New Mechanical Fuel Pump

[111Robin]

I may consider this if the latest "fix" doesn't work. At least I'm getting value for money with my AA membership !.

[checkrail]

Robin, Have you tried tightening the carb to manifold nylocs, I was getting what I thought was fuel starvation after swapping my existing one for a hand primer for with one from Kelveden.
The top needed turning to line up the fittings and you need really small hands to pump the lever, this is on a +2 with Webers.

Just a thought, John

[111Robin]

Hi John,
I did turn each nyloc one flat just incase, trying to maintain the washer gaps, maybe I should give them another flat just to be sure. The hand primer is pretty useless in two ways. Firstly you can't get to it easily enough to make it of any use and secondly the hex head screws on the manual lever prevent you from getting a socket or ring spanner onto the pump screws. Took me ages with an open ended spanner just getting a flat at a time. Now I've reverted to the non primer pump it's a two minute job getting the pump screws on/off.
Mine will run forever in the garage, idles very nicely and takes the throttle cleanly, never cuts out or any of the antics it does on the road. I don't see it being temperature related as in the garage I'm really letting it get up to and slightly beyond normal temperature and it never falters. I had one faultless run on the road of a bout thirty miles. The four times it has failed were random, a couple of times it was after only about two or three miles, another time it was after about twenty miles so there doesn't appear to be a common factor with the break downs.
I had always suspected fuel starvation so the first two times I disconnected the pump supply line and blew back to the tank after which it started and ran perfectly. However this was after letting it sit overnight so may have just been a red herring. The third time it just restarted after I pulled the king lead to check for ignition. Another red herring that resulted in me replacing the coil and electronic ignition unit only for it to break down again the next outing. The last time it just eventually started, running rough, but started to pick up as I limped home with the AA following, and it was fine by the time I got home. The previous owner has said he never had any issues so it must be something I've done . What I don't get is, if it is the pump eventually allowing the float chambers to run low, hence the spitting back and cutting out, why do the carb's not just refill as I'm cranking it to try and start it, to the point where it starts running again ?. Nothing about this makes any sense to me.

[steve.thomas]

Robin, I had very similar symptoms on my Plus2 some time ago. Eventually I traced it to a partial blockage of the fuel pipe where it joins the tank with a banjo bolt. There was something that resembled a piece of fine wire wool in there!
This was after I had spent much time and money on the ignition…..
Good luck
Steve

[gjz30075]

Robin, is the tank vented? Next time it fails, open the gas cap to see if normal pressure comes
back to the tank.

[111Robin]

Robin, is the tank vented? Next time it fails, open the gas cap to see if normal pressure comes
back to the tank.

Yes I did this,after it broke down, no sudden escape of vapour so definitely venting. I had the tank out a few months ago and blew through the vent hoses so I know they're clear.

[111Robin]

Robin, I had very similar symptoms on my Plus2 some time ago. Eventually I traced it to a partial blockage of the fuel pipe where it joins the tank with a banjo bolt. There was something that resembled a piece of fine wire wool in there!
This was after I had spent much time and money on the ignition…..
Good luck
Steve

I had the tank out and fitted a new line through to the pump at that point. One change I made though, rather than using the olive I changed the union on the banjo to one with a barbed tail and heat shrunk the nylon line onto it. I'm concerned that the bore of this fitting is too small and may be restricting flow. I have recently pumped the tank empty from the pump end and there was plenty of flow so no indication of a restriction but it is always at the back of my mind. There wasn't a single dirt particle from the tank, I checked it was clean when I removed it anyway.

[h20hamelan]

Ive had similar issue. RD pump orientation. Went to Electric, found the + & - wire too small (have oil pressure shut off and Inertia device too). Increased size, better. I have installed fuel filter while at it. Found a filter before and after made it more quiet and smooth.
Electric in-line vs T, I went with T.
What I do like, is having the pressure gauge in the engine. I am still using a clear filter up front, the pressure gauge give piece of mind.
When you step down or up a side of fitting or hose, there will be change of overall flow rate. Obstructions etc.

[gjz30075]

When I used an electric pump for diagnostic purposes, I kept the glass bowl 'pump' bolted to the block but
it was gutted, ie, no arm, no diaphram. This way, I can use its filter and watch the fuel in the glass bowl. It
also allowed me to keep the stock arrangement and not have to come up with fancy fittings to mate the
plastic line from the tank to the braided fuel loom on the output side

So, question to the OP, when the car 'runs out of gas', is there fuel in the glass bowl?

[111Robin]

Unfortunately the pump is aftermarket, no glass bowl. All I have done is crack open the banjos on the carbs and turned it over to confirm fuel delivery, which there is, but who knows if it's sufficient.
This afternoon I removed the smaller bore fitting at the tank and refitted the olive so I now have at least eliminated this as a possible restriction.

[snowyelan]

I couldn't recall having any line clearance issues with the lines when I installed the RD pump. See below. The picture is a bit deceptive since the block flange is actually well below the lines. Are you using the insulator block? If not it would reduce the clearance.

[111Robin]

The difference is you are using a solid radiused elbow to direct the line away from the block. If you use the oem braided type it has a straight pipe section at the pump before the flexible line, this means the flexible has to bend very tightly away from the block and probably causes a considerable restriction.

[Craven]

The needle valve is 1.75mm there are two so max flow possible is 3.5 mm at say 3psi. Supply pipe line of 6mm is plenty.
FWIW.

[111Robin]

The needle valve is 1.75mm there are two so max flow possible is 3.5 mm at say 3psi. Supply pipe line of 6mm is plenty.
FWIW.

The fitting I used at the tank only had a 3mm bore so could have been adversely affecting the flowrate. Now reverted to the full bore olive fitting so hopefully if this was the issue it's now resolved. Time will tell.

[111Robin]

After all of that there is no good news to report.
Car is performing perfectly at rest, idling nicely, good throttle response, yet as soon as I take it on the road it immediately starts spitting back and losing power. I got about 200 yards then turned and came back as I knew it would just get worse and break down as before. I am at an utter loss with this car now.