350i EFI system bleeding?
Discussion
Hi All,
Hoping for some advice. I drained down the tanks on my 350i and ran new pipes from tanks to swirl pot and onwards to fuel filter and pump.
Since doing that I can’t get her to run well. She starts from cold and runs ok but then conks out just down the road. There’s no smell of fuel, so I think fuel starvation is happening. I’ve checked the breather and even run without the cap on, but still conks out. Could I have airlocks in the system? Do you need to bleed it after changing out the pipes?
Any steer welcomed.
Thanks,
Mark
Hoping for some advice. I drained down the tanks on my 350i and ran new pipes from tanks to swirl pot and onwards to fuel filter and pump.
Since doing that I can’t get her to run well. She starts from cold and runs ok but then conks out just down the road. There’s no smell of fuel, so I think fuel starvation is happening. I’ve checked the breather and even run without the cap on, but still conks out. Could I have airlocks in the system? Do you need to bleed it after changing out the pipes?
Any steer welcomed.
Thanks,
Mark
You shouldn't need to bleed it. Have you definitely got the pressure regulating valve plumbed it the right way? It's high pressure to fuel rail then PRV downstream of fuel rail, and the return line post PRV back to tank. Might be interesting to pull hose off fuel rail and run pump (fInger in AFM) to check flow. I did this before connecting when I changed my fuel lines, to ensure no crap got down the lines. Has any debris been flushed into the injectors or PRV?
Hi. Thanks for the reply.
I haven’t touched the PRV so assume it’s right way round. It’s possible debris has come through though.
I did take the pipe off the fuel rail. Was expecting it to be pressurised but only a small leak occurred at the time. Is that normal? I put the end of the pipe in a jar and span the motor over on the starter for a second. Fuel did start to flow.
The fuel pump was changed by the PO in 2020 so not old. However I have found it to be noisy at times. The decaying pipes had a kink upstream of the pump so I put the noise down to it struggling to get flow. Due to the prior noise, I’m inclined to test the pump next a little more thoroughly.
I haven’t touched the PRV so assume it’s right way round. It’s possible debris has come through though.
I did take the pipe off the fuel rail. Was expecting it to be pressurised but only a small leak occurred at the time. Is that normal? I put the end of the pipe in a jar and span the motor over on the starter for a second. Fuel did start to flow.
The fuel pump was changed by the PO in 2020 so not old. However I have found it to be noisy at times. The decaying pipes had a kink upstream of the pump so I put the noise down to it struggling to get flow. Due to the prior noise, I’m inclined to test the pump next a little more thoroughly.
Markymark21 said:
..................... I put the end of the pipe in a jar and span the motor over on the starter for a second. Fuel did start to flow. ..............
Your words 'fuel did start to flow' worries me it should have been gushing.Did you replace the fuel swirl pot between the tanks? They have a filter in them which by now will have rusted and may well be either blocking flow in itself or have sent rubbish into the pump.
Steve
Hi All,
Thanks for the further replies. On my car there is a T piece between the tanks which then feeds a swirl pot next to the filter and pump. It goes tanks to T piece to swirl pot to filter to pump. I changed the pipes from tank to pump as PO had used the wrong stuff and it had all hardened and perished. The swirl pot is odd in that it doesn’t have a breather. It’s just a pot of fuel I guess.
The car has been in many pieces (gearbox change) but was running well for a short while before this incident. It smelt of fuel and the pump was noisy. I changed the pipes and smell of fuel has gone but so has noise from pump. I put that down to a kink in the pipe maybe starving the pump. I wonder whether it damaged it. Either way - pump is where I will look next. Thanks.
Thanks for the further replies. On my car there is a T piece between the tanks which then feeds a swirl pot next to the filter and pump. It goes tanks to T piece to swirl pot to filter to pump. I changed the pipes from tank to pump as PO had used the wrong stuff and it had all hardened and perished. The swirl pot is odd in that it doesn’t have a breather. It’s just a pot of fuel I guess.
The car has been in many pieces (gearbox change) but was running well for a short while before this incident. It smelt of fuel and the pump was noisy. I changed the pipes and smell of fuel has gone but so has noise from pump. I put that down to a kink in the pipe maybe starving the pump. I wonder whether it damaged it. Either way - pump is where I will look next. Thanks.
The original setup has the tee piece as part of the swirl pot. The pot has a vent pipe on top it also has a coarse filter inside. Replacements are available.
If your system has been modified and the main filter is before the pump then that could also be an issue as the type of fuel pump used does not like to suck which is why they have a larger inlet than outlet.
The ideal would be a coarse filter before the pump (To protect the pump as they clog very easily) and the fine filter after.
Steve
If your system has been modified and the main filter is before the pump then that could also be an issue as the type of fuel pump used does not like to suck which is why they have a larger inlet than outlet.
The ideal would be a coarse filter before the pump (To protect the pump as they clog very easily) and the fine filter after.
Steve
Hi Steve,
It has a Sytec bullet type filter before the pump. It was replaced by the PO in 2020 and it’s done hardly any miles since. Could it be clogged? When I drained the tanks the fuel looked very clean and clear….
I will look for the t piece with coarse filter. Where is the breather from that plumbed to?
Thanks….
It has a Sytec bullet type filter before the pump. It was replaced by the PO in 2020 and it’s done hardly any miles since. Could it be clogged? When I drained the tanks the fuel looked very clean and clear….
I will look for the t piece with coarse filter. Where is the breather from that plumbed to?
Thanks….
Markymark21 said:
Hi Steve,
It has a Sytec bullet type filter before the pump. It was replaced by the PO in 2020 and it’s done hardly any miles since. Could it be clogged? When I drained the tanks the fuel looked very clean and clear….
I will look for the t piece with coarse filter. Where is the breather from that plumbed to?
Thanks….
Try ACT SSP09 https://www.actproducts.co.uk/product/ssp09-tvr-we... for the pot. Web site says nil stock but I suspect they are low demand so made to order.It has a Sytec bullet type filter before the pump. It was replaced by the PO in 2020 and it’s done hardly any miles since. Could it be clogged? When I drained the tanks the fuel looked very clean and clear….
I will look for the t piece with coarse filter. Where is the breather from that plumbed to?
Thanks….
Is the Sytec filter a large bore with a coarse gauze filter? if not then it is likely restricting the pump even if it is not blocked.
If memory serves me (not a given at my age) the breather is 6mm and goes to the nearside tank at the top/front but one side is the breather the other is the return and I can't remember which.
Steve
I think some of the 350i's were different in that mine has a T piece between the tanks which goes to a swirl pot next to the fuel pump, this goes to a sytec gauze type filter before the pump. My swirl pot doesn't have a breather just an in and out, I tried fitting a new swirl pot with incorporated T piece last year but I couldn't physically fit it in between the tanks. Some people have reported that inside these type swirl pots was a gauze filter which corrodes and blocks the outlet but when I cut my old swirl pot in half it had a plastic filter inside and judging by the state of it, I would have thought it was original but who knows. But its probably worth checking the sytec filter isn't blocked and ideally needs a gauze type filter and if you rattle the swirl pot around you can probably hear if there's any metal loose inside. But if it's only started happening since the pipe change I would imagine the problem is elsewhere but will help narrow down the problem hopefully. As stated above, if you remove the fuel pipe from the fuel rail, the fuel should be coming out fairly rapidly when you operate the pump and a fuel pressure gauge is a good friend...
Thanks all. The sytec filter is large bore. 1/2” pipe on inlet and outlet. It’s also serviceable (I think) so will check it out at the weekend. I’ve also got a new fuel pump on the way. Worst case I’ll end up with a spare in the boot - no bad thing.
Will post back what I find. Thanks…
Will post back what I find. Thanks…
Can’t remember who it was but someone wise once told me “follow the fuel”
If you undo the T piece does fuel come out? Yes = move on
If you undo the swirl pot does fuel come out? Yes = move on
If you undo the pump intake does does fuel flow = yes move on
If 12v manually added to pump does fuel come out and pump work
And so on and so on until you get to the injectors
If you undo the T piece does fuel come out? Yes = move on
If you undo the swirl pot does fuel come out? Yes = move on
If you undo the pump intake does does fuel flow = yes move on
If 12v manually added to pump does fuel come out and pump work
And so on and so on until you get to the injectors
I have a sytec, the original owner had fitted the fine filter (paper like).
It MUST BE the gauze filter. Or else it will block and cause starvation.
1.Clamp the pipes.
2. Open the filter.
3. Look at the element.
If it's the fine one, remove for now, and put an order in for the gauze one. Close up the Sytec and take for a run.
It will be OK for now, then you can fit the gauze one when it arrives.
Also - the EFi system self-bleeds, once the pump is started, the air flushes back to the tank though the pressure valve.
It MUST BE the gauze filter. Or else it will block and cause starvation.
1.Clamp the pipes.
2. Open the filter.
3. Look at the element.
If it's the fine one, remove for now, and put an order in for the gauze one. Close up the Sytec and take for a run.
It will be OK for now, then you can fit the gauze one when it arrives.
Also - the EFi system self-bleeds, once the pump is started, the air flushes back to the tank though the pressure valve.
Edited by adam quantrill on Friday 7th October 15:21
Hi Adam,
I think you’re right about this. I know the PO well. Long time friend. He had a problem with overfuelling and changed pump and filter as part of his diagnosis. I’m almost 100% certain that it would have been fitted with the stock element. I bought the car from him as a non runner and fixed the overfuelling (ECU problem) so the car has done less than 500 miles on that filter. I bet it’s blocked. Will be taking it apart tomorrow to find out!
Thanks..
I think you’re right about this. I know the PO well. Long time friend. He had a problem with overfuelling and changed pump and filter as part of his diagnosis. I’m almost 100% certain that it would have been fitted with the stock element. I bought the car from him as a non runner and fixed the overfuelling (ECU problem) so the car has done less than 500 miles on that filter. I bet it’s blocked. Will be taking it apart tomorrow to find out!
Thanks..
Hi All,
My investigation today points to the filter being blocked. Loads of fuel flow prior to filter and the way I did it, no flow after the pump. So that points to filter and/or pump. I have a new pump to fit. The sytec filter has the paper element fitted that looked ok but I guess the particles will be small. I have ordered the metal mesh filter. Won’t get it back together for a few days but will let you know outcome. Thanks!
My investigation today points to the filter being blocked. Loads of fuel flow prior to filter and the way I did it, no flow after the pump. So that points to filter and/or pump. I have a new pump to fit. The sytec filter has the paper element fitted that looked ok but I guess the particles will be small. I have ordered the metal mesh filter. Won’t get it back together for a few days but will let you know outcome. Thanks!
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