Bosche Fuel Pump Piping idea

KP · Post by KP » 19 Oct 2007, 09:09

Just wondering what peoples thoughts were on an idea i had last night regarding the routing of the piping for the Fuel pump on my XUD engined Xantia

Currently fuel gets sucked up from the tank into the pump first flowing thru the fuel filter housing. I do not have a priming device on this feed line from the tank

Should i install a feeding device to help the pump keep its fuel as when the engine is warm and shut down i get the feeling the fuel can flow back to the tank causing poor starting which i sometimes get when i next go to start her. this would prevent that by having a one way valve built into it.

Also i was thinking of having a small pump fitted into the tank or on the lin to help suck the fuel upto the pump to make it less strained on the colder mornings we get?

Next idea was to 'T' into the fuel feed line to the filter housing and then feed the return pipe into this. The return to tank line would then get the Injector Leak Off pipes connected to it so the fuel from them goes back to the tank and then using a plug on the fuel pump itself. This would help reduce strain on the pumps suction side on the colder mornings.

This is all in the aid of helping my SVO fuelled Xantia run a bit smoother on the cold mornings as ive already noticed a lumpy tickover at idle when she first starts up and she now takes 2 glow plug heats to get going so i guess they need doing as well so ill get some duratherm plugs when i can

Thanks for the help,
Will

jgra1 · Post by **jgra1** » 19 Oct 2007, 09:23

Hi Will, sounds like some good ideas..

I dont quite understand though about the return pipe, you say you will feed it straight back into fuel feed, and then that leak off's will go back to tank?
Does this imply the leak offs and the fuel return are two different things, or that you will make them two different things? I assumed they were one and the same..

sorry red wine last night

John

edit..
It was about 1C this morning and I am lucky to be able to run my car for 10 minutes before I get in, despite this I had a blue cloud when I first accelerated on the road.. For the first time, I am 50/50 SVO...

leepasifull · Post by **leepasifull** » 19 Oct 2007, 10:08

I wouldn't T into the supply pipe with the return - it makes it more likely you'll get air into the system...

The pre CDTi Vauxhall diesel engines had the injector leak off pipes routed back to the in inlet side of the diesel pump - which means when they perish you get air into the inlet side of the system. Not a great plan.

Xaccers · Post by **Xaccers** » 19 Oct 2007, 10:35

You should have a grenade type priming bulb on the fuel line to the driver's side of the engine.
If fuel is returning to the tank over night, then you have an air leak in one of the pipes.
If starting is difficult, check your leakoff pipes and as a precaution, replace them.
That made a world of difference to TehAgent's car.

Check the fuel filter housing, down the bottom on the driver's side, there's a white dial, check that this isn't leaking.
If it is, get a high pressure airline blowing down your fuel return pipe as TehAgent's was blocked.
Find a replacement housing from a scrapper's (you'll need a 13mm socket with extension bar and the allen keys to take the top off).
Fill the dial with plenty of liquid metal and leave to set.
Once hardened, swap filter housings over.

The grenade itself can perish and let in air.
Because of the vacuum, you won't see diesel leaking out, you'll only know you've fixed the problem when you can't see any air flowing along the clear pipes and fuel no longer flows back into the tank.

Having hot unused fuel return to the tank is a good thing, it raises the temperature of the fuel in the tank.

KP · Post by KP » 19 Oct 2007, 14:14

Cheers guys for the help and info on my ideas

its nice to see that there are people out there that can be contructively critical of ideas without being fools

For some reason i dont have the priming bulb. Is it worth fitting one?

I haven't replaced the fuel filter yet as i have to get some clear pipe for the drain plug so i can do it without wasting fuel or making a mess on the drive

Ill have to see if i can buy a spare filter housing from the local scrappy, im lukcy i can walk to it in about 3 minutes from my door! I can then see about this white dial that i guess is a thermostat flow control valve to keep coolant flowing around the unit?

Another thing i want to check before my long journey is the Gauze in the fuel tank unit. The leakoff pipes are going to be done as well this weekend if i can get some time ut my main concern is getting the handsfree kit installed in the car

Thanks again guys

I want to get these little bits sorted before i start playing around with the fuelling like ive seen in other threads

jeremy · Post by **jeremy** » 19 Oct 2007, 17:27

As standard the system works very well - so if its not then there is something wrong. Answer - get the standard system right - as otherwise you will leave the original fault which will only cause trouble later.

Tank gauze filters seldom give trouble. Have you changed the filter above the thermostat? - What did it look like? was there something there to suggest a problem?

If the tank filter was blocked I would expect hesitancy on full power only - ie when climbing steep hills with the turbo running. If the thing does develop full power under these conditions then the fuel flow is adequate and not your immediate problem.

All that has been said about the priming bulb is good - B& Q and the rivals sell something remarkably similar for priming heating systems for about £10 which I understand is about the price of the genuine one.

KP · Post by KP » 19 Oct 2007, 20:24

Thanks Jeremy

The car does have a Flat Spot at about 3k revs sometimes.

Fuel filter i will find out this weekend as its another service item i need to do as well as another oil change this weekend or next week if i can get it booked in at National for one

Ill take pics of the filter when i get it out as well

TehAgent · Post by **TehAgent** » 19 Oct 2007, 20:45

From experience with my old fuel pump and return pipe leading from it, id say adding a T section and then running the return from the fuel pump back to the feed pipe, MIGHT take you down the route of a leaky fuel pump / fuel filter housing, as it was my fuel return line from the pump back to the tank that was blocked adding to the high pressure build up, that eventually found weak points in my fuel system.

Also, the fuel filter housing sits atop a water pipe bracket that acts as your fuel heater. when using the drain tap on the front of the fuel filter housing, either slacken off / remove the top cover or take off the feed line coming from the tank or you will not drain it because of pressure build up in the filter housing

Also, word of caution on the liquid metal fix for the leaky fuel filter housing, when i did mine, i still leaked so not sure what went wrong there, but its best to check your return hose first, if it is indeed blocked, remove the blockage before you change your filter housing.