Fuel Pump and fuel flow

[rustyrescue]

What fuel pump do people use on a stock FB?
The project was driven today before being mot'd to mot station. It now drives lovely...until, every now and then it grinds to a halt. Fuel flow would seem to be the issue, wait a minute, restart and away she goes for a few miles again. The non standard fuel pump is new but noisy especially with the rear seats etc out prior to a few small weld repairs!
When it stops the clicking pump makes a different tick.
The fuel flow and pressure test ok according to manual.
It had the fuel tank out and cleaned out.
a new filter in the back by the pump and and it does have an extra gauze tube filter before the carb as the gauze inserts are toast on the inlets and removed which may cause bit of a restriction?
Any ideas?? perhaps a better pump needed?? it was cheap just to get it running.

[DKWW2000]

Glad she is running well (excepting the fuel issue). It might seem obvious but have you checked for any soft/collapsing fuel hoses, or the fuel return system/hoses?

[rustyrescue]

Hi, yes it ran well except the 3 or 4 conk outs! feels good when it is not stopped
All flexible hoses are new,
The fuel tank was removed and cleaned out.
It can die even when at light throttle so not simply the pump will not keep up with high demand.
I almost wondered if the pick up is a bit high in the tank....but it has at least 3 gallons in it.
I think we may need to invest in a known quality fuel pump and pressure regulator.
Also look at it in daylight when conked out to see fuel levels in both floats through the windows.
On another note...my mate is a wee bit concerned at the Janspeed (poss??) exhaust lack of silencing in the mot....we shall see.

[Porters2]

Maybe a problem with the tank vent ?
The pump tone change could indicate a struggle to draw fuel, you could always try leaving the filler cap loose…

[rustyrescue]

good idea Porters2......I did clean out all pipe connections on the tank, and agree the change of tone could be a struggle to suck. I will also look in the new filter just in case a load of much has dislodged.
its frustrating! it seems so close to being right.
I would quite like to replace the furl tank but it is not a car you can just get one for!! a stainless tank was easy for one of my other toys! off the shelf and good value.
This car is 50/50 with our daughter and she does not get to go solo until it is right

[gt_james]

Check the fuel tank vent is clear, compressed air line down all the fuel hard lines, and make sure you buy good quality fuel hose, I use car builder solutions to buy fuel hose from, they sell loads of flavors. The market is flooded with dangerous Chinese fuel hose that springs leaks after a few months! Also remember modern fuel has a lot of ethanol in, so you need to replace all your fuel lines with ethanol compatible hose. I think stock is 8mm feed 6mm return

https://www.carbuilder.com/uk/gates-fuel-hose-8mm-516
https://www.carbuilder.com/uk/value-fue ... erman-made

make sure you use decent size fuel filters that flow a good amount, think stuff that works on V8s, not little 4 cylinder engines. Rotaries need good fuel flow. I think the fuel pump a lot of people use is the carter 4070. Don't put plastic fuel filters in the engine bay where they can get hot, I think a 10 ish micron near the carb and a coarser filter by the pump.

Stock fuel pump even when good barely keep up with a stock 12A. I use a holley blue and holley fpr, it works but its stupidly loud, so I can't recommend it aside from a race car.

[rustyrescue]

Hi, both. Well she got her mot today which is great..it can legally be tested now on the road. I took furl cap off and added a gallon on the way back. It was dreadfully wet so I drove gingerly, it runs lovely...a little spluttery foot off throttle but idle has dropped to 500rpm so that will cure I think with a tweak up.
I had no conk outs until.... deliberately induced I got heavy on the right foot ran 5-6000rpm down a straight through gears and it dies at the end! I turned off, turned on.....pump sounded a little odd until it sounded right and then started and finished the trip home from mot, about 9 miles.
I did replace all flexi hoses and I did blow all hard pipes with compressed air back when the tank was out.
I do think a more powerful pump may help, the one on it was a sort of temporary answer when the original went kaput after a short bit of use following restarting it. It does test to spec on flow and pressure according to my genuine manual but I suspect under duress it may not.
I also notice the tone changes as other electrics turn on....wipers, blower, leccy windows, lights etc and in the conditions lots were on! perhaps a new separate supply may be a good idea.
i can listen to the very noisy pump driving currently seeing as all rear trim is out
The Carter pump looks good but none seen in the UK?

[gt_james]

Yeah decent wiring to the pump and good grounds are also a must, but they shouldn't draw a huge amount of current, I think the holley is like 4 amps, I used 2mm^2 wire, nothing that beefy. Try summit racing, they normally ship from the states really quick. Might be worth installing a fuel pressure gauge just by the carb, and if you want to monitor fuel pressure whilst driving, run a T, and a length of fuel hose with the gauge at the end, leave the bonnet popped and tape the fuel pressure gauge to the windscreen. if it drops by 0.5psi then your pump is not flowing enough. Or just fit a decent pump, regulator and filters and forget about it! If you change to an aftermarket pump that puts out too much pressure, you'll need a regulator and gauge anyway.

[rustyrescue]

thanks again, yes after the holidays I will source a better pump anyway...the one in it new but suspect. I like the look of the Carter, says it is 72 gph which even US gallons is huge!
I have an original pump pre filter, new but must restrict flow a lot, plus the gauze washable tube one pre carb.
I thought better pre pump filter and perhaps a filter king type with fuel pressure gauge and adjustment may work well.
I can find no flow rates for filters, which is daft....a big pump is no good if the filters restrict flow.

[gt_james]

Yes it's annoying that a lot of filters don't state flow rates.

72GPH sounds a lot, but these rotaries need a lot! On a ported rotary and track use, 72 would not be enough, the holley blues are 110GPH and are pretty common upgrade also, but they're really loud. I'd stick with the carter for your set up.

The filter king reg might be ok on a stock carb set up, but they don't flow very well, the holley regs are better and cheaper.

It might be worth looking at a bypass type reg as these cars already have a return line. I've personally never used a return style reg though, but I do plan to. Dead head non bypass regulators mean the fuel pump is running at full pressure all the time and is louder. When you're idling and the float bowl is full, there isn't much fuel flow and the regulator is basically a massive restriction, and the pump is hammering full flow at 15psi at this restriction. With a return reg, the pump is always operating at your set fuel pressure and takes the load off the pump.

My old set up was holley blue and holley 12-804 reg. I've since removed this and put it on my track car where the noise isn't going to concern me.

When I get my street car out again I think I'll go with a carter 4070, holley 12-803BP or aeroflow AF49-4500P or KSE KSC2005. The holley and the aeroflow are kind of too high a range, the KSE is an ideal range but pricey. I think you can convert the holley 803BP 4.5-9psi to 1-4.5psi by swapping the spring to a longer one, and I think the rebuild kit for the non bypass regs comes with a spring you could use, but you can't use the diaphragm (12-807) but not done this yet so can't confirm. Annoying holley doesn't make a "12-804BP" reg for 1-4.5psi and return style.

Or I might go with an in tank pump module like holleys retrofit modules, these should be quietest but even more expensive and more hassle to fit.

If you go for a similar set up, rubber mount the pump, or even better rubber mount a plate, then rubber mount the pump to the plate. Look up wellnuts/rubnuts. The return style regs should go on the return side after the carb, like EFI regulators.

For S1/2 its 4.5psi
For S3 its 3.5psi