alcazar

iTrader: (2)

Right, when the car was mapped by Bob Rawle, the differential fuel pressure sat at 3.25 bar above boost and only varied by 0.1bar on full boost.

Now, for some reason, it's sitting on 3.8 bar above boost, but drops to 2.6 bar on full boost. That COULD mean it's leaning out on boost........... No knock visible though, and it only STARTED doing it since I put Octane Booster in.

Fuel pressure regulator? Or fuel pump? How to know?

Being over here in France, it's a bit scary if stuff isn't doing what it should...........

addi monster

iTrader: (6)

octane booster affects the viscosity of the fuel hence the varied readings

mickywrx

iTrader: (29)

Checked the vacuum pipe for splits?

Antony@indigo-gt

iTrader: (2)

Is the pressure sensor OK? Also as said check the vac pipe.

alcazar

iTrader: (2)

Which vac pipe? where does it run from, and to?

Antony@indigo-gt

iTrader: (2)

Will run from the fuel pressure regulator to the inlet manifold

dunx

iTrader: (3)

Is the LED still "on" on the controller ?

If not push "up" & "down" simultaneously....

dunx

P.S. Sorry if I'm stating the bleeding obvious

MartynJ

Tosh !

MartynJ

If it was like that originally I would have diagnosed it as a problem.
Fuel pressure on a boosted application should go up relative to boost.
ie .1 bar boost should equal a .1 bar increase in fuel pressure, 1 bar boost should equal 1 bar more fuel pressure and so on till full boost.
If this isn't happening you either have a leak in the pressure line to the reg, a pump which is faulty or cannot keep up with the fuel demands being placed on it or a faulty gauge.
Fairly easy test if you have a foot pump with a gauge or a mityvac.

Allow the engine to idle and check the fuel pressure, remove the vac line from the reg and it should increase .7-.5 bar depending how good a vaccuum your engine is pulling. If it does not rise at this point the chances are you have a leak in the vaccuum hose going to the reg from the inlet manifold. Repair it and continue to step 2, if it does on to the next step.

Fit the pump/mityvac to the reg with an appropriate hose and gently apply 1 bar of pressure to it, at this point fuel pressure should rise another bar too. If it doesn't and assuming the fuel filter is relatively new, replace the pump and go back to step one. Only when it passes both tests should you road test and check the same occurs on the road.

Martyn

alcazar

iTrader: (2)

Yes mate, still lit, was the first thing I checked.

alcazar

iTrader: (2)

Thanks Martyn, I'll check on that if it EVER stops raining here.

On mine, with Defis, the fuel pressure and boost gauge are linked, electronically, to show "differential pressure", ie how far above boost fuel pressure is. I can un-link them for the test.

But as stated, I've NEVER seen the difference drop like this since I had the car mapped on the original pump, BEFORE fitting a Walbro.

I hope the Walbro isn't faulty, it'll be a royal pain to get one out here and fit it in France.

Myles

iTrader: (40)

Love it!!

dunx

iTrader: (3)

Right ! Switch it out of "differential mode" and let us know what it's doing at idle, at idle with the vac pipe removed, and at 0.5 bar of boost ?

As MJ said, 0.1 bar increase in boost = 0.1 bar increase in fuel pressure.

dunx

alcazar

iTrader: (2)

Right guys, fixed it.

It was the vacuum line split, right at the end where it joins the f/p regulator. I cut a piece off and refitted it and all is OK again.

Thanks for the heads up about split vacuum hoses lads. Defis rule, without them, I'd have been running lean for a while

I assume this could also be why I got some knock? Leaning out the mixture via that line?

Antony@indigo-gt

iTrader: (2)

Yeah that would have been cause of the det

alcazar

iTrader: (2)

Well b*gger! Now I've used a bottle of octane booster I bet I never needed!

Still, if it cures the det and the leaning out, I'm glad it's solved.

The pipe was secured to another, beneath it, and it was under downwards pressure, so eventually the end split. I've now secured it to the FMIC pipework, and it runs in a straight line to the takeoff on the f/p reg.

dunx

iTrader: (3)

Gasp !

You sure don't have a stress free life do you ? Lounging in the sun down in that there France...

dunx

alcazar

iTrader: (2)

I wish. In the first part, I've only seen sun I could lounge in for two days. Since then it's been either fresh, or raining, or fresh AND raining, plus thunderstorms. I think it's trying to make up for three dry months in one go
In the second part, I'm working on the fitting of a new sink and actually BUILDING a unit under it from scratch, so don't see much of the outdoors.

harvey

iTrader: (48)

Miles : You obviously like to stir it on Scoobynet.
Have you ever made a useful contribution to any thread ?

Myles

iTrader: (40)

Hold on Harvey, point me in the direction of all the stirring I have done. And yes, I once told someone how to stop the seatbelt squeaking.

harvey

iTrader: (48)

Jeff : You were lucky to pick this up as in time it could have cost you an engine and you are one of a minority monitoring fuel pressure or more importantly differential pressure from "in cabin"
Issues with the signal line vac/boost are common on older cars and those with aftermarket FPRs.
The black O/E rubber pipe goes hard and splits close to one end at the nipple but the crack can be so fine that without close inspection it is not obvious. A small crack may only leak under boost at the beginning. With aftermarket FPR plumbed in with small diameter silicon pipe, the nipple at the FPR is usually quite small but that on the inlet manifold is much bigger diameter so as the silicon is streatched over the nipple it will in time split.
Worth everyone checking this periodically on older cars or those with silicon feed pipe.
When mapping I would think we come across this issue every other session so it may be a problem on say 1 in 12 cars.

dunx

iTrader: (3)

Only 'cos I told him to !



As do I

Paranoid dunx

P.S. Saved mine on the road using R888's off a local roundabout, even with half a tank of fuel I got chronic fuel surge on a sweeping uphill left-hand bend...

alcazar

iTrader: (2)

I have to say that it was dunx pushing me to get the fuel pressure gauge, (cheers Duncan), and link it to boost pressure, so as to show the difference between fuel pressure and boost. (something Defis can do). As soon as the differentail pressure drops 0.2 bar, the alarm goes off. That's what alerted me to this problem.

Without that, I'd just have kept pouring octane booster into it

Who says gauges can't save an engine?

dunx

iTrader: (3)

Only 'cos you had some to start with

Mine's been in bits for a month now, only two more to go !

dunx

harvey

iTrader: (48)

Dunx: You can substantially eliminate fuel pickup issues by adjusting the pump and pickup in the tank. The pressed bracket can be forced closer to the bottom of the pickup tray just for a start and one of my cars is now adjusted so that I can actually put 60 litres of fuel in it if I run to where I know it is about to run out. Fuel surge issues are now well below quarter tank.

dunx

iTrader: (3)

Cheers for the advice Harvey,
the car hasn't been anywhere near it's potential due to head/valve issues for the last three years.

Once the 2.1 is built, I will add a swirl pot for the odd track visits I fully intend to enjoy once built, installed, run-in, mapped and paid for !

Will ask my tame mechanic if some bracket bending is possible

dunx

harvey

iTrader: (48)

I resorted to altering the pickup and it has now become a matter of course on a number of customer cars that are driven hard. The idea of an extra pump and swirl pot taking up space would detract from the usefulness of the Wagons and I don't want a swirl pot warming fuel in the engine bay.