Hey all ...I hope someone can help me!

I've been having an ongoing starting problem with my EF on HOT days, I turn the key, starter motor cranks fine, but engine struggles to turn over ...then it starts really roughly for a few secs then settles down fine.

This only happens on hot days, when I've driven a little & had AC on ...at night-time or on cooler days there's no problem!

I've tried pretty much everything, new plugs & leads, new battery, injector clean ...I even had a Carbon Clean a couple of days ago, and replaced my thermostat in a bid to drop my engine temp a little, ...as some of you guys suggested it could be fuel bubbling in the rail due to build up of engine heat after shut-off.

However, during the 2nd phase of the recent carbon clean, where the car is started and left to run on it's own fuel (machine is tapped into fuel line just before rail) with the detergent from the machine also running thru' the fuel system ...the operator mentioned that the fuel delivery to the machine from my car seemed a bit slow on start-up, so he thought my fuel pump may have had flow problems.

My fuel pressure regulator was holding pressure fine, at 270kPa.

I am now thinking that my fuel pump may be the culprit for the rough starts, as it may not be delivering enough fuel flow ...what do you guys reckon?

Anyway, I'm seriously considering replacing my fuel pump now ...but with one that's rated at a higher Lph flow.

What flow does the stock fuel pump put out?

Would there be any problem with me replacing it with a higher-flowing Walboro pump?

I've heard there's a Walboro model GSS 341 that's rated at 255Lph (allows for up to 600HP) ...would this be an overkill pump, bearing in mind I'm installing an RPD Stage 2 cam next month?

If so, what would you recommend ...something smaller?

Please let me know your thoughts guys ...as I really want to nail my starting problem for good!

Cheers heaps!

without changing injectors and fuel pressure reg id almost call it overkill. It might supply more fuel to the fuel rail, but more fuel with nowhere to go but back to the tank will put more pressure on your fuel pressure regulator...

f**k, I'm sooo tired ...not slept yet!

Well, I guess I could just replace my pump with a new stock one.

The Walboro I mentioned is probably a big overkill, maybe I should find out about one that's rated a just a little higher than stock ...any ideas?

from what i have read and know a higher flow pump will be fine as any excess fuel will be given straight back to the tank


have u tried a new fuel filter?

yeh thatd be worth looking at. also its worth checking what i said with some1 else but basically injector flow rate is determined by fuel pressure not fuel avaliability *providing* enough fuel is avaliable, so while a higher flow pump will provide more fuel flow, it will not change the pressure because the fuel pressure regulator will simply return more fuel to the tank in order to maintain its pressure, now a different pressure reg and higher flow injectors, or maybe even just the pressure reg to some extent, will allow more fuel in, but unless u do some air intake mods it wont achieve much... can some1 confirm or reject what ive said

Yes fuel delivery is based on fuel pressure and the size of the injectors alone. Fuel flow only serves to maintain that fuel pressure, so the pump basically just has to keep up with the injectors. A stock pump if good for 180+rwkw so I would probably just throw in a standard one if I were you. The 255l/hr Walbro would be a good idea if you are planning some big mods later on but otherwise it will just circulate more fuel which just heats it up.

In terms of easiness, I'd go with changing the filter as mentioned, particularly if you don't know, or don't have record of when it was last changed. I can't see the pump being at fault, as I'd think your problem would be happening either hot or cold, but having said that, you could swap your pump with one of the other WA members, and run a few days to see if the problem clears. Check the gauze pickup on your pump as well, may have some crap buildup.

Yeah, I have actually recently replaced my fuel filter, made no difference.

The Carbon Clean guy (John Franklin, MD of the whole franchise in OZ), said that fuel additives like Wynn's Spitfire injector cleaner etc, are solvents and they actually attack the plastic fuel tank ...which can in turn cause plastic deposits & crap to eventually bung up the pump.

He gave me a knowing look when he said this, too ...I said nothing

It's just that he noticed that the incoming fuel flow from my car took a little longer than to register on his machine when it was started up, so he thought maybe my fuel pump was struggling a little.

Can't hurt to replace the pump anyhow, probably with a stocko one based on your opinions ...thanks guys!