View Full Version : Struggling to start after a run.
Got a starting issue, starts well as a 5 should when cold in a morning. When used and upto temp, you can turn it off and back on no problem, but leave it like 20 mins to a couple of hours, and it just turns over for like 10 secs and ****ters to life, never did this before. Has anyone had any similar issues, carbs rebuilt and set up, new fuel filter and pump, plugs leads and dizzy cap and rotor all new.
Sounds like fuel has perculated in the fuel bowl. Does it run an anti-perc fan still? It's not unusual for a GTT to take a few cranks to start after a good run...
Its running the perc fan still, the whole engine bay is standard. I thinking maybe crank sensor issue.
What you mean by perculated?
Matt Cole
22-04-2019, 10:01
The fuel evaporates from the carb when really hot. That's why Renault fitted the anti-perc fan to help with hot starting. Check to make sure the fan operates effectively and that the solenoid opens with ignition off to allow air to the boost circuit.
Yeh anti perc fan runs and runs after ignition is off.
Matt Cole
22-04-2019, 20:55
Ok. Worth checking voltage to aei module when cranking. You should be getting ~ 12v plus to the relay behind bulkhead. Also is it turning over reasonably easily?
Yeh over strong and easily, just cranks over for like 10 secs.
Have noticed theres a delay on when the anti perc fan comes on.
Matt Cole
05-05-2019, 21:45
Have you got both the thermal sensors installed? There's one in the carb and one in the turbo heat shield.
Only the one on the carb/manifold, there was never one in the turbo heatshield.
hi mate,
just a thought, after your run and left for a while like you said can you remove the 13mm bolt from the base of the carb bowl and check if there is any fuel coming out, sounds like a fueling issue. as the fuel pump doesnt deliver fuel to the carb untill cranking phase.
my thoughts are that the fuel is vaporizing in the carb bowl due to heat, this would explain the 10s or so untill starting. if there is fuel in the bowl you can rule this out.
hope this helps a bit
regards
john
hi mate,
just a thought, after your run and left for a while like you said can you remove the 13mm bolt from the base of the carb bowl and check if there is any fuel coming out, sounds like a fueling issue. as the fuel pump doesnt deliver fuel to the carb untill cranking phase.
my thoughts are that the fuel is vaporizing in the carb bowl due to heat, this would explain the 10s or so untill starting. if there is fuel in the bowl you can rule this out.
hope this helps a bit
regards
john
But that doesnt explain why it starts fine the next morning.
Have you got both the thermal sensors installed? There's one in the carb and one in the turbo heat shield.
Anti perc switch in the inlet manifold below the carb, is it screwed in a place where coolant is flowing or is just a dead end threaded hole, removed mine tonight to see the thread size, and it had a copper seal/washer on it but nothing really came out of the hole?
Anti perc switch in the inlet manifold below the carb, is it screwed in a place where coolant is flowing or is just a dead end threaded hole, removed mine tonight to see the thread size, and it had a copper seal/washer on it but nothing really came out of the hole?
It's not screwed into a water inlet. It should be dry
Going to be looking at the fuel pressure the weekend, does anyone know what fuel pressure i should be expecting at the carb, before the regulator etc, and should the system stop pressurised whilst the engine is off?
Matt Cole
22-05-2019, 21:10
You need 4psi base pressure at the carb. Ph2 pump is 2.5bar, phase 1 3 bar from memory.
You need 4psi base pressure at the carb. Ph2 pump is 2.5bar, phase 1 3 bar from memory.
And do you know if the system is suppose to stop pressurised whilst off? Does fuel pressure return back through the pump whilst not running?
Matt Cole
23-05-2019, 21:02
The regulator returns fuel to the tank. Once off, there will be no pressure in the system.
The regulator returns fuel to the tank. Once off, there will be no pressure in the system.
But the return to tank should only be open until pressure is down to 4 psi is that correct?
Matt Cole
24-05-2019, 21:08
But the return to tank should only be open until pressure is down to 4 psi is that correct?
The flow to the carb is always kept at 4psi above manifold pressure. The regulator takes reference via the vacuum pipe. The "surplus" fuel either not used or the float is full and shut off, return back to the tank. Have alook here:
https://www.rtoc.org/boards/showthread.php?39669-Fuel-System-Set-up&highlight=regulator at the PDF contained within. Second page shows essentially how the system works. Replace the "rail" with the carb and thats pretty much it.
The whole lot is quite low pressure and shouldn't be really pressurised when the pump is off.
The flow to the carb is always kept at 4psi above manifold pressure. The regulator takes reference via the vacuum pipe. The "surplus" fuel either not used or the float is full and shut off, return back to the tank. Have alook here:
https://www.rtoc.org/boards/showthread.php?39669-Fuel-System-Set-up&highlight=regulator at the PDF contained within. Second page shows essentially how the system works. Replace the "rail" with the carb and thats pretty much it.
The whole lot is quite low pressure and shouldn't be really pressurised when the pump is off.
Yeh i know it will relatively low pressure, but im suspecting that the return valve is some how not closing, so got no pressure at all/lines completely emptying to the tank, hence why its an arse to start after its been sitting for a week aswell.
So hooked up a pressure gauge at the carb, getting 3.6psi, which drops down to 0psi pretty sharpish when turning the engine off. Now my gauge has a pressure release/vent button, which i pressed to make sure i had no air locks in pipe to the gauge, once engine was off, the petrol in the vent pipe sucked back into the main fuel line when i pressed the button and you could hear a slight sucking noise from the pipe. Im still thinking it maybe the regulator isnt closing fully, hence the slightly lower pressure and the sudden drop once off.
Jimmy_GTT
04-06-2019, 14:03
There should be enough petrol in the carb for a start. And once you start cranking the pressure should build up quickly.
Maybe you should check the fuel level in the carb before you try to restart.
Im getting 6 psi, with the gauge teed in after the fuel filter, with the car running.
The flow to the carb is always kept at 4psi above manifold pressure. The regulator takes reference via the vacuum pipe. The "surplus" fuel either not used or the float is full and shut off, return back to the tank. Have alook here:
https://www.rtoc.org/boards/showthread.php?39669-Fuel-System-Set-up&highlight=regulator at the PDF contained within. Second page shows essentially how the system works. Replace the "rail" with the carb and thats pretty much it.
The whole lot is quite low pressure and shouldn't be really pressurised when the pump is off.
Just thought id tagged you in.
Matt Cole
09-06-2019, 22:27
Are the tank vents clear? Make sure all the vent pipes aren't snagged or blocked.
Are the tank vents clear? Make sure all the vent pipes aren't snagged or blocked.
Thats my next port of call, as the regulator change hasnt fixed the issue, slightly better but still well off, is the breather/vent pipe the top one at the back of the tank, just above the leaky bung?
Whats does the valve do up by the filler neck?
Whats does the valve do up by the filler neck?
Found out what this is now, a non return for the tanks breathing system.
Just thought of something, the main fuel line from the sender to pump as some thick foam type of tubing round the line, is this a standard thing, because im lead to believe that its kind tight between the body and the tank?
Matt Cole
17-06-2019, 21:14
The foam is standard to protect the line. The one way valve is in case the car rolls and prevents fuel spilling out the breather. Check it works or the tank won't vent properly.
Yeh the non return valve on the tank breather system was blocked, i now have a little pressure in the lines once off, so thats me cold starting sorted, removed sender to find the filter sitting in the bottom of the tank, cleaned out some little spec of debris and refitted, im suspected this and the fact the pumps probably been struggling against the vacuum in the tank has prematurely worn me pump out alittle, so new pump on order. Also i think ive sussed the hot start issue, its not a hot start issue, its an engine flooding issue, so looks like ive fuel entering the venturi into the engine once switched off, still got this to look at.
Yeh the non return valve on the tank breather system was blocked, i now have a little pressure in the lines once off, so thats me cold starting sorted, removed sender to find the filter sitting in the bottom of the tank, cleaned out some little spec of debris and refitted, im suspected this and the fact the pumps probably been struggling against the vacuum in the tank has prematurely worn me pump out alittle, so new pump on order. Also i think ive sussed the hot start issue, its not a hot start issue, its an engine flooding issue, so looks like ive fuel entering the venturi into the engine once switched off, still got this to look at.
Cant see no obvious, dripping down the venturi once ive got the lobster, so at a loss now.
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