There seems to be so much trouble with cold starting of diesels but my problem is starting a hot or warm engine. Starting from cold is excellent, first time every time. However, after a run of half an hour and then left for up to an hour it refuses to start on the key. It will bump start easily. As it cools it gets progressivly easier to start. Checked absolutely everything - been this way for over a year.
Any ideas?
ZX Diesel Hot Starting
Moderator: RichardW
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Dave Burns
- Posts: 1915
- Joined: 14 May 2001, 05:30
- Location: United Kingdom
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Well if it bumps ok I think that just about rules out the stop solenoid, but just incase this is something that you haven't checked do as John says and crack a union, see if there is fuel there as the engine is cranked.
If there isn't, and its not a keypad model, unscrew the stop solenoid and remove its spring and plunger, refit the solenoid and prime the pump with the rubber bulb, crank the engine again, if still no fuel at the injection pipe unions, you have a pump fault.
If there is fuel, get a length of heavy gauge cable at least equivelent to the glow plug supply lead and and fasten it securely to one of the glow plug terminals.
When the hot engine wont start, jam the other end of the cable hard on to the battery positive terminal for about five seconds or so then have an assistant crank the engine, if it starts easey you need to look at the glow relay, if it still wont start, or starts reluctantly and with alot of cranking then I think you will be looking at incorrect valve clearances as the cause.
Whip the rocker cover off and check the clearances are within tolerance, alternatively have a compression test carried out while the engine is at operating temperature, don't let it be done with a warm or cold engine as this will tell you nothing.
If the valves are being held open slightly due to inproper clearance when they expand, precious compressed air will be lost which may lower the the temperature of the remaining charge well below the flashpoint of the fuel.
The fact that the car will bump start easily leads me to think this is what the problem might be, starting this way will turn the engine over much faster than the starter motor is capable of.
The faster the engine turns the quicker the air is compressed and the hotter it gets, since air gets hotter the faster it is compressed, plus a much faster cranking speed also means less time for air to escape through leaky valves.
Dave
If there isn't, and its not a keypad model, unscrew the stop solenoid and remove its spring and plunger, refit the solenoid and prime the pump with the rubber bulb, crank the engine again, if still no fuel at the injection pipe unions, you have a pump fault.
If there is fuel, get a length of heavy gauge cable at least equivelent to the glow plug supply lead and and fasten it securely to one of the glow plug terminals.
When the hot engine wont start, jam the other end of the cable hard on to the battery positive terminal for about five seconds or so then have an assistant crank the engine, if it starts easey you need to look at the glow relay, if it still wont start, or starts reluctantly and with alot of cranking then I think you will be looking at incorrect valve clearances as the cause.
Whip the rocker cover off and check the clearances are within tolerance, alternatively have a compression test carried out while the engine is at operating temperature, don't let it be done with a warm or cold engine as this will tell you nothing.
If the valves are being held open slightly due to inproper clearance when they expand, precious compressed air will be lost which may lower the the temperature of the remaining charge well below the flashpoint of the fuel.
The fact that the car will bump start easily leads me to think this is what the problem might be, starting this way will turn the engine over much faster than the starter motor is capable of.
The faster the engine turns the quicker the air is compressed and the hotter it gets, since air gets hotter the faster it is compressed, plus a much faster cranking speed also means less time for air to escape through leaky valves.
Dave