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Fuel or electrical?

published by Old is good on Sun, 08/04/2018 - 19:43

I took the Holden for a 200km run up the highway.
It runs along fine at 110ks at 2800rpm.
After half an hour or so, if you push it up 3,000rpm it will just hit a wall. It doesn't want to rev any more. If you back off to about 80kph for a couple of kilometers it will pick up then run fine at 3,000rpm or more for another 20mins or so then lose power again.
Give it a fast run up a mountain road at high revs and it definately runs out of fuel after about 4 or 5km. Nathan just backs off to an idle for a minute or so and it's fine again.
It will run all day at 2,800 rpm and never miss a beat.
Driven hard off the mark it will rev to 6,000 through the gears, so Nathan tells me. But it will then play up after 20 mins.
It it slowly running out of fuel? I've got triple 48mm Dellortos and wondered if the fuel pump can't cope. But, on the highway it gets 10L/100km (28mpg) which is around stock motor fuel consumption, so that means the pump should cope.
Otherwise, I though my vacuum advance might be losing vacuum and therefore losing advance, or the advance mechanism in the distribuitor might be sticking.
Around town, using 1,500 to 2,000rpm it is happy all day, and will take the occasional big rev without any problems.
Any ideas? Should I be looking at getting an electric fuel pump with a higher flow rate than the stock pump?
David

Model: 
EH
Topic: 
General

Comments

Submitted by Kinswood on Sun, 08/04/2018 - 20:41.

It was the wrong fuel sender in the tank but l doubt that's the problem here what dizzy set up have you got anyway the old style used to have a capacitor thing on the side that did similar things,if it's electronic it needs a constant 9 volts l believe,wouldn't hurt to check the vacuum advance is working as it should as well.

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Life is too brief to build ya own time machine
With out old Aussie products an a few blurbombs 🥃🥃🥃🥃🥃🥃.

Submitted by a Holden Fan (not verified) on Sun, 08/04/2018 - 21:51.

Points is 9v, electric is 12v.

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Submitted by nitrox on Sun, 08/04/2018 - 21:48.

what carbies mate, not hot fuel or some thing like that?

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Cheers, Lindsay.

4305

Submitted by nitrox on Sun, 08/04/2018 - 21:48.

what carbies mate, not hot fuel or some thing like that?

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Cheers, Lindsay.

4305

Submitted by a Holden Fan (not verified) on Sun, 08/04/2018 - 22:04.

It does sound as if the bowls are slowly emptying over a sustained throttle opening. If it were me I'd put a Carter 4070 on it (regulator usually unnecessary with them) and go from there.

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Submitted by DDR on Mon, 09/04/2018 - 10:50.

from dodgey pump or carby ?
If i floor mine on take off, i sometimes get fuel starvation by time i'm looking to hit 4th, lift the foot then sink it again and comes good but i dont have your problems. (carby is 34ADM) Maybe your fuel pump is crook and struggling to keep up (?) Coil maybe breaking down too (?) .. i really dunno. Do you have spares to try prosses of elimination ?

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"Junk is something you throw out 3 weeks before you need it"

Submitted by hq3O8 on Mon, 09/04/2018 - 12:54.

Sounds like it's running out of fuel. The faster you go the more load there is on the engine, at 2800rpm there's probably just enough fuel supply to maintain the load but as you increase speed (and therefor load) from there it's getting to a point where the fuel supply can't keep up. Could be something as simple as a partially blocked fuel filter?

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Cheers
David

aka hq308belmont

My Archived Shed

Submitted by tonnacrap on Mon, 09/04/2018 - 21:50.

......is a fuel tank full of crud. I had that problem, and the car would starve of fuel. If I calmed down to normal driving it would fill the fuel bowls again and be ok. The first thing I would fit is a fuel pressure gauge inline and see how it fluctuates through the rev range. Dellorto's like Webers require a stable fuel pressure, 3-5 psi for memory, but you want plenty of volume out of your fuel pump so it can always supply that pressure at any load or rev range. It would not be a silly idea to run a fuel regulator to ensure the psi is stable too.

https://www.racetep....

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Submitted by ben simpson on Mon, 09/04/2018 - 21:41.

Check also the tank is breathing, either with the cap or whatever breathing setup it uses

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Submitted by Old is good on Tue, 10/04/2018 - 21:01.

Thanks everyone.
We've got a Malpassi regulator set at 2 1/2PSI, mounted on the inner guard, away from engine vibration. Started with a Redline regulator and ended up tossing it. We tried 3 1/2 to start with and worked down to 2 1/2, which it seems to run best at. It was checked with a pressure gauge.
I'll be replacing the filter on the weekend. It's at least 5 or 6 years old probably well past it's use by date.
I'll check the other suggestions.
It's got a blue motor dizzy with full 12 volts through a relay.
I'll aim to get an electric pump. I've seen some that flow 30 gallons per hour at low pressure. That should be plenty I hope.
The Dellortos are made with the fuel supply coming in from the back of the motor. When we go electric I was thinking of re shaping the original steel line to come straight up from the subframe on the driver's side and then run the fuel line across the firewall with a rubber flexible fuel line to the back carby, then to the front two. This will keep the fuel line well away from the heat of the motor and extractors.
David

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Old is good.

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