Wondering if anyone could shed some light on the following!
I have recently acquired a 1948 Bedford OLB... absolutely beautiful old girl
Spent a bit of time re-doing Water Pump, Carb and Fuel Pump. Installed a digital heat gauge to really monitor temp closely.
Recently also done timing etc.
The problem I’m getting is after approx 15 or so minutes of driving (max speed 30m/h) and heat reaching approx 65-75 degrees it will lose power and stall.
To recover... Foot flat to the floor for a bit, bit of choke then pump till fuel flows through again. I can then drive for approx 500m before it does it again.
Recently had at mechanics and tested fuel pressure. This read approx 2psi. Is this enough to keep the fuel flow in a hot engine?
I also notice when engine is off fuel level in bowl drops considerably to be only around 1cm in the bottom, is this normal ?
Have also insulated fuel lines from fuel pump to carb and installed insulation (similar to Bakerlite) between manifold and carb.
I’m really stumped!!
Anyone got some suggestions?
Does this have a sight glass to see the fuel level dropping when stopped?
Have you tried running with the fuel cap off?, tank may not be venting properly. After that does it have a fuel filter?
In filter (particularly in line filter, they often look OK but are blocked with super fine stuff)
If it empties the fuel bowl when stopped I would look at fuel tank vent. Sounds like 90% blocked allowing a little through but when the vacuum in the tank equals the vacuum in the pump you get no flow. The residual vacuum in the tank when stopped draws the fuel back out of the bowl.
Thanks Steve & Lang
Yes it has a site glass so you can see it drop.
I have cleaned lines to tank and have recently changed the inline filter
Will definitely try with cap off to see if it reduces the vacuum.
I did do a full re-line of the inside of the tank which may have blocked the vent. Will check check this.
Would I be right to say that venting in the tank becomes more of an issue when engine is hot?
Appreciate your pointers! Tomorrow’s drive will be interesting.
I’ll keep you updated
My initial thought was fuel vapourising but you have insulated the fuel line. Next was needle and seat sticking followed by all the other suggestions, filter blocked lines and fuel tank or cap vent.
I got caught with a blocked vent in a fuel cap once, such a simple problem to fix and a real mongrel to find. Also I have put a KBS fuel tank sealing kit through a tank not so long ago and I was fully aware of keeping all pipes open as the stuff cured. So definitely look at those inlets and outlets for blockages. I was luck with mine as they were all short straight pieces of tube and a 5/16" drill bit kept them open.
Welcome to the Forum and we all love your new toy.
Cheers Cobba & Cobbarette
Coopernook, The Centre of our Universe.
The engine warming up should have no bearing. Warming up is just a function of running time. It is the time it takes for the restricted flow to eventually become too much for the fuel pump as it uses the airspace in the tank to create a partial vacuum and tries then to collapse the tank walls. If the tank was full to overflowing it would stop more quickly as liquid is not compressible.
I would think a run without the fuel cap may well be your answer. If that fails start tracking the lines and filters.
Undiagnosed fuel delivery problems in these Bedfords seem to be fairly common, especially draining back when stood still for a while. Back in the day it was common practice to tip a bit of fuel in the carby to get her going after a spell in the shed. Common solution (assuming vent and fuel lines are clear) is to fit an electric pump.