Cutting-out problem on the 400SX
Discussion
Well - I've found it at last!
This has gotta be one of the bizzarest problems I've seen while tinkering on cars.
The inlet hose to the fuel pump - from the swirl pot - is a braided hose.
What I found is that when the pump is running it collapses almost flat under the vacuum.
So it starts to kink and restrict the fuel flow - big time.
But when you look under the car when the engine is off - it looks completely normal!!!
No leaks either.
Obviously, when I jink right, the hose flops over, kinks a bit more, and I lose fuel pressure. Now off to the garage to get some hose. Anyone know what inner diameter it is?
This has gotta be one of the bizzarest problems I've seen while tinkering on cars.
The inlet hose to the fuel pump - from the swirl pot - is a braided hose.
What I found is that when the pump is running it collapses almost flat under the vacuum.
So it starts to kink and restrict the fuel flow - big time.
But when you look under the car when the engine is off - it looks completely normal!!!
No leaks either.
Obviously, when I jink right, the hose flops over, kinks a bit more, and I lose fuel pressure. Now off to the garage to get some hose. Anyone know what inner diameter it is?
No wonder you could not find the problem on the injection !
Braided hose is a nightmare as you can't see what it's doing under the braiding, I have a severe fuel leak on a carb fed car as the rubber failed leaving fuel spraying all over the engine, someone else I know had their fuel line catch fire when the engine earth strap failed putting the cranking amps through their nice braided fuel line. Since I've stuck with rubber
I recall trying to get 1/2" onto the swirl pot and failing as the puddle of unleaded in my armpit grew so it must be around 15/16mm as the 1/2" would not stretch over the bead on the swirl pot.
Braided hose is a nightmare as you can't see what it's doing under the braiding, I have a severe fuel leak on a carb fed car as the rubber failed leaving fuel spraying all over the engine, someone else I know had their fuel line catch fire when the engine earth strap failed putting the cranking amps through their nice braided fuel line. Since I've stuck with rubber
I recall trying to get 1/2" onto the swirl pot and failing as the puddle of unleaded in my armpit grew so it must be around 15/16mm as the 1/2" would not stretch over the bead on the swirl pot.
Yeah it's not metal braided but nylon external braiding.
I managed to get some calipers on the swirl pot outlet and it seemed 10mm so that's what I got. Luckily my village garage was still open - just - and 2 quid towards their beer fund secured half a metre of hose. There's a pre-filter in the line too so I shall take that off and back-flush it for now (in case it too is gummed up aiding the vacuum effect).
I managed to get some calipers on the swirl pot outlet and it seemed 10mm so that's what I got. Luckily my village garage was still open - just - and 2 quid towards their beer fund secured half a metre of hose. There's a pre-filter in the line too so I shall take that off and back-flush it for now (in case it too is gummed up aiding the vacuum effect).
Hold your horses (sic!) just took it out for a spin - to steal a title from another topic:
OH MY FRIGGING GOD !!!!!
the top end is back with a vengeance!
So I will be reserving some of that 150 smackers ( minus 2 quid for the pipe ) for....
THE BBWF ROLLING ROAD!!!
Still, £100 should be a reasonable round ;^)
OH MY FRIGGING GOD !!!!!
the top end is back with a vengeance!
So I will be reserving some of that 150 smackers ( minus 2 quid for the pipe ) for....
THE BBWF ROLLING ROAD!!!
Still, £100 should be a reasonable round ;^)
Hmmm indeedy...
Well there's one advantage of only one exhast pipe - I could work in the garage with the engine running while I poked and prodded, and not gas myself:
with some bits of old drain pipe and damp cloths!
So I found this pre-filter
with this cartridge inside (which was pretty dirty). As I couldn't get a new cartridge quickly I washed the filter out several times until I got clear petrol and for good measure washed it in hot water and detergent, then finally petrol again...
I think the paper filter is a bit silly because there's the BOSCH one after the pump anyway which is much bigger (and will collect more dirt before blocking).
I've found out there's a metal cartridge you can put in instead which will protect the pump and should be flushable, to boot.
Lastly, here's the culprit:
Looks OK doesn't it? However it is fairly squeezy and just collapses under vacuum pressure inside.
What didn't help is the chap who installed the pre-filter tie-wrapped the pipe to the chassis pretty tight, which also started to kink it as well.
Well there's one advantage of only one exhast pipe - I could work in the garage with the engine running while I poked and prodded, and not gas myself:
with some bits of old drain pipe and damp cloths!
So I found this pre-filter
with this cartridge inside (which was pretty dirty). As I couldn't get a new cartridge quickly I washed the filter out several times until I got clear petrol and for good measure washed it in hot water and detergent, then finally petrol again...
I think the paper filter is a bit silly because there's the BOSCH one after the pump anyway which is much bigger (and will collect more dirt before blocking).
I've found out there's a metal cartridge you can put in instead which will protect the pump and should be flushable, to boot.
Lastly, here's the culprit:
Looks OK doesn't it? However it is fairly squeezy and just collapses under vacuum pressure inside.
What didn't help is the chap who installed the pre-filter tie-wrapped the pipe to the chassis pretty tight, which also started to kink it as well.
Looking back at your previous tread 'Started playing with the ecu/ignition', did I not predict that it could be fuel starvation? OK, I was wrong about the movement in the fuel tank , but fuel starvation was high on my list. I should of been a 'Prophet' with such accurate predictions.
Well done. Enjoy!
Tony. TCB.
Well done. Enjoy!
Tony. TCB.
As my mate Sherl used to say: "when you have eliminated the impossible, whatever remains, however improbable, must be the truth" ;^)
Cheers Tone!
Looked into the metal cartridge for the pre-filter but they are 20 quid. However I can buy stainless gauze for a fiver on the flea, and I'll have enough for 3 filters...... job done!
Cheers Tone!
Looked into the metal cartridge for the pre-filter but they are 20 quid. However I can buy stainless gauze for a fiver on the flea, and I'll have enough for 3 filters...... job done!
Yeah a fuel pressure gauge would be handy maybe I could use an oil sender, would that work? Some of the pipes on the rear have been renewed but this one has been in there since 2005 at the latest (same as the date code on the filter element. )
Putting a paper element in the pre filter is a bad idea. When I get my gauze I'll put a small magnet in there too to grab any metallic or rust particles. Hopefully it will only need flushing out every 20k or so.
Putting a paper element in the pre filter is a bad idea. When I get my gauze I'll put a small magnet in there too to grab any metallic or rust particles. Hopefully it will only need flushing out every 20k or so.
The impurities found in fuel is usually of a sand and grit type of consistency and so I'm not sure that gauze would filter the very fine particles. It's these very fine gritty elements that get into the pump and damage the bearings etc. Hence, why the use of paper elements. However I understand your concern about restricting flow, but maybe the type of paper element used is of a special type and can cope.
Tony.TCB.
Tony.TCB.
The gauze I've ordered is 70 micron size, big enough to only let through really fine stuff that (I thought) would pass through the pump unimpeded without damaging the pump. The paper filter on there was rated at 8 micron which also trapped so much fine stuff that it eventually clogged.
Also - the paper one doesn't flow nearly as much as a mesh one, so in order to achieve the same fuel pressure the pump must work harder. This may also reduce the pump's life so maybe the trade-off isn't so bad.
Also - the paper one doesn't flow nearly as much as a mesh one, so in order to achieve the same fuel pressure the pump must work harder. This may also reduce the pump's life so maybe the trade-off isn't so bad.
adam quantrill said:
Yeah a fuel pressure gauge would be handy maybe I could use an oil sender, would that work? Some of the pipes on the rear have been renewed but this one has been in there since 2005 at the latest (same as the date code on the filter element. )
Putting a paper element in the pre filter is a bad idea. When I get my gauze I'll put a small magnet in there too to grab any metallic or rust particles. Hopefully it will only need flushing out every 20k or so.
Fuel pressure transducer would need to be resistant to petrol (yes!), not certain if an oil pressure sender would be adequate. Holley do something that measures up to 100psi, but it's not cheap as I recall. Putting a paper element in the pre filter is a bad idea. When I get my gauze I'll put a small magnet in there too to grab any metallic or rust particles. Hopefully it will only need flushing out every 20k or so.
I use one of these as a pre-filter http://www.ebay.co.uk/itm/SYTEC-MOTORSPORT-FUEL-IN...
Yes of course - some transducers are petrol-rated.
I had a look for filter recommendations and most recommend 100 micron for the pre-filter and 10 micron post-filter.
So I would be wary about using something that is advertised as universal, the pre-filter should flow easier to avoid starving the pump, and after the pump the post-filter does the fine stuff, it matters less if the post-filter needs more pressure to flow the fuel because you have more pressure to play with.
I had a look for filter recommendations and most recommend 100 micron for the pre-filter and 10 micron post-filter.
So I would be wary about using something that is advertised as universal, the pre-filter should flow easier to avoid starving the pump, and after the pump the post-filter does the fine stuff, it matters less if the post-filter needs more pressure to flow the fuel because you have more pressure to play with.
adam quantrill said:
Yes of course - some transducers are petrol-rated.
I had a look for filter recommendations and most recommend 100 micron for the pre-filter and 10 micron post-filter.
So I would be wary about using something that is advertised as universal, the pre-filter should flow easier to avoid starving the pump, and after the pump the post-filter does the fine stuff, it matters less if the post-filter needs more pressure to flow the fuel because you have more pressure to play with.
There was a logical decision-making process when I bought the filter, although the logicality of the process escapes me 3 years and 15k miles later, so probably time for a change of filter. As I recall, part of the problem was finding something with the right tails. Please post a link to whatever you decide to fit.I had a look for filter recommendations and most recommend 100 micron for the pre-filter and 10 micron post-filter.
So I would be wary about using something that is advertised as universal, the pre-filter should flow easier to avoid starving the pump, and after the pump the post-filter does the fine stuff, it matters less if the post-filter needs more pressure to flow the fuel because you have more pressure to play with.
BTW, if your pump has been deprived of fuel then it might now fail fairly quickly, just thought I should add that! Mine failed after I ran the tanks low, I fitted a replacement and now carry another replacement in the boot, so it will never be a problem again.
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