Lotus Elan

mechanical pump expected pressure

PostPost by: davidc » Wed Jan 02, 2019 12:49 pm

my 73 plus 2 130 had been running fine, if a bit in need of a RR tune up, but was waiting for new exhaust to be installed before a trip out there.

took car to garage to have SS exhaust installed and after completion of job think it has either ran out of fuel and picked up some crud from bottom of tank or fuel pump has gone.

i'm thinking out of fuel as i've put 20 litres in and gauge is still reading empty :oops:

traced it to be a supply fault as it runs fine albeit briefly if i top up carbs from top.

i took caps of webber dcoe built in filter housing and cranked but barely a dribble comes through.

should i have expected fuel to be flowing freely out of the top on this housing with the cap off?

if so I intend to try blowing back through fuel line with compressor to see if that frees anything up.

if not likely my fuel pump is buggered i guess?

any comments on how much i should expect to flow out on cranking from filter cap and any other pointers?

thanks.

PS very pleased with new SS exhaust, they even fashioned up a stainless steel heat shield to protect the clutch slave at same time. its a compnay that used to be peco so had the ability to make me a late peco back box in SS :D
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PostPost by: billwill » Wed Jan 02, 2019 1:00 pm

I would have thought that the valves in a fuel pump would prevent you blowing-back down the fuel line.
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PostPost by: davidc » Wed Jan 02, 2019 1:39 pm

:( ah, ok, thanks so i can get to line where it attaches to pump and blow back from there. bit more tricky but doable :roll:
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PostPost by: nmauduit » Wed Jan 02, 2019 1:57 pm

I'm not sure I get the "out of fuel as i've put 20 litres in and gauge is still reading empty" bit, maybe an unrelated electrical gremlin?

regarding fuel supply, if all is well up to the carbs (tank not empty, mechanical pump ok, fuel line not interrupted, fuel sieve on top of the pump not clogged...) the fuel should squirt from the fuel line when disconnected from the carb and engine cranked (make sure to get the squirting fuel into a can and possibly disconnect the ignition coil power supply to reduce the risk of adverse consequences).
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PostPost by: davidc » Wed Jan 02, 2019 2:04 pm

i think i ran out of fuel as fuel gauge must have developed fault, it was showing a bit left but now shows empty despite me putting 20 litres in. i think in running so low i've dragged dirt up from bottom of tank and blocked fuel line.

in hind sight i should have took tank out and checked for debirs as it will have sat empty for over 15 years, i juect leak tested it not debris tested :oops: :cry:
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PostPost by: prezoom » Wed Jan 02, 2019 5:50 pm

Your Plus2 should take the fuel feed from the bottom of the tank. Any crud should be slowly pulled into the fuel line as you are driving and the fuel is sloshing around. A low fuel level should not make any difference. If the fuel pump needs rebuilding, a kit for a Triumph TR4 will do the trick. The only thing I found missing from the kit is the seal that fits around the shaft from the diaphragm to the lever arm. It keeps fuel from getting to the inside of the engine should the diaphragm develop a hole. This is needed because there is constant fuel to the pump with the tanks bottom feed, and conversely it keep engine oil from contaminating the diaphragm.
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PostPost by: Citromike » Thu Jan 03, 2019 4:04 am

Float valve could be sticking and starving the engine for fuel. Common with today’s gas and low pressure pumps - 2-3 psi.

Or you could have an air leak into the lin s because hoses are dry and cracked. Did you replace all the rubber hose bits in the fuel system?

I’ve had to do both cleaning out the carbs and replacing lines this year on 2 cars.

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PostPost by: davidc » Thu Jan 03, 2019 12:34 pm

Hmmm. may need to do a bit more checking then.

definitely not float valve, checked that and so little fuel coming through to carb filter on cranking makes me think its a supply problem.

as there were no leaks on fuel lines they haven't been replaced so will have to look closer at them.
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PostPost by: EPA » Thu Jan 03, 2019 6:43 pm

Did the car run after the exhaust was replaced?
It’s just a thought but if it didn’t they may have had to jack up the engine to get the new exhaust in and maybe this caused the fuel line to be impeded in some way or the pipe has been crushed when fitting the heat shield Doesn’t account for fuel gauge reading though. When my fuel gauge stopped working I had managed to pull a wire off when doing something unrelated
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PostPost by: davidc » Mon Jan 14, 2019 1:46 pm

was the fuel pump in the end.

new one on the way.

squeeze getting that off! actually felt like the bolts weren't tight enough so wondering if that might have been the problem but thought swap it out while it's off just in case.

taking the opportunity to rebuild girling servo at same time as brake force suggested this playing up and as expected vacuum full of brake fluid :roll:
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