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Intermittent no power issue


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2 nights ago on my way home the car felt like it lost all power (had the music up loud so didn't actually hear the revs drop) but it started judder like it was going to stall. Turned the music down and dropped into 4th with my foot to the floor I was getting 45mph.

Cleared up pretty quickly and all was back to normal until tonight on my way home when it done the same thing. However this time at lower speed, rolled up to some traffic lights, stopped and when I pulled away it was fine again.

It's a 1986 90 with a 300Tdi. I'm guessing some kind of fuel issue. Either bad fuel (was from sainsburys) blocked filter, something in the tank or an air leak. Lift pump is maybe 2 years old and was a Delphi one. Can't say I've noticed any smoke but I haven't really been looking.

Going to investigate tomorrow morning, also will change fuel filter, fill up with some shell diesel and add some of that diesel system cleaner thing.

But wondering if anyone has any other suggestions as to what to look for or check?

Cheers

Stephen

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It sounds like air being sucked into the system. Look closely at all the unions on the low pressure side, ie from tank to lift pump (inclusive). The olives on the plastic pipes from filter to lift pump can wear a ridge which prevents a seal even when the nut is tight, so upen those unions up for a visual check of the olives.

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If you do those and its still doing it check the metal pipes in the top of the sender unit ono the fuel tank, they corrode and let air in too. not sure if the 90's have a water seperator but if it does they probably have steel connecting pipes too so check those for leaks and corrosion allowing air in.

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So an update. I didn't mention this before but I don't think the fuel filter had been changed in a while so I thought I would change it. First checked if primed and it wasn't tried pumping the fuel pump for ages and nothing, then tried turning the engine over with the fuel solenoid disconnected still nothing. The car would start and run though. My thought was fuel pump, took off the old filter, and tried pumping the fuel pump and it seemed fine, put a new filter on, filled it with diesel first though and then topped it off with the hand pump. It squirted out like it always has so don't think its the pump.

Ive left it running just now and will go out once its stopped raining and see what happening. If there is air in the top of the filter again and I need to re-prime it does that mean I have an air leak on the low pressure side?

Cheers

Stephen

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More updates. Ran the car for 30ish minutes on idle. Which it seemed todo fine. Went to check how primed the fuel filter was and it took maybe 15/20 pumps of the fuel pump go get the diesel to come out the bleed nipple. So my thought is that air is getting in somewhere. No obvious signs of anything split but I guess it just needs to be tiny crack. Does this sound right to everyone else? And if it does are the fuel pipes a part or are they just make your own?

Cheers

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Everything appears tight, the lift pump connections got new olives when it fitted (1.5 years ago). I was going to start with replacing the fuel lines and pickup from the tank. Wondering if someone can help me with part numbers and what fittings I need as well as pipe size.

The tricky part or possible tricky part is thats its a 1986 90 with a 300TDi, so the pickup is going to be 1986 parts and sizes and the fuel pump is 300TDi.

Cheers

Stephen

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So this morning I tried swapping out the old pipe with some 8mm flexible rubber hose with jubilee clips. But I'm still getting air in the filter. But I have noticed that when hand pumping the fuel pump once I get diesel coming out the bleed nipple if I stop pumping for 5 seconds to tighten up the nipple the diesel drains away (I'm guessing back to the tank) and I need to re-prime it. Is this normal? I would have thought the pump would have had a 1 way valve or something to stop this happening?

Starting to wonder if the problem isn't my fuel pipes but the fuel pump, but it is a newish one and a delphi one. But I guess it could have just failed early.

Cheers

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It could be an air leak before the pump.

Have you checked the oil level and smell? If it is higher, then it may be diesel leaking through the lift pump diaphragm on the pressure stroke, which would allow air in on the sucking stroke.

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I did change the pipe out with a rubber one between the tank and the pump, the pipe I remove looked okay but I know it could be the smallest of holes or cracks that does this.

Cant say that there is a particular smell or anything different than normal. I will check the oil level though. Going to take the car out a drive and see how it behaves. Its been idling away fine and rev's fine but haven't tried it under load.

S

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Just a quick one, and it might be nothing but with the engine running, if you open the bleed screw should diesel come out or should air go in...? I think diesel should come out but then again I'm just guessing!

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Just a quick one, and it might be nothing but with the engine running, if you open the bleed screw should diesel come out or should air go in...? I think diesel should come out but then again I'm just guessing!

engine running any bleed screw that is opened should get diesel out.

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So if removing the bleed screen from the filter lets air in to the point the point the car stalls there is probably something wrong with the lift pump? And what's happening just now is the injection pump is pulling the fuel up from the tank but with the bleed screw open the injection pump just pulls air in?

Cheers

Stephen

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I've not no, will do that today. However it does seem to be running okay just now (I now know after saying that it will break down again tonight!). If the gauze strainer looks okay, I will order a new pump.

Just as a side question, what do people think about fitting electric fuel pumps instead of the mechanical ones? My current ones is about 1.5 years old and is a Delphi one, and this isn't the first time I've had one fail in 4ish years!

Cheers

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Delphi should be OK, but if there is an underlaying cause like a blockage, they will fail prematurely because of working so much harder. We all have to replace these pumps from time to time, but yours is premature. You could have been unlucky, but I'd be checking the rest oft he system over. If there is a fault, it'd likely ruin an electric pump quickly too, and I really don't see much of an advantage in one. They're not cheap, either.

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Just a silly suggestion, but might be wise to check the filler cap for the tank is breathing.

Helped with an incident a while back where pump wouldn't prime etc., and it turned out that all pipes and pump were good, but tank was being drawn into a vacuum state and stopping fuel flow.

Filler cap removed, all worked normally....

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I'm always puzzled by the lift pump, they run perfectly well without one so I think you are barking up the wrong tree.

I think you have either a restriction somewhere, an air leak or a blocked breather in the cap.

Try slackening the cap off as Uncle Freak suggests and taking it for a drive.

Mo

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Agree with these chaps ^^^

I fitted an electric lift pump as I was tired of changing the mechanical ones. My 110 runs just as well with it turned on or off! I do think it stresses the FIP less to have it on though.

Mine have failed through leaking diesel, noticeably, hence very poor performance/cutting out.

Pics of my electric pump install are here:

http://forums.lr4x4.com/index.php?showtopic=93879&page=2

in hindsight, this was overkill and a smaller pump would have done mounted back near the fuel tank. Main reason i was reluctant to do that was that i wanted to use fittings in the engine bay and not cut the pipe further back and introduce possible air leaks etc.

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Just a silly suggestion, but might be wise to check the filler cap for the tank is breathing.

Helped with an incident a while back where pump wouldn't prime etc., and it turned out that all pipes and pump were good, but tank was being drawn into a vacuum state and stopping fuel flow.

Filler cap removed, all worked normally....

I've had similar but it turned out the fuel tank breather. the pipe, which had been run up just behind the mud guard on the 300tdi.. was blocked with mud.

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