Fuel pumps

[Farmer42]

I am looking for some advice or recommendations for electric fuel pumps for an S30 2/2.

I am currently running a Facet silver top mounted at the back near the tank feeding twin HS6 SU carbs and although it runs fairly well with no stalling issues, it does seem to bog down at higher revs and speeds. I have set the carbs up fine and the float levels are ok but a recent check of fuel pressure at the carbs seems to be a bit low at 2 psi. I have checked all the lines and filters and they all seem ok and as I move the pressure gauge back the pressure increases slightly but not to the extent I was expecting. The Silver Top should be pushing out around 4psi and as far as I know, SU carbs operate on around 2.5 -3 psi so it should be ok.

My thoughts are that the pump is not strong enough to maintain fuel pressure along the length of the lines and I am not getting enough fuel to meet the demand when I kick down. Like I said, I don't have misfires but it doesnt seem to want to rev any further and feels like its holding back. Prior to installing my power steering, I had a mech fuel pump along with the Facet and I didn't have the issues. Unfortunately I had to do away with the mech pump to accommodate the 280ZX P/S pump which bolts where the fuel pump was.

To cut a long story a bit shorter, does anyone have any recommendations for electric pumps that will do the job but not overwhelm the carbs? Should I go for a higher rated Facet, possibly a solid state pump, or should I install a secondary 'pull type' pump in the engine bay that replicates the mech pump or are there any other pumps that I won't need a mortgage to buy that people have used?

 

[jonbills]

Sounds more like ignition timing to me. If it was fuel starvation you'd have popping and misfiring.

 

[Dale]

I was thinking ignition as well. Tired coil?

Could also be tiny bits of debris from the tank causing blockages at higher revs?

 

[richiep]

Given the issue having appeared since the mech pump was deleted, if it is inadequate fuelling (and not the ignition issue Jon and Dale note as a possibility) you could swap the Silver Top for a Red Top and use an inline regulator to dial the pressure in. That's what I use with triple DHLAs. Small rotary Sytec regulator set to 3.5psi.

Have you checked IN the fuel pump? I suffered my first ever breakdown in the Z in 2019 because the Red Top had clogged with rubber from the fuel hoses (the ethanol effect in practice). The material was actually collected in the upper part of the pump rather than the gauze filter. Basically killed it stone dead. If there's material in your pump, it could restrict flow?

 

[Rob Gaskin]

Just make doubly sure that the filter in the pump is clear and any additional filters. The translucent type can look clear but semi-blocked by fine rust particles.

 

[stevey456]

I have triple Dellortos on 2.8 litre in my 240Z with twin Red Tops (switchable for back-up) mounted in the engine bay (for ease of access to the filters) and that seems to work OK - even in 40 degree heat in Greece and Italy last summer. Only issue I have is that after a bout of high rev, low road speed work I get some fuel vapourisation which clears when I switch pumps, so think I need to rig some cooling air to the pumps.

 

[Rob Gaskin]

I have triple Dellortos on 2.8 litre in my 240Z with twin Red Tops (switchable for back-up) mounted in the engine bay (for ease of access to the filters) and that seems to work OK - even in 40 degree heat in Greece and Italy last summer. Only issue I have is that after a bout of high rev, low road speed work I get some fuel vapourisation which clears when I switch pumps, so think I need to rig some cooling air to the pumps.

Hi, as a matter of interested do you have non-return valves to stop the pumps feeding back into each other?

 

[Farmer42]

Thanks guys.

I have done all the ignition & timing checks and all is as it should be. The coil is fine & I'm running a 280ZX dizzy with new cap, rotor arm etc.

Didn't think to look inside the pump so will definitely do that. If that fails and the filter is clear, I will try a red top. I already have a regulator in the garage I can use. I just wasn't sure whether the solid state cube type were any better.

@Stevey46 - I didn't think you could run Facet pumps that far from the tank. It says no more than 12 inches or they run dry and damage.

 

[Rob Gaskin]

@Stevey46 - I didn't think you could run Facet pumps that far from the tank. It says no more than 12 inches or they run dry and damage.

I have.

 

[richiep]

I think the “correct” position for an electric pump is close to the tank. Reinforced in the S30Z design by the factory mounting point for a pump opposite the tank on the rear structural crossmember, regardless whether it came from the factory with one fitted or not.
In that location it is pushing to the engine bay rather than pulling the full length of the car.

 

[toopy]

I have a Facet silver top mounted in the engine bay next to where the OEM filter bracket is, works fine. I think the solid state cube ones you mention are push only, but the older cylindrical type can suck too, if the head is not to high!!

 

[mrzed]

Are your spark plugs ok?
I had the same trouble, was hesitant when on full revs
I thought it was fuel related starving of fuel the same as you
I decided to change the spark plugs
And it now runs like a dream

 

[Mark N]

Only issue I have is that after a bout of high rev, low road speed work I get some fuel vapourisation which clears when I switch pumps, so think I need to rig some cooling air to the pumps.

Is your fuel system return or returnless?
If it is returnless, I would have thought that high revs and load, requiring more fuel, would provide better cooling at the pump.
Are you sure it is not due to cavitation from the pressure draw in the line from the tank to the pump?

 

[stevey456]

Hi, as a matter of interested do you have non-return valves to stop the pumps feeding back into each other?

I don't - they're just tee'd into the feed to the pressure valve and onto the carbs. I suspect that the pumps have non return valves built in - otherwise they would just blow and suck.

 

[Rob Gaskin]

I think the “correct” position for an electric pump is close to the tank. Reinforced in the S30Z design by the factory mounting point for a pump opposite the tank on the rear structural crossmember, regardless whether it came from the factory with one fitted or not.
In that location it is pushing to the engine bay rather than pulling the full length of the car.

Yes, but they will work elsewhere.

I don't - they're just tee'd into the feed to the pressure valve and onto the carbs. I suspect that the pumps have non return valves built in - otherwise they would just blow and suck.

I asked because I had a VW van where the petrol tank was over the carbs (twin). The po had fitted an electric pump because the mechanical one didn't work (worn pushrod). Anyway the fuel would just run through the pump. I know this because I had a weeping needle valve in one carb (discovered later) and the sump filled with petrol! So perhaps a one way valve?