External EFI Pump noise - warm fuel?

Quagmire · Post by **Quagmire** » Thu Aug 13, 2015 11:15 am

Hi guys,

I have fitted MS2 to my Rover 3500s, and got the car running properly last week. Things have been going brilliantly until a couple of days ago when I noticed the fuel pump getting noisy... It had up until then been quiet enough to be totally undetectable with the car running.

This only seems to happen when the car has been running for a while (my commute is a 35 mile run between Kingston Upon Thames and Hook in Hampshire which takes about 1hr 15mins).

When it happens you can't hear the pump outside the vehicle, only inside. The pump is making a high pitched whine. Under the car everything sounds normal, no cavitation noise or anything like that.

The current setup is a cylindrical facet pump feeds a swirl pot in the boot, via the lower of the two feeds on the pot (cool fuel from tank in at the bottom). This pot then feeds the EFI pump through the outlet at the bottom and runs through a 13mm hose and sytec injection pre-filter.

The EFI pump then pumps forward through a post pump filter to the standard Rover hotwire fuel rail, and the return comes back from the front of the car to the swirl pot and into the upper return (hot fuel in at the top).

The very top most connection of the swirl pot is the return to the tank.

After a run the swirl pot is warm to the touch, but not hot. So my question is could this be causing my pump to get loud?

The EFI pump is mounted under the car in one of the those billet clamps which I have actually mounted on rubber cotton reels, this seemed to be pretty good before as the pump was too quiet to hear.

If the main suspect is the heat then my thoughts are to use the later Thor style "dead head" fuel rail, and fit a FPR at the rear of the car so that I don't having any fuel running back from the hot engine bay...

Does anyone have any ideas/experience of these issues?

Cheers

Quagmire · Post by **Quagmire** » Fri Aug 21, 2015 8:06 am

Update to this, went to flow test my low pressure pump and found that I had somehow got some of the connections to swirl pot arse about face. The main problem was that I had the feed connected to the top, where the return to the main tank should be!

This has been sorted and the pump has gone back to being quiet, for now...

Ian Anderson · Post by **Ian Anderson** » Fri Aug 21, 2015 10:17 am

Damn and blast
I was hoping you would find ou and publish

Mine draws from the right point but still sings once everything gets hot

Two different pumps and same thing, though one went really noisy as I managed to run it dry as crap blocked the fuel tank exit and I ran the swirl to empty

Ian

Quagmire · Post by **Quagmire** » Fri Aug 21, 2015 11:10 am

Hey Ian,

I haven't done any long distance running yet, or any in hot weather so we'll see what happens.

My next plan if it does become a problem was to fit a Thor style rail (no return) and "dead head" the line going forward.

The FPR would be moved to the back of the car instead near the pump. If you look on ebay there are lucas ones that were fitted to older Jags that have threaded fittings. This way no hot fuel ever gets back to the swirl pot and the only heating would be from the pump itself.

Might be worth a go? Not sure if it would need you to change injectors too (are Thor ones shorter?)

Jamie

DEVONMAN · Post by **DEVONMAN** » Fri Aug 21, 2015 11:30 am

Can you not just remove /blank off the current return and use your existing rail if you are fitting a return elsewhere?

I'm not familiar with the Thor Rail. Does it have a means to deal with hot fuel /air locks etc when the engine has been standing when hot.

Denis

Quagmire · Post by **Quagmire** » Fri Aug 21, 2015 11:51 am

Not sure - the Thor rail is fed in middle at the rear and so the two banks are separate in a "Y" configuration.

I guess you could just blank off the hotwire return but not sure what the effect would be on the injector at the end of the rail (number 7) as it would be getting the hottest fuel at the lowest pressure?

Maybe an adult can answer that for us!

DaveEFI · Post by **DaveEFI** » Fri Aug 21, 2015 12:31 pm

I'm also curious as to how/why the Thor fuel rail came to be. My gut feeling is the older system of pumping fuel round the entire rail would keep it cooler - and fuel vapour lock is a very real problem on my RV8 on a hot restart after stopping a hot engine for a short time.

When I first saw it, I assumed it was single rail throughout, with the pump itself controlling the pressure.

My SD1 has a series resistor in the feed to the fuel pump, said just to reduce the noise from the pump. The OEM Bosch unit is also quieter than some of the aftermarket types I've seen. The OEM Bosch is IIRC the same unit as used on the V12 Jag, so doesn't need the maximum output it is capable of.

Quagmire · Post by **Quagmire** » Fri Aug 21, 2015 12:52 pm

One thing that may compensate for vapour lock issues on the Thor setup is that I believe the injectors are fed at a higher pressure, more like 50psi compared to the 37.5 for the previous injections incarnations.