Lotus Elan

Mechanical fuel lift pump not working. Any ideas?

PostPost by: Keith Scarfe » Tue May 07, 2019 12:00 pm

Its just a mechanical lift pump what can be so difficult...

While doing some mods over winter, I decided while it was out, to rebuild the fuel pump (glass bowl type). New valves and diaphragm. When re-fitted it wasn't pumping fuel. Whirled the engine over until the battery went flat, just a dribble came out. I didn't have time to recheck it so just bought a brand new one assuming I had done something wrong (although being such a simple device I couldn't understand what). Anyway new one fitted, exactly the same. No pumping of fuel. I can suck the fuel out with my mouth no problem - watched the pump fill then go a gob full. Gross. At least I know there are no blockages and the fuel is there. Again whirling it over until the battery goes flat not much out. A little, but definitely not enough to fill the carbs.
What can be wrong? Is it possible to fit it such that the actuating arm doesn't engage with the cam? How can I tell?
I have a black spacer of about 1/4 inch between the block and pump (was there originally). Should/could this be removed? Will it make the arm engage harder to the cam? Why is this spacer there if the pump and block are original ford? I am wondering if the arm isn't going to its full travel where the pump action seems to happen. How can I see this?
I am a bit stumped. Can anyone give me some idea what else to check?
Thanks.
Keith.
ps. I may have to resort to an electric one but I wanted to keep it original really. Its only a road car so no huge demand for fuel. Just standard flow.
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PostPost by: types26/36 » Tue May 07, 2019 12:09 pm

Have you got the pump lever arm on top of the lobe? it is possible to install the pump with the arm underneath the lobe.
When you fit the pump you must make sure you keep the lever at the top as you fit it on the block, yes the insuating spacer should be fitted, the spacer/insuator is fitted so the pump does not get too hot.
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PostPost by: Keith Scarfe » Tue May 07, 2019 1:19 pm

Have you got the pump lever arm on top of the lobe? it is possible to install the pump with the arm underneath the lobe.

I have indeed thought this is the problem, guess it must be, but how do I know? I cant see in there when it is fitted. I tried to make sure I lifted the arm up as i fitted it but as you will know it is very tight in that area when fitting it in situ.
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PostPost by: types26/36 » Tue May 07, 2019 2:25 pm

Keith Scarfe wrote: but how do I know? I cant see in there when it is fitted. I tried to make sure I lifted the arm up as i fitted it but as you will know it is very tight in that area when fitting it in situ.

As you fit the pump (and with the lever on top of the lobe) the pump will have some tension on it pushing it up, you can usually feel this tension and pressing down on the pump will operate the pump stroke slightly.......dont know how else to describe it.......its a matter of feel :roll:
BTW. when you overhauled the original pump did you replace the pull rod seal at the bottom that seals it from engine oil, most kits do not have this seal.....at least not from Sue Miller.
This seal wont give you your pumping problems but just wondering if you got the seal?
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PostPost by: alan.barker » Tue May 07, 2019 4:22 pm

Before fitting a mechanical pump i turn the engine over with a spanner on the crankshaft bolt and position the lobe for the fuel pump in it's lowest position. You can feel the positon of the lobe with your finger. That way when you fit the mechanical pump you don't need to press the pump lever too hard against the cam lobe.
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PostPost by: prezoom » Wed May 08, 2019 1:53 am

I had the mechanical fuel pump for my Sabra rebuilt by a not so reliable source. The pump is identical to the mechanical pump on the Lotus, except for the shape of the lever operating arm. Both from Ford engines, who wudda thunk. The pump quit on me in a worse possible spot, and dead sticking from the fast late to the side of the road in heavy traffic was no joy. What I found was the shop, when installing the new diaphragm, did not get the shaft locked into the lever arm, and it slipped out. Thankful for the electrical priming pump that got me home. I also found that the rebuild kit for a Triumph TR4 is identical to the pump used on the Fords, without the premium price.
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PostPost by: StressCraxx » Wed May 08, 2019 3:50 am

The fuel pump will not lift fuel from the tank if there is a cracked rubber fuel hose. A hairline crack in the hose or fitting at the tank or the fuel pump fitting will give grief.
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PostPost by: Keith Scarfe » Wed May 08, 2019 8:29 am

Hi All.
Thanks for all your words of advice, I used all of the ideas while having another go at this last night and hooray. I have sussed it.

Took it all off again to have a look to check if somehow the arm was not on top of the cam lobe, but it was defo ok. My idea was to strip the pump to bits so I just had the bottom half (with the diaphragm in) and then fit this so I could see the diaphragm going up and down when I crank it. Then fit the top half on in situ. Seemed doable with a long and stubby screwdriver. When I stripped the pump apart, the diaphragm just popped out at me. It wasn't attached to the arm obviously and try as I might I couldn't re-attach it. So the next thing was to remove the arm to see what was up. To do this I had to remove the staked in retainers and the whole lot comes out and this is what I found:
img_20190507_232154.jpg and

The arm was broken. How could this have happened? Faulty from new? Maybe I broke it fitting it. Who knows, but anyway from the new one and my old one I managed to make a good one from all the bits. Fitted this using my idea of just fitting the lower half so I can check the diaphragm is actually going up and down while cranking. Like this:
img_20190507_213847.jpg and

Then assembled the top part on to it and now all is working fine. I have a good strong stream flowing from my pipe. Ooo errr.
Thanks again for all the ideas. They really helped me on with this. Hopefully will be able to drive it soon.
Cheers.
Keith.
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PostPost by: Keith Scarfe » Wed May 08, 2019 8:35 am

Oh yes and to answer Brian's question re. the oil seal:
Yes you are correct these are not supplied in the rebuild kit and I was, like you, surprised about this. I had no choice but to rebuild my old one with the original which was very shagged out. This is one of the reasons I decided to just buy a new one when my original didn't work (still not sure why the rebuilt original didn't work) because I was unhappy about not having changed this oil seal.
Not completely sure how much oil gets in there anyway, cant be much, but it would have obviously made sense to renew this.
Cheers.
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PostPost by: alan.barker » Wed May 08, 2019 8:46 am

Imho the pump needs to be assembled before fitting to the engine. Because you need to push the lever/foot up and keep it in position while tightening the 6 screws.
To make sure when the pump operates there will be no stress on the diaphram.
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PostPost by: Keith Scarfe » Wed May 08, 2019 9:03 am

I wouldn't worry about that Alan. Thanks anyway. When I assembled the top onto the bottom, the diaphragm was in a very neutral position laying gently on the bottom housing. I rotated the engine by hand until it was just so. Then assembling it was just like doing it on the bench while pushing the leaver up by hand.I am pretty confident this is OK. I am just so happy I have finally sussed this silly little problem. The only thing is, where is the broken off bit of the leaver arm? I haven't found it so I guess it is in the sump. Hmmm hopefully wont cause any further problems.
Cheers.
Keith.
Last edited by Keith Scarfe on Wed May 08, 2019 11:56 am, edited 1 time in total.
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PostPost by: alan.barker » Wed May 08, 2019 9:08 am

Well done Keith and now you can drive it and have fun
Alan
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PostPost by: billwill » Thu May 09, 2019 1:52 pm

If the broken bit was magnetic, do some fishing with a magnet on a string?
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PostPost by: Chrispy » Fri May 10, 2019 1:19 am

Do you have the spacer between the block and the pump fitted? I can't quite make it out on the photo.
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PostPost by: Keith Scarfe » Fri May 10, 2019 8:14 am

Do you have the spacer between the block and the pump fitted? I can't quite make it out on the photo.

Yes I do have this fitted Chris thanks for checking. In that photo, I don't think it is there at that time as I was just offering it up to check it and didn't have the spacer there when I took the photo. Cheers.
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