Fuel pressure

[mikey2]

Ok, this is getting boring now, the cars playing up yet again, this time its the fuel pump relay.

I need to know if there is a fuel pressure switch on the fuel rail that tells the ecu that the fuel pressure needs adjusting, so powers the pump up.

Reason being, i have a good 12v feed to the pump side of the relay, and i have a good switched power to the relay coil, however, i dont have an earth to the relay coil.
I know the ecu switches earth to the relay, and i am purely guessing that it does that by a pressure switch which earths the relay coil.

It seems to me that a lot of the wiring on this car is very complicated and crazy!!!

So yeah, basically, i need to know if there is a fuel pressure switch that controls the fuel pump!! and if so, where it is!!!

thank you kindly

Mike

[asperformance]

no pressure switch but their is a timer relay for priming................

[mikey2]

ok cool, thanks.
Can you think of a reason why the pump wouldnt prime then.
the problem has stemmed from the main relay i think, its been playing silly bu**gers for the last 2 days, i can drive, then the rev counter drops, the car cuts out, then it comes back again. i know the main relay is cr*p because its one from my old car that overheated and melted, i kinda bodged it as it wasnt as knackered as the original one out of the car.
Since then its been ok, but now its playing up, once the car has stalled i cant restart, and i cannot hear the pump priming. I have since removed the main relay and replaced with 2 switches until i can get a relay.
the only thing i can think of is the coil circuit also provides an earth for the fuel pump relay coil.
Would i be right in saying that??
thanks

Mike

[2-jaffacake-tone]

sounds like it needs to be scraped lol

[mikey2]

Originally Posted by 2-jaffacake-tone

sounds like it needs to be scraped lol

Dont say that, its too tempting at the moment.
I have done very little with the car apart from fixing some really shoddy work by the previous owner.

[scooberblue]

send me a pic of all the relays you need an i will pop them in the post if you want.
i couldnt be botherd with the side entry turbo and the 4 coil packs so i ripped out the entire loom from my silver 94 version 2 and put in a full version 4 loom complete with late dash.

[mikey2]

Originally Posted by scooberblue

send me a pic of all the relays you need an i will pop them in the post if you want.
i couldnt be botherd with the side entry turbo and the 4 coil packs so i ripped out the entire loom from my silver 94 version 2 and put in a full version 4 loom complete with late dash.

I would love to do that, i hate the coil packs too, such a ball ache all the time, i know they are supposed to be good, but such a nightmare if there is any problems!!
I only need the one relay, this one.........



From this part of the loom



Its right behind the dash on the right hand side, in the worst possible place to get to!!

I will PM you too,

ta

[mikey2]

interestingly, although the wiring diagram clearly shows that the main relay solenoid power comes direct from the ignition via a diode, and then direct to earth, and the fuel pump relay earth goes direct to the ecu, not having the main relay solenoid plugged in means the fuel pump relay has no earth from the ecu.
Short circuiting the main relay solenoid means the fuel pump runs when the ignirion is switched OFF not when switched on.
However, having the main relay plugged in, the fuel pump primes as normal.
There is certainly some strange wiring in this car, even though its completely normal and standard, it doesnt do what you would expect according to the wiring diagram!!!

Goes to show though, the main relay really is critical to the running of the car, it doesnt just switch sensors on, it completes the fuel pump relay circuit too!!!

[Scott.T]

Sounds like speed delimited playing up. Is there one fitted near to Ecu

[mikey2]

speed delimiter?? thats no where near the main relay coil curcuit, or the fuel pump relay.
Its still playing up though, runs fine for a while, then it starts clicking like mad, almost like its in a diagnostic mode, but the connectors are not crossed, and the fans dont come on, the only things that are effected are the boost solenoid, but then thats run by the main solenoid anyway, so if that goes a bit wonky then so will that one.
I think i will rewire the main relay plug and see if its just a dodgy connection.

I dont know where the de limiter is, its not in the main wiring loom at all, i havent even tried to go over the limit to be fair, so i dont know if it has one, and is working.
I dont recall seeing anything on the back of the dash clocks either.
the only thing thats out of the 'norm' is the black box that sits inside the ecu.

[Scott.T]

If it has a delimiter fitted it will be wired into the speed sensor signal on the Ecu. These are prone to mess about and a symptom is dash dials drop to 0 and engine cuts out. Can be quite intermitent

[mikey2]

ok, i will have a look at that. i dont think its that, purely because, when the main relay cuts, it shuts down all the sensors on the engine, including one which i cant remember off the top of my head, that is essential to run.
However, one of the symptoms, is that the rev counter drops to 0 even when its still in gear and coasting.

I will check which ones the speed signal, and see if the black box is wired in there.

ta

[mikey2]

the black box in the ecu is not connected to the speed sensor b11.

[mikey2]

its the 2 plugs that plug into the engine loom, i touch the plug and it all goes a bit mental. the problem is, they sit right under the vent, and some genius has decided that the rain tray wasnt needed.
Am going to go sort out the dodgy connections now. i might even have to get the vaseline out!!!!!