SU Pump Pressure

Started by tmsmini, June 03, 2021, 01:00:32 PM

Previous topic - Next topic

0 Members and 1 Guest are viewing this topic.

tmsmini

While trying to sort out what I thought was a pump issue, I temporarily installed a fuel pressure gauge.
I discovered the old pump operated the same as the new pump and the issue lies some where else.

I have seen people with fuel pressure gauges appearing permanaently installed, but this Aeromotive liquid filled gauge does not like the engine bay temps of a Mini. It does have a pressure equalization button, but even with that, its readings change from an bonnet open reading.

[youtube width=800]https://youtu.be/FmSjGH59e5U[/youtube]

94touring

That's odd.  My pump stays dead solid when I hook a pressure gauge to it. I had to setup my fuel pressure regulator with the pressure gauge.

tmsmini

This is the AUF0214 electric pump.
I assumed it was the action of the diaphragm as both pumps behave the same way.

94touring

Are you getting fuel starvation when driving?

MiniDave

Quote from: tmsmini on June 03, 2021, 01:31:30 PM
This is the AUF0214 electric pump.
I assumed it was the action of the diaphragm as both pumps behave the same way.

If that's the regular SU points style pump, then that's exactly what it's doing - those are high volume low pressure pumps.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

tmsmini

Long story on what caused me to start looking at the pump.
It is the points style pump.
I did have what I thought (could stillbe) fuel starvation at around 5K
But I had just swapped in a rebuilt HIF 44. The old one kept on going , so I never bothered to swap it. Eventually it looked like the seals were starting to go, a little fuel in the over flow every now and then and some running on. I had the rebuilt so why not just swap it in...

After a couple of episodes of what appeared to be fuel starvation, I swapped in a new pump. Declaring things all good, I let my wife drive it. She got stuck running errands and although I got it running, I almost got stuck with it not wanting to run well on another trip. Nursed it home and went about adding the gauge where the filter had been.

Anything I changed except the rebuilt carb has been swapped back. I have started it twenty time and it always starts. I have made some runs in the neighbor hood without issue.

I did replace the float and the jet tube on the carb, but there did not seem to be an issue with the old items.

I will do another run today  to get it over 5K and see what happens.

tmsmini

This engine has a different configuration as it is an MPi block. So there are some things that could cause an issue not normally found on an A series.
Distributor less ignition is provided by the SC Typhoon ECU. The fuel pump is activated by a fuel pump relay and there is an inertia switch in the circuit.
All those things appear to be working.

94touring

If you don't mind tossing money at new pumps, I used to run a Mr Gasket 42S on my mini (before I put an mpi pump in for the eventual turbo) and my bus.  Actually 2 on the bus, one for the carbs and one to transfer fuel from my aux tank. 

MiniDave

I've had mixed success with the Mr. Gasket pumps, I went thru three failures before I got one that worked OK.

Most people say the Faucet pumps are good, the little square ones. The only thing you have to know is that it's under 5lbs of pressure.

Remember when I couldn't get my Mini to run after I put the engine in? Check the choke o-rings carefully on the HIF carbs.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

tmsmini

Just took it out and ran to 5k in 1 and 2, held it at 5K in 2 for a period, up to 4K in 3rd, all with no issues and plenty of stops and starts.

This setup did 5000 miles two years ago and now I barely trust it to go five...

94touring

If it makes you feel any better my mini has some kind of carb fueling problem all of a sudden. I suspect the choke o rings like Dave had an issue with.  Either way the last thing I feel like doing is pulling the carb out to dig through it.  I've never had issues with the Mr Gasket pumps like Dave had. 

cstudep

They can be finicky that is for sure. I think I finally figured out on mine that one of the floats was sticking shut (dual hs4). I can tap on the bowl of the passenger side carb and it seems to run great. After it sits for a while it starts to run poorly again. Tapping on the float bowl seems to clear it up again. I need to pull them off and deal with it properly,  but I am trying to find an hif44, so if I pull the duals off I'd rather not put them back on.

John Gervais

I'm running a square Facet pump (never had a problem with them) and use one of them fancy Malpassi Filter King filter/regulator units.  The fuel pressure is regulated to 3½ psi using a separate gauge temporarily plumbed just before the carb and promptly removed once the filter/regulator is adjusted, delivering constant and reliable fuel pressure. 

The fuel pressure in the video clip seems awfully low to me -
- Pave the Bay -