S2 Stag Not Firing :(

[260tech]

Good idea, thanks. Sometimes it starts first go, other times it idles bad and really low for as long as 10 seconds thereabouts (no throttle input) before returning to normal (which means revs up to 2k then back to ~1k). I've replaced the pump and the only odd thing I've noticed which is different to before, is that there's no vapour pressure when I open the cap now like there was before.

" blown compressed air down the rubber & metal lines..." Maybe cleared something here?

[DaveB]

Maybe; but doesn't everyone else get that "hiss" when they open the fuel cap? I think pretty well every other fuel-injected car that I can remember driving does this?

[pyro-ns]

there's generally two options for losing the hiss off the fuel cap. first is the the fuel cap itself isn't holding pressure anymore, other is that the rubber seal where the pump cradle goes into the tank is worn etc.

[DaveB]

Interesting! Since the cap seems ok and I didn't change it. But the rubber seal looked a bit mashed and worn. I might have to try to fast it and get a replacement. Also does anyone know what that red goo is on the cap which screws onto the tank access hole where the line goes in? It never sets hard but is obviously not bothered by fuel fumes at all.

[pipster11]

will just be a gasket goo/sealant

supercheap have a stand with about 10 different types - pretty sure all auto places should have one, just read through their descriptions

[KiwiRS4T]

Interesting! Since the cap seems ok and I didn't change it. But the rubber seal looked a bit mashed and worn. I might have to try to fast it and get a replacement. Also does anyone know what that red goo is on the cap which screws onto the tank access hole where the line goes in? It never sets hard but is obviously not bothered by fuel fumes at all.

Will be a special grease that doesn't damage the rubber. I screw that ring down really tight - using a blunt screwdriver and a hammer to drive the ring around!

[DaveB]

Ah - I was only game to make it tight by hand (as I removed it by hand) - maybe I will be a little more 'persuasive' next time Yes needs to be a special sealant that won't dissolve from the petrol too, as every sealant I've tried does. And this stuff doesn't set hard, so thought it might be something special. Never mind I'll experiment

[DaveB]

Hmm just tested the old pump in a bucket of kero; it took about 15 volts to start pumping, but after pumping through a litre or so it'll now pump on as little as ~12V

[QWK32]

did any crap come out? maybe something got sucked up into it and jammed it up?

[DaveB]

I suspected the same; I ran it in a clear container and checked it outside for signs of sand etc. but I couldn't find anything... just made the kero smell real bad :S

Shook lots of petrol out of it for a few minutes beforehand though; seemed the fuel was trapped in there. I'm not sure about this pump; for ~$200 I'm not about to chuck it, and since it seems to be running fine and I've had a couple of tunes on it... maybe I'll just put it away as a spare.

Edited January 4, 2010 by DaveB

[pyro-ns]

can fuel pumps hydrolock? be a pretty poor design if they could i guess...

lol, maybe whatever was in there dissolved in the kero, but wouldn't dissolve in the petrol?

Edited January 5, 2010 by pyro-ns

[DaveB]

Must've been something nasty not to dissolve in petrol :S Just seemed to want more volts to kick over, which perhaps my electrical system would not always be up to...

[pyro-ns]

i'm not an auto-elec, but my guess is if it requires more volts than normal, it's pretty worn.

Edited January 5, 2010 by pyro-ns

[KiwiRS4T]

Time to directly wire your new one before that flogs out! They like full 13+ volts.

[66yostagea]

In my R30s, the S13 and the Stag, when you turn the key on you can hear the buzz of the fuel pump priming the system.

All these are stock. Only trouble I ever had was with one of the R30s. It stopped pumping. Hah! the pump is stuffed. Got

one that was working, put it in but no go. Turned out to be a bad earth connection.( after 24 years!)

I think there is so much electrical stuff on modern, post 1983, that many earth links are necessary to get everything to work. There are even earthing kits you can "BUY".

The other thing that comes to mind is if the priming noise, buzzing, does not stop, then it could be the fuel PRV is farked.

[DaveB]

Time to directly wire your new one before that flogs out! They like full 13+ volts.

Well all that has really been holding me back from doing this is the two-stage pump control. ie. it seems that under low-load conditions like partial throttle or idle, the pump is run with a dropping resistor to lower the voltage, make it quieter etc. I want to keep this function if at all possible because I've heard what the pump sounds like at full-bore at idle and I think it would be audible in the cabin.

After looking at the ECU pinout it appears that this two-stage control is taken care of on the ground side of the pump connection, so hopefully it is possible to give it a direct 12V feed at the right place, and still have the FPCM ("fuel pressure control module"???) which controls switching the dropping resistor in and out, regulate the pump's duty as before.

Here is what I plan to do... the original pump-related part of the ECU circuit:

I plan to splice in an extra relay to switch my 8ga direct battery connection (fused separately) like so:

Unfortunately I don't think that I'm going to be able to easily access the connection I want on the pump (near connection 2) and I think instead it's going to be right at the pump itself, leaving the FPCM connected to the original relay output. Hopefully this is only a power connection and nothing more and hopefully FPCM==Fuel Pressure Control Module and it therefore hopefully has another connection (like fuel pressure) and thus the connection near 2 is just for power... if that is the case, it won't care about the pump not being connected there anymore.

Otherwise it might sense voltage drop or something, and having a pretty much constant load with my new connection (original relay just switching coil on new relay) may fool it to running in its "idle mode" all the time... but I doubt it. Fingers crossed.

After seeing how difficult it is to get these pumps going on the test bench, I wonder if this may well make it easier to start... fingers crossed

[KiwiRS4T]

My intank Walbro is directly wired for full voltage at all times and the relay is switched on/off only. The only time I hear the pump is when I first turn the key and hear it priming. I am not aware of it when the car is at the lights or otherwise idling. Maybe if you listen very carefully you could pick it out but I honestly don't think it will be annoying. The alternatives, short pump life or engine destroyed by insufficient fuelling, seem infinitely worse. For my purposes - big horsepower and track days - I am getting the extra insurance of a surge tank and a second pump (Bosch 044).

[DaveB]

Thanks Bob

My intank Walbro is directly wired for full voltage at all times and the relay is switched on/off only. The only time I hear the pump is when I first turn the key and hear it priming.

...

Sounds like yours is still running in dual-stage mode, cool. This idea might work then. Another possibility is to connect about a 5 ohm / 10 watt resistor from the earth connection on the pump to earth, which would have the effect of running the "slow" stage of the pump a little "faster" too.

Edited January 5, 2010 by DaveB

[DaveB]

In my R30s, the S13 and the Stag, when you turn the key on you can hear the buzz of the fuel pump priming the system.

All these are stock. Only trouble I ever had was with one of the R30s. It stopped pumping. Hah! the pump is stuffed. Got

one that was working, put it in but no go. Turned out to be a bad earth connection.( after 24 years!)

I think there is so much electrical stuff on modern, post 1983, that many earth links are necessary to get everything to work. There are even earthing kits you can "BUY".

The other thing that comes to mind is if the priming noise, buzzing, does not stop, then it could be the fuel PRV is farked.

Thanks for the reminder I should check the earth too. PRV==pressure relief valve?

[KiwiRS4T]

Thanks Bob

Sounds like yours is still running in dual-stage mode, cool. This idea might work then. Another possibility is to connect about a 5 ohm / 10 watt resistor from the earth connection on the pump to earth, which would have the effect of running the "slow" stage of the pump a little "faster" too.

No Dave my pump is on all the time or off. When it is on it runs at full voltage the whole time.

Is your car otherwise going OK now? if you are ready for a tune they should be able to put a meter on your fuel system and see what is happening at high revs and also to ensure that it is not leaning out at full throttle.

Good luck

Bob