Dolomite 1850 fuel pump problem

[davidmorr]

I have been having some fuel supply problems. The car would start up, run for about 15 seconds then just gradually run down. No amount of choke or accelerator made any difference. Spark plugs and ignition seem ok. A mechanic friend suggested it was a fuel supply problem.

I took off the fuel pump and checked the diaphragm - it looked like it was past its use-by date. No diaphragm kits could be found so I bought a new fuel pump.

This is a bit of a story. I bought a the 1850 in 1976. Somewhere along the line (1990s?) the original fuel pump failed and had to be replaced because it was sealed. The mechanic who replaced it managed to break off the lever somehow. (I did my own work after that...)

My recollection is that there was originally a spacer between the pump and the block. He had not replaced the spacer which I am guessing is why the lever was broken off?

He then welded on the lever from another pump and fitted it, again without the spacer. It has worked like that for many years.

That pump was the one with the failed diaphragm.

The lever on the new fuel pump - claimed to be suitable for Dolomite 1850 - was a slightly different shape, a bit shorter than the welded on lever. I tried it with a 5mm spacer, but it would not pump. After a lot of checking, I then tried it with no spacer. Again no pumping, although when I turned the engine over on the starter, there was a regular squeak which suggested it was contacting something.

It dawned on me a little while ago that the lever might be below the cam instead of rubbing on the side of it. I am not sure if this is possible but it might explain the squeaking.

Just looking for ideas on how to figure out what is going on and get the pump working.

[BobM]

Hi
Check this thread.

https://forum.triumphdolomite.co.uk/vie ... er#p336232

[MIG Wielder]

Hi David, The above link is good. While you have the pump off the block I would do 2 things. If you operate the pump lever by hand does it pump fuel ? If you put a torch onto the cam for the fuel pump lever in the block is it smooth or is it worn and grooved ? Then does the pump lever profile match either of the sketches ? TBH I would get a recommended new fuel pump for the car rather than a "fits" . Too often they don't . There is a graph with the correct two profiles in the link, if you print it out and compare the pump levers.
HTH,
Tony.

[davidmorr]

Thanks for the great advice. It looks like the new pump is the long arm type, while the old one is the short arm type, so a spacer will be needed. However I am concerned whether the arm is long enough and also the shape of it. All the diagrams have a flat surface in contact with the cam whereas this is on a curve. It is also just pressed metal and quite rough on the edge - needs grinding I think if I use it. (The rubber band is to pull the lever in to the start of the stroke.)

[dollyman]

If you need a spacer this one does the job https://www.ebay.co.uk/itm/193623956934 ... SwSSZfNlug As the Dolomite ones are hard to get.

Tony.

[MIG Wielder]

Hi David, Yes, I agree that looks very much like the long arm pump. I reckon the area of the pump where the operating cam bears is also quite close. Here is a photo of my old one from some time back. The shiny area between the 2 Snopake markers is where it runs. So a new spacer block and you should be running again .
But yes, if there is a burr on the arm gently removing it with a fine file would be a good idea.
Tony.

[davidmorr]

But yes, if there is a burr on the arm gently removing it with a fine file would be a good idea.
Tony.

The arm has been hardened and is really resistant to filing. Might have to try a grinder.

[davidmorr]

But yes, if there is a burr on the arm gently removing it with a fine file would be a good idea.
Tony.

Thanks for the confirmation. The arm appears to be pressed out of a sheet of metal then hardened. I have tried filing it but the file does not mark it. I am thinking I may need to use a grinder. However, I am wondering whether it is a good idea to grind a hardened metal item? Could it breach the hardened layer?

[MIG Wielder]

Hi David, Yes, I see what you mean. Oh dear that burr is more than likely going to saw its way through the cam on the jackshaft. My first choice would be to send it back and get a replacement. 2nd choice would be a careful grind to remove the burr.
Hope you get a good result,
Tony.

[Bumpa]

I replaced the pump on my 1850 a year or so ago and got one from Robsport. It fitted perfectly, didn't need a spacer and has given no trouble so far... It was the same as the TR7 pump.
https://robsport.co.uk/index.php/online ... 051-312167

[cleverusername]

But yes, if there is a burr on the arm gently removing it with a fine file would be a good idea.
Tony.

Thanks for the confirmation. The arm appears to be pressed out of a sheet of metal then hardened. I have tried filing it but the file does not mark it. I am thinking I may need to use a grinder. However, I am wondering whether it is a good idea to grind a hardened metal item? Could it breach the hardened layer?

The problem isn't just the hardened layer, when you grind it you will introducing heat and risk loosing softening the metal near the grinding area.

[davidmorr]

Well, I am back to this again, after a short episode involving being injured while hiking, being rescued by helicopter and spending a couple of days in hospital....

I finally got the pump to work using a 5mm spacer. However, according to the workshop manual, the vacuum on the inwards side should be 2.5-3.5 psi. In fact, it is about 6 psi. The manual suggests if it is too high to add extra gaskets to reduce the pump stroke. I will try adding extra gaskets tomorrow, but in the meantime, the pump seems to be working ok, as shown in this video:

http://davidmorrison.id.au/Fuelpump.mp4

Does this look like a normal fuel pump flow?

The car starts after some churning, but backfires (spitting fuel out of the carb opening), hesitates and eventually seems to run out of something, as it just slows down to a stop.

Just to make sure that the engine would actually run, the other day a friend and I set up a funnel to run fuel into the carburetors by gravity. It was a bit rough initially, but after cleaning the plugs and points, checking spark plug leads and the coil, and adjusting the timing it was running very smoothly.

Today, with the same setup and the fuel pump disconnected, it does the same as with the fuel pump connected above. I wondered if the SU carbs were flooded, but there is no fuel in the overflow hoses.

Mystified! I do not know what could have changed.

[cleverusername]

Well, I am back to this again, after a short episode involving being injured while hiking, being rescued by helicopter and spending a couple of days in hospital....

I finally got the pump to work using a 5mm spacer. However, according to the workshop manual, the vacuum on the inwards side should be 2.5-3.5 psi. In fact, it is about 6 psi. The manual suggests if it is too high to add extra gaskets to reduce the pump stroke. I will try adding extra gaskets tomorrow, but in the meantime, the pump seems to be working ok, as shown in this video:

http://davidmorrison.id.au/Fuelpump.mp4

Does this look like a normal fuel pump flow?

The car starts after some churning, but backfires (spitting fuel out of the carb opening), hesitates and eventually seems to run out of something, as it just slows down to a stop.

Just to make sure that the engine would actually run, the other day a friend and I set up a funnel to run fuel into the carburetors by gravity. It was a bit rough initially, but after cleaning the plugs and points, checking spark plug leads and the coil, and adjusting the timing it was running very smoothly.

Today, with the same setup and the fuel pump disconnected, it does the same as with the fuel pump connected above. I wondered if the SU carbs were flooded, but there is no fuel in the overflow hoses.

Mystified! I do not know what could have changed.

Some of the new pumps produce too much pressure, my solution was to place a pressure regulator between the pump and carbs.

[davidmorr]

Some of the new pumps produce too much pressure, my solution was to place a pressure regulator between the pump and carbs.

Could you provide a link to the type of device please? I have not come across these before.

But still, it was backfiring even with gravity feed of fuel.

A friend suggested the fuel may have been too old, which is possible although I would think it would be very old to cause these symptoms.

[cleverusername]

Some of the new pumps produce too much pressure, my solution was to place a pressure regulator between the pump and carbs.

Could you provide a link to the type of device please? I have not come across these before.

But still, it was backfiring even with gravity feed of fuel.

A friend suggested the fuel may have been too old, which is possible although I would think it would be very old to cause these symptoms.

https://www.ebay.co.uk/itm/353380120509 ... SwDQVgHSNZ

I used something like the above. Not that I am recommending that particular one but it is an example of the kind of thing you need. Better more expensive regulator are available.

The issue is the new fuel pumps can put out 6psi or more, when the carbs need around 2psi and that pressure overwhelms the float and floods the carb.

Having thought about it, your symptoms sound very like the ones on my Sprint engine, it was backfiring and wouldn't run probably. The problem was, it was running far too lean. I just dialed up the mixture till it ran smoothly, which I admit isn't very scientific.