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Aftermarket Fuel Pump = Less Fuel Capacity?

sonicz

By sonicz,
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sonicz Rising Star

sonicz

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Posted (edited)

I just put a walbro gs432 style fuel pump in today. The car left me stranded on the road immediately after a test drive because I ran out of fuel, but with the stock fuel pump I had easily another 100km of driving left in it.

I could pull up to a servo and fill up with 55L of petrol with my original fuel pump. With the new pump I imagine I lost about 10L of that figure (The gauge wasn't even below the last marker before it stalled)

Is there any way to modify an aftermarket pump to have the same reach as the stocker?

Edited by sonicz
sonicz Rising Star

sonicz

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Theres only so low I can mount it. If I want to match the original length I have to cut bottom part of the metal mounting bracket that the pump normally sits on and hang it off with just one hose clamp?

The car is a R33 GTS by the way GTRSean. The guage definitely has not changed, Like I said I know the car has 10+ litres left inside and this pump just cant get to it that the stocker would have easily

Edited by sonicz
scotty nm35 Grand Master

scotty nm35

Posted
Posted

Considering there are thousands of threads on the subject and even a few "How to's" I would have thought a quick google search would give you the answers you are looking for...

Walbro pumps don't like sucking fuel up a hose, you need to fit the pump lower.

sonicz Rising Star

sonicz

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Ok. I will try mount it lower tomorrow.

Though I don't see how a pump can not like sucking up a hose or not as you say? If there is a longer hose there it will suck it up just like any other pump. They just don't come with a hose and filter long enough to have the same reach as the stock is the way I see it.

One last question. I used crimps to join the pump to the existing wiring. They are pressed tight but not shrink wrapped. Any change of them causing a spark and going kaboom?

I will add chemical resistant shrink wrap to them tomorrow. I hope jaycar has em.

Edited by sonicz
Ben C34 Grand Master

Ben C34

Posted
Posted

Ok. I will try mount it lower tomorrow.

Though I don't see how a pump can not like sucking up a hose or not as you say? If there is a longer hose there it will suck it up just like any other pump. They just don't come with a hose and filter long enough to have the same reach as the stock is the way I see it.

One last question. I used crimps to join the pump to the existing wiring. They are pressed tight but not shrink wrapped. Any change of them causing a spark and going kaboom?

I will add chemical resistant shrink wrap to them tomorrow. I hope jaycar has em.

There is no o oxygen in the tank for an explosion to occur, but I would definitely sort that out. Good practice is staggering the connections so they can't touch each other.

Do a search on pump types. There are heaps of different types, but typically a high pressure pump can't suck much. (like a turbo can't such much, its a pump)

sonicz Rising Star

sonicz

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Good to hear, but I'm not sure about having no oxygen. When you working on the fuel pump you have the lid at the top open so plenty of air gets in. You could be unlucky enough to have a perfect air fuel mixture in there for the first few moments after you put the pump and close it all up.

Even during normal operation when the tank is say half full, whats the other half made of? It would be air but you are saying this air has no oxygen in it?

The system could also have a leak in it etc. I've seen plenty of skylines that don't hiss when you open the petrol cap.

Anyway I took the pump out to have a proper look at it, it seems the cause it the filter with my new pump is HORIZONTALLY mounted instead of vertically. This makes reach way less down, in addition to the filter being much smaller anyway.

Is there any reason I cannot mount the new pump as low as I can? I mean like almost pressing against the bottom of the tank low?

Does anyone know if red bendy vacuum hoses material is petrol proof. I was going to put some silicone around the wires but I herad silicone will break down in petrol over time!

Edited by sonicz
scotty nm35 Grand Master

scotty nm35

Posted
Posted

Twist, solder and heatshrink, making the joins staggered just in case, or solder the new wires directly to the plug if possible. Solid connections don't spark, crimped ones can let go.

If the tank isn't hissing when the cap is released then they have removed the carbon canister. Naughty naughty.

The filter on the walbro needs to be almost touching the bottom, and horizontal, or it won't work. Does your tank have a surge cup the pump sits in?

sonicz Rising Star

sonicz

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I was told heat-shrink is NOT petrol resistant. My crimps are fairly strongly pressed in. They should be ok.

I don't know what a surge cup is. The bottom of the original bracket where the stocker sat on a piece of rubber has been cut of, and the new bare pump with filter attached is just hanging down on the lower end of the metal piece held in with metal hose clamps. I will mount it really low tomorrow and see how far down I can get it with a single clamp.

By the way The stock petrol pump on my GTST was a huge jecs. Its easily twice the size of the new one. Are people sure these tiny fuel pumps flow more than the stock?

I never had any problems with the stocker. TBH im not sure if it was worth it. Furthermore I'm being told the new pump needs to run at 14v whereas the stock made to run fine at 12, so it needs a direct battery feed mod.

Furthermore the stock computer reduces teh voltage to 9c when at idle, further complicating matters. I wonder if that would cause a stalling issue when easing of the throttle at low speeds, at the lights etc.

I just bolted mine to the stock wiring. I wouldn't be surprised if with this set-up the stock pump is ironically better. And if you have to bump up the voltage for the new pump by rewiring, then it just begs the question how much better the stock pump would have flowed if that had new wiring as well.

Bloody mods...

sonicz Rising Star

sonicz

Posted
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Posted (edited)
Anyway scotty, in regards to the "thousands of threads and how tos on the matter", I had a look at about 3 guides and none of them seemed to state needing to mount the fuel pump lower. Nor did they mention the horizontal vs vertical position of the fuel filter.


That said, I have seen a lot of people say," my walbro is noisy", or "yeh they like to gurgle lol" etc, so it may not be as common knowledge as you think. I bet lots of people are monting it high not knowing about it.


So heres how I re done it.


I grabbed a piece of radiator hose about the same diameter as the pump, cut it to size and slipped it over the pump. I used some vasoline to help it slide on good.


9bepfq.jpg



This not only reduces noise, vibration, but also isolates the outside of the pump electrically just in case, as opposed to sitting bare on the metal frame with a metal clamp etc.

I used one clamp to hold the pump as low down as I could. The rubber keeps it very grippy.


The result is very good, the pump now sucks almost as low down as the stocker and is inaudible


I also cleaned all the contacts with Q-tips so they come out fresh instead of covered in carbon and oil and filth from years of exposure. They contacts were literally black when I pulled it out. It could be the reason why so many people get low voltage issues as well with the stock wiring.


dxodqs.jpg


Hope that helps someone.

Edited by sonicz
scotty nm35 Grand Master

scotty nm35

Posted
Posted

Good job there, although mine are silent, so I don't think the rubber was required. Here's my attempt for the Stagea.

https://www.dropbox.com/s/c5p2f6v5tpfnpe8/Walbro%20Twin.jpg

Beware the Walbro will possibly fail if you continue running it on low voltage...

sonicz Rising Star

sonicz

Posted
  • Author
Posted (edited)

Good job there, although mine are silent, so I don't think the rubber was required. Here's my attempt for the Stagea.

https://www.dropbox.com/s/c5p2f6v5tpfnpe8/Walbro%20Twin.jpg

Beware the Walbro will possibly fail if you continue running it on low voltage...

Thanks. Your setup seems solid. What are you running it on? Why not just go for one bigger pump?

As for the pump, Oh I believe you it can easily fail. It doesn't seem anywhere as robust as the stocker, and I am hugely disappointing with the flow of the 255. The jecs stocker is twice the size and in my opinion bulletproof. 20yrs old and it definitely provided more flow than the walbro at 9v. The car now dips rpm at the lower revs because the puny 255 pump just cant flow as much it seems.

After fitting it, and no other changes my car is dipping revs at the lights and almost stalling. Response at lower RPM feels much worse too. This is 100% from a reduction in flow.

I don't understand why people are are recommending this as an upgrade if it flows less than the stock unit at the same voltage.

It makes sense too, at the same voltage for a pump half the size of another to flow less?

I understand the walbro is not designed to run at 9v, but its still just a DC motor in there just like the stock pump which runs at 9v like a champ.

Are people actually saying when both pumps are at 9v, the walbro flows hugely less than the stock, so little in fact my car almost stalls, but when both pumps are at 12v suddenly the 255 overtakes the stock pump and flows more?

I am so damn curious and reluctant to just blindly trust other peoples claims that its an upgrade I feel like hooking each one to a 12v battery and testing the flow myself.

Edited by sonicz

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