Help X/F Loss of Fuel Pressure - Update

[virden]

 I have  a mechanical fuel pump on my 96 Super Sprint (25K miles).  The car had been running well and then refused to restart, we diagnosed lack of fuel going to the carbs, the filter was changed and the fuel lines blown through, but fuel flow was insufficient to fire her up.  A new mechanical pump from Burton was fitted, the fuel filter, sited at the tank exit fills with fuel, but next to no fuel exits the pump. It is possible to mis-install the pump,  the fact the filter fills suggests not?  HELP!

Update:

I have blown the pipe from the tank both ways and all is clear, also the filter is free flowing, checked the tank breather (2mm hole in filler cap)and it is clear.  Flow from the pump to the carbs appears good, when I switch off and loosen the banjos fuel sprays out.  Have checked floats, valves, pumps and jets in the 40's and all were clear, float chamber appears to fill and the starter jets spray when the throttle is open, but for some reason the engine does not seem to draw fuel when turning over.  Have tighten the carb nuts and done a cold compression test, which showed an average of 10.2 bar.  What have I misse?

[john g]

Hmmm, am I reading this correctly.......

You have the fuel tank then the filter then the fuel pump, is this correct?

If it is correct remove the filter and see what happens??? Does fuel then exit the pump?

[HJF]

My Crossflow has a silver top pump next to the tank, low down, then a filterking pressure regulator with filter in the engine bay.  Provides good flow at the correct pressure, works a treat.  Suspect putting a filter before the pump will stifle the flow?

[elie boone]

To know if the fuel pump is good connect it to an external reservoir both inlet and outlet and see how much flow you get. you said the fuel lines where blown trough but did you checked that air flowed freely trough ? and did you blow through the pick up pipe of the fuel reservoir ? if you do so open up the fuel filler !

[elie boone]

10.2 bar as average seems a tad low, are all four measurements in the same bracket ? did you check the filters next to the banjo fuel connection ? and are you sure you get ignition ?

[HJF]

When you turn the engine over, attempting to start, have you then taken the plugs out to see if they are wet with fuel?

[virden]

 Elie, the readings varied by.4 bar, and were taken on a cod engine

HJF,  we have  spark, and no, the plugs are dry

[Nigel Riches]

Do you have access to an electric pump to by-pass the mechanical one?

Ok, I understand you have a new mechanical pump installed, however, if, what was causing the original to be a problem is manifest with a brand new component I would be looking in a different direction.

When you removed the original pump was the "lifter" arm worn? or was the pump drive cam worn? thus reducing the pump stroke and capacity, if a new pump behaves as the original one, driven from the same cam lobe I would be looking there. 

A Facet electric pump fixed my low fuel flow problem, but that was more down to demand / capacity. 

Good see a X flow question here these days, don't seem to be many about now.

Nigel.

[elie boone]

Did you try to start it with starter spray ? do you still have the plastic/metal Lucas Rotor ? the are known to come apart.

[virden]

Nigel, Elie,

 I had a mechanic drop by to look her over, sadly he is too young to have knowledge of X/Flows (!!!)  but he had a good look through, reckons the new pump pressure is acceptable, but confirmed that for some reason fuel is not being sucked through the carbs, timing & sparks being OK.  We tightened up the carbs to the manifolds to avoid any possibility of air leaks, but to no avail.  On the bench all jets  and channels within the carbs appear clear.  No idea where to look next.

[Andrew Gilbert]

don't forget that the carbs should not be tight on the manifold, they need to move/flex otherwise you'll get frothing and fuel starvation when you do get it running.

[Jim 123]

Fuel not getting through both carbs seems strange based on what you have done to date.  As HJF says in #6, as a cross check, if you disconnect all plugs and crank the engine are all 4 plugs dry? Is it worth checking compressions on each cylinder?

[Jonathan Kay]

What's the typical pressure of the fuel arriving at the carbs in a set-up like this?

Jonathan

[elie boone]

Here is your answer https://www.weberperformance.com.au/product_info.php?products_id=31 and this is the one i always use https://www.dellorto.co.uk/shop/car-accessories/fuel-pumps-regulators-accessories/fuel-pumps-carburettor/huco-low-pressure-12v-fuel-pump-133010/

[Jonathan Kay]

Thank you, Elie.

4 psi is about 2.7 m head of water or about 3.3 m of petrol. (Please can someone check this: Côtes du Rhône and a Mediterranean sunset seem to be optimised for something other than mental arithmetic.)

,,,

There seem to be two possible causes: simultaneous faults in both carbs or insufficient fuel supply. At 3.23 m head you could rig a gravitational feed to the carbs and see if it all then works.

Jonathan

 

[Jim 123]

If you have found that the float chambers are filling and the pump jets are squirting it sounds like pump supply should not be inhibiting at least an initial start up.  Are the throttle butterflies and linkages functioning as well as opening to spec? Could mixture not be getting through to the idler needles and associated drillings? 

[elie boone]

Or the balance between carb's could be way off IF it has fuel and correct ign timing.

This winter i did some work on a Tiger 6 with a X Flow, initially i just needed to make a new remote gearlever, the guy swore it drove up the trailer but in the end i replaced all 4  mishab, there where no end washers and nuts on the Webers i changed the dizzy as the gear was badly worn, replaced the Lumenition trigger wheel as i could rotate it more than 5 degrees !! the central carbon in the dizzy had no spring action anymore and i changed the clutch as i couldn't engage gear because a few fingers on the pressure plate where off on top of that the diff sounded like a bag of nails, turns out someone changed the ratio without proper adjustment

[virden]

Hi All, thanks for your input,  some progress has been made, an air leak was found in the rubber hose connecting the fuel line in the tunnel to the pump, the trumpets refitted and now the plugs are now getting wet, but she is still not firing. Attention is turned again to the ignition, the timing is correctly set and there are no voltage issues with coil or distributor which is fitted with a Pertronik LU143 Igniter kit, could have gone wrong rather than simply failing??

[elie boone]

If you crank the engine do you have a strong spark at the coil ? if yes do you have the same strong spark at the spark plug ?

[Jim 123]

In addition to Elie's suggestion, if you haven't done so, a check on the static timing with a light would be worthwhile.

[elie boone]

Did you get it sorted ?

[virden]

 Found a +5 degree movement in the distributor shaft so have ordered a replacement from Burton, shall let you know when fitted. Thanks for your support.

[virden]

At last it works!

The distributor had "excess "  lateral movement and we suspect the electronic ignition was also delaying its spark.

Oh the joys of owning a X/F

 Thanks again for your support.