The mystery of 1k miles and 3 fuel pumps

[herukano]

We'll just made it back from Somerset , this journey killed 2 fuel pumps !

Bit of background , skip ahead for the main issues :

Subaru EJ25 conversion from jx lump , new tank , pump , fuel lines , rjes kit etc. within 500 miles first fuel pump started making cavitating noises and eventually got really loud and died. I replaced the pump with another from a donor van (free) and used that when within 100miles this started making really loud cavitating noises and started cutting out power to the van on throttle pick up. I bought another new pump and was going to fit it when the pump on the van started behaving again .... Drove down to Somerset and pump made really loud cavitating noises . I looked under van and suspected the main 12mm I/d pick up hose , bought from bw, looked like it was collapsing under the load . Replaced pump and new pick up hose with thicker inner braided stuff from local motor factors , was quiet and performed well for this duration of the holiday up and down Cornish hills , when on route home the new pump started making cavitating noises after a long motorway blast, also starting bucking and stammering under throttle and coasted to a stop in a layby . We let the van cool a bit and then tried again , got most of remaining 40 miles home before having to stop and let it "cool" again.

Problems : [b/] fuel starvation symptoms and noisy (cavitating) pumps eventually failing , 3 in under 1kmiles

Possible causes:[b/]
fuel tank blockage ? Noticed when changing the pump that the fuel flows freely for 5 seconds or so before stopping completely ? Is this normal behaviour for fi tank ? Friend seems to think not , might signify a blocked tank ?

Overheating fuel pump ? My homebrew mount system utilised mikalor clamps and sme old boost hose to protect the pump from clamping forces , possible that this is insulating the pump and causing premature death? Not sure how this relates to cavitation noises though.

solutions[b/]

1. Change fuel pump and remount using Already purchased fuel pump mount - a close up photo of mounting system would be really helpful !
2. All the above but + change the fuel tank


TLDR:
Ej25 conversion new:pump,tank,lines
Pumps keep dying , cavitating noises
Suspect either blocked tank or suspect mounting system causing overheating pumps
Could really use a photo of mounting location for fuel injection pumps from original van and confirmation of fuel tank behaviour when main outlet disconnected.


Any help or comments appreciated , please , my brain is burning.

[bigherb]

If the hose was collapsing there is too much suction either blocked fuel line or tank breathers not breathing.

[marlinowner]

Take the fuel cap off and see if the fuel flow improves . If yes then breather problem.

[herukano]

Interesting , didn't even think about breather issues , will try that today and see if Cavitation noise dissapears . Now I didn't change the breather system from the old diesel ones , perhaps I should have

Thanks guys much appreciated

[herukano]

Ahh quick question , breathers being the expansion tank system ? Or the main fuel filler one ?

[bigherb]

Ahh quick question , breathers being the expansion tank system ?

Yes, should be the same but did you connect them up correctly?

[herukano]

Will have a gander in a bit

[Aidan]

tank pump filter engine yes ?
The 2.1 tank has filter sufficient to protect the pump which is cooled and lubed by fuel and the filter after the pump is high pressure metal cannister type to protect the injectors

[herukano]

Yeah tank -> pump -> filter -> engine , couldn't make tank replicate the fuel flow stoppages today and pump that was dying yesterday is behaving today. Checked the breather hoses ! Too hard to see what's going on , need to drop the tank and replace the scabby old hoses . Can't find anywhere stocking replacement expansion tanks to judge whether there is a diff between the diesel and petrol tanks

[wozza825y]

had a similar problem with the old boys v8 range rover classic, first pump died so i replaced it as norm as it was the original, the new one lasted a couple of weeks. Turned out the breather was blocked so the pump was sucking fuel out of the tank creating a vacuum and putting the pump under a lot of strain and then failure. It was cured by drilling a small hole in the fuel cap, but i am not recommending this fix to anyone.

[herukano]

How did you diagnose a blocked breather ? I have removed the tank today , pulled all the breather hoses off and blown through them l I can't detect any obvious blockage. Pipes were arranged as per standard from Bentley .

I have drained the tank and will clean the outside and inspect the inside tomorrow , will give it a good blast with the compressed air hose as we'll to be safe and see if any blockage appears .

I have fabricated a new pump mount similar (as far as I can tell from the photo's InThe haines and Bentley ) and intend to refresh fuel filter and rubber lines. Is it 7 or 8mm lines after the fuel pump ? I think it must be 8 as I have the hard plastic lines going under the body and the rubber pipe has to go on top of that

Current plan is , to buy a new pump (is the Bosch worth it?) keep the current one as a spare and see what happens , if another one fails replace the tank.

Any other suggestions for me ? Gotta say I have a list as long as my arm and I hate revisiting jobs I thought were already done , drives me nuts

[DavidPallister]

check the expansion tanks in the front arches

these should have 1 way valves on top, to let air in but stop fuel from getting out, check these aren't blocked and are actually letting air in

and whilst you've got the tank dropped probably worth shining a torch into the filler hole and seeing If there's any rust or crud swilling around at the bottom of the tank

[herukano]

We'll , yesterday I stripped the tank out , removed the breather system Compressed air through every hose and hole . checked the function of valves , stop when upside down- open when normal , so no problem there. Checked tank and no obvious amounts of crap I there , a few dust particles but that's it.

Have remounted pump and just waiting for my filter holder to finish re-plumbing then trying again .