Should the S2 2.9 fuel pump run all the time?

[abercoms]

So I finally built the garage and got the S2 into it, it hasnt been started for about 10 years but prior to that it started on the button every time. Now it just turns over with no attempt to fire, Ive got spark and compression, on turning the ignition on, I get ignition light and pump runs for a couple of seconds then stops, Ive never worked on fuel injection but assumed that the pump would run all the time to maintain pressure feeding excess fuel back down the return pipe, am I right or wrong? Ive taken the fuel pipe off where it heads into what I take to be the fuel rail and fuel comes through but not exactly pressurised more of a squirt. any suggestions appreciated

[GreenV8S]

I would expect the pump to run for a second or two at power up, and then run continuously while the engine was cranking or running.

If you're starting from scratch, I'd start with the basics - do you have a spark at the plugs, is fuel getting into the cylinders? A passive strobe in series with an HT lead is a good way to check for a spark.

[abercoms]

Thanks for reply, Ive done the basics as far as spark compression and fuel as far as knowing there is fuel, worry was the run and cut off of pump, if thats normal im down to electronics and injectors both are unknown areas for me, code readers are impossible to find and Ive yet to investigate getting to the injectors or even a meter across them to see if they are firing but I guess thats the next path, Id been suspecting electronics as all had been well when last taken in to the light, I may have to give my local mechanic a shout and invite him round

[GreenV8S]

You getting any sign of life at all when you crank it? If the plugs are clean and you're getting a spark, even a trace of fuel would get you signs of life. You could disable the fuel injection and just spray some damp start into the intake if you wanted to prove it was a fuel supply problem. Remember to keep the battery charged up whatever else you try - a low battery will make it much harder to start even after you fix whatever other problems there may be.

[abercoms]

Theres not a cough hence why I was thinking fuel but I was at the limit of diagnostics at this point, with a plug out there seemed to be no fuel, its the why thats now the problem

[mentall]

Mine had no fuel pressure, after the 1 second pulse.

The problem was crud in the tank, filter screen and pump.

Here's the procedure to find out:

Remove the pump relay and bridge the 30 (common) and 87 (n/o) terminals on the socket. Then the pump will run whenever the ignition is on.

Remove the fuel feed pipe from the fuel rail. (not the one on the regulator: that's the return to the tank). Put the end of the pipe in a suitable container.

Best to have an assistant here: you don't want to spray petrol around the garage. Briefly turn on the ignition, and petrol should come from the pipe at a good rate. If it does, you can measure the output rate (a 1 litre container?) to see if all's well.

If it doesn't, you have a blockage.

Typically this is what happens when the car has been off the road a long time. Water under the petrol in the tank corrodes the tank, and the resultant rust blocks up the system. It can also result in a perforated tank. Ask me how I know!

And it's bad for the pump to run dry for very long,

Good luck, and take care!

John

[phillpot]

Wet plugs = fuel no spark

Dry plugs = spark no fuel

There is a valve, like a tyre valve, on the fuel rail. If you press that once the pump has primed fuel should spray out with some force! The more technical (and safer) way is to use a fuel pressure gauge, think it should be around 1.5 bar.

[mentall]

The Haynes Granada manual says the pressure should be greater than 5 bar with no flow, regulated to 2.5 bar at the fuel rail Schrader valve.

But with the engine not running, you can get 2.5 bar even with a blocked pump inlet; you need the flow as well, for the engine to run!

Edited by mentall on Thursday 12th November 11:06

[phillpot]

mentall said:

, regulated to 2.5 bar at the fuel rail Schrader valve.

Oops, only 1 bar out

Agree you need flow (volume) as well as pressure but should at least try to fire up with pressure but die out if no volume of fuel?

[abercoms]

Thanks for all the tips, Ill get out and work my way through them, cutting out the fuel pump relay I think will be telling, Ill let you know how I get on.
I also got a code reader today, count the beep job but better than nothing in case I got a sensor issue

[abercoms]

Thanks for all the tips, been out today and worked my way through them, its not the fuel pump it runs and has pressure that pushes my finger off the end of the pipe, the tyre valve also spews out when opened, Ive also got signal to the injectors, I cant tell if plugs wet or dry, think they are wet but maybe not as only thing I can think of is blocked injectors, that means further strip down and finding plenum gasket which Im struggling with at the moment
Maybe need to go back to basics again and get an extra pair of eyes, Ill have to dig out my special bottle of whisky....
Any other suggestions welcomed as always

[phillpot]

Here's your gasket . . . . . . . clicky

[abercoms]

Oooh ta, helps when you know what you are looking for, ordered, hopefully get to the back of beyond here in the highlands by the end of the week and I can have another tooter

[GreenV8S]

abercoms said:

Ive also got signal to the injectors, I cant tell if plugs wet or dry, think they are wet but maybe not as only thing I can think of is blocked injectors,

All injectors blocked at the same time? Seems unlikely to me.

It would be worth finding out whether you do actually have fuel on the plugs. It should not be hard to do, if you clean, dry and warm them all before refitting.

You don't say how you check the signal to the injectors. Are you measuring the voltage across them, or just the positive supply? If you want to confirm an injector is working, put a pressure gauge on the fuel rail and confirm it's holding pressure, then confirm the pressure bleeds down when you put 12V across an injector. Don't do it too long else you'll flood the cylinder, but you can see the rail pressure drop pretty quickly when you open the injector. You can also hear a loud click as it opens and closes, which will confirm the injector's working mechanically.

[abercoms]

Back to basics, Ive run through the bleeding obvious again, spark, compression, fuel etc, while plugs out thouroughly cleaned and turned over again, now convinced no fuel getting to spark plugs, pump works, got pressure on rail (no way of checking what it is) Ive also put 12v straight onto the injectors I can reach, they click, I think I expected more of a clunk but hey ho, its possible after this that I got a cough. Is there a crank sensor, where is it, any likely candidates for a sensor issue that will stop the injectors firing.
Im slowly getting my garage organised and my head, going to make a road trip for some engine start, its proving harder than I thought it would be to go back 20 years and clearly diagnose stuff, that and the job keeps getting in the way
ta Dave

[GreenV8S]

If you want to confirm it's a fuel supply problem, give it a squirt of cold start before you crank it over. If it shows signs of life, that suggests it's mainly lacking fuel.

The ECU would only inject fuel if it detects engine cranking. It has been a couple of decades since I worked on one of those but I don't recall seeing a crank sensor and I think it may have been ignition triggered.

[Penelope Stopit]

No the fuel pump shouldn't run all the time, check for incorrect or faulty relay

[tvrgit]

Penelope Stopit said:

No the fuel pump shouldn't run all the time, check for incorrect or faulty relay

I think his question is that his DOESN'T run all the time, but he was asking if it should? It shouldn't, as you say, so that's not the reason his car won't start.

[mentall]

No crank sensor: the ECU does it all with the Hall effect sensor signal from the distributor module.

All the injectors should be permanently connected to the live 12V supply; the 'signal' wire from the ECU grounds each injector at the appropriate time.

[Penelope Stopit]

tvrgit said:

Penelope Stopit said:

No the fuel pump shouldn't run all the time, check for incorrect or faulty relay

I think his question is that his DOESN'T run all the time, but he was asking if it should? It shouldn't, as you say, so that's not the reason his car won't start.

Feel stupid now, I'm an idiot at the best of times, thank you for pointing this out