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S2 keeps flooding!

T

Tashman

New member
Hi, my 944 S2 3.0 won't start and floods staright away.
I have changed the sparkplugs, distributor cap, rotor arm, and DME relay. I have checked with sparkplug test lights and I'm getting a strong spark.

If I take out the plugs and dry them, and dry the cylinders with compressed air and put the plugs back in, it will fire for about 1 revolution before flooding again. The sparkplugs will be soaking at this point.

If you keep cranking, the cylinders quickly fill up with petrol and have to be dried out again.
I have checked the "Coolant temperature sensor" for resistance and I'm getting 2380 ohms.
Anyone got any ideas why its flooding so much and won't start?

(Hello by the way! (new to the forum))
Many thanks Adam.
 
Hi Adam,

I would supect the Fuel Pressure Regulator - when the fail, they fail open so allowing too high a fuel pressure.

 
Maybe a sticky injector? You can send them away and cleaned for about £12 each

EDIT: Just read your post properly, is it ALL the cylinders? Does sound more like the FPR, all four injectors wouldn't stick open at once. I thought the injectors shutdown when the fuel pressure is high?
I've just thought actualy, are you touching the throttle at all while starting?

p.s it might be worth changing the oil when the problem is fixed as the bores will be washed of oil by the petrol and oil plus petrol isn't healthy for the engine.
 
I wold suspect the fuel pressure regulator too. I would stand by for an oil change - all that petrol is probably in the sump diluting the oil...
 
Yes I will change the oil as soon as it is fixed.
So where is the 'Fuel pressure regulator' located, and is there a way I can test it? Or do you just have to replace it?
Thanks again [:)]
 
You can take the nut of the end of the fuel rail, run the car without the fuse in the fuel pump first to drop the rail pressure, then put a gauge on to read the fuel rail pressure.
 
I'm looking at the fuel rail, and there are two short cylindrical objects plumbed into each end of it. Are they fuel pressure regulators?
They also have vacuum pipes attached if that helps?
 
One is the regulator and one is the damper. The regulator is on the return line, but I dont knowwhich is which on an S2!

Edit - Checked PET, regulator is the one at the rear of the engine
 


Is the Mass Air Flow flap jammed open...? Do S2's have a falp or hot-wire...?

What about the Coolant Temp Sensor ...?

Just thinking outside the box... Right enough these would not flood the cyclinders !

 
I've checked the air meter and it moves freely.

The coolant temp sensor is reading 2380 ohms with a cold engine which seems plausable.

So that fuel pressure regulator seems the most likely culprit so far.....
 
I have a spare FPR but it is from an early car, think the S2 has higher rail pressure..

Following Donals lead, outside of the FPR, the only other thing would be a short keeping the injectors open all the time, either in the harness or the ECU.
 
Umm, it sounds like there is a LOT of fuel coming into this engine chaps. If the plugs are sopping wet within a revolution then things are way out of kilter. Would a duff FPR 9and hence high fuel rail pressure) really make that much difference to the quantity of fuel delivered?

I'm with Mike in suspecting a wiring problem, holding the injectors open. The injectors on a 944 are ground switched; they are fed +12v all the time, and the ground connection on the other leg is switched on and off to make them squirt. If you have a wire that has shorted to earth then it could cause all the injectors to be open all the time.

Testing it is simple; with the ignition on but the engine not running, test the two contacts of one injector. If one of them is permanently shorted to ground then you have your answer.


Oli.
 
FWIW, I think this is a short to the injectors too.

I had a peugeot 205 GTi before that had exactly these symptoms, changed everything before I gave up and gave it to a garage to look at, they gave up too, then gave it to Peugeot. Too many £ down the line to repeat here it turned out it was a simple short, I think where the harness passed through the bulkhead.

On the PUG all the injectors fire at the same time, and suspect its the same with the 944 since I've never read any marketing puff about 'multipoint' anywhere. If that's true then having all of them on all the time would very quickly flood the engine I guess.

I think Oli's test procedure sounds good, but I guess an oscilloscope would really tell you the full picture if you can get one, if the reading on the voltmeter fluctuates a bit it could be misleading. I've been temtped by ebay specials for £30...
 
An oscilloscope is a very useful tool for automotive diagnostics, but for checking injectors as described here you won't need one. All you are doing is to see if there is a constant earth at one of the legs of all the injectors (I don't think they are sequenced), and a normal multimeter will do this fine. (Some bits of wire, a battery and a lightbulb would also do the job.)


Oli.
 

Each injector has a resistance of 2.4 ohms across its 2 pins does that mean they're ok?


Assuming they are, then I would go ahead and change the Fuel pressure regulator.
Here is a picture to see if I've got the right item?

S2engine.jpg
 
It's not the injectors you need to test, but as they are all the same it shows they are probably ok, its the wiring.
Check the resistance across the plug contacts in each injector plug, and each to earth. If ithere are not 1 we're on the right track!
 
The injectors are insulated: no current would earth trough their pins from a live feed.

Testing the injector's plug: Infinity ohms between the two contacts and also infinity ohms between the contacts and earth.

What now?
 
Would need to check the plug contacts with the engine running, but I'm not sure how!
Getting to the limit of my electronic knowledge at least as for as injection systems are concerned.
 
Well I did the test with the ignition switched on - The right hand pin on each of the injector plugs had 12V.

I guess its that fuel pressure regulator to change next?
 
Changing parts on the off-chance that you will find and solve the problem isn't great diagnostics, and is time-consuming and expensive.

An oscilloscope to monitor the injector signals would be a good thing to try; it'll allow you to see when they are being opened. This should tell you whether the problem is with them, or with the supplied fuel pressure.

And I'd think about putting a fuel pressure gauge on the fuel rail before changing the pressure regulator - that will tell you whether the regulator is duff or not.


Oli.
 
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