In line fuel injection pump

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mshaw1980
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In line fuel injection pump

Post by mshaw1980 »

Wondering if someone can help, well begging on my subaru ej20 n/a converted van:-(

In the time my van has been on the road, approx 2000 miles I am on my fourth inline injection pump. The first and second were cheapies, the third a bosch one that was replaced under warranty and the fourth is also a bosch.

I have lowered the mounting of the pump so it is now slightly lower than the chassis leg so it is now a little below the fuel tank outlet, approx 30 cm from the tank. It is a fuel injection tank (brand new) with 12mm hose from tank to pump, followed by 8mm hose from pump to fuel filter and then to engine fuel rail. I never tend to have more than half a tank of fuel and I do sometimes let it get quite low before refilling.

After two days of the fourth bosch pump being fitted and the van driving ok, the van was left for two days sitting on my drive which is a slight decline away from my garage, front of van facing downwards. It then refused to start that is the pump wouldn't prime with the familiar 2 sec buzz. I checked with my multimeter on the positive terminal and negative mounting point on the chassis leg and when the ignition is turned on, not the engine, it is getting over 11volts which should be enough for it to prime but it does not. Yet again it will only work if I start tapping it with a soft faced hammer. After a few goes of this it will prime, van will start and drive fine. Just getting sick of having to carry a hammer everywhere as its embarrassing if the thing doesnt start and also inconvenient if its pouring down.

I think this could also be the reason why I am getting a knock sensor fault code. Originally I got that and a lambda code but I found and fixed an air leak after the maf sensor and also replaced the lambda with a new bosch one and now thats ok, however if the pump isn't delivering the correct fuel pressure then this I assume could be causing a bit of engine knock as the knock sensor voltage and resistance is within spec.

I am at a loss as to why this keeps happening. Anybody with an inline pump circuit that is reliable PLEASE let me know how yours is done photos, explanation etc.

Many thanks all

Mark
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937carrera
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Re: In line fuel injection pump

Post by 937carrera »

I assume by inline injection pump, you mean a standard electrict fuel pump, as used on injected cars

The answer I thought wass quite simple. Rust from the tank contaminating the pump and causing it to overheat / jam. It does not take much at all to do this. I have seen pumps fail after as little as 15 minutes because the fuel tank was rusty internally and the filtration was not up to the job.

But then I see you say you have a new fuel tank.

Is it new, is there a possibility that crud elsewhere in the fuel system has found its way back to the tank and that is killing your pumps. One of the reasons for having an in tank filter prior to the pump
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mshaw1980
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Re: In line fuel injection pump

Post by mshaw1980 »

937carrera wrote:I assume by inline injection pump, you mean a standard electrict fuel pump, as used on injected cars

The answer I thought wass quite simple. Rust from the tank contaminating the pump and causing it to overheat / jam. It does not take much at all to do this. I have seen pumps fail after as little as 15 minutes because the fuel tank was rusty internally and the filtration was not up to the job.

But then I see you say you have a new fuel tank.

Is it new, is there a possibility that crud elsewhere in the fuel system has found its way back to the tank and that is killing your pumps. One of the reasons for having an in tank filter prior to the pump

The tank has less than 2000 miles, bought from brickwerks and has the standard in tank strainer and it being new I cant see how there would be rust. How can you put an in tank filter on one of these tanks other then the strainer that its manufactured with??
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937carrera
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Re: In line fuel injection pump

Post by 937carrera »

That was more of a comment from a design perspective, rather than a mod you can easily do.

All the BW stuff will be fine I am sure - could there be crud still around from when it was fitted it (so clean tank, now with added rust particles).

see what others think, but it may be worth removing the filter and cutting that open as a first step, maybe followed by tank removal / inspection.

My only other thought is that these pumps need fuel to cool them. If the pump is running without fuel then it could overheat. The tolerances are very very small
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Oldiebut goodie
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Re: In line fuel injection pump

Post by Oldiebut goodie »

It has always struck me as strange that a filter isn't fitted before the pump in these vans, obviously a filter before the pump will save the pump but the standard fitment is after the pump to protect the rest of the system.
I agree about the possibility of overheating of the pump if drained of fuel - Webasto heater pumps can overheat with prolonged use without the fuel flowing to cool them. ( and they are only pulses not full flowing )
What about the 8mm hose causing a constriction making the pump overwork? My fluid dynamics knowledge is basically nil but surely it should be the same diameter throughout, any excess fuel being dealt with by the return line?
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937carrera
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Re: In line fuel injection pump

Post by 937carrera »

mshaw1980 wrote:it will only work if I start tapping it with a soft faced hammer.

Just reinforcing this point. This is an almost certain dead giveaway that the pump is jammed

My fluid dynamics knowledge is slighly above nil, and I know enough to know that I know virtually nothing......... Can you clarify one thing, without wanting to get into the semantics between a pipe and a hose, is the 8mm you mention the OD of the hose or the ID ?
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slowcoach
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Re: In line fuel injection pump

Post by slowcoach »

I wonder yes if the pump is just straining too hard, and failing.

If you disconnect the return line where it connects to the fuel tank, you'll be able to run the fuel pump via a jumper (just give it a straight 12v from the main battery), and see how much fuel is doing the loop through the engine bay, and into a pot or bottle. It should be a pretty steady flow.


You can also measure the volume of fuel pumped into a bottle over a minute , against the pump specs.

The tank/filter/pump setup you have is correct.

Also, I wonder if the fuel pressure regulator is creating too much line pressure, and over working the pump? Just thinking aloud ..
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Oldiebut goodie
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Re: In line fuel injection pump

Post by Oldiebut goodie »

slowcoach wrote:I wonder yes if the pump is just straining too hard, and failing.

If you disconnect the return line where it connects to the fuel tank, you'll be able to run the fuel pump via a jumper (just give it a straight 12v from the main battery), and see how much fuel is doing the loop through the engine bay, and into a pot or bottle. It should be a pretty steady flow.


You can also measure the volume of fuel pumped into a bottle over a minute , against the pump specs.

The tank/filter/pump setup you have is correct.

Also, I wonder if the fuel pressure regulator is creating too much line pressure, and over working the pump? Just thinking aloud ..

His set up is tank/pump/filter which I gather is standard method.
Keep thinking aloud... after all you are already set up. What ID is your fuel line after the pump/filter ( whichever way round yours is)?
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Re: In line fuel injection pump

Post by slowcoach »

After my filter, it goes to 7 or 8mm Id (7.5?). That then connects after a short length to the nylon 'hard lines' (not rubber) to go off to the engine bay. Those hard lines are factory VW, not sure if they're on DG engined vans, but they're on 2.1s.. know what I'm talking about?
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Re: In line fuel injection pump

Post by Oldiebut goodie »

No constriction any different to standard then if you haven't experienced the same type of problem. That's my theory out then. :D
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Re: In line fuel injection pump

Post by pkrboo »

Pump is gravity fed from the tank so make sure it is low enough to get a good feed.

What is the Bosch pump number you are using?



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mshaw1980
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Re: In line fuel injection pump

Post by mshaw1980 »

The fuel rail on a subaru engine takes an 8mm bore hose from the fuel pump which is why that size hose is used. I assume the 12mm bore input from the tank is so there is sufficient fuel coming into the pump and then the reduction to 8mm on the fuel pump outlet is to increase fuel pressure to an adequate level.

Surely a fuel filter before and after the fuel pump would cause a further obstruction putting the pump under more pressure.

It is stated that the pump needs to be lower than the tank outlet for gravity feed however that doesnt work if parked front end downhill or driving downhill as the fuel is flowing away from the pump at that point and so the pump will have to work harder. The only way for gravity feed to work in all scenarios would be for the pump to be mounted further down which would mean it would be too near to the road.
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Re: In line fuel injection pump

Post by 937carrera »

OK, so 12mm id feed and 8mm id supply to the fuel rail is standard, so no issue there

The larger bore on the feed is to allow greater flow, the pump supplies flow at pressure, which I suspect is 3 bar set by the FPR

The arrangement you have is normal. Some vehicles have a lift pump in the tank, which provides flow greater than gravity can provide, or where the pressure pump has to be located above the bottom of the tank.

Fuel pumps maintain a supply of fuel through a suction / syphon effect as well as gravity. I am learning much more about this on something called a diesel which I am trying to rescue. No fuel pump at all on those, just the injection pump. Bleeding hell is an apt expression

I think the mechanical design aspects of your installation are fine, so you are looking for some other fault.

Some ideas

Cut the existing filter open for inspection (shears, don't hacksaw it)
Make sure the 12mm feed pipe is completely clear
Drop the tank and make sure there is noting in there that could block the outlet
As a test, how about putting a filter before the pump with delivery straight back to the tank and wire up a temporary electrical supply to the pump

Do post back with what pump you are using
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Re: In line fuel injection pump

Post by Oldiebut goodie »

Is it beyond the realm of possibility that the feed line in the tank has a pinhole allowing air into the feed constantly causing fuel starvation in the pump? Or even inadequate sealing of the tank spigot/pump spigot allowing air ingress ( Jubilee clips used instead of hose clips are a favourite for distorting the rubber joints) - as there is no pressure that side you wouldn't be aware of any air getting in/fuel leaking, happens quite often on diesels as you have a long suction line.
If a see-through filter is used after the pump any large quantity of air being pumped would soon be seen.
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Re: In line fuel injection pump

Post by 937carrera »

Oldiebut goodie wrote: If a see-through filter is used after the pump any large quantity of air being pumped would soon be seen.

Can you get see through filters that will take 3 bar ?
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