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Series 3 Yr 1975 Air in Fuel Lines Problem

Keiths Landy

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Hi Forum Members.

My name is Keith and I am a new member, and currently live near Alicante in Spain.

I own a 1975 Series 3 with a 2.5 Diesel engine. Over the last 6 months I have been undertaking a complete restoration of the the car in the sun.

Having completed all bodywork and running gear etc, I am now working on the engine, the engine had been running very well although a bit of a pig to start sometimes.

I have changed the glow plugs to the new 12v ones and done modifications to the wiring setup and these heat up really quickly now.

I thought I would change the fuel filter as it looked quite old, having done this I now cannot start the beast although I have bled the fuel lines, I still seem to be getting a lot of air in the system and after various checks I don't appear to be getting fuel up to the injectors.

I have checked fuel cut off solenoid and this is working as far as I can make out (Clicking on key turn). When cranking the engine the voltage on the solenoid does drop to around 9.5 volts. Question - could this be partially closing thus restricting fuel flow to the pump.

I have checked all connections in the pipework and cannot find any leaks where air can pull back in. Question- Is it possible that the lift pump is faulty and fuel leaking back across the valves.

I would welcome any suggestions, or similar problems others may have experienced.

Hopefully speak again soom

Keith. (Keiths Landy)

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2.5 engine will have 12v glow plugs as standard - it was the 2.25 that had glow plugs wired in series. Did you prime the system with the lever on the lift pump on the side of the engine, or are you just trying to start it on the key? If the lift pump has failed, then it'll not start on the key as there will be air in the system. It will start if you tow it, but the battery will go flat most likely otherwise.


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The cartridge type has 3 x seals - a large one at the top and the bottom between the two halves of the housing, plus one small one on the top where fuel will enter the filter. The canister types has 2 - one small one where fuel enters the filter, and one large one to prevent fuel from leaking to the outside.


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Hi Les,& other members,

Many thanks for your quick reply. Today I have been carrying out several checks on the fuel lines.

a) The fuel is pumping through the filter on operating the lift pump lever.

b) Fuel is also pumping through to the injector pump inlet when both operating the lift pump and cranking the engine.

c) The stop solenoid opens and allows for the air to be bled out through the top cover on the injector pump on operating the lift pump.

d) Fuel is passing back through the banjo on the filter into the return pipe to the tank when pumping through the lift pump.

e) There appears to be no fuel in any of the pump to injector tubes after carrying out these checks.

I would assume that everything was OK according to the aforementioned checks. I guess that there would not be any fuel in these tubes until the engine is cranked over with the throttle opened. Question will it be necessary to bleed each of the injector lines while cranking, or will they eject the air present back into the spill tube as fuel is pushed up.

Today I ran out of time in doing the last check, and I thought if I charged the battery up fully I might have more of a chance in getting it to fire up.

Just one last question, am I right in thinking that once the injector pump has been primed fuel cannot syphon back beyond the filter level even if the lift pump is syphoning back due to a faulty valve.

Your comments would be most welcome.

Kindest regards

Keith (Keiths Landy).

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