Thread: 94 classic fuel pump woes

Hi all,
This is probably a stupid question, but here goes.

Background. I have a recently acquired dual fuel '94 classic vogue. It has the under rear 70L LPG tank and a 30L petrol tank. The fuel pump recently started making a hammering noise and the vehicle started running rough at high throttle openings I decided to replace it. It ran perfectly on gas.

I found a replacement pump hard to get in Melbourne as every had "just sold the last one in stock". I obtained a slightly used one and fitted it. As this was my first time, it was quite a pain. No dice! Turn out the pump was a dud. I tried yet again to get a replacement pump and failed. As I work quite a lot and have limited time for repairs, I went to Bursons and got a VN-VP commodore pump unit and replaced the pump unit in the original frame.

It fits well and once you have the wiring polarity right, it pumps well and seems to have good flow. I am not able to test the pressure. I found the steel fuel lines were quite kinked as they bend around the LPG tank so I went to Enzed hydraulics and had flexible braided lines made up with a quick-connect fitting on the fuel outlet. I cut off about 20cm of the kinked lined and fitted the hoses up with compression fittings. The idea of the quick-connect fitting is that I have another male fitting so I can quickly connect a hose to the outlet and empty the tank or transfer fuel to another vehicle.

In this process, I lost track of which of the fuel lines is the inlet and which is the return. I have connected them and the vehicle starts well and runs up to a point but surges at throttle openings more than about 50%.

Here is the question. Would this happen if I connected the lines around the wrong way?

I guess it would as the fuel pressure regulator will be on the wrong side of the circuit and the pump cycling would make the fuel pressure in the rail fluctuate but this is all a little new to me.

Thanks for any advice.

Originally Posted by TimOz

Here is the question. Would this happen if I connected the lines around the wrong way?

I imagine fuel pressure wouldn't build up in the rail as the reg is upstream of the rail. To check, just pull the outlet hose off the fuel rail, fit a couple of extension hoses into a container, and observe the direction of fuel flow. Easy.