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Intermittent power loss - Help!


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Hi everyone,

I know this has been covered before, but I'm rapidly running out of ideas.

The background: 1988 Ninety into which I put a 200tdi a couple of months back. The engine starts without smoke, and most of the time runs sweet as anything - bags of power, etc.

However, on almost every trip now, at some point it will suddenly lose all power. At this point, it'll tick over quite happily, but simply will not rev properly - in neutral with my foot on the floor the revs start to rise then drop, rise then drop - in gear it simply will not rev at all, and I'm lucky if I can get up to 20mph.

If I stop the engine and start it straight away, chances are it'll still misbehave. If I wait 5-10 minutes and then start it, all is well with the world and you'd never know there'd been a problem.

Things I've done: Flushed intercooler, replaced lift pump, replaced fuel filter, lubricated and freed the pin under boost diaphragm. The intercooler pipes were brand new when I fitted the engine (aluminium tubes with silicon joints).

The fact that it's intermittent, and the engine doesn't display any symptoms when it's running properly means I'm at a loss as to what to look at next. I've tried to be systematic - only changing one thing at a time, and then driving the car until it misbehaves again.

Any ideas what to look at next? What could cause the engine to behave like this?

Thanks in advance,

Ian.

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Hi Peter,

It happens even with a full tank. One of the things I plan to do when I've run the tank quite low is take the lid off and have a look inside to see if there's crud in there. Having said that, this problem started right after I fitted the 200tdi - whilst the previous 19J engine was a fuel-hungry, oil-burner, it never exhibited these symptoms.

When I did the conversion, I joined the rigid fuel pipe from the tank, to the rigid fuel pipe on the injector pump using flexible fuel line and jubilee clips - I'll check these are nice and tight.

As you say, it feels like a fuel problem - it's like it's being partially starved of fuel. But the intermittent nature does make it tricky to diagnose!

Ian.

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Be careful with that rigid pipe, it can collapse!

When I converted my 200Tdi to vegggie I had a lot of those connections to make and also rigid to flexible. I always used a short length of brass tube inserted into the rigid tube to stop it collapsing when the clips were tightened.

Cheers

Peter

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Then it's definitely worth a look to make sure that (a) the rigid tube hasn't collapsed and that (b) the hose clips are nice and tight. Out if interest, where would I get little sections of brass pipe in small enough diameter to fit inside the fuel line?

Ian.

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Any good model shop (cars, planes, trains) there are boxes of brass and steel in 12" lengths of different shapes and diameters.

I always used to take a length of the rigid pipe with me and get one that was a night tight fit.

This is a link to Antics (a model shop chain) you can see the sort of material I'm talking about - http://www.anticsonline.co.uk/1381_1.html

Cheers

Peter

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I'd also check the gauze filter on the end of the fuel pick up in the tank. I know you said it started after fitting the 200Tdi but it could be a coincidence. Also check the steel part of the pipes where they come out of the tank haven't corroded excessively, they can pin hole and draw air in.

Mark.

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Hi Mark,

Now that's interesting (and not in a good way!) I took the top off the tank to check the pick-up pipe the first time it happened - there was no filter on the pipe, it's just an open-ended metal pipe going into the fuel. I hadn't even realised there was meant to be a filter on it!

Ian.

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  • 4 weeks later...

A quick update - this hasn't gone away :(

I've replaced the fuel hose from tank to lift pump, and also the return hose. I've taken the top off the fuel tank and had a good look around inside - it's clean as a whistle in there.

The loss of power is very random - I drove from Basingstoke down to Southampton and back the other day without a problem. Yesterday I drove to work and back twice - on the second return journey I was just pootling along at 30mph and I lost power. I crawled at 15-20mph into a bus-stop. After 5 minutes I started the engine again and it was perfect.

It's so frustrating as 99% of the time the engine has plenty of oomph!

I wondered if there's anything on the turbo side of things that could cause these kinds of symptoms? I'm running out of things to look at!

Ian.

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I had similar symptoms with my 300 TDI. I did all you have done and the problem would not go away. It would drive OK for months and then do as you describe every 100 yards. I checked everything i could find but could find nothing wrong. After some years or this i became aware of electrical interference on the radio at the same time as the engine problem. So i thought it must be electrical but there are almost no electronics on the engine. I made a wire to go from the battery to the fuel pump solenoid to see if this would sort out the problem but as i pulled the loom wire off the solenoid i found the fault. The spade connector was not tight. So i cut the old connector off and soldered the wire to the tag on the solenoid. That was two ish years ago and the fault has not returned I would suggest you check this connection and the whole length of the white wire for breaks and shorting. I hope this helps you fix your fault as it nearly drove me mad

Cheers Rob

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Hi Rob,

Thanks very much for the reply - does the fuel solenoid not cut off the fuel completely? I'll certainly check it out as I'm getting to my wit's end! I would have thought that the engine would stop altogether if it was power to the solenoid. Having said that - could it be partially opening/closing and so restricting the fuel flow?

Hmmmm.... it's certainly something I've not looked at yet - and that in itself gives me a little bit of hope!

Cheers for now,

Ian.

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Hi Ian

Yes the solenoid would cut the fuel off totally if the electrical connection was totally broken. In my case the lose spade connector made an intermittently poor connection . I could see it sparking at night

Cheers Rob

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  • 3 years later...

Thread revival time

Hi everyone,

I know this has been covered before, but I'm rapidly running out of ideas.

The background: 1988 Ninety into which I put a 200tdi a couple of months back. The engine starts without smoke, and most of the time runs sweet as anything - bags of power, etc.

However, on almost every trip now, at some point it will suddenly lose all power. At this point, it'll tick over quite happily, but simply will not rev properly - in neutral with my foot on the floor the revs start to rise then drop, rise then drop - in gear it simply will not rev at all, and I'm lucky if I can get up to 20mph.

If I stop the engine and start it straight away, chances are it'll still misbehave. If I wait 5-10 minutes and then start it, all is well with the world and you'd never know there'd been a problem.

Things I've done: Flushed intercooler, replaced lift pump, replaced fuel filter, lubricated and freed the pin under boost diaphragm. The intercooler pipes were brand new when I fitted the engine (aluminium tubes with silicon joints).

The fact that it's intermittent, and the engine doesn't display any symptoms when it's running properly means I'm at a loss as to what to look at next. I've tried to be systematic - only changing one thing at a time, and then driving the car until it misbehaves again.

Any ideas what to look at next? What could cause the engine to behave like this?

Thanks in advance,

Ian.

Having more or less exactly the same problem with mine currently. Only difference is mine is a 110 ;-)

Tried all of the above to no avail. Only thing I haven't tried is replacing the fuel filter but got one today and will try that tonight.

Is there anything else that could be causing it that isn't mentioned above?

Cheers,

Rich

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