: Renault Clio - Fuel System Problem


tommannix
27th September 2007, 05:02 PM
My 1996 renault clio 1.2 engine code d7f, (diet engine). wont start as it is overfueling? i have had an autoelectrician out to check my ecu and he tells me that i have a overfueling problem ,when trying to start the car ,the pressure in the fuel line builds up so much that it blows the fuel pipe off ,and the engine will only run for approx 1 second
hi thanks for the reply,i have just changed the fuel pressure regulator and checked the return line by blowing down it ,and there was no blockage but still the line to the fuel rail blows off,if i take one of the plugs out it will start and revup ,( very noisely ) and then put the plug back and it will start and tickover untill it chokes with fuel and cuts out again , any ideas ????forgot to mention i have also changed the lambda sensor

madnoel10
27th September 2007, 05:30 PM
Hi Tom - could be down to the temperature switch. What makes you think the car is overfuelling.:)

937carrera
4th October 2007, 06:06 AM
If the fuel line to the injectors is overpressuring to the point it is being blown off then I would suspect that the fuel pressure regulator has failed in a fairly significant way.

The flow of fuel per duty cycle would be correspondingly higher and would therefore cause overfuelling.

madnoel10
4th October 2007, 11:47 AM
I would agree with Carrera - sounds very much like the pressure regulator is furbarred or its fuel return line is blocked.:)

937carrera
4th October 2007, 06:55 PM
It's simple to eliminate the return line from the equation - simply disconnect it at an appropriate place & allow the fuel return to empty into a suitable container. No fuel = blockage

You could even do this by bridging the fuel pump relay instead of cranking the engine & measuring the amount of fuel coming out of the return pipe. This is the method for testing the delivery from the fuel pump. I don't know the spec for a Clio but it will probably be around 0.4-0.5 litre fuel in 30 seconds

tommannix
7th October 2007, 02:56 PM
If the fuel line to the injectors is overpressuring to the point it is being blown off then I would suspect that the fuel pressure regulator has failed in a fairly significant way.

The flow of fuel per duty cycle would be correspondingly higher and would therefore cause overfuelling.

hi thanks for the reply,i have just changed the fuel pressure regulator and checked the return line by blowing down it ,and there was no blockage but still the line to the fuel rail blows off,if i take one of the plugs out it will start and revup ,( very noisely ) and then put the plug back and it will start and tickover untill it chokes with fuel and cuts out again , any ideas ????

937carrera
7th October 2007, 10:13 PM
Hmm, question is do we think you have one problem, or two ? - Can we segment the issues:-

You say the fuel line still coming off, - are you satisfied that the connection is sufficiently secure in the first place ? - in other words, is the pressure too high, or is it normal, but the line connection is not sufficiently secure.

You mention starting the car with one (spark ?) plug removed. Are you saying that the fuel line stays in place then ?

When you blew down the return pipe, where did you disconnect it - could there be a blockage between the fuel rail & the pint you disconnected the return line ?

Why did you remove one spark plug & then start the car - would it not start with all 4 in place ?

Does the car start when cold, but not run when warm, if so that way indicate a problem with cold start enrichment.

Loads more questions I know :confused:

Lagdti
31st October 2007, 08:22 PM
Any news Tommannix?.Have you found out whats causing the problem?.:)

tommannix
1st November 2007, 07:58 AM
Any news Tommannix?.Have you found out whats causing the problem?.:)

still no joy i'm afraid ,i have tried 3 fuel pressure regulators,a new relay for the fuel pump,but i have been told that there is a road speed sensor in the speedo cable that talks to the ecu and tells it how much fuel to send to the injectors , so this weekend i will give that a try :) :)

937carrera
10th November 2007, 07:02 PM
????? I'm confused

What has road speed to do with petrol delivery - you can do 15mph in at least 4 different gears, & therefore 4 different engine speeds.

If you can answer some the the earlier questions I'll still try & help

tommannix
12th November 2007, 07:15 AM
????? I'm confused

What has road speed to do with petrol delivery - you can do 15mph in at least 4 different gears, & therefore 4 different engine speeds.

If you can answer some the the earlier questions I'll still try & help

hi and thanks for your reply
i am clutching at straws .it says in the haynes manual that the injection sub control system recieves signals from various sensors including the road speed sensor
in answer to your previous questions ,if i run with 1 spark plug out ,it will run in a fashion but loads of fuel comes out of the spark plug hole ,it will not start any better if if i run it till warm then put the plug back in,the fuel rail fuel pipe connection is very solid .and there is no blockage between the fuel rail and the fuel tank,i have actually tried to start it with the fuel return pipe in a jar so i can see there is no blockage .the car ran fine till one of my children who is doing a motor mechanic apprenticeship changed the clutch and since then we have been unable to start it ,i cannot see anything obvious that he has left off such as earth wires etc ,i have tried a new crank sensor,and a second hand throttle body that houses the map sensor and throttle position potentiometer ,i have had the ecu checked ,and last weekend changed the oil and filter and found it to have loads of petrol in it . i am now running out of ideas i phoned an auto electrician but he never turned up

937carrera
13th November 2007, 06:13 PM
Hmm, this one looks tricky...........especially as everything was fine before the clutch change & it sounds like the problem was introduced them. Here's my thought process:

Your initial complaint was that the fuel pipe was getting blown off - is that still happening or is that now cured.

Petrol in the oil & the comment about lots of petrol coming out seems to indicate that the car is indeed overfuelling.

The volume of fuel injected is controlled by the ECU, which opens the injector for a certain % of each stroke (called duty cycle), depending upon primarily upon throttle position, airflow and engine temperature. By knowing the amount of time the injector is open, the ECU is metering a precise amount of fuel in based upon flow at the given system pressure, which then gets adjusted by the lambda sensor.

If too much fuel is being injected then the cause can be

1. Too high pressure = more flow - you have already replaced the FPR, & lets assume the replacement was not faulty.

2. By getting a signal that the throttle is fully open, the ecu will allow a longer duty cycle. You have already changed the throttle body, so lets assume that the pot & sesdor are working properly. However, are you sure that the signal is actually getting to the ECU - is there a damaged wire that may be sending a "wide open throttle" signal back to the ECU

3. That leaves the temperature sensor. I've seen other cars (usually running K-Jetronic) that won't start fine when cold, but are OK when warm (if you ever get them started). If the signal to the ECU from the temperature sensor says "its very cold", then the ECU will dump more fuel in to compensate. Can you check the temperature sensors ?

4. Are you sure all the electrical connections have been made correctly after replacing the clutch - & to the right place.

5. or...........lets assume that the fuel system is fine, but the reason the car won't start is on the ignition side. Have you checked that all the spark plugs are working, that the plus leads are connected to the right plugs & that each plus is sparking when the engine is getting turned over. No spark = no go, but fuel still gets put down the cylinders & unburnt gets into the oil.

6. or............ what if the replacement lambda sensor is faulty or incorrectly connected.

It's been a bit of a brain download, but , fingers crossed, it might help you diagnose the problem