It's never just one problem is it...
- Thread starter pauljmcnulty
- Start date
FPR is the one on the return line - not sure which is which is an S2 though
Managed to get my gauge rigged up on the S2 this evening... the battery is a little low - not enough to try and start it, but certainly enough to run the fuel pump. So with the DME relay jumpered, I have 3.8 Bar... absolutely spot-on book pressure. Damn, and I though that was looking to be the problem:-( Assuming the idle pressure is the same (hopefully I can check that tomorrow) I assume that rules out the FPR?
Step forward Mr McNulty and say: "Na, na, na-na, na, Told you so, told you so..." I have managed to replicate the fault with some test equipment on it. It might be useful to others sometime, so I'll note it here... OK... cold, both fuel pump running with bridged DME relay, and running on idle as it should be. 3.8 Bar/ 3.1 Bar (ok, the latter is a little down, but within spec limits). Runs perfectly ok. Switch off, wait a couple of minutes, restart... starts, runs for a couple of seconds, dies, and won't restart. Check the fuel pressure, zero. Nothing. now here is the bonkers thing I don't understand... after a while the fuel pressure goes up according to the gauge! WTF? How? The pump isn't running, even if the FPR does suddenly (or in this case, slowly) decide to maintain pressure where it didn't before... Checked for a spark to prove it wasn't the pump shut down by the DME relay, and there is a spark, nice and regular if not the fattest I have ever seen. After a while it will restart and run, fuel pressure restored to 3.1 Bar running, 3.8 Bar immediately after switch off. So... I am now of the belief that it could be the FPR failing open (one of the less common failure modes) after all... unless anyone has any other comment or advice before I order a replacement?
pauljmcnulty
Active member
Only na, na, na na na, told you so. [
][][] Joking aside, I'm no technical expert at all. What I do get is a lot of people telling me they've had a certain thing happening, and what fixed it. All I do is collate what individuals are finding so it helps us all!
We have, touch wood, just sorted a similar problem on our S2, an intermittent refusal to start or dying while in motion. Pulling out the DME relay and putting it back in would often apparently restore it to health for an indeterminate time that could be weeks or minutes. After consulting numerous fora which pointed at the DME relay (now got two new spares in the glovebox) and the oxygen sensor, we think we have found the cause, essentially corrosion in the fuse box. Removing the fuse box is easy. Dismantling it is scary as it is in layers with some layers conductive and some insulated. Remove the layers one at a time and take lots of photos. Once down to the connection layer, there was a lot of corrosion which has been laboriously cleaned up. All in all, once the fault lasted for long enough to do some testin and identify which bits weren't working, it was all fixed with a few hours work. There is an option which is to buy a new fusebox, a snip at about £700. All that remains is to find out which set of connections got swapped connecting everything together so that the headlights work as advertised again!
So between us, we have one S2 that doesn't stop, and one that doesn't go... if we put the two together, we could build one good one that didn't stop or go![:-] I don't think it is the ignition amplifier any more, as when I was able to replicate the problem I had a consistent spark - something I didn't have when the Ignition Amplifier failed. Fuesbox could I guess still be a possibility, if it were affecting the fuel pump running... As I have now ordered a replacement FPR, and away from the car again for another week or so, I'll see if that fixes it.
VanhireBoys
Member
And us Irish are a nation of tractor mechanics and "it will be grand" thinking My thoughts are the fuel pressure valve on the return line to the tank (does an S2 have one ?) I had a 9000 Saab a long time ago and the valve jammed shut not allowing any fuel back to the tank ! The fuel pressure was through the roof and the only place for it to go was the combustion vhamber... Massive amounts of fuel were being injected in and flooding the cyclinders... You said the fuel pressure climbed and then she woulnt start ! After she throws a fit check the plugs for wetnessORIGINAL: peanut Us Brits can't be deterred by a few minor setbacks ....we are inventors....a Nation of shed-people. [
I had a Lancia which had an FPR problem with the same Bosch setup and similar problems
peanut
Active member
Luckily I am half Irish so I always think it will be grand as I work on my tractor in my shed lol[
] you can test for over-pressure from a stuck FPR valve by disconnecting one of the injector connectors. The reduction in fuel pumped into the inlet should allow the engine to recover a bit ....allthough it will still run rough on 3x cylinders.Well at last I have a nice, shiny, new fuel pressure regulator of the right type, and all fitted, a nice 46mile jaunt to prove it out... another 46 miles today, guess what? It has not cured the problem!!! So whilst sat at the side of the raod, wondering why I had bought a new fuel pressure regulator... I thought about what the fuel pressure gauge was telling me, and why the car was behaving as it was... Well how about if the fuel pump wasn't running? car will run for a seond on residual fuel pressure in the fuel rail, and then it will stop, and fuel pressure will have dropped, because the fuel has just been injected into the engine until the pressure drops... Doh! I have replicated the problem twice again now, and back to it being temperature related... The first jaunt I hadn't shut the bonnet properly - extra air getting in keeping things cool? First time I felt the ignition amplifier, and it was warm. second time, it wasn't. second time I checked the temperature of the DME relay too - it was warm... so... I have changed the DME relay once already, but my spare is a few years old now... but could also be a fusebox issue? Second time round after waving the DME relay around to cool it down it started again fine...
peanut
Active member
have you tried running the car for a few days with a 3x way bypass fitted instead of the DME relay ? Because this seems to be an intermittant fault I'm leaning towards it being either a poor connection or a heat related problem or a combination of both. By using the 3x way bypass you eliminate the DME relay , the ECU , various sensors and a lot of associated wiring . If it runs ok with the bypass it might narrow down your search. Have you removed and cleaned the 2x earthing points to the ECU which are under the dash behind the glove box next to the fuse box ?
Well fingers crossed, I have a solution - the good old (un)reliable DME relay. I thought I had two good DME relays, it looks like I only had one! Why am I so sure I have fixed the problem? because I have the next - ABS light on now! Prey for a simple wheel sensor fault!
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