Fuel pump cavitation.. at a loss
Discussion
Evening All, long time lurker here but now at a loss.
Since re-installing my fuel tank I've had an intermittent fuel problem which is rendering the car undriveable.
The pump will go from wirring away quietly to making a noise like a dentist drill and the engine dies. Sit for a few minutes and you can drive another couple of miles and repeat.
The (Bosch) pump is new, tank to pump hose is new, the tank has recently been out and I replaced the internal filter with an external one before the fuel pump. Checked that and it's clean. Oh and the fuel tank is confirmed full.
The pump always has power, but will suddenly go from quiet too sounding like its running dry.
Thoughts anyone? I'm at total loss now!
Since re-installing my fuel tank I've had an intermittent fuel problem which is rendering the car undriveable.
The pump will go from wirring away quietly to making a noise like a dentist drill and the engine dies. Sit for a few minutes and you can drive another couple of miles and repeat.
The (Bosch) pump is new, tank to pump hose is new, the tank has recently been out and I replaced the internal filter with an external one before the fuel pump. Checked that and it's clean. Oh and the fuel tank is confirmed full.
The pump always has power, but will suddenly go from quiet too sounding like its running dry.
Thoughts anyone? I'm at total loss now!
I'm having a very similar problem on my Tasmin. To solve it I'm going to try fitting this...
It's a central heating air separator. It holds 150cc which should be enough to keep the pump primed on most corners. Top vertical will be a vent back to the tank, top horizontal will be fuel in and the bottom one fuel to the back of the pump. What do you think?
It's a central heating air separator. It holds 150cc which should be enough to keep the pump primed on most corners. Top vertical will be a vent back to the tank, top horizontal will be fuel in and the bottom one fuel to the back of the pump. What do you think?
Thanks both!
Going to give the vent a try tomorrow. If that fails I'll take the element out of filter and see if that improves matters.
I like the mini accumulator idea, I'll be keen to hear how that goes. I did have thoughts of fitting a lift pump and header fuel tank in the boot, which is a more complicated way of doing the same thing.
Going to give the vent a try tomorrow. If that fails I'll take the element out of filter and see if that improves matters.
I like the mini accumulator idea, I'll be keen to hear how that goes. I did have thoughts of fitting a lift pump and header fuel tank in the boot, which is a more complicated way of doing the same thing.
I had a mondeo once upon a time. It would intermittently stop. Start up and drive fine, and then stop. After changing many parts, I found the (oh the irony) little 'quality' sticker had fallen down into the pump chamber. Every now and again it was covering the pump inlet. It took bloody ages to find, dropped the tank twice, and £?00's of punds of parts. Dear god it was a mare.
Oiyou said:
I replaced the internal filter with an external one before the fuel pump.
Was that trying to fix this problem, or for some other reason? Fuel injection pumps are great at pushing against back-pressure on the outlet but very bad at pulling against suction on the inlet. The resistance of a normal fuel filter could be enough to provoke cavitation in the pump and effectively stall it. If you're going to fit something to keep debris out of the pump, it needs to be a relatively coarse strainer rather then a conventional fuel filter. The main filter, of course, needs to be downstream of the pump.I would look at the way you have installed the pipe from the tank to the pump, you don't need the internal filter if you have a external fuel pump pre-filter. A 100 micron pre filter would be a good choice and a 10 micron post filter would be a better option. Like GreenV8s some pumps don't like to suck against a suction, Which bosch pump have you fitted. I would also see if you have something still in the tank being sucked into the sump and restricting the fuel. Bosch pumps are good at sucking so there must be something in what you have done since re fitting the tank and pump.
Another thing about Bosch pumps is they don't like to suck fuel they need to be as close to and as low as you can get them so you have a gravity feed to the pump
Another thing about Bosch pumps is they don't like to suck fuel they need to be as close to and as low as you can get them so you have a gravity feed to the pump
Edited by Alan Whitaker on Sunday 16th April 10:33
Suggest you hot-wire a fused 12v supply directly from the battery to the pump just to rule out any electrical problems. If the voltage is browning out, the pump will sound strange and lose pressure. There are several points in the supply circuit that are vulnerable to corrosion and for example the impact switch is also sensitive to side loads. A failing relay is often temperature sensitive and will run OK for a few minutes until it heats up, and then recover when it has been left to cool down for ten minutes.
This is the surge tank made from the air separator shown above....
If you think it looks like it was designed by a committee you'd be right. It took three of us in the plumbers merchant to come up with the right combination of parts
And with a splash of paint to make it look "proper".....
But does it work? Unfortunately I don't know yet. I couldn't get the hoses to seal properly on the small pipes. So the whole lot had to come off again so that these could be replaced with longer ones. Of course re-soldering these has loosened one of the adjacent joints which of course now leaks. For the time being the fuel lines have been reconnected back to normal. At least this way I'll find out whether the new pump makes any difference on its own. Once I'm down to the last gallon I'll have another go.
Oh yes, and the new copper washers on the pump banjo leak!
It's been a long day!
If you think it looks like it was designed by a committee you'd be right. It took three of us in the plumbers merchant to come up with the right combination of parts
And with a splash of paint to make it look "proper".....But does it work? Unfortunately I don't know yet. I couldn't get the hoses to seal properly on the small pipes. So the whole lot had to come off again so that these could be replaced with longer ones. Of course re-soldering these has loosened one of the adjacent joints which of course now leaks. For the time being the fuel lines have been reconnected back to normal. At least this way I'll find out whether the new pump makes any difference on its own. Once I'm down to the last gallon I'll have another go.
Oh yes, and the new copper washers on the pump banjo leak!
It's been a long day!
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