Fuel starvation??? 5.0 RV8, Stage 3, eddy carb in a Landy 90

DaviesDJ · Post by **DaviesDJ** » Sun Aug 26, 2012 6:31 pm

Hi guys, Wonder if anybody else is having this problem, sice completing the above project I have been overjoyed with getting it on the road! But sadly a problem has arrisen. It coughs and splutters when I put my foot down and goes past about 3000rpm, 3800-4000 when revving at a standstill, will not rev any further. The AFR gauge does tend then to read lean (as it coughs) at 15-17. It only has a standard landy carb fuel pump, I think it is fuel stavation, but am i missing something, thought it was timing/dizzy at first but idles well, and fine up until these points. Have taken the pump out, removed the motor and bits and essentially made the pump a simple tube/take from the tank, have ordered an external 'gold flow' pump to replace it. Has anybody ever experienced this before. Thought it would be ok with the standard pump when just revving at a standstill?? Obviously i knew it needed changing eventually hence the swift move (nitrous plate in and upgrade planned). If It does not work I will move to the ignition. It has a series 3 v8 coil and RPI (I know!!) 'Power amp'. All thoughts appreciated guys. Thanks Dave - Daventry Northants

sidecar · Post by **sidecar** » Sun Aug 26, 2012 6:58 pm

It sounds like your pump is not up to the job! Someone on the Cobra forum had the same problem when his regulator decided to restrict the flow of fuel as well as its pressure.

Did you get my PM?

DaviesDJ · Post by **DaviesDJ** » Sun Aug 26, 2012 7:52 pm

I did thanks mate, really appreciate your advice, just thought I would "put it out there":-). Hoping it will solve it, took the old pump and replaced with a simple pickup made of fuel hose, it could be the filter I am running (generic) but realise I need a new pump anyway. Think if it doesn't work will change ignition

DaviesDJ · Post by **DaviesDJ** » Sun Aug 26, 2012 7:53 pm

I did thanks mate, really appreciate your advice, just thought I would "put it out there":-). Hoping it will solve it, took the old pump and replaced with a simple pickup made of fuel hose, it could be the filter I am running (generic) but realise I need a new pump anyway. Think if it doesn't work will change ignition

sidecar · Post by **sidecar** » Sun Aug 26, 2012 8:10 pm

Are you saying that it won't rev over 3k even at a stand still?

If so I don't think that it will be a fuel pump issue because your engine will require hardly any fuel under no load. Having said that it is very important that you're sure that your pump can supply enough fuel. If your pump is nowhere near good enough that is better than it being just not quite good enough. If the pump can 'nearly' supply enough fuel your can run the engine lean without knowing about is which is really bad.

I can't see a standard LR pump being good enough for 300+ BHP not that I know anything about Land Rover stuff!

In any case 15-17:1 AFR with the throttle being even half open is too lean but I guess if the ignition is shutting down this could show up as lean as fresh air will be being pumped into the exhaust when the engine does not fire the mixture.

Eliot · Post by **Eliot** » Sun Aug 26, 2012 8:44 pm

Std pump should be man enough to allow you to rev it in idle, but i wouldn't suprised that it wont allow you under load.
You need a red top in there - but be prepared to upgrade your inlet and outlet hose sizes (3/8"??) (sorry stella brain....

)

DaviesDJ · Post by **DaviesDJ** » Sun Aug 26, 2012 9:13 pm

It revs slightly better at rest then under load, to nearly 4000, have a feeling it may be the ignition:-( but have to hope, it needed doing anyway, so am not that phased about changing it. What could it be I'd not? Runs beautifully up untill this point, idles well so didn't think it was a vacum leak, will rev higher on a "blip" then a slow build up wich makes me think fuel. If not think I will just bugger it and go for a full megajolt! Or is that too hasty??

DaviesDJ · Post by **DaviesDJ** » Sun Aug 26, 2012 9:16 pm

Didn't think fuel hose can be changed as the carb has the standard fuel banjo fitting with a fixed size... Hmmm... Got me thinking - could the banjo fitting be a problem??

ChrisJC · Post by **ChrisJC** » Mon Aug 27, 2012 7:30 am

Surely those carbs have a float bowl, so at least initially when you open the throttle they will have sufficient fuel as it's in the float bowl??

So it could be ignition. Can you ditch the RPi thing?

Chris.

Ian Anderson · Post by **Ian Anderson** » Mon Aug 27, 2012 7:48 am

What carb are you running?
If it is an eddy500 it may be too small for your engine

Ford 302 or 5 litres tend to run Holly 600 or 650 CFM

It could also be the manifold is way to restrictive for your setup. What manifold are you running?

Lastly what exhaust system? Likewise if itis restrictive it will not allow the engine to rev!

That said 17 air file ratio is rather lean
Ian

sidecar · Post by **sidecar** » Mon Aug 27, 2012 9:02 am

DaviesDJ wrote:Didn't think fuel hose can be changed as the carb has the standard fuel banjo fitting with a fixed size... Hmmm... Got me thinking - could the banjo fitting be a problem??

The banjo on the carb won't be a problem, really your first port of call should be to suss out whether the pump can flow enough using the formula "Fuel in CC per minute" = BHP x 4.7. This will give you at least a starting point. With a bit of a safety margin your pump needs to flow 2 litres per minute. (1 litre every 30 seconds). The formula does not take into account that there is less flow as the pressure goes up but at least its a start. If your pump only flows say 500 cc in 30 seconds you've got no hope of it working!

I agree that you should ditch the RPI gizzmo!

When the engine is under load the fuel in the float bowls won't last more than one second before the level drops too much and the engine runs lean.

DaviesDJ · Post by **DaviesDJ** » Mon Aug 27, 2012 11:12 am

It's a 600 eddy carb, I Would like to ditch the ignition amp but what would I replace it with??? The old pump is now just a pickup and new pump dispatched, then I suppose all will be revealed. But if it doesn't work, am tempted to
Risk my marriage and splash out on mega jolt! But what would you guys do?? Its a lucas blue electronic dizzy, ballasted series 3 coil and rip power amp, basically the kit they supply. Bought it when i knew no better 2 years ago. Self teaching is expensive;-)

DaveEFI · Post by **DaveEFI** » Mon Aug 27, 2012 11:18 am

I doubt anything ignition wise is going to make the AFR lean out to 17:1.

DaviesDJ · Post by **DaviesDJ** » Mon Aug 27, 2012 4:37 pm

It seems to make sense, although because it won't rev freely (although. Enter then under load) at standstill, but if you. Blip the throttle it does not
Occur, but in this engine you cant really "blip" Over 4000rpm, it coughs with sustained pedal. If the new pump solves it then at least it will make it know that a bog standard pattern part land rover petrol fuel pump is insufficient.

Ian Anderson · Post by **Ian Anderson** » Mon Aug 27, 2012 8:26 pm

Secondary jets blocked?