12 replies to this topic

[CUBBACUB]

Greetings to you all.

 

I've been having a few issues with mechanical fuel pumps. 

 

My vehicle is a Moke Replica (Might be a AMC Cub, Might be  Jimmini Mk1 but thats a discussion for another day!) Its got a 1989 1000cc engine, single carb and a mechanical pump.

 

The car wouldn't start, it  was turning over ok but not starting, after a bit of digging around I established there was no fuel getting the carb. I bought a new fuel pump (making sure it was the right type) and fitted it and hey presto, the car started up straight away and ran fine for a week.

 

Then the same issue struck, wouldn't start but was turning over OK. After further digging around, again I established no fuel was getting to the Carb. I checked all pipes from the fuel tank, to the fuel pump and fuel pump to carb for blockages and there are no obvious issues. So yet again I took the new fuel pump off.

 

On inspection of the new fuel pump, I noticed the arm that goes into the back of the engine block was looking a bit worse for wear, considering it was a week old. This new fuel pump has a moulded plastic end and it was looking a bit shredded.

 

Finally. With the pump in my hand, I manually pumped the arm and fuel appeared in the carb immediately.

 

Has anyone come across such an issue before? I was thinking my next step would be to just ditch it and fit a facet.

 

Thanks in advance

 

( all engine components are totally standard 1989 1.0 if that helps)

Edited by CUBBACUB, 07 June 2017 - 03:51 PM.

[Cooperman]

Fit an electric pump. For extra reliability you could fit a pair of Facit pumps in parallel. That's what I have and they are individually switched. Also, a hidden fuel pump isolator switch is added security.

[wile e coyote]

Hang on a mo... do I read this right - the pump arm is plastic???? - if so I'd suspect the wear has been very rapid indeed - works off an eccentric lobe on the cam so although exceptionally well oiled in that position plastic & fast spinning steel not a great option for longevity.....pump arm should be steel....

 

A decent mechanical pump is pretty reliable and although I wholly agree with advice above it may be a bit of overkill for the application...... and far more involved than swapping out a mechanical...

[CUBBACUB]

Hang on a mo... do I read this right - the pump arm is plastic???? - if so I'd suspect the wear has been very rapid indeed - works off an eccentric lobe on the cam so although exceptionally well oiled in that position plastic & fast spinning steel not a great option for longevity.....pump arm should be steel....

 

A decent mechanical pump is pretty reliable and although I wholly agree with advice above it may be a bit of overkill for the application...... and far more involved than swapping out a mechanical...

 

The arm is steel but has a moulded plastic end on it, which is a bit odd!

[Dusky]

Doesnt the end just pull off( fitted as protection)? I had that on otter pumps before.

[CUBBACUB]

Doesnt the end just pull off( fitted as protection)? I had that on otter pumps before.

 

I did think this at first and tried to remove it but there was no budging it! 

[cal844]

They haven't been an issue on the pumps I've replaced, theyve all had plastic caps which don't come off

[CUBBACUB]

They haven't been an issue on the pumps I've replaced, theyve all had plastic caps which don't come off

Cheers, I was starting to think I'd been a total idiot :)

[cal844]

They haven't been an issue on the pumps I've replaced, theyve all had plastic caps which don't come off

Cheers, I was starting to think I'd been a total idiot :)

No no not at all, thats why this forum exists, to help others..
After all every day is a school day ;)

[CUBBACUB]

They haven't been an issue on the pumps I've replaced, theyve all had plastic caps which don't come off

 

Do you use a spacer when you've fitted these? I've come to my own conclusion that the problem is the arm on the mechanical pump is not engaging properly. I've used the spacer that was already fitted with the original pump, when I compare the original pump and the new one with the moulded plastic end, there is a slight difference in the angle of the pump arm.

[cal844]

Yes I use the spacer, remember the gaskets

[tiger99]

There was a discussion some time back about those pumps with the plastic end on the arm. I think that someone else found them to be unsatisfactory but can't remember the outcome. Pumps used to have a forged steel arm, with a (presumably) hardened and ground running surface. An exotic plastic such as PEEK would also be acceptable, but not nylon or even PTFE (Teflon).

 

One point to watch, and it has possibly been responsible for wrecking possibly tens of thousands of pumps over the years on many different cars, (guessing from the probably tiny sample of such tales which I have seen) is to ensure that the arm and plastic follower is pushed against the cam, and has not gone up behind it. The sort of stuff that used to be emphasised in car maintenance books, and yet there were sad tales regularly in the monthly comics of 40 years ago....

 

By the way, I am sure we would all be interested in seeing pictures of the vehicle in question some time. It sounds very interesting!

[CUBBACUB]

Thanks tiger99, 

 

You are spot on! At the angle I was fitting the pump I was having to hook it into place and the steel arm must have been going behind the cam.

 

2 weeks of frustration solved!

 

Thanks again