has the carb been set up?

Has anything else (fuel lines etc) been moved or modified?

Mechanical or electric fuel pump?

Fuel filter replaced recently?

GTC Cologne - Hard to start when hot

Posted: Sun Jun 30, 2019 3:16 pm
by JPL1
Thanks Scimjim - I always forget some key info!
Electric pump mounted at the rear. The carb appears to have the fuel return connected (a pipe arrives at and leaves the tee junction at the front of the carb). The fuel lines all seem to have been routed very sensibly as far away from the manifolds as possible. I am having a full service done this week, so while it is on the ramp I will ask the mechanic to check the wires form the starter solenoid for cracking/failure. I would do it myself but I am without a suitable garage at present (storage only!). I am mid cleaning the K&N filter as I type. I took it our for a run this morning (12 miles each way to pick up filter cleaning kit) and I found two things. It being a longish run at a decent speed (45 - 55mph) the temp on the gauge remained at the desired 88 - 90 degrees. Having switched off to pick up the kit and got back in, as long as I did not touch the throttle at all (contrary to advice in manual) it fired up OK. It did the same when I stopped for fuel. The problem was bad on Friday when it was really hot and the car was in use around town. The temp on the gauge always rises in this kind of use to above 90, and after this kind of motoring the re-starting is a problem. I am thinking that the engine is running too hot under such conditions, which is only exacerbating a known weakness. Your thoughts?

GTC Cologne - Hard to start when hot

Posted: Sun Jun 30, 2019 3:21 pm
by Old and Slow
Just a thought...
If not touching the throttle helps, then perhaps it implies that touching the throttle is pumping fuel via the accelerator pump, making it too rich, when the engine is hot.

GTC Cologne - Hard to start when hot

Posted: Sun Jun 30, 2019 6:24 pm
by peter freeman
A strobe to see what sort of spark you have and bit of fuel down the carb throat should tell you if its electrical or fuel - my guess would be fuel evaporation.

GTC Cologne - Hard to start when hot

Posted: Sun Jun 30, 2019 8:05 pm
by scimjim
Sounds like fuel vaporisation is unlikely then. I agree with Philip, it sounds like you could be running rich and it’s flooding - would be worth getting the exhaust fumes measured?

GTC Cologne - Hard to start when hot

Posted: Sun Jun 30, 2019 10:43 pm
by JPL1
Just had MOT done and emissions were very good, but guess that does not actually analyse for rich/lean? The problem is knowing what to do with the throttle - I gave to estimate how hot the engine still is! I guess I could try to be more scientific and check the temp gauge before starting each time and noting how it behaves with what throttle opening - but I know I will keep forgetting! Anyway, I'll get the service done and then tackle it knowing other things are sorted. I can't help thinking part of the problem is lack of use. It gas done just 7500 miles since a full resto back in 2005 - it needs some proper miles on the clock!

GTC Cologne - Hard to start when hot

Posted: Sun Jun 30, 2019 10:51 pm
by scimjim
As a rule, I only ever pump the throttle to set the choke if it’s sat overnight or longer. The emissions should be a good indication of rich/lean, high HC and CO mean it’s rich (obviously it actually means there’s excess fuel at the probe - but on a simple engine in reasonable condition, it’s a reasonable, if simplistic, assumption).