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Discussion Starter · #1 ·
Hello, continuing with the threat:

I get to a point where the engine only starts with brake cleaner, once it starts if i press the pedal engine runs between 1500 and 4000 rpm aprox. Once i take off pedal it stops.
Timing belt is OK, Injectors are tested on a bench and are OK. High pressure pump gives the correct pressure acording to Clip, and other parameters seems ok. Compresion test is OK.
Returning test is OK. Also checked the valvs and noone seems to be gripped at all. I Virginized the ECU and its working good, vin is o now and there is no faults on Clip. I cant test the injectors pulse, but as adding the brake cleaner it starts i assume the electronic part is ok. Other parts i changed ar the Turbo, the oil pump and the refrigerator thermostat, but dont think noone of those can be the problem.

Realy donno what more to do, only take off the engine and reassembly from the begining, but i did this 2 times now. Its realy frustrating. Any idea from the experts? thanks in advance
 

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Super fantastic Mod Technical Supremo Nice Guy
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Below 1500 its dying then would you say
What about fuel filter, has this been checked?
 
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Super fantastic Mod Technical Supremo Nice Guy
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Title now changed
 
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Diesel....assuming all tests were done properly and compression is sufficient to assure ignition, I can think of two things.

Return line for fuel. Blockage can effect starting but then there would be a lot of smoke from exhaust.
If you can, connect vacuum meter to the intake plenum. On starting, if meter reads anything above 1 bar, that indicates problem in exhaust pipe. Or you can take off exhaust all together for testing.
If exhaust is blocked in any section, engine will not inhale fresh air but just pumping exhaust gases in and out of cylinders.

Are there flaps for intake air on that engine?
 

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Discussion Starter · #7 ·
Bosch fuel pump yes. Thanks for the update. Once the engine starts with brake cleaner it runs smooth and exhaust smoke looks correct.
I added a new backflow valve as the current one was broken and fuel was returning back. Maybe it's the cause. Will try with an external fuel bottle to test.
There is a flap on the egr but it's not connected on this model so it's always open.
I have the return tester always connected and return flow looks ok
 

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If the engine is running fine once it starts, then forget about blocked exhaust and fuel return line.
If there is no smoke, then the engine is not getting fuel, rather then overflowing, which would create a smoke screen.
That leaves two possible problems. Not enough compression to ignite the fuel or no fuel at all when cranking.
 

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Bosch fuel pump yes.
Guesssing but the symptoms fit one issue with some Bosch pumps, easy to check.
Many have a low pressure lift pump bolted onto the back of the main pump.... a sorta rectangular cover with 3-4 bolts holding it.
Behind the cover is a gear pump driven by a shaft from the pump main body.
Those fail, either the shaft breaks or the gears break up.

This means that there is no low pressure feed to the main pump and it will not start at crank speed, the HP side of the pump is good at pressurising fuel but rubbish at sucking it, it needs the feed from the low pressure.

Second thought is if you have an electric lift pump as opposed to a manual priming bulb in the system?
If so, is it working.
 

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Discussion Starter · #10 ·
Checked today with an external fuel deposit and kepps the same, so fuel its not the problem. There is no low pressure pump on this model.
The problem is that car was working before i reworked it so its hard to think its a mechanical issue, i think its more like something i did wrong. There is rail pressure, but it drops realy fast after engine stops, donno if its normal.
There is fuel in the inyectors, there is pressure, there is compression and keeps no starting, so might be an air flow problem? maybe an obstruction somewhere, or it will start with lot of fog or something? or maybe inyectors dont work at low pressure?
 

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G9T engine (that's 2,2 dci)

191559


No 1 is low pressure pump which is inside the rezervoar
No 3 is HP regulator bolted to the HP pump (4)

Air: there should be a flap on the intake tube, electrically controlled, when activated it closes flow of air into the engine to shut it down. I can post a picture but that's not your problem.

Injectors: they are also electrically controlled. If they work, they open at any pressure. Also, not your problem.

Usually, non-return valve is located on LP pump. And that may be your problem. Also, if there is a puncture in the return line system, that can cause the fuel to return bak to the tank, and we don't want that.
Problem in the LP pump means that HP pump must draw fuel from tank at starting. As it can not, spraying brake cleaner starts the engine and then HP pump can supply some fuel.
 

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Discussion Starter · #12 ·
I added a external fuel tank directly to the filter by gravity, purged it and had the same problem. Will need to check the auto suction pump in the HP pump maybe.
Other test i did some days ago was taking off one injector outside of the cilinder with a flexible tail to check the spray, and at start there was almost no spray at all.
 

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Discussion Starter · #13 ·
Also my model dont have LP pump, i know because the space where the fuse must be its empty. There is a hand fuel pump instead.
 

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Gravity pressure may not be enough to open fuel valves. Also, if there needs to be 1,2 bar pressure in the fuel line and there isn't, you would have a problem starting the engine.
From everything you described, I can't think of anything else then low pressure pump.

Don't know if I ever saw a diesel without LP pump.
 

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Discussion Starter · #15 ·
Bosch cp3 pump have an auto suction pump on it so no need a LP pump, thats what i was reading about this pump. Only need to take off all the air in the circuit. Also in the Clip there is no LP pump to test.
 

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Don't know if I ever saw a diesel without LP pump.
there may be a language/comprehension issue.... please neither of you get hung up on it.

If Eolas has what they call a hand fuel pump.... I think that is the squeezy primer ball.... there is unlikely to be an electric lift pump.

There will be a low pressure pump within the main fuel pump driven from the engine.... many people do not realise there are two parts to the pump.

Eolas has just said it, Auto Suction Pump..... in my language that is the low pressure section of the Bosch pump, the one that sucks fuel, is located at the rear of the main pump and is known to fail.
 

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Bosch cp3 pump have an auto suction pump on it so no need a LP pump, thats what i was reading about this pump. Only need to take off all the air in the circuit. Also in the Clip there is no LP pump to test.
Have you tried priming the circuit?
Squeeze hard on that hand pump to keep up the pressure and try starting the engine then. Kepp pumping untill the engine starts, if it will.
 

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Don't apologise Eolus, your English is better then my Spanish.
It's just when we have mixed nationalities talking about technical issues and who have different terms for the same thing, we need to be patient and try to be clear.

This is an animation of the CP3 pump.
Bomba Common Rail Bosch CP3 - YouTube
See at the back are two gears.... this is the low pressure (auto suction) part.
They pump a reasonable amount of fuel at low pressure into the main part where they HP pistons pump a small amount of fuel at potentially silly high pressures.
Those gears have been known to break up or the drive shaft snap...no low pressure feed so no HP fuel pressure and the injectors will not open until the common rail has enough pressure... around 300-400 bar if I recall correctly.
 
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