Club G40 Forum

Technical => Engine and Transmission => Topic started by: cookie79 on June 03, 2017, 10:46:32 am

Title: Fuel pump
Post by: cookie79 on June 03, 2017, 10:46:32 am
Looking for a new fuel pump, just replaced mine with a eBay buy as my old pump developed a leak, now however under heavy acceleration the car stutters & dies then bursts back into life with smack of power all in a split second, I'm putting 2 & 2 together that's it's the replacement pump (may not be I guess?)
The car did very rarely produce the same symptom on the original pump but only once in a blue moon.

Now getting a new pump appears to be difficult, classic VW parts do a pump with the same part number 867906091 but it's followed with a (B) suitable for engine codes AUU & AVV, the G40 pump is just 867906091 followed by no letters I believe this pump is suitable only for G40 & GT models.

Does anybody know a secret place where I can buy a new pump? Or any ideas about the issue the cars having, you might have knowledge that it's not the pump & just a coesidence that I replaced pump.

Any advice always welcome.
Title: Re: Fuel pump
Post by: ereeiz on June 03, 2017, 12:11:24 pm
Ever replaced your tank? They LOVE to corrode at the base of the filler neck where it meets the tank, mud gets in between the pipe and tank then sets, then gets wet and sets over and over, rotting the tank and pipe. Could also be internal corrosion from low fuel over a long period.

I assume you have changed your fuel filter?

Have you checked your fuel pressure? It could be the Fuel pressure regulator. Think it's on the end of the fuel rail from memory with the vacuum pipe coming from it.

Also, your new fuel pump..... does it meet the min. flow rate of the G40? Ultimately it's only a 1.3 SC so getting an overpowered pump and manual fuel pressure regulator may be the way to go, overfuel the line and it'll just recirc back to tank. Having low flow rate could allow the qty of fuel (therefore pressure) to build in the line, but as soon as you go flat out, the injectors piss all the fuel into the engine but the pump cannot keep up.

Lastly, it may be the in tank lift pump. They're renowned for going wrong, the gauze can also get blocked. They can be quite fragile now with age so watch the plastic bits on it when you look at it. It's under the rear seat.
Title: Re: Fuel pump
Post by: cookie79 on June 03, 2017, 12:34:55 pm
Thanks for your post lots to look into by the sounds of it.
It's a brand new tank fitted about 4000 miles ago, along with a new fuel filter too.
The replacement pump was a 2nd hand item from eBay, originally came off a GT I think but sure G40 & GT share the same pump.

Not sure how I could test the pressure or flow rate, is it something that requires specialist testing equipment?

The in tank pump is original I've never replaced that although I don't recall it looking dirty or knackered when I fitted the new tank, may be worth replacing either way.

Thanks again.
Title: Re: Fuel pump
Post by: ereeiz on June 03, 2017, 01:03:23 pm
Fit a fuel pressure gauge and watch it. If it drops when you go from idle to full throttle, there's your answer.  I've not watched this video myself but have watched a lot of Chrisfix's vids and they tend to be very down to earth and good;

As for flow rate, disconnect the pipe from the fuel rail, short out the fuel pump relay connectors (remove the relay and put a wire across 2 terminals to run the pumps, apologies, don't have the pin info to hand). Run the pumps for a minute, letting the fuel drop into a jug or something (bear in mind if you use a kitchen jug thats plastic, it may eat through it). After 1 minute, measure how much fuel is in the container and there's your litres/minute for the pump. Times it by 60 if you want to know litres/hr.

The figures for the pumps may be in Haynes manual.

The GT (3F), G40 (PY) and another model (NZ) all share the same line pump (the external one)
Part 24-   867906091- Cancelled since 01.11.2013-   fuel pump-   Model data: NZ,3F,PY

Can't find the page for the in tank lift pump. I think they are the same for all petrol Polos of that age.
Title: Re: Fuel pump
Post by: cookie79 on June 03, 2017, 02:26:46 pm
Great stuff, very informative, I'll give it a try before splashing out on pumps & regulators.

Many thanks
Title: Re: Fuel pump
Post by: SamG40 on June 03, 2017, 07:38:01 pm
If you do need another pump I've got the old one from my car. Changed it because of an issue that wasn't solved by the pump so it was working fine when I took it off.
Title: Re: Fuel pump
Post by: cookie79 on June 03, 2017, 07:48:08 pm
Thanks, if it's down to the pump I'll be in touch, it's the in line pump you have?
Title: Re: Fuel pump
Post by: SamG40 on June 03, 2017, 11:20:38 pm
Yep, the in line one.