Fuel pump issues

[JimH]

If the fuel pump circuit / operation on the KV is the same/similar to the WR (and I suspect it is), then the fuel pump will not run when you just turn the ignition on. It will not run just from turning to the start position either - the engine must attain a minimum rpm on the starter motor before the fuel pump engages.
The idea of that is to provide crash protection - fuel pump stops pumping fuel if the engine stalls...

[Julian]

Originally Posted by JimH

If the fuel pump circuit / operation on the KV is the same/similar to the WR (and I suspect it is), then the fuel pump will not run when you just turn the ignition on. It will not run just from turning to the start position either - the engine must attain a minimum rpm on the starter motor before the fuel pump engages.
The idea of that is to provide crash protection - fuel pump stops pumping fuel if the engine stalls...

The KV is different, (certainly on my CGT) the fuel pump runs for a second or two every time you turn the ignition on. It's an additional feature over and above the WR's system, presumably the result of development and improvement....

[mikes2]

Not on my Cq. The pump doesn't run when the ignition is engaged for the first time.

I'm running a relay from a JS Coupe GT just now so it's not relay related.

My 90q 20v does prime the pump when you enage the ignition and it's very noticeable

[JimH]

Certainly priming the pump is a good feature, and is bound to result in shorter cranking times (assuming that's a good thing).

I wonder why they would do that on the GT, but not on the CQ with the same engine. Is it only very late GT's that do that? Does the MB do that?
I'm not too hot on GT build years, so I don't know when they stopped production.

[Phil Payne]

Originally Posted by mikes2

My 90q 20v does prime the pump when you enage the ignition and it's very noticeable

And the next time you get a 20V's fuel pump check valve out, you'll see why. There isn't one - no 20V engine maintains residual pressure - that's a feature of CIS but not EFI (in any form).

I was recently stymied for a while by a WR that wouldn't start. Well, actually, a very large and well-known Audi dealer was stymied by it. When I put the fuel pressure gauge on, the residual pressure died as fast as the needle could move. The reason was that a 20V fuel pump had been fitted, and the adapter on the end of the pump contained no check valve - so the fuel accumulator powered its contents straight back into the tank when the fuel pump stopped.

[Julian]

Originally Posted by mikes2

Not on my Cq. The pump doesn't run when the ignition is engaged for the first time.

I'm running a relay from a JS Coupe GT just now so it's not relay related.

I'll bet you it is relay related. My 87 KV cgt ran the pump for a second every time the ignition was turned on. One day this function stopped working, but as it didn't make a blind bit of difference to engine starting (obviously the system was holding pressure well) I didn't worry about it.

A year or three later I had some problems with starting (long hard starts IIRC) and changed the pump relay. This didn't cure the problem but as an added bonus the fuel pump now ran again for a second with ignition switch on.

There is, I would suggest, a ''soft'' failure mode of certain pump relays. Also I'll bet that there's a few different modification states, supersession and interchangeability possibilities on pump relays.

[beermonster]

My cq's runs for approx a second too.... Maybe it's designed in behaviour?

[chezz]

This relay also provides power to the hall sender and the control pressure-regulator as well as the fuel pump.
Observing the relay contacts with the cover removed whilst moving through the ignition stages, with the starter relay/bridge in place
1st stage - nothing
2nd stage - nothing
3rd stage - movement!
Checking the power at the pump/connector and 9ish volts was showing.
It needs the starter relay/bridge in order to run the fuel pump!

10 points for those of you that got this right and 0 points for me

So pissed off that I'm going to award myself with the Kevin Websters - shite mechanic of the month award.I think I deserve it.(lets make it a regular feature!)
http://corriecanuck.files.wordpress....webster_cs.jpg
I'm of to the Rovers for a pint now!

[Julian]

Originally Posted by chezz

So pissed off that I'm going to award myself with the Kevin Websters - shite mechanic of the month award.!

Yes but isn't he going to cover the big bird with the blue eyes soon.

It seems to me that every character has shagged every character at some time or other over the last decade in The Street!

[chezz]

Originally Posted by Julian

Yes but isn't he going to cover the big bird with the blue eyes soon.

It seems to me that every character has shagged every character at some time or other over the last decade in The Street!

The parallels between myself and Kevin end in the garage...Gods been writing the script for my life for some time now and I've come to the conclusion that I must have severely upset him at some very early stage of my life.