73 replies to this topic

[Exmantaa]

That pressure build-up is not right, as said here. You see that it starts when the pressure reaches ~3+bar

Priiming with no manifold vacuum should be 3.8-3.9bar. Idling, with vacuum, subtract ~0.6bar from that.

 

Looks like an internal leaking pump hose. (you could try hotwiring the fuelpump (relaiy in the back) and see if it then starts instantly)

[JG]

easy job if you have a standard tank. 

An absolute pig with the pro-alloy one

[Chris P Duck]

easy job if you have a standard tank.  An absolute pig with the pro-alloy one

It's the 60L pro alloy one

[Sutol]

Mr Duck, a question about your video. At the start you turn on the ignition and the pressure rises. It then falls to zero, why? shouldn't it stay at the primed pressure. Sorry if this is a silly question.

[Chris P Duck]

Mr Duck, a question about your video. At the start you turn on the ignition and the pressure rises. It then falls to zero, why? shouldn't it stay at the primed pressure. Sorry if this is a silly question.

It's not a silly question. OEM pump primes then maintains the primed pressure. Most who have a Walbro see the pressure drop after it's primed. Opinions are varied and trusted people with far more techie knowledge than me sit both sides of the fence regarding if that's as it should be with a Walbro or not. Gaz at Spitfire engineering said that most with a Walbro don't hold primed pressure but that's because they are just swapped one for one and more work should be done (he also said when installed properly the Walbro won't be much louder than the OEM pump). However many have just bunged a Walbro in, have the pressure drop after prime, and have no problems at all. All this is not to do with my starting problem though which I'm hoping is a simple split hose.

[Sutol]

I wonder if it's a safety feature, ie the pressure isn't maintained unless the engine is running. Anyway good luck with your problem.

[Chris P Duck]

Inspection hole exposed and enlarged. That's all I had time for after work today though.

[vocky]

make sure the hole is large enough to get the pump assembly out, before you remove the retaining clip. You do not want to have to enlarge the hole with the tank open.

 

Do not go any nearer the seats, enlarge the hole towards the bulkhead - if required 

[Chris P Duck]

make sure the hole is large enough to get the pump assembly out, before you remove the retaining clip. You do not want to have to enlarge the hole with the tank open.   Do not go any nearer the seats, enlarge the hole towards the bulkhead - if required 

Thanks for the tips I'd planned on trying - and if it didn't fit, reinstalling the housing and pipework and giving it a few minutes for the fumes to disperse before cutting more away. Though having seen JG say getting the housing into Pro alloy tank is "the 2nd worse job on a VX" I think I'll try and get it big enough first! It already bigger than the top of the housing, it just depends how much twisting and manovering space is needed.

Edited by Chris P Duck, 04 March 2015 - 02:06 PM.

[Chris P Duck]

To wrap this up for anyone who finds it whilst searching with a similar problem. This is with a split in the feed hose inside the canister, pressure drops almost instantly when the pump is not running. And this is without, seems to drop about a PSI per minute, if that.

Edited by Chris P Duck, 04 April 2015 - 12:55 PM.

[Bargi]

Is it a Walbro 255 or OEM pump you've got?

[Chris P Duck]

Is it a Walbro 255 or OEM pump you've got?

It's a TRE-255 now. It's a turbine rather than a displacement like the Walbro and has a few advantages. MUCH quieter, lower power draw and slightly higher flow

[Bargi]

Ahh. Explains it holding pressure.

[pete-r]

Glad you got it fixed, one of those annoying as hell fixes!