fuel pressure

[Z320]

Hi,

on our tour to Belgium (Euromeeting) and back we sometimes had problems to get get power from the engine.

The issue was like not getting enough petrol for uphill and + 2,500 revs, even in low gears.

"New" (cleaned) spark plugs cured the problem for some time, but not long. Spare part fuel pump - the same issue.

At the meeting we had no problems at all, also today the car run lovely without any problems, also uphil and with 130 km/h on the Autobahn.

The mechanic fuel pumps are suspisious, perhaps both don't produce the pressure needed?

The internet tells 0.1 - 0.35 bar would be fine for my SU HS6.

With a manometer fitted in the car the fuel pressure is only (but constant) some less than 0.1 bar.

Anyway the engine runs lovely, as it always did before.

Any idea, apart from continue to measure and hope for a failture?

Ciao, Marco

[stuart]

Check flexible fuel pipes up to the pump Marco, should be one at the rear between hard line out of the tank to the chassis hard line and then one at the engine bay from the chassis hard line to the short feed to the pump. Possibly one is collapsing and restricting flow?

Stuart.

Edited September 18 by stuart

[BlueTR3A-5EKT]

6 hours ago, stuart said:

Check flexible fuel pipes up to the pump Marco, should be one at the rear between hard line out of the tank to the chassis hard line and then one at the engine bay from the chassis hard line to the short feed to the pump. Possibly one is collapsing and restricting flow?

Stuart.

Something tells me some other forum user had identical problems.

  It turned out to be as you state Stuart the inside of the flexible fuel lines collapsing. (Ethanol fuel?)

That prompted me to renew all the flexible fuel lines in my car with Gates Barricade ethanol proofed flexible hoses.

[Hamish]

I had fuel starvation on my 3a snd it was a rear flex hose that joined 2 metal pipes

not sure if the 4/4a is the same. 
I went for a huco elec pump which has the ideal pressure for su’s

now on facet and pressure regulator with the webers

Edited September 18 by Hamish

[TR Rob]

19 minutes ago, Hamish said:

I had fuel starvation on my 3a snd it was a rear flex hose that joined 2 metal pipes

not sure if the 4/4a is the same. 
I went for a huco elec pump which has the ideal pressure for su’s

now on facet and pressure regulator with the webers

+1 for Facet and pressure regulator 

Edited September 18 by TR Rob

[tim hunt]

1 hour ago, BlueTR3A-5EKT said:

Something tells me some other forum user had identical problems.

  It turned out to be as you state Stuart the inside of the flexible fuel lines collapsing. (Ethanol fuel?)

That prompted me to renew all the flexible fuel lines in my car with Gates Barricade ethanol proofed flexible hoses.

+1 Pete. R14 spec Barricade from www.scimitarparts.com

Tim

[Z320]

Thank all, I check this tomorrow.

But why does the problem ony occur sometimes?

Ciao, Marco 

[Trumpy3]

Have seen intermittent problems with failed hoses. The issue turned out to be a piece of hose partially detached from the inner lining. At times, this piece of hose would flex and act like a stopper and reduce the flow. 

 Was there any pattern as to when the problem occurs?

Brian

[Z320]

Indeed!

I only us 95 octan E10 since years and to please a friend 2 fillups with E5 directly before the problems stsrted!

[Trumpy3]

Mmmmm. Cant help with that. That could be coincidental. If I have interpreted you right, the car can be working fine then changes. Is it after long or short stop, high or slow drive, etc?

As you would know, finding the pattern makes it easier to narrow target.

While we have E10 @ 94 Oct, TR drivers here use unleaded 95 or 98 so cant help with problems associated with E5 or E10 but can't see that it would be a problem.

Brian

Edited September 19 by Trumpy3
correction

[Z320]

Simple test:

I locked the fuel tap in front of the fuel pump,

disconnected the L shaped pipe, opened the tap and petrol poured out LOVELY.

Anyway I drained the tank, disconnected all hoses, put the tank out and looked inside through the level skimmer:

nothing wrong at all, no dust, only some rust sediment, the hoses that came with the car 18 years ago are like new (Goodyear DIN).

Using E10 for years did nothing damage at all.

This side of the pump: no problem.

That‘s sad….. to find a problem there would have been easier.

Ciao, Marco

[Hamish]

Did you check the inside of the pipes as any deterioration is from the inside out. 

[Z320]

Hi Hamish,

I did check the indide of all hoses but only the inside of the pipe that goes inside the tank.

This is the only straight one.

It is without any fault (all are zinc coated steel, d = 8 mm 5/16“).

Apart from that, with the pipe to the pump disconnected, petrol pours out to empty the tank in I guess less than an hour.

52 l/h (fuel capa ity) x 9 kWh/l (petrol energy) x 0,25 (mechanic engine effeciency) = 117 kW

I‘m sure petrol comes enough from the tank.

Ciao, Marco

[Z320]

What I did,

I removed one gasket and the safety steel plate of my repro pump (to secure the lever axle) to get more fuel pressure from the pump.

As I‘m convinced to shim or not shim does not change the pressure, what „surprise“, the pump pressure did not increase.

Ciao, Marco

[RobH]

As you say - the pressure from the pump comes from the return spring Marco, so doing that will not increase pressure by anything appreciable. You would have to compress the spring a lot more to make any significant difference.    

 

Is the anything floating loose in the petrol tank that might now and again get into a position which covers the outlet, to restrict flow?  I seem to recall reading of someone who had  dropped in a bottle-cap cardboard washer which did that.  

[Z320]

Hi Rob,

good point, this is what I found:

Some rust sediment by blowing the pipes and hoses empty with 8 bar air in a plastic bottle, not connected to the pertol tank.

A piece of paper gasket, broke in pieces when I grabbed it. A small spring d = 3.9 mm x 8 mm from what ever and a circlip from the fule cap.

Pretty sure they have been in there for a long time and now caused 2 times problems?

Test drive today: mostly 0.1 bar with a few short drops down to 0.07 bar (no retrurn valve?) but without any problems,

even with 3,000 revs and faster than 120 km/h on the 2+2 lanes Bundesstraße.

Next I consider which of my other fuel pumps I fit.

I want to stay with the mechanical pump.

Ciao, Marco

 

 

Edited September 21 by Z320
typo

[Trumpy3]

I'm sure this is not your problem but back a number of years ago while still working at Cummins, we had a truck come in with a reported problem similar to yours.

Turned to be a plastic bag in the tank. As it floated around in the tank it would occasionally cover the outlet fitting cutting off the fuel. Once the engine stoped the bag would float off the fitting. When looking into the tank, it was very hard to see the clear bag floating around. It wasn't till a sharp eyed tech spotted it that the issue was cleared.

Maybe your small bits of paper?????

Brian

[multipletriumphsinner]

We have had similar on a couple of customers cars.

We had a PI saloon come in with a nitrile glove floating about in the tank doing the same thing. We also had a TR6 with a big glob of of orange silicone occasionally blocking the outlet.

The worst was another TR6 where the customer had his tank 'reconditioned' by a 'specialist' who had done nothing more that pour some of that liquid tank liner stuff in. A year or two later it had started to peal off in big sheets, what a mess.,

[john.r.davies]

A nitrile glove?  They weren't around until the mid '90s.  Latex, yes.

John

[multipletriumphsinner]

Latex then!

 

Pedant!😉

[stuart]

I did have a problem many years ago with a 250 on Webers that was fed by a Huco type pump in the boot, it kept burning pumps out, turned out after all the flexible hoses were replaced it was actually the front to back hard line that was nearly completely blocked as it was actually the lowest point of the system and the steel pipe although looking fine on the outside was corroding internally. 

Stuart.

[Charlie D]

Back in the 1970's I knew someone who took TR6s on car transporters from the factory in Coventry to the docks, (I think it was Southampton) where they were shipped to America. When they left the factory they were filled with 1 gallon of petrol , more than enough to load the car onto the transporters, off at the dockside and  drive around the docks in America. Because of this all the drivers used to siphon off about half a gallon for themselves from each car (They classed it as a bonus to their wages.)

Apparently there  were several occasions when the yard security guard would be doing their rounds while they were in the process of siphoning , and the only thing to do was to hide the evidence and push the tube right into the tank.

I wonder how many cars ended up several years later with bits of rotted rubber tube floating around inside the tank.

I don't know how true the story is, but the bloke who told me seemed like an honest sort of chap.

(But then again, if he was stealing petrol I guess he was not as honest as he looked.)

Edited September 21 by Charlie D

[Z320]

Hi,

could also be a low fuel pressure be the problem?

My spare pump on the engine produced about 0.1 bar, but leaked.

So today I fitted my restorend and faced (flange) pump with steel lever again.

With a short start of the engine in the garage it also produces 0.1 bar, the manual tells 1 1/4 - 2 1/2 PSI (0.086 - 0.17 bar).

The pump that came with the car I remember with 0.2 bar, but it leaking at the glas bowl (housing bend).

All these pump housings are sadly soft like butter...

BTW, my spare part pump: the plug helped to get it out without petrol disaster.

A bit tricky on LHD TRs with the steering coulumn, rev cable and brake + clutch pipe.

But easier than to get the starter out at a RHD TR 😉

Ciao, Marco

 

[Trumpy3]

Marco

What makes you so sure it is a fuel pressure issue? A suspect coil could also give a similar problem.

This is why I ask if there were any patterns in when the problem showed. I know from experience that a lot of time can be wasted because I was so sure I had isolated the issue but it turned out to be something totally different.

Trouble shooting over the phone or on line can be very difficult as we, on the other end of the phone/line, can not see/hear/experience all the subtle indications that the problem can cause. Patterns can be very helpful. 

Brian

[Z320]

Hi Brian,

thank you for your explanation.

On our Belgium tour the problems appeared with two different coils, condensers, petrol pumps and set of spark plugs…..

Why the fuel pressure: a friend of mine pointed me on the best fuel pressure of 0.2 bar for HS6 carbs.

And this is what the AI also tells, at the manual I found no information about this.

What I now will do is to drive the car with the IMO better pump fitted (not oil leaking) and manometer on the dasboard and see.

Perhaps it was the old paper gasket and The HS6 work well with only 0.1 bar?

Ciao, Marco