Hot start problem
Discussion
Afternoon all,
MOT in the bag yesterday so I've driving about today and starting the car when hot is becoming more of a problem.
This isn't the usual starter motor problem as that's fine, the bugger just won't start as if it's being deprived of fuel. Once it does start it clears it's throat and runs fine. On a cold start it fires up almost instantly.
Any ideas, fuel pump perhaps?
Ta
Ian
MOT in the bag yesterday so I've driving about today and starting the car when hot is becoming more of a problem.
This isn't the usual starter motor problem as that's fine, the bugger just won't start as if it's being deprived of fuel. Once it does start it clears it's throat and runs fine. On a cold start it fires up almost instantly.
Any ideas, fuel pump perhaps?
Ta
Ian
Now.... before you shoot me down for being crazy, I had something that sounded like this a good few years back... as well as these symptoms, had some other weird things which started to creep in as well. Was extremely confusing for a while...
Anyhoo... turned out to be the big fuse. It had corroded and the result were intermittent symptoms, and not starting when hot was the main one. Obviously the changed resistance and the physical stresses when hot made it come to the fore.
Like I said... bit far out there but worth checking and ruling out.
Anyhoo... turned out to be the big fuse. It had corroded and the result were intermittent symptoms, and not starting when hot was the main one. Obviously the changed resistance and the physical stresses when hot made it come to the fore.
Like I said... bit far out there but worth checking and ruling out.
The_Edge said:
Now.... before you shoot me down for being crazy, I had something that sounded like this a good few years back... as well as these symptoms, had some other weird things which started to creep in as well. Was extremely confusing for a while...
Anyhoo... turned out to be the big fuse. It had corroded and the result were intermittent symptoms, and not starting when hot was the main one. Obviously the changed resistance and the physical stresses when hot made it come to the fore.
Like I said... bit far out there but worth checking and ruling out.
Thank you for that. I haven't long since changed the fuse and holder with the terminals having a smear of copper slip so I'm thinking it won't be that but often it's best to check the cheapest stuff first.........Anyhoo... turned out to be the big fuse. It had corroded and the result were intermittent symptoms, and not starting when hot was the main one. Obviously the changed resistance and the physical stresses when hot made it come to the fore.
Like I said... bit far out there but worth checking and ruling out.
Cheers
Ian
I can't see the fuse being the issue if the engine is cranking but won't fire.
My guess is fuel is vapourising in the supply pipe as it runs over the top of the engine. This happens to me occasionally when I forget to wait for the fuel pump to prime fully and don't give it enough throttle to fire quickly. I've always wondered if the fuel system should be better routed but quite hard to do unless you have it on show or go close to the exhaust which would sub-optimal for obvious reason.
Other things to check just in case:
Spark. Does it have any problems under high load, might be a sign of a weak spark which would also hinder starting.
Air. Any blockage in the intake system, collapsed pipework, foreign bodies etc.
Compression. Would should up as rough running in normal use.
My guess is fuel is vapourising in the supply pipe as it runs over the top of the engine. This happens to me occasionally when I forget to wait for the fuel pump to prime fully and don't give it enough throttle to fire quickly. I've always wondered if the fuel system should be better routed but quite hard to do unless you have it on show or go close to the exhaust which would sub-optimal for obvious reason.
Other things to check just in case:
Spark. Does it have any problems under high load, might be a sign of a weak spark which would also hinder starting.
Air. Any blockage in the intake system, collapsed pipework, foreign bodies etc.
Compression. Would should up as rough running in normal use.
From an old Cerbera document I have (Joospeed Useful Stuff.doc)
Hot stalling
This can be due to the fuel vapourising in the lines, the wrapping of the fuel lines in heat-reflective material was a factory mod for the earliest cars only.. all cars now have fuel lines which run inside the cabin under the centre console (they're metal, so no chance of bursting unless someone drills through for a mobile phone or similar). Also air con cars have the added advantage of a fuel-cooler which is the metal canister in front of the engine just visible under the lower fibreglass cover. Excessive heat transfer through the boot floor from the exhaust back box to the fuel tank was cured by fitting a plate barrier between the rear box and the boot floor on early cars.
As a result, hot stalling because of vapourisation was all-but eliminated, and any stalling problems occurring are either as a result of a fault, or more commonly because the butterflies on the O/S bank are becoming blocked with oil from the breather trap in that side airbox. On cold start, the ignition timing is advanced which takes care of the cold-start fast idle, and the timing is gradually trimmed as the coolant temperature increases. It's important that the butterfly area is cleaned every service to maintain the idle speed...it shouldn't be raised just by opening the idle speed stop screw since this ruins the relationship between the rate of opening of the butterfly and the expected change in airflow possibly resulting in uneven slow speed running (for each incremental increase in butterfly angle, the rate of change of airflow decreases).
Hot stalling
This can be due to the fuel vapourising in the lines, the wrapping of the fuel lines in heat-reflective material was a factory mod for the earliest cars only.. all cars now have fuel lines which run inside the cabin under the centre console (they're metal, so no chance of bursting unless someone drills through for a mobile phone or similar). Also air con cars have the added advantage of a fuel-cooler which is the metal canister in front of the engine just visible under the lower fibreglass cover. Excessive heat transfer through the boot floor from the exhaust back box to the fuel tank was cured by fitting a plate barrier between the rear box and the boot floor on early cars.
As a result, hot stalling because of vapourisation was all-but eliminated, and any stalling problems occurring are either as a result of a fault, or more commonly because the butterflies on the O/S bank are becoming blocked with oil from the breather trap in that side airbox. On cold start, the ignition timing is advanced which takes care of the cold-start fast idle, and the timing is gradually trimmed as the coolant temperature increases. It's important that the butterfly area is cleaned every service to maintain the idle speed...it shouldn't be raised just by opening the idle speed stop screw since this ruins the relationship between the rate of opening of the butterfly and the expected change in airflow possibly resulting in uneven slow speed running (for each incremental increase in butterfly angle, the rate of change of airflow decreases).
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