Hi people
Quick question 2004 td6
If the secondary fuel pump fails would the intank fuel pump still run

Mine did with reduced performance and the fault for injection system displayed .

I’ve replaced intank fuel pump and sender with brand new one
Drove all day now won’t start
Cranking over but can’t hear intank fuel pump working
New relay
Do you think I need new secondary fuel pump

The answer to your original question is yes, I had secondary failure and in-tank still ran.

I had live data from an iCarSoft 930 which was lower than desirable on the LP reading and zero on the HP.

Replaced the underneath pump and it fixed it.

Is there more to this issue than changing the in-tank? I'm assuming it wasn't running right before you did that, now it still isn't?

Mine which needed the secondary started becoming hard to start then failed to start completely. Sounds like it may be that the secondary was failing and has failed and changing the in-tank hasn't changed that.

Post the full background to it as currently there's not much to diagnose it.

Hi thanks for your reply
I’ve had car just over a year and it’s ran fine
Had full engine service six months ago
New 020 yuasa battery three weeks ago
After fitting new battery and driving around for two or three days I drove to a friends house and did some work for him all day then went to start the car and it would turn over fine but wouldn’t fire up at all and couldn’t hear intank fuel pump so towed it home
Bought second hand intank fuel pump and fitted that and it fired up straight away but strangely there was a lot of smoke coming from FBH exhaust but eventually cleared
Drove around for two or three days then went to petrol station then same thing happened went to start and it would crank over but would not fire so stuck on petrol station forecourt
Waited 6 hours for Rac and he turned up and told me to turn it over so he could hear what’s going on and it fired up straight away
He followed me home and once there he plugged his diagnostic computer in and monitored engine fuel pressure while running and he said they were fine
He did say my fuel pump sounded a bit loud
I bought a brand new intank fuel pump and sender and fitted that and again it fired up straight away and FBH smoked again then cleared
Exactly the same drove around all day went to start later and wouldn’t start

This is the Rac report

FBH smoke might be because the mixture was terrible because pressure was low, total guess here but that says to me there's fuel in the engine bay but start is inhibited because injector rail pressure sensor flags the code, but FBH still attempts hence the smoke.

There's also a few historical posts I found when researching mine - where you could leave ignition on to prime the pipes and it would fire, then when you have fuel demand that acts as a siphon which mean it'll run with a dicky pump because you have manual suction in lieu of the fully working pump. Not really sure how much truth there is in that and mine wouldn't do it - it refused to fire at all despite any messing running with ignition to attempt to prime etc.

Given the in-tank is new and if you're sure that's all installed OK then your choices now are secondary pump under the car or HP. My view there would be secondary is a relatively cheap off the shelf thing to buy and install, far less messing than trying to diagnose the HP side, there's definitely a case to changing that to see what happens.

Alternatively if you don't want to throw money at diagnosis then leaks around the HP side, there is a common job changing seals or worse case you could renew that but it looked to me like a far more involved and messy job so I went for changing the secondary and luckily that's where the story ended as it fixed it.

Worse case you'll end up with a spare secondary for stock, best case that might do the job. Or there might be another way to establish what is going on but someone else will have to take that up, I've no knowledge of the HP side.

Thanks for your reply Ian G very helpful
I’ve ordered secondary fuel pump so hopefully that’s the problem
I’ll update if all goes well 👍🏻👍🏻👍🏻👍🏻👍🏻

Yes, worst case you have changed it preventitively as if its not been done it won't be far away.