Idle Problem, only in the morning.
03-28-15, 01:21 PM
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Idle Problem, only in the morning.
Hello all,
I have 1st Gen RX-7 Fb 1980, UK model manual choke.
I have a very strange Idle problem. When I start it in the morning I will start it using the choke and drive it to work, putting the choke back in as early as possible. My journey to work is about 10 miles and the latter half is on 70mpa roads. However, when the car is idling it will start hunting at about 500rpm and eventually stall.
This make being stuck in traffic at the end of my journey really difficult as the engine is stalling when you need to brake. To stop it from stalling I need to press the accelerator slightly.
When I get to work and park up, with the car hunting to the point of stalling, I check the fuels levels in the carb sight glass, the one on the back is half way but the one on the front the fuel level is at the bottom of the sight glass.
This is where it gets very strange. When I leave work at the end of the day. I star the car as normal using the choke. drive home with no idle problems. I check the carb fuel levels at home and they are both in the middle of the sight glass.
I have had a full service done on the car by a rotary engine specialist. The fuel filter has been changed and the carb has been stripped down and cleaned.
Does anyone have any idea why this is happening? Thank you for your help
Here is the story of what has been done on the car and why:
At first there was too much fuel was going into the carb so much that the fuel level was at the top of the sight glass. AT the same time fuel was still pouring into the carb when the ignition was turned off.
I took it to the specialist They found that the floats had been adjusted upwards so that the fuel level was higher than it should have been. Also, they cleaned the carb.
2 days later the car was back at the specialist the fuel level of the front sight glass was above the glass and the back sight glass was showing half way. Took of the front inlet to the carb and fuel pour out. Then took the fuel cap off, heard a huge hissing sound and the fuel stopped flowing. So he cleared the fuel tank vent valve. Since then the I have been having the problem I have described at the beginning. There is no hissing sound when I take the fuel cap off now.
Can anyone help?
Sorry for such a long post.
I have 1st Gen RX-7 Fb 1980, UK model manual choke.
I have a very strange Idle problem. When I start it in the morning I will start it using the choke and drive it to work, putting the choke back in as early as possible. My journey to work is about 10 miles and the latter half is on 70mpa roads. However, when the car is idling it will start hunting at about 500rpm and eventually stall.
This make being stuck in traffic at the end of my journey really difficult as the engine is stalling when you need to brake. To stop it from stalling I need to press the accelerator slightly.
When I get to work and park up, with the car hunting to the point of stalling, I check the fuels levels in the carb sight glass, the one on the back is half way but the one on the front the fuel level is at the bottom of the sight glass.
This is where it gets very strange. When I leave work at the end of the day. I star the car as normal using the choke. drive home with no idle problems. I check the carb fuel levels at home and they are both in the middle of the sight glass.
I have had a full service done on the car by a rotary engine specialist. The fuel filter has been changed and the carb has been stripped down and cleaned.
Does anyone have any idea why this is happening? Thank you for your help
Here is the story of what has been done on the car and why:
At first there was too much fuel was going into the carb so much that the fuel level was at the top of the sight glass. AT the same time fuel was still pouring into the carb when the ignition was turned off.
I took it to the specialist They found that the floats had been adjusted upwards so that the fuel level was higher than it should have been. Also, they cleaned the carb.
2 days later the car was back at the specialist the fuel level of the front sight glass was above the glass and the back sight glass was showing half way. Took of the front inlet to the carb and fuel pour out. Then took the fuel cap off, heard a huge hissing sound and the fuel stopped flowing. So he cleared the fuel tank vent valve. Since then the I have been having the problem I have described at the beginning. There is no hissing sound when I take the fuel cap off now.
Can anyone help?
Sorry for such a long post.
03-28-15, 01:54 PM
#2
It seems your specialist adjusted the floats to compensate for a pressurized tank. He shouldn't have touched them. Now that the pressure problem is fixed, the floats need to be put back to factory spec.
Think about it. Floats don't just go out of spec on their own. I've only ever had to tweak a float about 1mm in height after a new needle goes in due to slight differences in manufacturing. This is meansured at the end of the float. 1mm out here equals very little actual adjustment to the tab.
Also check your float bowl vent solenoid. Make sure it functions properly (opens when 12V applied) as it can lead to flooding after shutdown as well. I had a sticky one once on a carb that sat for ages that lead to all kinds of headaches.
Think about it. Floats don't just go out of spec on their own. I've only ever had to tweak a float about 1mm in height after a new needle goes in due to slight differences in manufacturing. This is meansured at the end of the float. 1mm out here equals very little actual adjustment to the tab.
Also check your float bowl vent solenoid. Make sure it functions properly (opens when 12V applied) as it can lead to flooding after shutdown as well. I had a sticky one once on a carb that sat for ages that lead to all kinds of headaches.
Last edited by Jeff20B; 03-28-15 at 01:57 PM.
04-22-15, 04:16 PM
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Thanks Jeff20B,
I took the car back to the specialist a couple of time. He check the float bowl solenoid and it is OK, The carb is not flooding but the float level is low. He also said that when he adjusted the floats with the fuel cap removed so that the fuel tank was not pressurized.
The specialist checked the fuel pressure without the engine running. it measured just over 0psi. This lead to the specialist to reason that there must be a blockage in the fuel line, being dirt blocking the 'sock' in the tank. So he used an airline on the fuel line between the in-line filter and the tank. He said it felt like it was restricted and the airline removed some of the dirt. He checked the fuel pressure again and it measured about 2.8psi. Since then the problem has occurred a couple of time and has been idling low but only when the temperature is low, the lower the worse the problem. The idle screw has been adjusted correctly.
I haven't had a chance to check the fuel line pressure again or the condition inside of the tank. Do you have any ideas of what else it could be?
Just a thought, I noticed the check valve on the return line, near the engine, is missing. Would this cause the float level to be low?
I took the car back to the specialist a couple of time. He check the float bowl solenoid and it is OK, The carb is not flooding but the float level is low. He also said that when he adjusted the floats with the fuel cap removed so that the fuel tank was not pressurized.
The specialist checked the fuel pressure without the engine running. it measured just over 0psi. This lead to the specialist to reason that there must be a blockage in the fuel line, being dirt blocking the 'sock' in the tank. So he used an airline on the fuel line between the in-line filter and the tank. He said it felt like it was restricted and the airline removed some of the dirt. He checked the fuel pressure again and it measured about 2.8psi. Since then the problem has occurred a couple of time and has been idling low but only when the temperature is low, the lower the worse the problem. The idle screw has been adjusted correctly.
I haven't had a chance to check the fuel line pressure again or the condition inside of the tank. Do you have any ideas of what else it could be?
Just a thought, I noticed the check valve on the return line, near the engine, is missing. Would this cause the float level to be low?
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