Need an expert opinion please..

[mrzigazaga]

Hi Peeps..
After looking underneath the car yesterday i noticed that my petrol pipe route is not the same as the diagram set out by TVR..Would this cause starting and running issues..It kinda makes sense that when i wiggled the pump feed the noise of the buzzing stopped and started again and the fact that when rooodboy had the car facing downward on his ramp with the back end up in the air that it started on the key with no pumping of the throttle which i normally have to do.It looks like the return line from the metering head is going into the fuel pump feed..I suppose it would be ok if there was fuel being constantly returned but what if there isnt?..Also what could be connected to the fitting on the tank designated for the fuel return from metering head.I have it going into a garage tomorrow to re-route the lines and will take pics and drawings of before and after..I just hope im not wasting more money..Cheers..Ziga
This is how it should be..

And this is how it is..

[jeff m]

If there is one way to not get a thread answered it is to ask for an expert.

How about a best guess.

In thoery, I think it's ok, (the second pic) but in practice I think having the return there could only be detremental to a smooth uninterupted flow into the pump.
Hydraulics; cavitation is a pumps worst enemy, I'm not sure this would cause cavitation as it is fuel being pumped back, but I can't see it helping.

BTW no swirl pot should not affect your cars problems.

[TVRleigh_BBWR]

It not going to be ideal, as the return is having to fight the gravity feed fuel from the tanks, (does it run better near empty, i.e. less force from fuel in the tanks) the 1st diagram show the return going to the top of the tank, and hence will not have any resistance. This extra pressure could affect the correct workings of the fuel pressure regulator, and also cause incorrect fuelling.

Also as said quite a few times unless your using a pre-filter before the pump, the pump will not last long (the original swirlpot had one built in), as from ready you have had to fit a few, your just wasting money by not fitting one.

Also I'm sure they used a swirlpot for a reason.

A quick way to test to see if the T is a problem, take the T out and just use a hose joiner, and then feed the return to a fuel can. and then do some test starts. BUT DONT DRIVE IT LIKE THIS)

[mrzigazaga]

Cheers guys..I think you have helped with what you have said..The cavitation could be causing the pump to make noise as said when the back end was up in the air facing downward on rooodboys ramp the car started straight away on the key and the pump wasnt making any noise plus the flow to the pump would of been greater because of the fall..
I would of thought that the return line from the metering unit would have had greater pressure as it is being pumped to it unlike the gravity fed fuel pump..
A swirl pot will definitely be in order once i know it runs ok..It doesnt run any better if the tank has less fuel it seem the same either way.
I did notice a small kink as well in the pump feed which would hinder the gravitational fall of fuel..
I suppose under fuelling could have some of the same symptoms as overfuelling..i:e.Popping in the exhaust when revving or de-accelerating..soot build up in tail pipe..It does get worst as it warms up..what do you think..Cheers..Mark

[TVRleigh_BBWR]

mrzigazaga said:

I would of thought that the return line from the metering unit would have had greater pressure as it is being pumped to it unlike the gravity fed fuel pump..

No the return had to fight against the pressure from the fuel in the tank trying to go down the return. it's not going to be much but could be enough to affect correct operation.

as said get a pre-filter ASAP as you just end up damaging the pump regardless on how the rest of the system is setup.


On the racer I run my return to my swirl pot (as my tank does not have a return), without any problems, but I have a different system.

[Wedg1e]

jeff m said:

If there is one way to not get a thread answered it is to ask for an expert.

Too true; the real experts are out there earning sh!t-loads of money, not wasting their lives on internet forums (fora?)

See how often the likes of Joolz Lane get on these days.

[taz turbo]

Wedg1e said:

Too true; the real experts are out there earning sh!t-loads of money, not wasting their lives on internet forums (fora?)

How true, now then, my hydraulics tutor was John Savage the Director of the British National Fluid Power Association (BNFPA), a fantastic tutor and scary amount of knowledge on the subject, designed small projects like the London eye and the Thames barrier, I guess you won't find John on forums either, but if you wish to believe me.....

The main issue with the return fuel feeding into the hose from the tank tee piece is that, as the fuel return will always be less than the pump output so there will always be fuel coming from the tanks towards the pump, if you pick up any air you run a real risk of the air circulating around the fuel system, if the return went back to tank, this would let any air surface whilst allowing pump inlet being properly submerged.

As correctly already said a restricted inlet to the pump would try to cause a vacuum at the pump inlet as correctly said this can cause pump cavitation, pump cavitation can also be caused by drawing air (think above) either can cause pump failure.

The issue as said of pump inlet pressure is incorrect, the return flow is just that, a flow. Feeding back to the pump inlet will not cause a change in either the fuel system pressure as this is regulated externally after the pump or either the pump inlet pressure. The fuel still has the same head height, with pump petrol having a density of ~0.75 a 1000mm head would give you a pump inlet pressure of 0.075bar, but we would never see a head of this height, I would estimate the greatest head you would see is ~500mm, you would see the pump inlet pressure increase far more when you hit a good sized bump with the Wedge fuel tanks being funnel shaped, but this will still make no difference to fuel system pressure.

Zig,

I would suggest to remove the return tee and feed the fuel back to the tanks to stop the risk air being recirculated around the system.

Chris.

[wooly350i]

Hi zig,still haven't located swirlpot but just to say when I re ran my fuel pipes from tanks to filter then pump via a new swirlpot I tried to ensure the pipes dropped all the way without rising thus causing air lock before pump etc,sorry got my plumbing cap on.!

[hallsie]

Zig

From the looks of your drawing, it seems you need to remove the 'T' from the pump feed line and return the meter return line back into the tank.

Call me tomorrow for a more in depth and probably more coherent explanation. ( stella head on )

Stu

[mrzigazaga]

Thanks for all the input chaps..Okey cokey stu will do..Although i plan to have it remedied tomorrow..I really hope so anyway...Everything crossed..Ziga

[Wedg1e]

taz turbo said:

[snip] ... but if you wish to believe me.. [snip]

... which technical input goes to prove that there are exceptions to every rule

Edited by Wedg1e on Wednesday 6th April 01:41

[mrzigazaga]

Hi Folks..Right there was two "T" connections on the fuel line as well as the main "T" between the tanks..The return from the metering head was going into the pump feed and then a little further back was another "T" with a pipe going to the return connection on the tank..Although starting still is a bit of an issue i can no longer hear the pump buzzing and so far it hasnt cut out or stalled..Touch wood..It cost me £20 drink at a local garage..he put a straight fitting to connect the metering head return to the tank only and jubilee clipped a bolt into the cut bit of pipe on the "T"...It still will need doing properly once the guy at the ford garage comes back off his holiday as im not happy with what he did...I only had 3 hours kip last night worrying about it..But hopefully its all gravy..This is how it was...


This is how it is now..


Cheers for all your help...Ziga

[jeff m]

No wonder your pump was struggling, removal of that extra T should at least give you a sporting chance of a consistant fuel pressure.

I'm guessing nobody has used a pressure gauge on your car. ('cos I'm sure it would have been jumping up and down)

If you see a repair shop with a couple of Porsches outside (older ones) or a blue Boshe sign on the wall pop in and ask "can you check the system pressure on my CIS?" (as I've had a new pump)
To just adjust the system pressure should not be too much as he just has to put in, or take out a shim on the pressure regulator.
He may ask what system it is tell him "it is the same as a 2.7 but without an ADR" That should get him interested enough to to work on a car other than those with slopey fronts.

5.1 Bar (73psi) if he bites

ETA or PS Mark don't worry about the bolt clamped on the T, that's what I would have done
However......is the kink in the supply hose still there?
If it is....get a scrap bit of hose the next size up, slit it along its length and force it over the kink.

Edited by jeff m on Wednesday 6th April 13:29

[mrzigazaga]

Hi Jeff..Never had a fuel pressure gauge on it and i might now that its running better book it into a rolling road, Ive found one that does the K-Jetronic set up..The kink is still there in fact there are two but i have contacted the ford garage over this and told him im not happy but all he keeps saying is "Theres nowhere to put it,Its so cramped in there" But if it was done right in the begining then i wouldnt have had all these issues..
I have found a company in Germany that still makes parts for the V6.. Injectors..WUR..Accumulators..And they refurb metering heads,None of which is cheap but eliminates any future drama's..Its such a releif to not hear the pump buzzing..AArrhh..Chill winston.

[jeff m]

Mark,
I'm not sure set up with a rolling road is relevant to a CIS car. Once you get past the System pressure adjustment it then relies on the WUR for control pressure which has no adjustment.

By relevant, I'm really saying "not cost effective"

So for set up the guy would first adjust the system pressure then switch his gauge over to output of the WUR and make sure that the control pressure was within the range for the temp of the car. If it was not he could fudge the system pressure to try to bring the C press into range. He might not want to do that (maybe) because now he has to check the control pressure stays good through all temp ranges (which a good guy would do anyway), but now we are talking hours of work not 30 minutes

Another reason some may not fudge the sytem pressure is that if it goes to another mechanic the second mech will tell you the first one was an icehole and ripped you off. Whereas the first one charged you fifty quid, the second guy in his blue Bosche overalls will charge you 250 plus a 1,000 for a new WUR.

But if these guys do K tronic, then go for it.
Ask them to take a quick look at your lift plate before they start.
Put another bottle of fuel condioner through the tank before taking it in.

I shall add at this point (before someone jumps all over me) adjustable WURs do exist. Some guys experimented with set screws that acted on the diaphram and do sell them. (no you don't want one)