My 405 TD needs the primer bulb pumping before starting. It then fires after quite a lot of cranking. Within a mile, it starts to judder, and dies, often if idling/at low revs. Prime the bulb, and it will go again. If kept at cruising revs it seems to be better, and runs OK. The probelm seems to be far worse when the engine is completely cold.
When priming you can hear the fuel flowing into the filter chamber. The filter was changed three days ago, and has made no difference.
It is running on veg oil/diesel, mixed, but this problem has only recently occurred, after several months of veg oil use. It has a Bosch injector pump, which should tolerate veg oil.
My gut feel is that the injector pump is partly knackered, but do BRers have other ideas?
Edited by Webmaster on 05/04/2008 at 15:31
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This sounds like it could be the fuel filter restricting flow. Clues include 'veg oil' and 'far worse...when cold'. The veg oil will have a pretty high viscosity when cold, and one which will be higher than mineral diesel at warmer temperatures. The filter on these is quite small (assuming it's the 1.9) and sits on the thermostat housing which provides heating to the fuel. Higher viscosity and fairly small filter surface area could equal lack of flow especially when cold.
Incidentally I recently had filter plugging problems caused by 'diesel bug' growing in the tank of my Passat tdi. Symptoms involved the engine cutting out after ascending long hills. I soon noticed a green algae-like substance sitting in the filter. A treatment from a marine chandler sorted this out, so may be worth looking out for green stuff in the filter too...
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a quick experiment could be to run the engine without the fuel filter, if the problem isn't there then viscosity is the likely cause,
being what the engine is though id go for a combination of either fuel leak back due to an air leak (thats why it needs priming first thing) along with viscosity problems, for air leaks carefully check the primer bulb for small splits and replace the injector leak off pipes and check all other fuel line connections are secure.
for viscosity issues add 1% petrol to the oil and leave it to stand for 3 days before putting it in the car, this will thin the oil down dramatically and will stop viscosity problems
chris
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....and alternatively a monster air leak? Perhaps the fuel pipes have been affected by the veg oil, plus the igher viscosity of the veg oil mix will mean a higher negative pressure in the pipework between filter and pump.
Don't get me wrong, I'm not against veg oil as I'm about to run a 205 d turbo on a mix (this car now has a bosch fuel system as opposed to the original-fit lucas.
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Update - when using the primer bulb I noticed a weep/ooze from the fuel filter cap - it's in two parts with a cup-shaped housing, and a cap held in place by four allen-keyed bolts. As I pumped the bulb of the primer I could see movement of fluid/fuel around the outside of the cap/body joint.
I changed the filter for a Crosland, which has a metal disc on the top, rather than the plastic disc of the old one. It seems to have a slightly better gasket round the rim of the metal disc.
This has made some improvement, but it's not a total solution. The car won't idle once air starts getting through, though it's fine once moving, at revs of 2,000 or more.
I can now trace the problems back to the first time I changed the fuel filter, but I can't see how I can have damaged the filter assembly when changing filters. It's not possible to run the car without a filter, as the gaskets on the top of the filter disc are critical.
Clearly it's not possible to use any form of flexible compound on the gasket, as it will get drawn into the fuel system.
The fuel filter housing is heated by engine coolant, so it does get better once up to heat, but I can't see how I can get back to the situation I was in before I changed the filter for the first time, without trying every brand of filter.
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my suggestion of running without a filter was only aimed at identifying if the filter was causing fuel starvation.
it's possible the rubber seal at the bottom of the filter has gone (take fuel filter out, remove 13mm bolt in bottom, seal is on bottom. or the filter housing has been damaged or distorted at some point try a new one or one from a scrap yard, plenty of psa cars use this engine so lts around.
once you source another housing fit it then replace the fuel line from the primer bulb to filter housing with a clear pipe, and do the same for the pipe from the filter to the injection pump. once they are done you will be able to start diagnosing where the air leak is coming from as id say it's more than just a leak at the filter top.
or another quick idea, get a sheet of reasonably thick gasket paper, cut out square of paper bigger than filter housing, remove filter lid, trace shape onto paper, pierce the 4 bolt holes then put the square over the fuel filter and replace and evenly tighten the lid (do it diagonally) that should provide enough of a seal to show if it's just the filter housing
chris
Edited by thomp1983 on 10/04/2008 at 18:22
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I've had a similar problem with my 405 diesel, the cause was a leaking water drain screw on the bottom of the fuel filter. Worth checking if that weeps fuel when you use the primer bulb...
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The issue was two-fold:
1) viscosity of the veg oil I use - much higher than an earlier batch compounded by:
2) sludge/slime inside the fuel strainer that sits around the feed pipe in the tank.
I cleaned out the strainer assembly and have raised the ratio of derv in the mix to 25%, and it goes well. Gives about 8 miles to the litre driven briskly (75 mph on French autoroutes) which is about 10% less than straight derv. The veg oil costs 40p/litre, so I'm on a winner.
Cheers all.
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hi there
i seem to have same problem with fuel starvation as you...
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do you mean the fuel tank at rear of car or the fuel filter tank?
cheers, neil.
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Gives about 8 miles to the litre driven briskly ...
Even driven briskly, that's pretty terrible - 36mpg from a PSA diesel? Is veg-oil a particularly poor fuel?
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