right, bought a punto 75 sx with a broken fuel feed from the pump. bought one off ebay, fitted today and no joy,

now pump is working, stays on with ignition tho, that normal?

have fuel pressure at the injector rail,

have a spark

will only fire if i pour a drop of petrol down the carb, but obviously wont start,

tried fuses under dash, both sides, tried ones under the bonnet, even more annoyed as taking the battery off my other car as the puntos one kept going flat quickly, i managed to short the connector to the ecu (right next to battery terminal) and think ive fried it as

need the punto running even more now

right, think the injectors arnt putting fuel in, got fuel in the injector rail, and alot of fuel going back through the return, any ideas? :bang:

disconnet plugs and turn it over, remove plugs and see if they are wet.

plugs dry, no smell of fuel in inlet.

have you definitely got spark? If no spark and no fuel then it'll be crank sensor.

If you do have spark then yeah probably injectors, i'd just be surprised that all of them are blocked tbh but not knowing its past it is a possibility.

blu73 said:

have you definitely got spark? If no spark and no fuel then it'll be crank sensor.

If you do have spark then yeah probably injectors, i'd just be surprised that all of them are blocked tbh but not knowing its past it is a possibility.

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id assume there is a spark, tip some petrol down the throttle body and it fires up and then dies, even re done the timing , previous owner had it in a garage when it kept cutting out, there the ones who broke the fuel pump, and the cam cover being off too i had no idea if they had touched the timing, so re did it.

im more worried that the ecu may be at fault. as you say, cant see all injectors going down all at the same time. plus with the fuel pump running the whole time the ignition is on.

any more ideas?

right ok, had anouther play with it this eve,

definetly got a spark

fuel pump runs constantly,

fuel at the injector rail,

cranked with no sparkplugs no fuel going into bores AT ALL..

fuel pump goes faster when lamba sensor unplugged.

next thing on my list is test volts at injector plugs.

will not fire at all, trickle some fuel down the throttle body will fire up and sounds like its running good for a split second and then dies.

:bang:

well your doing the right stuff, woth a bit of luck it will just be blocked injectors, or a fault with the wiring to the injectors.

blu73 said:

well your doing the right stuff, woth a bit of luck it will just be blocked injectors, or a fault with the wiring to the injectors.

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cheers,

right , took fuel rail off, and the petrol in indeed getting to the injectors, but they dont seam to be fireing, they were all sealed in with some sort of black silicon, tested all injectors, and they all appear to be working with a 12v supply applied to them,

getting 12v at the wireing for each injector,

surely there not all blocked?

wasn't it you that had the fuel pump full of black silicone stuff.. They can be cleaned i believe but not something i ever had done before so no idea how much it costs. Worth finding out before going and buying some other injectors

blu73 said:

wasn't it you that had the fuel pump full of black silicone stuff.. They can be cleaned i believe but not something i ever had done before so no idea how much it costs. Worth finding out before going and buying some other injectors

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no sorry not me,

right, had anouther brainwave, just had the injector rail and injectors back on the car, put 12v to each injector and sure enough they all squirt petrol.

so seams i have a electrical fualt somwhere,

what tells the injectors to fire it is the ecu? an has anyone got a diagram of what pins on the ecu do what? so i can rule out a break in a wire etc.

oh and the voltage to the injector wireing drops when turned over, dont know if this is enough for them not to fire tho, but there certainly not fireing when turning the engine over, but do squirt out plenty of fuel when put to a 12v feed off the battery

I must be getting confused between threads.. i'm not the best person to ask when it comes to wires tbh.

The ECU usually grounds the injectors not gives them a feed (that is assuming it's the same a cinq one).

The voltage will drop slightly when you try to start the car (the whole electrical system will do the same as a starter draws muchos amps) the ECU is programmed to account for this and adjust the injectors accordingly. Poking an injector with 12v for any lengh of time is a bad idea as it could overheat they are only designed to be on for milliseconds.

Sounds like your problem is with the ecu side of things. That doesn't mean it's the ECU, it could be wiring or a sensor, infact any number of things causing it to cut fuel.

With the ignition on there should be 12v to plus side of the injector terminals and nothing to the other (with the injector unplugged).

If you put your meter in each injector plug pin with the injector conected you should get a voltage (will be lower than 12 or fluctuating) with the engine turning over. But basically if they're not squirting and not clicking the ECU is almost certainly not giving them an earth (or the wiring in between).

Very hard to diagnose this for me without actually being able to see it myself. :bang:

Best thing would be to see if there any fault codes (can you this on a 75 ecu?? I guess you can).

Hope that helps a bit I'm no Punto expert.

thanks for the reply

so do the injectores get there signal to fire from the big white relay on the bulkhead? or from some sort of signal from the coils or somthing? if i know what makes them fire i can narrow down the problems im having a little better.

The injectors fire by the ecu connecting their ground/negative once every revolution of the engine. It happens for milliseconds so it won't be easy to measure. The ECU gets it's refference to fire the injectors from the crank signal, however so does the spark so if you get a spark the crank sensor in theory should be working.

Other things that could cause a fuel cut are immobiliser, bad earth on the ecu, short in the wiring, the ecu it self (since you mentioned you shorted something out) inertia switch and various other things. Thing is most of these would normaly cut the pump not stop the injectors and the the fact your pump speeds up when you disconnect the lambda is just plain bizzare. Taking into account it also keeps flattening batteries at a fast rate would also suggest there may be a short circuit somewhere.

Honeymonster said:

The injectors fire by the ecu connecting their ground/negative once every revolution of the engine. It happens for milliseconds so it won't be easy to measure. The ECU gets it's refference to fire the injectors from the crank signal, however so does the spark so if you get a spark the crank sensor in theory should be working.

Other things that could cause a fuel cut are immobiliser, bad earth on the ecu, short in the wiring, the ecu it self (since you mentioned you shorted something out) inertia switch and various other things. Thing is most of these would normaly cut the pump not stop the injectors and the the fact your pump speeds up when you disconnect the lambda is just plain bizzare. Taking into account it also keeps flattening batteries at a fast rate would also suggest there may be a short circuit somewhere.

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cheers for the reply, i shorted out my other vehicle while taking its battery off to swap them over while trying to sort the punto, blown a relay at least so have two cars not working at mo :bang:

got a good blue spark and immob light comes on and goes out so dont think its immob problem. going to take all earths off today clean and refit, see what that does,

Connect one of your HT leads to an old spark plug and rest it on top of the motor. Turn the engine over and see if it sparks.

Stick a meter or a bulb into an injector plug (use a bulb wit the bent metal tangs for instance) and see if it flashes when you turn the engine over.

If you have a live coil but no spark and fuel injectors that work on their own.. but don't get a "pulse" when you turn the beast over then it's your crank sensor.

ECUs contrary to myth are really the least likely thing to go wrong. If your crank sensor is good, then it may be the injector relay.... though I don't have a Punto so I'm not sure where it'll be. Under the bonnet though.

Ralf S.